Stringer Talk.....

[Old Charger]

Hey, so what's the deal with full length vs partial stringer setups.
What are the advantages of full length? Why did most of the boat manufactures in the 70's even bother with partial stringer setups?
Is it possible to retro fit my ride with full length?

[Heatseeker]

I'm no expert, but the obvious advantage is overall strength. When I was shopping for my jet boat, I was told by people in the know to only consider a full stringer boat. I've heard a couple of stories about pumped engines tearing out of partial stringer boats. That would really ruin your weekend!!!

[Hondo Jet]

I have a Hondo with full length stringers and the motor mount holes in the stringers are enlarged from to much horse power. So what I did was take aluminum angle and run it about 6'down the stringers this really beefs them up. This trick would work on any stringer full length or not.

[okie dave]

just my opinion but tunnell hulls have the benefit of four full lenth stringers in the shape of the hull as far as stiffening of the length of the boat goes. you need something to mount the motor on but not necessarily ruin the floorspace of the boat by having something else to trip over when standing up in a crowded boat. aluninum rail type motor mounts bolted to the short or long stringers is a given.

[Blown509Liberator]

Like okie dave said...
on a V hullit adds strength and helps stop a hook/rocker from forming on you hull

[custom-cruiser]

Production boat builders in the 70's (Tahiti ect..)just wanted to crank out boats the quicker and cheaper the better so quarter length stringers helped that process along.
True custom boat builders that were genuinely
intrested in the longevity of thier product(Howard,Hallet,Eliminator,ect.)wouldn't have dreamed of doing it.I have seen some 25yr old quarter length stringer boats with absolutly no hook or rocker simply because the trailer is properly fitted which is often over looked.

[rivercrazy]

The faster you go, the more the bottom of the boat wants to distort. Fiberglass will flex when put under a lot of pressure. Without full length stringers and good speed, the bottom will start to distort causing handling problems and limiting your top speed. It can also cause stress cracks to form as the boat is not as rigid.
Stay away from boats without full length stringers if you want any kind of performance and longevity...

[Old Charger]

How about the whole retro fitting idea? How big of a pain in the ass is that gonna be?
I gotta replace the floor anyway, so are talkin just glassing in some 2x20's or something along those lines?

[spectras only]

I do have full stringers in my boat,however you guys forgot to mention one thing.A few boats in the seventies had mediocre layups [some as thin as 3/8 " in the bottom!!!]and required stringers to keep the hulls in shape.As custom-cruiser mentioned ,the placement of the boat over the trailer ruined many boats,as these light layup boats started developing hooks,because of overhang.In the seventies many boats ,you could feel the floor flexing just by walking on it.Speed was king so some manufacturers built their hulls superlight on purpose.That goes on today with balsa coring to make the hull stiff without a heavy layup.Schiada's ,Sangers ,Howards,Spectras etc...had heavy layups [sometimes as thick as 1" at the keel,so even with partial stringers they kept their shape better than lesser boats with full lenght stringers.Since inboard hulls didn't have horsepower limitations,most people overpowered their rig with dire results.Case in point ,a 24 Campbell was built up [had full stringers]with two 427 BBC inline with blowers,connected with a shaft,firing order was setup as a 16 cyl ,producing around 2000HP.The first time it was taken out for a test,it ripped all the stringers out by torque.After they modified the stringers the boat performed well.Just for last,Lincoln Continentals in the sixties didn't have full frames ,yet they had the stiffest body of all american cars in that era.I had a 64 until 4 years ago ,and I can attest ,there wasn't any creaks no matter what road surface I drove on. It was called torquebox frame construction with partial frames.
[This message has been edited by spectras only (edited August 02, 2001).]

[okie dave]

when you are going fast, the only part of the boat touching the water is the very back end. the stringer up front isn't doing anything. if you really want long ones, simply cut out what you have, grind the area smooth, and install whatever you want. no big deal. v-bottoms and flats need full stringers. tunnels don't.

[HavasuBarney]

They are nice to add as a point of attachment for seats, motors(if it's inside the boat)but you will never duplicate the strength they provide when built with the hull. Tunnels can be stiffened with them but are faster when allowed to flex.

[77Spectra]

Most of the people that desighned these boats knew a little about stress points. Thin hull with a somewhat forgiving stringer sett up would allow the boat to flex evenly. This is also true with aerodynamics and spar strength in planes( I am a pilot ). If you add strength to one area, the stress points will move to another. Full length stringers in a thin hulled boat, the stress moves to the hull. If you hit a nice wake at 90, your motor may stay attached to the stringers but the glass around them may dissintigrate. I am sure you have all seen this happen in a race or two. The best thing you can do is to make sure your existing stringers are solid, replace the floor if weak or soft at all, and make sure you glass the bottom of it. A good floor will add tons of strength and spead out the load across the entire hull.

[77Spectra]

Okie Dave and the rest. When the boat is running on the pad. The water has been replaced by air. The entire hull will see as much stress as when going slow. Now, throw in a wave and see what happens.

[spectras only]

77 Spectra, I think when spectra did their boats with partial stringers with a floor ,they did it for the reason you mentioned,ie;distribute the load to the entire hull.They also made cross members [5]under the floor as well,and encapsulated the marine plywood with resin on both sides.Their 20 footers had a 1" layup at the keel.My 24 is slightly less ,but has four full lenght stringers ,the middle ones being 2x12's ,the outers 2x8's tapering off towards the bow.Spectras and
schiadas proved themselfs in "ocean " racing for their stoutness ,that not many boatbuilders did with 20 + footers.

[77Spectra]

Bottom line....Resin and glass cost $$$$$ There is more glass in my 19's top deck than most hulls. Not to be bragin. There are a few builders that spend the extra money. Yeah they are heavier, takes a little more power to push. But when you are running that OB. over chop. The last thing you want to worry about is falling apart.

[77charger]

My next boat will have full stringers as my current one has partial stringers.Was fine when the motor was stock but as torque and hp increased so did the height on the left stringer(partial
)

[77Spectra]

Charger, what kind of boat? The design has alot to do with full or partial. The 19' Spectra, along with a few others, have partial yet I would not be afraid of 800 ponies. Hull thickness plays into it.

[77Spectra]

spectras only. you mentioned the tapered stringers. Some manufactures, like the 20' Hawaiian would just stop the stringer at the front bulkhead. Look under the boat and you could tell where the stringers stoped. Anyone adding stingers should taper the last few feet. Let the stringers follow the curve of the hull will work. Also most floors extend past the bulkhead and stop, straight line across paralelle to the bulkhead. Go ahead and cut the middle out and taper about 6 inches at the edges. This way instead of the floor showing one solid stress point near the front of the hull, perhaps delamming at that point, it will have a gradual building of strength. For grins, check the bottom of your boat and see if you see cracks where the floor ends.

[HAVNAFIT]

I have a 79 20' HAWAIIAN, It has full stringers with no hook. I have to replace the floor, should I fill the cavity with exspanding foam?

[77Spectra]

That is a pretty tuff hull. I would not recomend that for that hull. Glass the bottom of the ply before you install with matt. Bevel all edges, you do not want any sharp edges. Make a bed out of 6 inch wide matt along the hull where the floor will rest. Lay the floor and glass edges with 6 inch wide matt, then 8 inch woven, then the entire area with matt. I would then paint with a brush, use gell coat. Fiberglass is not waterproof. Every boat I did I would then drill a large hole under the rear seat and fill with a rubber freez plug. You can check for water under the floor that way. Every floor I redid had water trapped under the floor.

[Old Charger]

Hey 77Spectra,
The boats a 77 Charger 21' Mini day cruiser. It's still on the same trailer it was sold with and it extends far enought past the stern that the hull hasnt developed a hook yet. Gonna swap in a 454, so the aluminum reinforcements sound like a good idea.
The things definately flexs under speed and chop. The top of the gunnels do the ol' flex and wiggle all the time. Is this normal? They are taller than the smaller type boats, being a day cruiser and all.

[77Spectra]

I do not know that boat. Many would fall under that catagory. If your floor is weak or there are split seams where it meets the hull you can get alot of flex. I once did a 21, open bow. The new floor really made a differance. A little twist at the floor = a big twist up high. What condidtion is the floor in? and I would drill a hole to check for water.

[spectras only]

77spectra,the taper I've mentioned is on the outside stringers of my 24 footer and the layup is still like just being made.This boat can cut through 3-4 footers without a hint of flex or shudder.My 20 footer has two full lenght stringers put in long time ago by a friend who's building boats locally for the ocean going bunch.He put transverse frames [5] in with marine ply floor on top ,[3/4 thickness] resin coated both sides.I like it because of the level floor instead of walking on angled surface. If you see spidercracks on the older quality boats it's only surface deep ,the structural srenght is still there.The only real test is a sea trial for any boat.My boat still rides solid like a sherman tank.The most important aspects of hot boats still depends on how the hull and deck joined together.If it's not glassed together ,it won't stay together long!I've seen fancy Wellcrafts ,26 Novas ,Scarabs they were merely screwed together every 6 inches and just sealed at the seem.I think Cobalts are one of the best built boats [only my humble opinion]but they haven't made it to hot boat territory [california].They're conservatively styled but the Caddilac of boats.

[77charger]

Hey old charger as far as the flexing i get that all the time with mine too 19 mini cruiser.Glad to know im not the only one.Personally i dont think these boats were made that strong but i have yet to crack the bottom or sides even at 65-70.

[spectras only]

Old Charger,I never seen a 21 Charger in life,seen their ads in the seventies.Their flagship was a tipical 30 foot offshore model. However I know a guy in my area with a 24 footer that he bought as a hull kit. The hull is a light layup compared to Schiada,Spectra,Campbell or Sanger etc,which is evident when you look it the hull alongside and underside .He's is a 1980 vintage and require a complete stringer floor replacement.The gelcoat is in good shape but not the same finish as the afformentioned model's.Charger tried their luck with offshore racing ,but I haven't got any info on that.You should drill a drain plug hole at the keel under the engine [good to keep moisture,water accumulation out of the bilge]and epoxy a female thread for a pipe plug. Same time you'll gain some knowledge of your hull layup.Last bit of info,originally he had a 454 LS6 with a Berkeley jet in it that he changed to a bravo 1 ,like his buddy with an Omega 22.5.I think the torque from the sterndrive caused him some of the warpage in the hull,since he didn't have problem with the jet before.

[spectras only]

Havnafit,boats 20 feet and longer don't require positive flotation. Some foams may retain water ,thus adding weight to the hull.Make sure you have drainholes through the bulkheads and into the bilge. You can put a drain plug into the bulkhead that devides the bilge from under the floor area.Also an inspection hole with lid under the carpet to check occasionally for condensation buildup.

[HAVNAFIT]

spectras only-thanks you made it easy to understand. I will go this way about it this winter. as for now I'm off to the river.{the mighty MO.}

[77Spectra]

You can goto your local Bass Boat dealer and get live well plugs in many sizes. Chances are you may already have a drill bit that will work instead of making a hugh hole.

[spectras only]

Havnafit, we were talking about flotation for your boat earlier,and I remember a solution for you without foam and absorption.Some of you old salts may remember Donald Campbell's boat that he filled with thousands of ping-pong balls for flotation [didn't help him survive at his record braking attempt though].You could substitute the p/p balls with the larger diameter plastic balls [steal some from Mc Donalds http://free.***boat.net/ubb/biggrin.gif]to keep the numbers down.Most daycruisers have saddle tanks,and when they're less than half full,they add positive flotation to a boat and stability.A boat with a single tank in the bottom less than half full is more prone to capsize in rough water .
[This message has been edited by spectras only (edited August 18, 2001).]

[77Spectra]

Floatation suggestion: Climb up in your bow with a couple tubes of silicon and seal all of your rubrail rivets and screws. Son't forget the bowlight. If there is a screw, seal it. Saw a jet sink at Lavon once. Two feet of the bow was out of the water. The guy thought he could save it but the rubrail screws screwed him....

[old rigger]

Old Charger,
Good question, pro and cons of full length stringers and short ones.
First of all the short stringers were used in jets in conjunction with a floor strictly to get the seats lower in the hull and offer a more appealing seating arangment to the buyer. Besides, that's all that a family jet needed at the time. It has nothing to do with cutting corners in the production of the boat as custom cruiser stated. And yes Howard, Hallet, Elimanator, almost everyone used the short stringers in their jets. Some of the boats with this set up also have a stringer running the length of the floor in the center of the keel . Think about it. That is alot more work to build a hull like this than running full length stringers. Personaly, I would rather have full stringers, but there is nothing wrong with the short ones.
I have never seen a bottom crack where the floor ends or the little stringers stop. if it is cracking there it is because of a crappy lay up.
Adding full stringers to your boat is a pretty easy process but it's not a no brainer. You have to make sure that the new stringer is cut to the exact curvature of the inside of the hull. If it's off you can create more problems . If there are low spots on the bottom of the stringer this will create preasure points and crack the hull, not allowing the the stringer do its job by displacing the load across the hull.
Unless you are going to dump gobs and gobs of HP into your boat there isn't anything wrong with short stringer set up, and if done right , makes for a pretty strong hull.
I don't know what 77spectra is talking about when he says that fiberglass isnt water proof. If he means that the resin mixed with the glass is still porous, yes that is correct. But putting a coat of gel coat (still porous) over the floor and stringers is a waste of money. On the final coat of resin, called a flo-coat, you add what is called surfacing agent, a waxy chemical, that is mixed with the resin and catalist. This allows the resin to cure to the touch and is water tight. It can even now be sanded and polished if you want to.

[77Spectra]

Old rigger, I will try to clarify what I was talking about. If the fibers are not completly sealed they can absorb water and will rot over time. Resin in itself is not the perfect barriar. Take your freshly refloored boat and trow a pail of water in it and let it sit for a while. The resin will actually absorb some of the water. You will notice it turn slightly milky till it dries out. All that I know was taught to my by Terry Brown of Contender boats.
Term correction for spectras only. The stringers on the outside are called lifting strakes.
I am no expert, old rigger and a few others do a better job of that. As a rebuilder there are very few however that know more about resin and glass, lexan, and carbon fiber than I.
Keep em comming, there is always more to lear.

[old rigger]

No need to clairify, I know what you were talking about. To seal it properly, surfacing agent must be used in the final coat of resin to make it water tight. Even if your final coat is gelcoat the agent must be used as gel coat is still pourous without it.
The two stringers on the out side ( on either
side of the center stringers on a four stringer boat) are called the outside stringers. Lifting strakes are on the bottom of the boat, and create lift, putting the boat on plane.
[This message has been edited by old rigger (edited August 18, 2001).]
[This message has been edited by old rigger (edited August 18, 2001).]

[77Spectra]

Looks like we are on the same page oldrigger. This is just not the best media to get all ideas across.

[beached1]

77spectra,
I would like to know more about Carbon Fiber.
What is involved in laying it up as opposed to Fiberglass? All I know that it's stiffer and lighter, but I haven't met anyone that seems to know much about it. I have talked to a few shops that make Carbon Fiber hull reinforcements, parts etc. But they were kind of evasive when asked any questions. Thanks.

[old rigger]

77Spectra,
If you think that a lifting strake and a stringer are the same thing, as you stated eariler, we're not even close to being on the same page.

[BADAXE]

Old Rigger is correct.
Lifting Strake = OUTSIDE bottom design feature (proturding ridge) meant to aid lift.
Outside stringer = INSIDE bottom design feature (wood or laminant) meant to add strenth and reinforcement.

[77Spectra]

I agreed with what you said and whatever

[BADAXE]

Originally posted by 77Spectra:
The stringers on the outside are called lifting strakes.
I am no expert.
As a rebuilder there are very few however that know more about resin and glass, lexan, and carbon fiber than I.
WHATEVER?

[77Spectra]

badaxe, stfu, I agree with your previous post. Stringers inside, strakes outside. How we got on this I don,t know. Perhaps I said something stupid, not meaning too, Been doin glass since 78. Mostly in aircraft and I stand by what I say, when I say it right. If you are wanting to start crap, go elsewhere. Last post this topic, later much.

[old rigger]

77Spectra,
Lighten up man. You are the self-proclaimed expert, the best in your field, and you made a couple of statements that did not make sense, that's all. I don't think anybody is trying to start any crap.
I've never been the best, so I don't know the feeling. I've worked next to and had the opportunity to hire guys who I thought were the best in the boat biz , and I learned plenty from them. On the other hand I also have had the pleasure firing guys that told me they were the best, and it turned out they were just another hack. I am not making any reference to your personal talents because I have never seen your work, so please don't be offended. Maybe you could post some pictures of it so we could check it out.
On another note, what I know about carbon fiber material, lexan and all the other high tech fiberglass related material, could be fit into a dixie cup and you'd still have room left over for a rhino's dick. I'm old school I guess, got out of the boat building thing in '95. A guy I've know since child hood is in charge of the glass (carbon fiber) dept. at Boeing here in Long Beach Ca. and it was my understanding from talking to him that these high tech materials were not compatiable with the material used to build boats in the early days, ie. the 60's 70's 80's . So using them to repair an older boat does not make sense to me. If a boat is built from this stuff from the begining than obviously that is a different story. He said it was the bonding capabilities of the older product to the new, that were the problem. Take what I am saying with a grain of salt because when he starts to talk about this stuff with the vacuum bonding process and everything else, it's way over my head and I get lost. I need to actually work with the stuff to understand it.
He also has his own boat shop (a very tiny one, as he builds RC stuff. 'Hoover racing', they're on the net too.) and the hulls he builds out of this stuff are awesome. Tough as nails and extremly light. I'm not into these little things, but they are very impressive.

[SB]

I hope that fiberglass is waterproof, since my boat is made of fiberglass and I want it to float. Hee Hee. Beached one re: carbon. I'm not an expert, but I can tell you that a windsurfer board is a piece of foam covered with glass and weighs about 25lbs. If you want to reduce weight, you can replace glass with carbon fiber, it costs about $100 for every pound you reduce. Racing sailboats use carbon parts, masts, etc. and Kevlar. It saves weight and costs $. You wouldn't think guys racing around at 10 knots would care that much about speed, but there you are.

[RiverDave]

They say most speed boats were struggling to keep up with the America's Cup Catamaran that we built a while back. I don't remember the exact speed but I think it was something like 50+ mph!! I remember I was shocked when I read about it.
RD

[BADAXE]

77spectra,
No hassle here dude. Spectra is one of my favorite boats (I'm old school) so if your smart enough to like spectra's your smart enough for me.
Looking back I guess I was a little smart ass in my post. I just thought you should have said, whoops I goofed, instead of "whatever".
On the subject of carbon fiber. Is it not to brittle for boats? This may be a stupid question but the only time I hear materials being used other than glass it is kevlar. Maybe carbon fiber is just to expense to build a whole boat from.

[77Spectra]

It's cool dude. Some of my posts you may notice I did at 3am, not to good at that time of the day. I quit working on boats about 8 yrs ago and started back about 2 on my own. In the painting I left out a simple step and it cost me about 30 hrs labor and $4oo. so I find I am having to relearn some things and finding out new things.
Carbon fiber would make a great boat but would cost way too much. Kevlar I am told is stronger than glass but it is hard to work with and I have seen it try to delam in high stress areas. It is no fun to repair. I could see in the future builders laying glass and adding carbon to stress areas. It seems to work well if added before the resin cures. Cabon works even better if it is sandwiched between layers of glass. This is a messy subject that could go forever...hehe

[spectras only]

Badaxe,there were some offshore boats built with Kevlar and had delamination problems as spectra77 says.It works better for sailboats.So obviously powerboat builders gave up on that one.Carbonfibre were used for springs ie; corvette rear with good results.Don't know if it's still used for that.The new Corvette ZO6 has a balsa cored carbon fibre floor to save weight [They trying to beat Viper performance http://free.***boat.net/ubb/biggrin.gif].Model racing cars had carbon fibre chassis for some time with less fatique than alloy chassis.Their rear section is designed as part of the suspention with monoshocks.It only comes down to dollars and senses.I've heard some large yacht builders already building carbonfibre hulls.

[beached1]

Thanks guys for the info on Carbon. Since I'm going to be replacing my foor and transom wood and adding full stringers to my Omega, I was dreaming of the possibility of going with Carbon instead of wood with Fiberglass. Just a thought.