old and new theory of v-drive location

[63stevens]

can anyone explain the new and old theory of v-drive location along with strut location and angle. also does the same theory apply to cruisers?

[Fiat48]

Lot of controversy over v drive location and strut angles. Go here and read this first. http://www.faulkerson-motorsports.com/

[havasulew]

WOW!!! My brain is still smoking a little bit. I just got done reading the article by James Faulkerson. I did understand what he is talking about. Can't wait to pull that little bit of info out of my ass while standing around bench racing. wink wink wink :D

[Sked]

Propeller angle and location are a major key due to the fact that the point which the boat is being pushed is at the face of the propeller blade. V-Drive location or where the shaft attaches to the boat is insignificant. I don't agree with the simplicity of Faulkerson's theory that the pushing force follows in line with the prop shaft and intersecting above or below the boats center of gravity creates the changes because I don't believe the push is traveling up the prop shaft or even in line with it. If it was then V-Drive location would be important. The point of push is at the propeller blade. Part of what's missing from his theory are the forces created by the rotating propeller which cause certain amounts of lift depending on factors such as RPM; depth, diameter and pitch of the prop and how much bottom area is aft of the prop among other factors. Prop rake is also a variable to shaft angle which changes the pushing angle of the prop especially when you consider that the blade that is going through the lower part of the prop rotation is the one that is doing most of the pushing. The rudder, fins, and water pickups are all creating forces that are also working on the static center of gravity. Also to be considered is hull design including rise, bottom width and rocker if any and the speed at which the boat will be required to perform at. Bottom line is that the boat is being pushed at the prop and the location and angle of the prop combined with all the other factors must be such as to create a situation where they all compliment each other at the speed you are designing the boat to run. Consider all of this and then add changing speeds, direction, and wind and water conditions and you can easily see why Race and High Performance Inboard V-Drive Boats can be so challenging to set up correctly.
[ October 09, 2002, 12:44 AM: Message edited by: JSSK88 ]

[VD CRUISER]

I have to disagree with you on location of the v-drive not making a difference. Of course shaft angle and strut placement pretty much determine where the v-drive will be anyway. Moving the strut forward 6.5 inches and bringing the shaft angle from 9 deg down to 7.5 deg made a hell of a difference in my 21' day cruiser. That change also moved the v-drive ahead 13".

[Sked]

VD CRUISER:
I have to disagree with you on location of the v-drive not making a difference. Of course shaft angle and strut placement pretty much determine where the v-drive will be anyway. Moving the strut forward 6.5 inches and bringing the shaft angle from 9 deg down to 7.5 deg made a hell of a difference in my 21' day cruiser. That change also moved the v-drive ahead 13".If you had left everything alone (except of course prop shaft length) and just moved the V-Drive up 6.5" to 13" you would not have seen any difference. The only possible exception would be due to the movement of weight.

[CircleJerk]

DR.JSSK88, FIVE STARS FIR YA! Would it be incorrect then, to say the v-drive box pulls the hull from its center point? Like a sled being pulled along with a short rope {causes the front to rise} or a longer rope {causes the sled to move forward without the upward movement}? I didnt agree with the Faulkerson theory even though it made sense to a degree. NO pun intended. Pushing at the blade: now you've got me screwed up, but it somehow makes sense......Can you supply a training Manual? JerkSK88
[ October 10, 2002, 01:12 AM: Message edited by: CircleJerk ]

[ACCEPTENCE]

I have to disagree with you on location of the v-drive not making a difference. Of course shaft angle and strut placement pretty much determine where the v-drive will be anyway. Moving the strut forward 6.5 inches and bringing the shaft angle from 9 deg down to 7.5 deg made a hell of a difference in my 21' day cruiser. That change also moved the v-drive ahead 13".
Good job VD Cruiser, your so right on. Now that about covers it. If your wanting the boat to stop posposing like a jumping tuna fish in heat, lower the strut angel and add more power.

[superdave013]

JSSK88:
VD CRUISER:
I have to disagree with you on location of the v-drive not making a difference. Of course shaft angle and strut placement pretty much determine where the v-drive will be anyway. Moving the strut forward 6.5 inches and bringing the shaft angle from 9 deg down to 7.5 deg made a hell of a difference in my 21' day cruiser. That change also moved the v-drive ahead 13".If you had left everything alone (except of course prop shaft length) and just moved the V-Drive up 6.5" to 13" you would not have seen any difference. The only possible exception would be due to the movement of weight.You would see a big difference in your ass after all the money for a new prop shaft came out of it. LOL

[Jetboatguru]

Why even run a Vdrive then. Why not tilt the motor at an angle like a jet boat and run the prop shaft directly to the crank hub, down through shaft log and and through a strut. Perfect.
V-drive placement is as crucial to proper set up as the strut location. This is the push point of the boat not the propeller.

[MikeF]

Jetboatguru:
Why even run a Vdrive then. Why not tilt the motor at an angle like a jet boat and run the prop shaft directly to the crank hub, down through shaft log and and through a strut. Perfect.
V-drive placement is as crucial to proper set up as the strut location. This is the push point of the boat not the propeller.Add a Lenco w/ OD gears and a reverse! :D
Probably good on a flat!, but not so good on a hydro.
Here's an idea (most will probably not like eek! :mad: :rolleyes: :p wink )(no more rooster off the back of the boat).
Why not put the prop at the front of the boat so it pulls instead of pushes eek! . Seems it might be a better handling boat!? What do you think?

[CircleJerk]

I,m sure you cruiser folks don't mean to imply that SK88 is wrong but re-read his statement. He only disagrees with Faulkersons theory that thrust follows the shaft line to determine lift and handling. I think you are saying the same things. Look at the boat that he drove with NO down pedal! Most of you have the advantage of stabbing a down pedal to fine tune handling and launch! His is ALL built in and has run 100+ circle racing! This is GREAT food for thought SKJS. Maybe someone here can shed some more light to us fools and amatures, who are'nt afraid to ask and would like to understand our boats a bit better. Thanks Skeg for the great stuff you share with us dummies! :confused: StilltheJerkandlearning?

[CircleJerk]

Jetboatguru:
Why even run a Vdrive then. Why not tilt the motor at an angle like a jet boat and run the prop shaft directly to the crank hub, down through shaft log and and through a strut. Perfect.
V-drive placement is as crucial to proper set up as the strut location. This is the push point of the boat not the propeller.JetBoat: Your picture and statement seem to match! Jerkout

[Jetboatguru]

Jerk,
Let's look at it this way. Put the propeller anywhere you want. Now, don't connect the prop shaft to the boat. Where is the push point now? eek! eek!

[superdave013]

Jetboatguru:
Why even run a Vdrive then. Why not tilt the motor at an angle like a jet boat and run the prop shaft directly to the crank hub, down through shaft log and and through a strut. Perfect.
THAT'S HOW MY DAD'S CORRECT CRAFT IS SET UP!! :rolleyes:
[ October 10, 2002, 11:20 AM: Message edited by: superdave013 ]

[ACCEPTENCE]

Jetboatguru:
Jerk,
Let's look at it this way. Put the propeller anywhere you want. Now, don't connect the prop shaft to the boat. Where is the push point now? eek! eek! I just gotta think the push point would in the main mast sails...yes,no,maybe???lol

[Sked]

CircleJerk:
DR.JSSK88, FIVE STARS FIR YA! Would it be incorrect then, to say the v-drive box pulls the hull from its center point? Like a sled being pulled along with a short rope {causes the front to rise} or a longer rope {causes the sled to move forward without the upward movement}? I didnt agree with the Faulkerson theory even though it made sense to a degree. NO pun intended. Pushing at the blade: now you've got me screwed up, but it somehow makes sense......Can you supply a training Manual? JerkSK88CJ, yes it would be incorrect to say the V-Drive box pulls (or pushes) the hull from its center point. The pushing force does not travel up the shaft to push the boat at the V-Drive. The pushing force does not run in line or even parallel to the shaft which is my major disagreement with the Faulkerson theory. All the pushing force that acts on the boat is at the prop and accordingly the leverage point is at the prop.
No manual, all this stuff is pretty much common sense, you just have to think on it. Hell, I didn't need Newton or an engineering degree but I did have some great tutors in the art of boat racing.

[CircleJerk]

ACCEPTENCE:
Jetboatguru:
Jerk,
Let's look at it this way. Put the propeller anywhere you want. Now, don't connect the prop shaft to the boat. Where is the push point now? eek! eek! I just gotta think the push point would in the main mast sails...yes,no,maybe???lolHeck, that happened up here on Long Lake and the PUSH came from the guys friends who insisted he find a NEW hobbie!!! And, it happened to me when the coupler slipped! The PULL came from a Jet ski, all the way to the ramp! AndyouthoughtJerkwouldnthaveananswer.....HA

[DUCKY]

The push point absolutely is at the v-drive! I had a 1960 Biesemeyer 4 point Hydro tha twas the worst handling pile of dung on the face of this earth. The prop was 6" from the rudder, and the v-drive was a foot behind the front seats. It used to lift the transom, bow steer and do every other bad thing you can think of including 360's with no input from the steering wheel! A later owner moved everything forward (v-drive, strut, stuffing box, etc, and added cavitation plates to make it right. The boat is still running around and drives very well now. In a mono-hull application, the v-drive must be mounted in front of the center of gravity for the bare hull. This theory does not apply to a lifting hull like a three point hydro or tunnel hull, because these hulls lift naturally. A flat has no built in lifting device (strakes, tunnels, etc...)

[Sked]

DUCKY:
The push point absolutely is at the v-drive! I had a 1960 Biesemeyer 4 point Hydro tha twas the worst handling pile of dung on the face of this earth. The prop was 6" from the rudder, and the v-drive was a foot behind the front seats. It used to lift the transom, bow steer and do every other bad thing you can think of including 360's with no input from the steering wheel! A later owner moved everything forward (v-drive, strut, stuffing box, etc, and added cavitation plates to make it right. The boat is still running around and drives very well now. In a mono-hull application, the v-drive must be mounted in front of the center of gravity for the bare hull. This theory does not apply to a lifting hull like a three point hydro or tunnel hull, because these hulls lift naturally. A flat has no built in lifting device (strakes, tunnels, etc...)If what you're saying was true, "The push point absolutely is at the V-Drive!" the later owner could have just moved the V-Drive to correct the problem and would have saved himself all that extra work. Everything was moved so how can you say the placement of the V-Drive alone is what made the difference. Chances are the V-Drive had to be moved to accommodate the prop relocation and the shaft angle change. Oh, and by the way my theory applies to all.

[FlatRacer]

Sked, Sked, Sked! How can you say that the pushing force is on the face of the blade? Yeah of course it is intially, but then that force is transferred to the prop shaft, then to the input shaft of the v-drive, and ultimately through the thrust bearing in the front of the v-drive case. From the front case the thrust is spread to the v-drive mounting plates, then to the stringers and throughout the rest of the boat.
I think what you're trying to say is that the ultimate thrust vector has little relationship to the angle of the prop shaft. In addition to the force vector traveling up the prop shaft there is a force vector component induced by gravity (pushing the boat straight down), additional vectors induced by the drag of the fins, strut,rudder, bottom of the boat and (controlled to varying degrees) the cavitation plates. Of course the amount of air (chop) under the boat at any given moment, as well as the variable amount of drag (varying depending on whether the boat is lifting out of, or falling into the water at the time) has an effect on these vectors as well. I could get into other variables such as water temperature, water salinity, and the altitude (feet above sea level) of the body of water you're running in, and the effect they have on the density of the water ultimately resulting in changes to the thrust and drag vectors, :D but I won't.
All these vectors add and subtract from each other to result in a foward thrust vector that (most of the time) is straight ahead.
Ever notice the way a flat will "bumble bee" up the chute? You're holding the wheel straight, but the boat is continually altering its course by tiny increments. That's because all these vectors are constantly changing. ie: differential drag over time on the left and right sides of the running surface caused by waves.
Eric

[63stevens]

Let me get this right! The prop does all the pushing! Where does the energy created by the push of the prop apply itself to the boat? Strut, propshaft, v-drive.

[Sangster]

The V-drive, thats why Flats have there v-drive so far forward, to carry the nose......

[Sked]

Eric, Eric, Eric! The prop shaft is held firmly in place to prevent it from going forward. The force doesn't travel anywhere. The force can't travel through the solid shaft. The force that's pushing the boat is generated at the prop and because the prop is held in place mechanically that is where all the effect is at. That's why the angle and placement of the prop is so important. All the other stuff you mention does have an effect on the boat, but it's unrelated to the point in question which is where the boat is being pushed from. MAY THE FORCE BE WITH YOU.

[Sked]

63stevens:
Let me get this right! The prop does all the pushing! Where does the energy created by the push of the prop apply itself to the boat? Strut, propshaft, v-drive.It applies itself at the prop.

[ssmike]

OK, OK, I think I will need a re-cap explaining the conflicting opinions.
Just a bit confused on this end....
ssmike

[FlatRacer]

Sked, my good friend:
Every action has an equal and opposite reaction.
Action: The propeller is spun through a fluid medium. Bernouli's principle creates positive pressure on the back side of the blade and negative pressure on the front side of the blade.
Reaction: The boat is propelled foward.
There are equal forces being transmitted in BOTH directions along the prop shaft. The net result is that water is being pushed back, and the boat is pushed foward.
Yes, the "thrust" occurs at the blade, but it is transmitted through the prop shaft to the v-drive, in the same manner that the force of cumbustion is transmitted through a connecting rod to a crankshaft, so that it occurs again (minus frictional losses, of course) at the mounting plate. The energy must be harnessed somewhere, otherwise the shaft would launch itself right through the deck.
You can look at it both ways because the force goes both ways. Action = reaction.
Eric :p
P.S. "The force can't travel through a solid shaft." Huh??? If I put one end of a dowel against your forehead, and hit the other end with a mallet, would you tell me then that the force can't travel through a solid shaft? eek!
[ October 10, 2002, 09:17 PM: Message edited by: FlatRacer ]

[Mr Dumass]

FlatRacer:
Sked, my good friend:
Every action has an equal and opposite reaction.
Action: The propeller is spun through a fluid medium. Bernouli's principle creates positive pressure on the back side of the blade and negative pressure on the front side of the blade.
Reaction: The boat is propelled foward.
There are equal forces being transmitted in BOTH directions along the prop shaft. The net result is that water is being pushed back, and the boat is pushed foward.
Yes, the "thrust" occurs at the blade, but it is transmitted through the prop shaft to the v-drive so that it occurs again (minus frictional losses) at the mounting plate. The energy must be harnessed somewhere, otherwise the shaft would launch itself right through the deck.
You can look at it both ways because the force goes both ways. Action = reaction.
Chew on that! :p Now dat iz da story o' how da Placement o' da vdrive iz o' utmost importance ta da handling o' uh boat. So Jerk breath an' JSSK88 can jet chew on dat. I like dat.

[Sked]

Eric,
Sorry to see you're still not getting it. You know me better and should be trusting me on this one even if maybe I have a hard time explaining it. Believe me, been there done that and took more than just a few minutes thinking on it. Back before I knew any better I moved the bearing cage on a skiff 15" without making any other changes. Did it in about 45 min. then retested. Same day, same water, same prop, same plate settings, SAME EVERYTHING. It made absolutely no difference whatsoever and I was looking to achieve a change. Much later on I was considering doing the same type of maneuver with the V-Drive on the SS. Because of my previous experience with the Skiff and the fact that it's much harder to do with the V-Drive, I decided to run my ideas past many I consider to be far more knowledgeable than myself. After all the discussion and arguments I understood why what I am saying now is in fact true. Next time I see you in person I will try to explain it in a way that makes it clearer as I don't seem to be able to do it here.

[theman]

flat racer is right,in if sk88 can drive his flat with no down pedal it must not be very fast are he is parking it in the turns.

[Mike Oxbig]

Why is everbody so hostile towards JSSK88? He is very knowledgable and has "been ther done that" So, could you please enlighten us all and remind us of all the world records and championships you have won? Maybe you were nominated for some nobel prize? Iknow nothing about these boats so I will just step down to his greater knowledge.

[SK48]

The winningest flat bottom circle driver of all time Julian Pettingil, who owned Biesemeyer with Dr. Basako, and Ray Brown set all of his boats up according to the V-drive placement. The theory is that the propeller is actully pulling the boat not pushing the boat. They were more concerned about the v-drive location than the strut or prop location. I don't think anyone knows more about circle boat set up than those guys. I respect the Spitfire boats from up north, but none of them ever beat Pettingil in the 70's and 80's.
There are bubbles and turbulent water behind the propeller. Don't you think maybe the propeller is pulling more with each revolution than pusshing.
Just more to think about.

[Sked]

OK. One last try. What is the point at which a car gets it push? Where the tires meet the road, where the springs attach to the frame, at the clutch, where the motor attaches to the frame? Think hard. This is not a trick question. Those who miss the correct answer could easily qualify for a position as an APBA Inboard Commissioner.

[Sked]

theman:
flat racer is right,in if sk88 can drive his flat with no down pedal it must not be very fast are he is parking it in the turns.Don't be talking out your ass. Put up YOUR theory on why you think it works the way you think and YOUR records and accomplishments or stay on the porch. Mine are documented.

[Mike Oxbig]

JSSK88:
OK. One last try. What is the point at which a car gets it push? Where the tires meet the road, where the springs attach to the frame, at the clutch, where the motor attaches to the frame? Think hard. This is not a trick question. Those who miss the correct answer could easily qualify for a position as an APBA Inboard Commissioner.As soon as you show us all one bit of credibility we will answer your "CAR" question. Until then, please refrain from posting.

[Sked]

SK48:
The winningest flat bottom circle driver of all time Julian Pettingil, who owned Biesemeyer with Dr. Basako, and Ray Brown set all of his boats up according to the V-drive placement. The theory is that the propeller is actully pulling the boat not pushing the boat. They were more concerned about the v-drive location than the strut or prop location. I don't think anyone knows more about circle boat set up than those guys. I respect the Spitfire boats from up north, but none of them ever beat Pettingil in the 70's and 80's.
There are bubbles and turbulent water behind the propeller. Don't you think maybe the propeller is pulling more with each revolution than pusshing.
Just more to think about.Here's a little enlightenment for you. Except for the times I broke, the only SK boat to beat me was Jack Kiely's "Sweet Caroline" with it's builder Bob Goettel driving and he had to set a new SK Competition Record to do so. Maybe not a big deal unless you consider the fact that I was running against him in a legal Super Stock boat. And Bosacco, forget about it, couldn't even get close. I ran second to Julian when I first started in SS, right from my first race with the first Starfire I had. I did beat him to win the E. Divisionals one time in the old boat but that was due to a technicality, he jumped the gun so it really doesn't count. Unfortunately I never had the opportunity to run him with the second boat when I really had most all my shit together. As far a driving goes, Julian Pettingil in my opinion was probably the best ever. OK, maybe a toss up with Duff Daily and Dave Villwock. As for designers/builders Steve Jones in runabouts by a long shot. Twenty-one career records and his boats held the SS Comp Record since 1967 and still do, not to mention the numerous E, SK, and PC/PS records.
Pulling or pushing is another debate but it still acts upon the boat at the prop.
[ October 10, 2002, 10:58 PM: Message edited by: JSSK88 ]

[Mike Oxbig]

That is not enough to establish credibility. Please try harder. Holy cow, I just read where you are from, New Jersey. Now I understand
[ October 10, 2002, 10:13 PM: Message edited by: Mike Oxbig ]

[theman]

i just want to no how you drive in ss with out a down pedal

[Mike Oxbig]

theman:
i just want to no how you drive in ss with out a down pedalEasy, you start in the back and you end in the back and you go slow enough that the nose doesnt bounce.

[theman]

o yea two words FULCRUM IN LEVERAGE,I DO THINK V DRIVE PLACEMENT WILL LIFT THE BOW OF THE BOAT THE FARTHER FOWARD YOU PUT IT BECAUSE THE PROP IS PUSHING IT FOWARD BUT THAT ALSO CAHAGES THE ANGEL OF THE PROP SHAFT WHICH ALSO CHANGES THINGS ,JUST MY OPINION

[theman]

SK88 I THINK LANCE IN GORDY HOLD MOST THE RECORDS BUT ONE YOU BETTER CHECK ,

[Sked]

Mike Oxbig:
[QUOTE]As soon as you show us all one bit of credibility we will answer your "CAR" question. Until then, please refrain from posting.Man I hate doing this but here goes.
DELETED
[ October 10, 2002, 10:48 PM: Message edited by: JSSK88 ]

[theman]

ME IN MIKE JUST HAD A BET TO SEE IF WE COULD KEEP YOU UP ALL NITE WHAT TIME IS IT IN NJ ANYWAY LOL

[Sked]

theman:
SK88 I THINK LANCE IN GORDY HOLD MOST THE RECORDS BUT ONE YOU BETTER CHECK ,I don't have to look.
Check this: SS-70 (http://www.superstockracing.com/ss70.htm)
Then check this: Steve Jones (http://www.starfireboats.com/steve_jones.htm)
Can you count?
[ October 10, 2002, 11:14 PM: Message edited by: JSSK88 ]

[CircleJerk]

Sked, You have more patience than I. I salute you!Glad you shared wink the Steve Jones site, I'll pass it on. Jerk

[Rexone]

quote:
--------------------------------------------------------------------------------
Originally posted by Mike Oxbig:
[QUOTE]As soon as you show us all one bit of credibility we will answer your "CAR" question. Until then, please refrain from posting.
--------------------------------------------------------------------------------
Man I hate doing this but here goes.
DELETED
[ October 10, 2002, 10:48 PM: Message edited by: JSSK88 ]
Damn, I just went out to get popcorn and I missed the good part! :D

[schiada96]

We know the strut lifts the back of the boat couldnt the prop be pushing from this area also from load on the strut bearings?

[63stevens]

It took awhile but I finally see what JSSK88 is saying. Strut angle and location is the determining factor that changes the performance of the boat and once those positions are determined the v-drive will go only in the position that the angle of the shaft allows it to go. Also being that everything is hooked together(prop,propshaft,v-drive)the push does come from the Prop.

[DUCKY]

I can't believe I actually have to post this! I you race a super stock flattie, you have to know this! This is basic physics! http://forums.screamandfly.com/forums/attachment.php?s=&postid=141268

[WILDERTHANU54]

IS THAT autoCAD ? WAIT.......................NO NO IT'S FOR SURE MECHANICAL DESKTOP! !
[ October 11, 2002, 12:17 PM: Message edited by: WILDERTHANU54 ]

[FlatRacer]

Okay first off, whoever thinks they can besmurch Sked's qualifications to engage in this "debate" is WAY off base. Sked is the designer and builder of the finest finished, best handling, fastest Jersey Speed Skiffs ever to hit the water. He performs absolute miracles with fiberglass (I personally vouch for this) and is an ace machinist. When you realise how much he knows and what level of skill he possesses, in so many areas, you will come to respect him as I do.
Furthermore, any questions about his driving ability would be answered by watching the video (was it St. Pete?) in which he dessimates the field by driving around the OUTSIDE of everyone and leaves them in the dust! His little joke about not needing a down pedal, at least on the now defunct (thanks, APBA) long 1 2/3 mi. course, is no idle boast.
As far as this current debate, I reserve the right to disagree with him until such time as he can clarify his position to me, which I have no doubt he will.
Eric

[FlatRacer]

Okay, here's another angle: Being than everything is bolted together,it doesn't make a difference where the thrust is applied. It acts upon the whole boat. Everything else is just semantics. I'd say the positioning of the v-drive has an effect on the boat's handling more because of weight distribution than for any other reason. No?

[DUCKY]

As to JSSK88's comment about moving the v-drive..... The v-drive had to be moved forward. Every thing else had to be moved to accomadate this change. Propshaft angle reamined the same. All he did was move the push point in front of the "pivot point" I say it doesn't so much matter where the prop is, but angle definitely plays a major part of it. For example, the guy I sold my old boat to may have been able to alleviate the problem by increasing the angle of the shaft(at a cost of performance), but probably not cured it. By moving everything forward, he didn't have to buy any parts, just do a lot of glass work.

[missilemud]

guy with the stupid avitar,helmet face.. listen jack ass you might learn something.but i think you have a learning disablity, or maybe your mom dropped u ? whatever it was you never got it and couldn't read it either if you took reading comp 1-0-1. and Eric may the force be with you arlo !!! ha i love the internet

[missilemud]

oops sorry helmet guy, got my mad on to soon

[missilemud]

i think i need reading lessons now

[FlatRacer]

I've been thinking about this some more. Let's see if I'm getting warm.
The best way to change the overall handling characteristics of a boat, aside from increasing drag with the cavitation plates, is to change the angle of (initial) thrust.
Since, as Sked says, thrust occurs at the propeller blade, there are two ways to accomplish this:
1- change the angle of the prop relative to the direction of travel. Easy to do if you have an outboard, stern drive, or a surface drive. Not so easy if you have a direct drive or a v-drive. In order to change the shaft angle, one must change either the height or longitudinal position of either the strut, or the engine (in direct drive boats) or v-drive.
If we move the engine or v-drive, the effect of the change in propshaft angle is hard to quantify because we've changed two variables at once, prop angle and weight distribution.
2- the other way to change the direction of thrust is to change the rake of the propeller blade. The results of this change is easier to quantify because we're only changing one variable, and leaving the weight distribution alone.
Like I said before, being that everything is bolted and bonded together, the thrust is distributed evenly throughout the entire vehicle, and the merits of what attaches where are moot. The effect of moving a v-drive is mostly an effect of the resultant change in weight distribution by doing so.
Sked, am I getting warm?
Eric :)
[ October 11, 2002, 02:33 PM: Message edited by: FlatRacer ]

[stump]

If you were to loosen the propshaft coupling the propshaft will slide backwards and fordwards.So lets assume the propshaft went all the way through the v-drive unit,had a long key slot and the lower gear inside v drive slipped onto the prop shaft,the end of prop shaft exited the forward side of the v-drive .Now ,we start engine and what happens prop moves towards front of boat and shaft protrudes further out other end of v -drive case,boat dosnt go anywhere.Now,inside v drive case we have bearings and a thrust surface somewhere to stop the forward movement of the propellor shaft,at this thrust point is where the boat is propelled forward.So ,the mounting position of the v-drive case will determine where the thrust point of boat is.

[missilemud]

the prop is the thrust spot the vee-drive simply turns the prop that makes the thrust, this is not rocket science,if theres thrust bearing in the vee-drive its there for protection of vital parts inside of the case that requires no or little pressure, correct?. if not my bad and sorry helmet head i should read before i blow my wad all over the net

[FlatRacer]

Stump, you're right. And I used to think the same way, but now I realize that the "thrust point" is irrelavent. The thrust, or force is transferred to the entire boat. Whether the thrust point is at the v-drive, another thrust bearing at some point anywhere along the shaft (pick anyplace), or at the strut (picture the prop hub grinding away against the ass end of the strut barrel in the event of a failed thrust bearing and enough gap closed up in the coupler to allow it), the net result is the same with no change in the attitude of the boat.
Yes, the force must be harnessed somewhere, but it doesn't really matter where.
[ October 11, 2002, 03:41 PM: Message edited by: FlatRacer ]

[FlatRacer]

OH MY GOD! eek! I can't believe I didn't get it until now. "Mike Oxbig"???!!!
Freakin' hilarious man! Got tears in my eyes,.....great! :D :D :D :D :D

[Sked]

DUCKY:
I can't believe I actually have to post this! I you race a super stock flattie, you have to know this! This is basic physics! http://forums.screamandfly.com/forums/attachment.php?s=&postid=141268I don't know why but I'm going to try this once again hoping all will understand more clearly. I've either got to be right or pig headed and I sure hope it's not the later as I've always been afraid of loosing the open mind I think I have so far maintained even though I've lost a few brain cells along the way. Hope you don't mind me borrowing the drawing to make my point.
http://members.aol.com/jssk88/theory.jpg
http://members.aol.com/jssk88/theory4.jpg
Now I could go on and on with this by trying to explain shaft angle and prop rake effects, strut drop effects, etc., etc., and so on, and how it all relates to all the other components of the boat just to prove my point but you really don't expect me to give up all my "secrets" just to convince you all on just this one point, do you. You'll all just have to get out the Crayola's and work on it or find a physicist or someone whose knows and is better than me when it comes to explaining it. Or on the other hand maybe you can find some physicist or naval architect that could explain to me where I'm going wrong.

[Snowboat]

What I wonder about is............if the CG is supposed to be at the v drive, wouldn't you need an inline six in the bow for a counterweight? If I were to rest a boat, centered on a fulcrum, directly under the v drive, it would be ass heavy. Coming late to this topic and skimming it, I'm missing something.

[Sked]

FlatRacer:
Whether the thrust point is at the v-drive, another thrust bearing at some point anywhere along the shaft (pick anyplace), or at the strut (picture the prop hub grinding away against the ass end of the strut barrel in the event of a failed thrust bearing and enough gap closed up in the coupler to allow it), the net result is the same with no change in the attitude of the boat.
There you go. In your example you would have moved what you thought was the thrust point over what, 4 to 5 feet. If what you used to (I hope) think was true don't you think that would have a dramatic effect on the boat. Technically some change did occur because you did actually move the prop up a bit, what 1/4 to 1/2 inch. On closely balanced or worked out combinations just that small amount of movement can change handling. Ever hear of the "nickel" trick. Search the forums for more "nickel" info.
Here you go.
nickel (http://free.***boat.net/ubb/ultimatebb.php?ubb=get_topic;f=8;t=000324#000002)
[ October 11, 2002, 05:20 PM: Message edited by: JSSK88 ]

[FlatRacer]

Snowboat, you're forgetting the other forces at work. At speed, the drag induced by the rudder, strut, fins, plates, and the very bottom of the boat itself act to bring the bow down. The hydrodynamic drag on the underwater gear is much much greater than the aerodynamic drag on the topsides, therefore, the bow pivots downward to counteract the upward thrust of the propshaft.
Add to that the fact that at very high speeds the hull begins to lift its butt out of the water because it's trying to plane on the strut barrel and prop hub...just like a.....hydroplane.
This is why K-boat racers were looking for ways to plant the ass back down in the water. Without sponsons for a stable stance, prop riding provided a real hairy ride! First they tried wings, but they finally settled on lots of rocker and long plates to create negative pressure under the transom to suck the tail back down into the water. Mind boggling!
[ October 11, 2002, 06:03 PM: Message edited by: FlatRacer ]

[DUCKY]

Hey sked,
I like what you did to the drawing!!! Think about it though, the thrust coming up the shaft would push the boat up and over backwards and you are right. This force is counter-acted by boat weight and motor placement for an overall balacing act. Look at a SS or K boat. The v-drive is way far forward, but the motor is as well. The weight of the engine balances all of the force to make the boat take a set.

[DUCKY]

I thought of something else. Yes the boat would go up and over backwards, if your were submerged in water! Think about an improperly balanced boat, the boat will porpoise, which is the propellers thrust travelling up the propshaft, trying to lift the front up and over backwards, that is until the prop runs out of bite, then the bow falls and it all starts over again. This would be the extreme opposite to my previous example regarding my old boat.

[theman]

WHEN BUILDING A VDRIVE BOAT THE LOCATION OF THE STRUT IS THE FIRST THING YOU SET,THERE FOR WHEN YOU DRILL THE HOLE IN THE BOTTOM,IN PUT THE PROP SHAFT THRU IT THAT WILL DETERMONE WERE THE VDRIVE GOES WHICH ALSO DETERMINE THE SHAFT ANGLE IN THE PUSH POINT

[stucknohio]

Has anyone tried to run vdrives in a offshore boat?

[GofastRacer]

theman:
WHEN BUILDING A VDRIVE BOAT THE LOCATION OF THE STRUT IS THE FIRST THING YOU SET,THERE FOR WHEN YOU DRILL THE HOLE IN THE BOTTOM,IN PUT THE PROP SHAFT THRU IT THAT WILL DETERMONE WERE THE VDRIVE GOES WHICH ALSO DETERMINE THE SHAFT ANGLE IN THE PUSH POINTRight on!!, couldn't say it better myself!!!!!... http://www.plauder-smilies.com/happy/xyxthumbs.gif

[missilemud]

I HATED MATH TOO

[Sked]

DUCKY:
I thought of something else. Yes the boat would go up and over backwards, if your were submerged in water! Think about an improperly balanced boat, the boat will porpoise, which is the propellers thrust travelling up the propshaft, trying to lift the front up and over backwards, that is until the prop runs out of bite, then the bow falls and it all starts over again. This would be the extreme opposite to my previous example regarding my old boat.Nice try. But then how do you explain a boat porpoising when the prop remains submerged, maintaining bite, say like at slower speeds?
What was done to fix your old boat was the correct approach for the problem it had and falls in line with both our theories. Where we seem to part company is on the subject of how and why it works. I'm saying the boat's problem was corrected because the prop location and angle were changed and that's what made pretty much all the difference. Your contention is that by moving the V-Drive, the point of push was moved making the V-Drive location what pretty much made all the difference.
There's all kinds of forces at work here that can create a cause and effect on any one of a set of different scenarios you may want to introduce.
Like I said before: "I could go on and on with this by trying to explain ....(see post)"
I think maybe looking too far past the basic point we are discussing and adding in one or two elements outside the point of discussion without taking in to account ALL the other factors at work here tends to distort the view and justify about any position one could take. What I'm trying to say is that maybe by moving all that other "debris" out of the way and just looking at and sticking to the basic point of disagreement it will make the things relevant to the argument clearer on the battlefield. If one has to counter every single additional element one would have to eventually introduce ALL the elements involved to explain it all thus truly and completely justifying ones position. It took me the majority of my life to be able to determine what all those different elements are and all that they do to the overall boat and to the other elements as well. Not that I would or would want to even try to explain all that it took me years to learn, but it would take a book at least and certainly more room than what's afforded here and more time than I would be willing to spend just to prove my point. (Although you wouldn't necessarily think that based on all the time and trouble I've gone through on this topic so far)

[Rexone]

I'm just guessing here guys so don't think this is some kind of expert opinion... I would think that the prop location is the pivot point of the boat because I know for fact that when you change the angle of the prop (prop shaft) OR the position front to rear of the prop, or even the blades of the prop themselves, you can get some drastic differences in the way most any boat rides as far as attitude, how much it carries the nose (or doesn't). I know the drag guys fine tune these things by moving the prop mere fractions of an inch front to rear (the nickle thing) and it works.
The v-drive seems to me like it's the point of thrust transfer into the boat but doesn't really seem like it's the pivot point because to me the thrust is transfered into the entire boat through this vdrive and mounting hardware, braces etc. The v-drive and it's related hardware location in the boat seems like it would make a difference only because of it's weight (which can't be underestimated). In ski racing we run ballast tanks in many of the boats (weight) just to regulate the attitude so the weight of the v-drive in one location vs. another could be considered substantial in it's effect on boat attitude I would think. Just my guess.
[ October 11, 2002, 10:41 PM: Message edited by: Rexone ]

[Sked]

Rexone,
Real close. You're almost completely there. Your first paragraph is basically correct and is also contradictory to your second paragraph. If you could see your way clear to get rid of the second paragraph and replaced it with: "The thrust point (propeller) is held in place by the shaft, V-Drive and mounting hardware, braces, and stringers." then you'll have it.

[CrazyHippy]

Rexone:
I'm just guessing here guys so don't think this is some kind of expert opinion... I would think that the prop location is the pivot point of the boat because I know for fact that when you change the angle of the prop (prop shaft) OR the position front to rear of the prop, or even the blades of the prop themselves, you can get some drastic differences in the way most any boat rides as far as attitude, how much it carries the nose (or doesn't). I know the drag guys fine tune these things by moving the prop mere fractions of an inch front to rear (the nickle thing) and it works.
As a v-drive rookie, i would have to agree with this. If the v-drive is the transfer point, wouldn't the boat run the same w/ 6" whacked off the prop shaft if the casale was in the same spot???
Then why would people spend the time to tune their prop shaft length to the nickles thickness??
My 2x .05
BJH

[Rexone]

What I've attempted to state (probably not very well) is that the v-drive is simply the hardware that transfers the power into the whole boat as a whole. The boat as a whole is a solid object, vdrive included, only the propeller is moving and pushing. I don't think the vdrive's actual location affects much, given a constant propshaft angle (which would affect much however, if changed to relocate the vdrive). That is as stated before other than the weight factor of the vdrive (which again cannot be discounted since they're heavy little bastards when you consider all the hardware attached to them which moves right along with the box itself). The thrust coming off the propeller and the precise angle of that thrust is the primary factor in boat attitude and performance. Again, just my guess.

[Sked]

Rexone,
OK. If I'm understanding you correctly would it be safe to say we are in agreement? Yes? No? Just a c-hair away?

[Mike Oxbig]

Disconnect the propshaft from the boat and you have no push point. Simple as that. You guys can go on playing mental masturbation.

[Rexone]

JSSK88, yes I think we pretty much agree
Ox...I see an element of distance between our views on this thread and probably most things :D

[Sked]

Rexone:
Ox...I see an element of distance between our views on this thread and probably most things :D Second that. No question of agreement on that point.

[Rexone]

posted October 11, 2002 11:33 PM
--------------------------------------------------------------------------------
Disconnect the propshaft from the boat and you have no push point. Simple as that. You guys can go on playing mental masturbation.
So by disconnecting the prop shaft would you then create a jet boat that would suck & blow instead of push & screw? Or would that mean your prop just smacked the rudder and you wish you'd have bought that safety collar as you're viewing the lake with the boat on the incorrect side of rightside up? Or would that mean that the vdrive in the absence of the prop shaft would now become the point of thrust and the center of gravity of your mind? Or would it mean that you're just tryin to keep our east coast members up all night again? think about it. You guys are too funny!!! :D :D :D
[ October 12, 2002, 02:39 PM: Message edited by: Rexone ]

[SP]

I thought I would get into this a little bit. I have a 1967 Donzi Bench Seat Hornet with a V-Drive. This boat came from Donzi in 1967 with a Daytona Marine Turbo Charged small black Chevy. This was an option they offered and there where only 2 or 3 made. Mine being one of them.
All of the the other Bench Seat Hornets V-Drives came with Big Block 427 Fords.
Ok...so my point is this. The prop shaft angles are different between the Big Block Fords and the Small Block Chevys. And the V-Drive locations are totally different. On the small block set up the boat really rides on top or out of the water. The Big Blocks run deeper.
Just thought it was interesting info. Dont know why Don Aronow did it like this.
(NJ)Scott
[ October 12, 2002, 05:26 AM: Message edited by: SP ]

[missilemud]

YEAH WHAT THAT GUY SAID

[DansBlown73Nordic]

That picture with the helmet kills me!!! :D The guy looks like he just got done eating a Dog Shit Sandwich!!!!!! eek! eek!

[Sangster]

Where would you put the v-drive in this...
http://free.***boat.net/gallery/Forum_Graphic_Depot/PA110032.JPG

[missilemud]

YUCK WHAT AN UGLY ENGINE COLOR , GREEN IS BAD LUCK ON ANY BOAT

[Sangster]

And besides that its a jet hydro converted to a v-drive.....

[Rexone]

That picture with the helmet kills me!!! The guy looks like he just got done eating a Dog Shit Sandwich!!!!!! NOW that's FUNNY! :D

[Sked]

FlatRacer:
Okay first off, whoever thinks they can besmurch Sked's ..............................
As far as this current debate, I reserve the right to disagree with him until such time as he can clarify his position to me, which I have no doubt he will.
EricEric, buddy,Thanks for ALL the compliments. Glad to see that you still have confidence in me after that little episode at the ramp. :D :D "besmurch"???? :D
[ October 12, 2002, 05:10 PM: Message edited by: JSSK88 ]

[Sked]

FlatRacer:
OH MY GOD! eek! I can't believe I didn't get it until now. "Mike Oxbig"???!!!
Freakin' hilarious man! Got tears in my eyes,.....great! :D :D :D Yeah and his signature should read: "and my brain's small" :D :D
Eric, Now I know why I'm having problems explaining things to you. :D

[Sked]

Snowboat:
What I wonder about is............if the CG is supposed to be at the v drive, wouldn't you need an inline six in the bow for a counterweight? If I were to rest a boat, centered on a fulcrum, directly under the v drive, it would be ass heavy. Coming late to this topic and skimming it, I'm missing something.Snowboat,
For the purposes of this discussion the CG location is irrelevant. The CG in the drawing is in that position just because it's the way the original drawing showed it, but for the purposes of this discussion it could be in a number of different locations.

[superdave013]

http://www.sdplastics.com/dedhorse.gif

[VD CRUISER]

Damm, this has gotten too deep. Does anyone know what shaft angle is best, where to locate the strut, and how much drop the strut should have? I won't ask about V-drive location, since it will fall in place once the other 3 questions are answered.

[missilemud]

:rolleyes: here we go again :rolleyes:

[Sangerboy]

Late to this party but I've been debating on not posting and looking less dumb or posting and proving my ignorance. I agree with JSSK88. Although my experience is only related to 2 boats my practical experience bears his theories out. When I bought my circle runner it had a terrible hop at speed. To make a long story (years of trial and error-mainly error) short I've moved the engine and V-drive all over the place with no real improvement. The one thing that finally settled it down was moving the prop back-way back. With this boat anyway prop position had the greatest effect on the attitude of the boat.

[Sangster]

Sangster:
Where would you put the v-drive in this...
http://free.***boat.net/gallery/Forum_Graphic_Depot/PA110032.JPGAre these the same boats.....
http://www.dragboats.com/classified/images/hannah_bill.jpg

[missilemud]

man that thing is ugly :D

[missilemud]

http://hometown.aol.com/nuclearwinter076

[Sangster]

I'm jest wondering if it ran better as a jet or a v-drive...Should have named it "The Tranvestite" eek! eek!

[FlatRacer]

What do you mean? What "little episode at the ramp"? You didn't think I'd waste such a valuable ace in the hole in such a place as this, did you? No, my friend, I'm saving that little tidbit of potential blackmail for when I need a really big favor! :D :D :D
FR

[Stab-n-Steer]

A boat ramp story?!?!? Man, I love those... Come on Flat, give it up! :D
S&S

[CircleJerk]

Ya Flat, Dont make us guess!!!! :mad:

[V-Drive Tom]

PUSH PIONT IS AT THE PROP SHAFT TAPER.
Shaft angle
Prop placement
Prop Depth, determine how the boat will react.
V-drive could be anywhere....
This is a determination that was hard for me to completely accept at first...But I have.
It still depends on how much power is being put to the boat.
Carb power= Deeper-Steeper-and further back.
High blown power=Shallower-flatter-and further forward prop placement.
Propeller blade rake wants to be a few degrees more than prop shaft angle.
There is a lot more to be said about it, But...Bottom line is that MR.JSSK88 is sharp racer. TOM.. :)