Blowing the tail on a hydro

[infotraker]

I have heard the term blowing the tail on a hydro pickle. What does that mean and when does it happen ? I have a 77 Sanger Pickle Ski hydro (medium hull) with BBC 468 roller motor (just painted, some of you have seen at CFW). When I get on it the front will bounce a little and then when it is really set the front will shimmie back and forth a little (very smooth water). The ride is smooth. I have seen 6000 rpm and there seems to be a lot more to go.

[78Eliminator]

Blowing the tail is when the back is pretty much riding on the prop and skipping on the front two sponsons......
It's what makes a hydro a hydro and not an air entrapment hull. When the tail is "blown" the air is allowed to travel under the hull and away.

[Big Proppa]

Not like this
http://www.***boat.com/image_center/data/500/1641584296RmGUuc_ph-med.jpg
But more like this except my nose should be down more, I think I hit a roller
http://www.***boat.com/image_center/data/500/16image00.jpg

[78Eliminator]

Isn't blowing the tail also something kinky you do to your girlfriend? :D

[INEEDAV]

Originally posted by 78Eliminator
Isn't blowing the tail also something kinky you do to your girlfriend? :D
Watch out for her feet when ya do, she may go to buckin' on ya.

[Bob Hostetter]

Keeping in mind this info is based on expereince from the early 80's when we ran a BAH and BFH....................
Blowing the tail is a term used to describe the way a drag hydro is supposed to take a set. The boat should 3 point........the trailing tips of the front sponsons and the prop should be the only parts of the boat in contact with the water. It will ride almost in a nose down attitude, the oppisite of a flatbottom.
It takes a properly set up hull and a lot of power to "blow the tail" on a ski hydro and hold it. Depending on the power/speed of the boat alot of them will also carry at least one sponson out of the water. You will know if the tail comes up as the boat will feel like it rolls forward and it will get very smooth and light feeling. If it starts to walk back and forth on the sponsons with the tail up you are very close to getting wet..........
You should have your rudder mounted behind the transom and it should be a very deep rudder as well. If not you can use all steering control when the tail comes up. Be sure you are running a whirlaway.
Once you settle on a engine/prop setup you can get a little adjustment by moving the engine forward or backwards. You can also play with the v-drive angle and prop to generate some additional lift. The red hydro in proppa's pictures is running very loose in the front. It takes a lot power and brass balls to run them that loose. At that point you have very little control of the boat and are at the whims of the boats gods.........
Proppa, nice pic's, brings back some very good memories of my younger (and dumber) years........

[LakesOnly]

http://www.***boat.com/image_center/data/500/350BlownTailHydro.jpg
LO

[FLYTE RISK]

Sangster should know somthing about a tail!!!:D :D

[Kurtis500]

Sounds like your boat is trying to lift the tail up but it wont quite do it. If its the same as my Kurtis, the rocking back and forth is the tail fighting to come up and transfering its imbalance between the left and right sponson. I noticed in the Kurtis 500 that the tail doesnt go up and stay up until 105 or so, and only then while its accelerating. When running the 10 second class the boat would never really blow the tail. Only when I have run 9.50's or quicker has it done it. Once the tail is up the rpms shoot up immediatly and the boat rides perfectly smooth, no rocking at all. And you feel the mph come on more. I always tell people that it rides smoother at that stage than my truck does driving to the track. The Mize shovel nose is way different. A different design with the sponson tips much closer to the bottom of the hull. The prop and strut are recessed against the hull bottom in a semi-circular area designed into the hull. The same thing that the new What-a-Tomato boat has. The boat sets asap and never looks back, but it only runs 18 gears.
Do you know what kind of gears are in yours? Mine are 35's (or 37's) and seem to be way too much. Along with a 3 blade cleaver, the set-up was high gear in a pro gas hydro. I try to pull it from the start and it doesnt work very well,in fact, the boat never really gets the tail up until its near the et lights. I'm dropping my gearing way down for a race next month and having the prop cut down too along with adding some hp to the motor. Not sure what you have for a motor, but when I hold a blown injected motor at wot and keep it under too much of a load it only serves to fill my oil pan up with alcohol. I've been nice to the 392 hemi, but now its time to make it work in the high rpms.
Anyways, heres some pics of them, you can see how much difference there is in the sponson/prop heighth locations. Hope it helps, sorry for the winded post.
http://www.***boat.com/image_center/data/524/73kurtis-med.JPG
http://www.***boat.com/image_center/data/524/7Dougwin-med.JPG

[DUECE'SDAD]

I have been wondering about hydro "lift" myself,ihave 71 sanger shovelnose with a conservative 450hp i have messed around with gears a props and made several changes to get into the 90's and was stoked that making changes gained me about 16 mph, however the bookreaders around here says if i got the ass end outta the water and quite ridin like a flatbottom i would really be going somewhere, I was happy with what i had and thought i had maximized my potential but was tired of hearing everybodys idea of how it should look when running, so i slide the propshaft back and but 4 nickels into the coupler and put it back together now it is acting all stupid and bobbling every where and tries to fly when it hits any wake and wont turn at all and i have a long outboard rudder so i have come to the realization that i dont have the power to make a hydo do what a hydro does and that is 3 point but someday i will so dont get discouraged get more hp
takin it easy in oklahoma, Dustin

[Bob Hostetter]

A shovelnose runs a lot different then a picklefork. A picklefork usually has deeper sponsons and a more open entry into the air entrapment portion of the hull. This allows it to carry the nose much better, traping more air.
You can do a couple of things to get the tail lighter......You can run a steeper v-drive angle, move the v-drive back towards the transom, run a prop with a lot more lift, and move the engine forward.
Also a 2 speed works very well in these boats especially with lower HP motors. Remember if you can get the tail up they will MPH higher then a 'v', or flat with the same HP because of greatly reduced drag from the water. You want to turn the prop as fast as you can to generate lift. The MPH will take care of itself untill you run out of rpm.
You will be able to tell when the tail goes up, the whole boat will feel different. A little movement thru the yaw (side to side) is ok, the sponsons are probaby just skipping around on the water. Remember, you don't have a center skag in the hull for directional stability. If the nose the rocking back and forth from one sponson to the other, that is not such a good thing. If the sponson edges in with any yaw you are going to get wet. If you have never tried it, it hurts...........
Finally, keep in mind that it is not speed that keeps the tail up. There is no air entrapment behind the sponsons like in a tunnel. You want the hull chasing the prop, once the hull catches the prop and acceleration drops off the tail will try to drop back down. The only lift you have in the back is mechncial lift from the prop.

[V-Drive Tom]

Well, Thats some decent commentary on how hydros work, but I think he wants to know WHY his SKI hydro doesn't BLOW the tail.
It has Little to do with his engine location, and nothing to do with his v-drive location.
Come on dudes, lets come up with the answer.:)

[Kurtis500]

Originally posted by V-Drive Tom
Well, Thats some decent commentary on how hydros work, but I think he wants to know WHY his SKI hydro doesn't BLOW the tail.
It has Little to do with his engine location, and nothing to do with his v-drive location.
Come on dudes, lets come up with the answer.:)
Ok, heres the skinny of it. Need more horsepower.
You never know, his hydro may have been set-up wrong and giving him some info about how they work will help him out. Everyones got a different prop, gearing, strut, boat weight. I had my motor too far back over the transom and it fought the prop when trying to blow the tail really bad. Moving the battery from behind the motor and into the left front sponson then moving the engine forward made a WORLD of difference. I ran a 105, then made those changes overnight in the pits and came out the next day to a 118mph after the tail blew(finally). No motor changes, just the weight distribution.
I'm guessing this is his boat in the picture below. From eyeballing a number of ski sangers I would say the motor in this one looks a little far back. Only a guess though, nothing scientific.
http://www.***boat.com/image_center/data/524/450P1010136small-med.jpg

[Bob Hostetter]

Based on the picture of the blue and white boat I would start by moving the motor forward...............And then start adding horsepower by the bucket full.
Hydro's are very sensitive about weight on the tail. Getting as much weight forward as you can reduces the amount of power required to get the tail up.
I also notice a ski tow bar on the motor. Once he gets the boat setup to run hard with the tail up it won't be very good at pulling skiers.

[Kurtis500]

Originally posted by V-Drive Tom
Well, Thats some decent commentary on how hydros work, but I think he wants to know WHY his SKI hydro doesn't BLOW the tail.
It has Little to do with his engine location, and nothing to do with his v-drive location.
Come on dudes, lets come up with the answer.:)
Wait.... I forgot the real answer...MONEY

[DUECE'SDAD]

Kurtis 500 when you say that you moved the motor forward what are you talking an inch or two or more? What did you do for your drive shaft going into the v-drive cut it down? Moving the battery definately could make some difference as mine is at the very rear. I am begining to wonder again now b/c my boat was running a blown small block at 109 in 1000ft and it has a series of mounting holes in the aliminum stringer brackets i kinda just used the driveshaft length to position the motor in place. If it was rigged for a small block which is lighter maybe they didnt have to move it as far forward. How far is the gear box from the transom in your boat? How long is your drive shaft? I know our boats are totally different but at least i will have an idea. Any pictures of your boat on here anywhere?

[DUECE'SDAD]

I reread the post and see the pics of your boat Disregard the stupid question (only the last one)

[Kurtis500]

Originally posted by DUECE'SDAD
Kurtis 500 when you say that you moved the motor forward what are you talking an inch or two or more? What did you do for your drive shaft going into the v-drive cut it down? Moving the battery definately could make some difference as mine is at the very rear. I am begining to wonder again now b/c my boat was running a blown small block at 109 in 1000ft and it has a series of mounting holes in the aliminum stringer brackets i kinda just used the driveshaft length to position the motor in place. If it was rigged for a small block which is lighter maybe they didnt have to move it as far forward. How far is the gear box from the transom in your boat? How long is your drive shaft? I know our boats are totally different but at least i will have an idea. Any pictures of your boat on here anywhere?
How far back it sits depends on weight and horsepower. My boat would be hard to take from since the hull is one of the lightest Kurtis layups and the 392 hemi is one of the heaviest motors made. You'll just have to try different combos. I pulled my driveshaft out and took it from the track to a shop here in town that cut it down right then. With everything set-up fine it can take one item like the wrong prop or over geared to keep the boat from doing its thing. I've never been too focused on motor placement numbers, but just made sure it stayed where it worked best.

[DetroitJim]

So you want it to do......
This?
http://www.***boat.com/image_center/data/524/181JULY28_1-med.jpg
You need to throw some big power at it. My hull is very light so it lifts easier. I also have fins added to the strut barrel.This pic is just past the 1/8 mile, at about 120. At the end of the track it hits about 140 and it does weave a little from side to side when I let off the throttle. Bottom line, however you get there, you simply need to go fast enough to climb up on the strut.
DJ

[LakesOnly]

Nice photo DJ...says it all.
LO

[Slap Dawg!]

Should the center of the boat look like this while "Blowing the Tail"?

[DetroitJim]

Kurtis 501's RULE!

[V-DRIVES RULE]

http://www.***boat.com/forums/attachment.php?s=&postid=817101 HORSEPOWER-HORSEPOWER-HORSEPOWER