Please opionions on best COMPOSITES for stringers

[gofastsandman]

George wasn`t at the shop. When recoring my coffin cover he asked me what I was using . I said marine ply and MAS epoxy.
He said he only uses epoxy below the water line in places that you don`t need flex. He said boats were designed to flex, not shear... He also said if laid properly wood and poly can and have lasted since the `60s . Glass doesn`t like to make extreme bends when laying up. The more you can fill w/ smaller pieces to build up the bend and lessen the transition angle the better. Also makes a stronger bond.
This was obviously a different job than stringers. I`ll bring more next time.

One other note , and this almost sent me in for an evaluation. Be POSITIVE that the marine plywood is not made with oil based glue. The poly will delam over time.

Still making mistakes and learning. My ply was made in Oregon and not oil based. Phenol Formaldehyde.

Sea Cast has extreme compression strength, not so sure of the tensile rating!

GFS

[Baranx4]

Mas epoxies has a video on stringer installation using composite. They use prisma or somthing like that the email address is at the end of the video. I was surprise to find out that the bonding for composite stringers is easier time wise atleast that's what they said.

[3rdday]

Great videos,thanks for the suggestion.

[flyingfrizzle]

bump on this older post, Like to know some more current info on today's composites that are available to core stringers and bulkheads out of. Thinking about using Coosa Bluewater 26 3/4" For the stringers and bulkheads. Is this a good product for this type or application and would like to know the best way to wrap it in and glass it to the hull. I herd that you don't need to use 1708 over it. Like to know opinions on how it should be glassed and tabbed in.

[65Bowrider]

The 1st post above states: "He said boats were designed to flex". And I agree with that statement. Coosa does not flex. I heard 2nd hand, a new manufacturer tried using Coosa for stringers and they were failing (separating from the hull) due to the lack of flexibility. Maybe do a little more checking into this....

[flyingfrizzle]

Thanks for that thought, I got a 2001 Mitch craft Flats boat and the same thing happened to it (failure from no flex plus bad glass work) It has foam filled box stringers similar to the SC boats. I think flex had a lot to do with that boat failing as well and also the bad prep of the lay up. (didn't help that I had the 200 merck. wide open in a stout close chop) The glass that was wrapped to the hull that was tabbing it down separated and while doing this ripped a 2 foot slit down the chine under the stringer. Looked like the glass didn't bond at all except where the rip was. Need less to say it was good that it was a foam filled boat or it would of went to the bottom. Boat sat at a 45 degree angle with water pouring over the 25" transom and shin deep at the console while inching to the ramp. Don't want to repeat this. Carla do you think Divinycell Foam would be a better choice for the stringers and bulk heads or should I stay with the wood that I'm very much more familiar with.

[flyingfrizzle]

This is what I wanted to do to the seacraft on the link below. This is on a 25 Dusky but would work well on my boat I think as long as I went with the right materials. They used coosa 26 but I am now leaning towards the Divinycell Foam instead of the coosa to allow more flex and I think it will be lighter as well.

http://www.thehulltruth.com/attachme...iginal-143.jpg

[Beaver]

Wow that Dusky looked pretty heavy duty!

[blindmullet]

I like the 2"-4" polyurethane foam for the stringers. Very easy to work with. You do need to add more glass than you would with a wood system.

[Blue_Heron]

Originally Posted by flyingfrizzle

Like to know some more current info on today's composites that are available to core stringers and bulkheads out of.

All of the folks who mentioned flex are right. You need a stringer and bulkhead system that absorbs shock, so it doesn't overstress any single component.

While you will get some good ideas from this and other forums, you may get some ideas that are not so good as well. If you find yourself contemplating materials or methods of construction for your project that are not in common use by quality boat manufacturers, ask yourself why. Those guys have a strong incentive to build for light weight (less material=less cost), good strength (fewer warranty claims), and durability (a good rep in the industry sells more boats).

You will find DIY boat restorations that are every bit as good, or in some cases better than the original (strick's work comes to mind). But you will also find half assed jobs that result in heavy structures that are not as strong or long lasting as original and look like crap to boot. Which end of the spectrum do you want your work to be on? The key difference is how well you educate yourself before you start.

Do yourself a favor and buy Dave Gerr's The Elements of Boat Strength. He does a good job of explaining boat structural components and why they are constructed as they are, as well as why some fail. If nothing else, it will help you tell the difference between good and bad advice.

Dave