Foam stringers

[joseph m. hahnl]

Did any one see the video on you tube donzi tour part I.
About 1/2 way into it, they come to a boat ready for stringers.
The guy asks "what are the stringers made out of"
She says "FOAM" !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:shocking::s hocking::shocking:
:cool: :cool:
I don't know about you ??????????????????????????????:wink: :wink:
:shades: :shades:
But one some one say "FOAM" I don't think of rigid!!!!!!:confused: :confused:
:cool: :cool:
When did they start using foam stringers?????????????:frown::frown::frown::frown:

[zelatore]

I haven't seen the video - I'll have to look for it when I get a chance.

I know it's not unheard of for boats to be built with hollow stingers. The outer shell is what provides most of the strength anyway. This only works in areas where nothing is thru-bolted; it doesn’t work if there is a compression load. Of course, I wouldn't want to take a boat that was designed with wood then just remove it; you'd want to design for this process from the start
.

[chappy]

http://www.youtube.com/watch?v=EWmh1vsjyiM

About the 5 minute mark. Not the best video/audio quality, makes me question the validity of points made during the tour.

[MOP]

You would be amazed at just how many critical items have foam cores, a number of boats have and probably still have foam core stringers and bulkheads plus coring in the hull its self. The coring is more for shape then rigidity, they cur a hole and insert solid blocks of glass and glass over them where ever something needs to be mounted. Getting away from the boating industry many would be surprised as to how many fairly large 4-5 story buildings are built with steel frame work covered with foam panels then sprayed with stucco. Some may have wondered how the heck they went up so fast, plus they are very cheap to build.

[Carl C]

Hmmmm. Does the 22C have foam stringers now? Did they in the 2005 model? The tour guide has a nice butt.

[Morgan's Cloud]

All of the wood I took out of the St Tropez during the resto with the exception of the transom was replaced with foam core. (All epoxy too .. no fiberglass resin here , thank you very much )

Amazing strength to weight ratio , better sound absorbency beautiful to work with (I aint no carpenter ..)

Definitely the way to go ..

[BlownCrewCab]

It's the shape of the fiberglass over the stringers that gives the hull strength, the wood is basicly just a jig to get the desired shape, Except for as mentioned earlier where motor mounts or anything else is going to be thru bolted thru them. Look at an I beam (or H Beam) it's not the center section that gives it strength it's the space between the two parallel beams, To bend it you would have to compress one side, and stretch the other side,which you can't do, and you aint gonna stretch fiberglass either.thats where the basis of core came from to begin with. The larger the space between (thicker core/foam) the stiffer the panel.

[gcarter]

Blown is correct.
We (the general boating populace), are used to wood stringers in wooden boats and wood cored stringers in newer boats. Our minds see that and it thinks "That's right and good". That kind of thinking is dangerous. If a person builds a boat, stringers, or what have you by eye, it'll be too heavy in the hull probably, and the stringers won't have enough glass on them.
The ideal would be hollow stringers with rigid spacers added where it's through bolted.
Wood makes a cheap core and it adds reasonable strength to the glass. It's also easy to form. It allows the builder to through bolt wherever he want's.
But the emphasis should be virtually all the strength in the glass, and none in the core.

[f_inscreenname]

Some may remember I used a two part epoxy foam to fix a broken strike. Did it early this spring and beat the piss out of it all summer. Stronger then the rest of the boat now. This closed cell foam is so strong you can beat it with a hammer and only put slight dents in it.
The damage. >> http://www.youtube.com/watch?v=5KmemM_uk0M
The fix. >> http://www.youtube.com/watch?v=yarQ-GF6zII

[zelatore]

Blown is correct.
We (the general boating populace), are used to wood stringers in wooden boats and wood cored stringers in newer boats. Our minds see that and it thinks "That's right and good". That kind of thinking is dangerous. If a person builds a boat, stringers, or what have you by eye, it'll be too heavy in the hull probably, and the stringers won't have enough glass on them.
The ideal would be hollow stringers with rigid spacers added where it's through bolted.
Wood makes a cheap core and it adds reasonable strength to the glass. It's also easy to form. It allows the builder to through bolt wherever he want's.
But the emphasis should be virtually all the strength in the glass, and none in the core.

That's pretty much how we do it with the Carver and Marquis lines. Every once in a while I have somebody freak out because the stringers are 'hollow'.

[mike o]

:wink:...http://continuouswave.com/whaler/reference/13/originalHullDesign.html... Good stuff, the higher density type. As long as it stay dry as a (bone).

[Carl C]

I just wonder why my hull keeps cracking just below where the engine bolts to the stringer. Too much stringer flex maybe?

[donzivol]

Foam has been used for years by most major, reputable builders. There are several manufacturers of foam core. There are also many densities of foam available.

Having more than a passing knowledge of boat manufacturing, and having visited Donzi on several occasions, I was amazed at the materials and the processes used to build them. There is certainly no cost cutting, since the foam core costs considerably more than “marine” plywood. Welcome to modern boat building.

As for the video quality, it appears that the lady giving the tour is not a boat building expert, but rather a helpful woman from the sales office showing a customer’s friend his boat. Most manufacturers would not have bothered and certainly would not have allowed him to film it. I feel it is great customer service.

:) I applaud them.

[Lenny]

I have a supplier in Vancouver who purchased a block of longitudinal glass, all custom fabricated from Japan, about 8' x 8' by 40'. Continuous fiber. It was for a specialty application, (some high Tech something) but was never used. He purchased it and had it machined into 18" by 1 1/2" by 40' long "strips" for use as stringer material in boat building. The stuff is like steel once layed up. Not a foam, but true glass. Amazing stuff.

[gcarter]

I have a supplier in Vancouver who purchased a block of longitudinal glass, all custom fabricated from Japan, about 8' x 8' by 40'. Continuous fiber. It was for a specialty application, (some high Tech something) but was never used. He purchased it and had it machined into 18" by 1 1/2" by 40' long "strips" for use as stringer material in boat building. The stuff is like steel once layed up. Not a foam, but true glass. Amazing stuff.
I bet that would be great in a heavy cruiser.

[Conquistador_del_mar]

:wink:...http://continuouswave.com/whaler/reference/13/originalHullDesign.html... Good stuff, the higher density type. As long as it stay dry as a (bone).

Mike,
Back when I did boat repair work professionally, I had a customer bring me a Boston Whaler with a delaminated bottom which had ripped a section about 1' across and 4' back after hitting something. It was the only repair that I ever remember turning down since I couldn't figure out how to make the repair and guarantee it to hold. Bill

[mike o]

Mike,
Back when I did boat repair work professionally, I had a customer bring me a Boston Whaler with a delaminated bottom which had ripped a section about 1' across and 4' back after hitting something. It was the only repair that I ever remember turning down since I couldn't figure out how to make the repair and guarantee it to hold. Bill... Bill, You would have to cut the whole bottom open 6" beyond the damage and let the foam dry for a year here. Where you are, with the heat, dry - air it'll be less. Kind of a total loss with that one. Fix'em and give it to some less fortunate kid to play with.:wink:

[joseph m. hahnl]

Well I have one thing to say and that is: technically wood is stronger than steel. As it is an organic cell structure it has the greatest structural integrity out of any other building material.

Why would anyone be shocked by foam stringers?:shocking:

I can understand the use for eliminating degradation of the wood or even
as lighting aspect but as for rigidity Not in a million years. May be if it were carbon fiber where it's molecular structure is interlocked. Fiberglass is certainly not stronger than wood. If it were they wouldn't use wood in the transom still. Not to mention you never ever see stress cracks in an old wooden boat.

My point here is that I am sure that if the research is done"dates of first implementation" that these added stresses are a direct result of this new stringer and not the widening of them.

I am by no means cutting down the quality of Donzi.It is a hand laid boat made in the good old USA. No body builds stuff better.
This is all just food for thought.

[cutwater]

Fiberglass is certainly not stronger than wood. If it were they wouldn't use wood in the transom still. Not to mention you never ever see stress cracks in an old wooden boat.

Umm... wooden boats ARE one big stress crack. Are you kidding me? Every pair of planks has an associated "crack."

Second, let's be a little more thorough. You might want to qualify the "wood is stronger than steel" statement in some way... You can't say things like "molecular cell structure", and then make a generic, crass statement like that. I'll call you on it. :wink:

[onesubdrvr]

I did work for them for a couple of years, they make a very large percentage of the stringers / etc used in most boats.

They have also patented their process, and are instructing boat builders as to how to perform it, so the boat builder can do it themselves instead of waiting for their orders to come in from CompSys.

Basically, they have a wooden frame made to the shape of the parts they are making, spray it with the close cell foam, and seal the frame up, so as the foam expands, it has no where else to escape to, thus, just making it even tighter / tougher. Pretty interesting concept.

They don't know crap about compressed air or nitrogen generators, but know how to make their stringers.

http://www.preforms.com/stringers_bulkheads.php

Wayne

[joseph m. hahnl]

Umm... wooden boats ARE one big stress crack. Are you kidding me? Every pair of planks has an associated "crack."

Second, let's be a little more thorough. You might want to qualify the "wood is stronger than steel" statement in some way... You can't say things like "molecular cell structure", and then make a generic, crass statement like that. I'll call you on it. :wink:

Sorry: it is not stronger in every aspect but this should sum up what I meant.



Physical Properties.
The principal physical properties of wood are strength, http://www.history.com/encyclopedia/icons/info.gif (http://www.history.com/encyclopedia/article.jsp?link=FWNE.fw..ha020900.a)HARDNESS, (q.v.), stiffness, and density. Density is generally an indication of the mechanical properties, inasmuch as dense woods are usually hard and strong (see http://www.history.com/encyclopedia/icons/info.gif (http://www.history.com/encyclopedia/article.jsp?link=FWNE.fw..ir042100.a)IRONWOOD,). The term strength covers a number of essentially different properties; a wood that is high in one kind of strength is not necessarily high in others. Moreover, the strength varies greatly with the state of seasoning, or dryness, of the wood, and with the direction of the grain; wood is always much stronger when cut along the grain rather than across it, and for this reason planks and such articles as poles and handles are always cut with the grain running the long way. Wood has high compression strength, in some cases higher in proportion to its weight than steel; ,.

[gcarter]

Wood's problem is like what Cutwater said..they're full of cracks. It's interesting to compare samples of different materials about the size of your typical give away paint stick. You'll soon see that wood is pretty superior to most anything else except for exotic materials like carbon fiber. If you stick, or nail pieces of wood tgogether, they'll work, leak, or break up.
The answer is wood strip/WEST epoxy construction. Where the boat is constructed on a male mold from thin, narrow wood strips epoxied together and saturated.
For a 22C type boat, you would probably use strips that are 2" wide and 1/8- 3/16 thick and stapled to the male mold. Each coursed (or layer) is laid up at 45* angle to the one before. Also, you would probably want to end up w/the longitudinal layer on the exterior.
A few years ago while visiting Britain, I saw a four engine wooden bomber at a museum being restored. The construction was identical to what I described above except they used resourcinol glue which has nothing on epoxy, but yet it had lasted 60 years.

[DonziJon]

A few years ago while visiting Britain, I saw a four engine wooden bomber at a museum being restored. The construction was identical to what I described above except they used resourcinol glue which has nothing on epoxy, but yet it had lasted 60 years.

I have a DN-60 ICEBOAT that was built in 1964 of solid mahogany and glued together with resourcinol glue. The Runner Plank (A Major "Flexible" structural member) is Sitka Spruce laminated together in three layers with resourcinol. It's still good to go. This boat is good for well over 60mph On ICE. John