stringer repair

[wayne74447]

I was wondering what the best foam is to use for my stringer repair on my 1830 Chaparral is. I have bad wood rot and only want to do this project once. it needs to be 3/4 inch wide Any info is greatly appreciated.

wayne

[Bill Dunn]

The type of foam used to repair stingers is less important than the quality of the laminate repair its self. You will need a clean dry area to laminate to so all of the old rotten material has to be dealt with. You will also need to make sure you degrease any area you may suspect may have been contaminated by oil. The manufacturers use wood or urethane for stringer core because its cheap and easy to install. What really needs to be used for the longhaul is a good closed cell material like PVC foam. Its not too expensive but gets along with moisture better. But most importantly the laminate needs to be done as tight as possible. Water will migrate through any laminate but you don't have make it easy by leaving air voids and not sealing your new stringers with either epoxy or gelcoat not just bilge paint.

[catman021]

Am I understanding you correctly in saying that you're not going back to the plywood at all but intend to use some kind of foam to replace them? If so, what kind is it, where do you get it, and what's it cost? I'm in the early stages of a project like yours and iny information I could get would be appreciated.

[mtnrat]

I used coosa composites bluewater 26. Pricey but 40% lighter than ply and will never rot.

[catman021]

I went to website and looked it over. How expensive is 'pricey', did you use it for your stringers as well , and since it comes in 4x8 sheets I'm guessing you're using it for your decking as well? I plan to go with back to back seats or driver passenger pedestal seats in my build, would this material be up to the task(weight/stress loading underway) or would I need to build up the sole to augment the support?

[mtnrat]

Here is a price list from fishery supply.
http://www.fisheriessupply.com/onlin...ct/A01/Ntk/All
I used it for stringers and floor as well as the transom.
Here is a pick of the stringers and the floor with a loose test fit.
I would say it is strong enough for pedestal seats. That is what I will be using. I will epoxy the screws though.
I put my pedestal seat on some oak plywood to help decrease the forces on the screws. This pic was with the old floor right after I redid the interior.

[mike steiger]

Hi,
The foam or coosa board is really just a form for the laminate,I would go with about four or five layer of 1808 which should give you about a full 1/4 inch thickness when completed and that should be good. Your strength comes from the laminate itself, on the Steiger Crafts they went to a full fiberglas stringer and bulkhead system but the foam inside the system is just for sound reduction and flotation. Just make sure you have a full radius(3/4 inch) on the top of the stringer to allow the glass to conform more easily.

[mtnrat]

Originally Posted by mike steiger

Hi,
The foam or coosa board is really just a form for the laminate,I would go with about four or five layer of 1808 which should give you about a full 1/4 inch thickness when completed and that should be good. Your strength comes from the laminate itself, on the Steiger Crafts they went to a full fiberglas stringer and bulkhead system but the foam inside the system is just for sound reduction and flotation. Just make sure you have a full radius(3/4 inch) on the top of the stringer to allow the glass to conform more easily.

I have to respectfully disagree. Coosa bluewater 26 is structural panel that is used in exactly the same way as plywood.

"Thank you for your email. Yes, our Bluewater 26 material is appropriate for your decking, stringer and transom applications. For your stringer application, whether you laminate several of our thinner panels together or merely use our 1.5" thick material - the strength is the same. The decision is up to you.

As for the decking application - as a general rule of thumb, we suggest using the same thickness in our material as the floor you are replacing. So, if your existing floor was 3/4", then use 3/4" in our material. If you see some flex, you can increase in thickness. Typical floor thickness are either 1/2", 5/8" or 3/4" - it just depends on the boat. You would glass in our material the same way you would plywood. Our material works well with all typical marine resins: epoxy, vinyl ester and poly ester resins.

With regard to your transom - again, use the same thickness as your existing transom - 1.50" is typical, but we also manufacture up to 2" thick, should your transom require this thickness.

Our material is available through distributors. Should you need help in locating one, please let me know the city and state where you are located and I will be glad to assist you.

Thank you for your interest in Coosa Composites. Please feel free to contact us with any additional questions.

Sincerely,

Jennifer Donaldson
Coosa Composites, LLC
PH: (205) 663 - 3225 ext. 106
FX: (205) 663 - 4645
E: Jenn@CoosaComposites.com
Visit Us Online at: www.CoosaComposites.com

"We always recommend that you glass in our material the same way you would if you were using plywood. You would probably get a better hold using a mat layer instead of just resin for your stringers. Our material works well with all typical marine resins - epoxy, vinyl ester, poly ester resins.

Regards,
Jennifer Donaldson
Coosa Composites, LLC
P: (205) 663 - 3225 ext. 106
F: (205) 663 - 4645
E: Jenn@CoosaComposites.com
www.CoosaComposites.com "

[mike steiger]

I am not saying you can not use coosa as stringer material in fact I happen to like the B.W. 26 and have used it in several transom jobs but it is expensive and there is nothing wrong with using plywood as a stringer material. The glass work is what is important here and keeping water out of core material. Water permeation is uaually a result of holes that are drilled for various fixtures and fittings that are not properly sealed. Grady, Mako and a lot of other top notch builders continue to use ply with great results but if coosa is the choice that would also be great, but if I were doing this repair I would still go about this with the same laminate schedule. Yes coosa B.W.26 is a structural material and I am not debating that but with stringers the laminate and how it is done is what give's a stringer it's strength. I also strongly suggest that you use epoxy as opposed to poly or vinylester resin.

[mtnrat]

Your points are well taken and from reading your post again, I see you are referring to catman021 using poly resin and likely not epoxy and in that case it would be little more than a form. I used silvertip epoxy and staggered layers of 12oz biax to tab in the stringers and floor. I am an amateur and am still learning. Thanks for the clarifications.
Cheers

[naturewaterboy]

I cut open the stringers on my Silverton cause the wood was very rotten - lots of holes had been drilled in them over the years and not all sealed. I contacted Silverton and they responed that for my boat, the plywood in the stringers was simply there for a form to mold the glass (about 1/8-1/4 inch thick). They said it was not necessary to replace the plywood. I could have used foam, but I had some treated plywood that I put back in. If I need to bolt to the stringers, at least now they are not hollow and won't collapse when I torque down a thru bolt.

I have some hardware store foam board (with aluminum foil or aluminum paper on each side) that I plan to use to buil some reinforcing for my transom. I talked to a guy who has done a lot of work on a commercial dive boat and he's used this stuff a lot to make parts. Just have to be sure to get enough glass or other fiber wrapped around it to get the strenth you need. Remember, the strength is in the fiber, not the resin.

[mike steiger]

Hi,
I would stay away from the hardware or homedepot type stuff, if your looking to use foam go with something like penskie board, coosa,or kledgecell. Of these three kledgecell being my last choice as it does not posess the structural properties of the other two. Both penskie and coosa are great products and price would be the determining factor as to which one you would use. Good luck with your boat.

[mike steiger]

Hi,
I missed something here you said reiforce TRANSOM,why do you have to do this, is it soft, flexing, or are their cracks. Are you installing a bracket? Transoms are serious business and I am just wondering why you have to do this.

[catman021]

I did go take a look at the Coosa product but sheesh it's expensive! For my build and situation, I'm going to go with exterior plywood treated with CPES(top/bottom), cutting out the rotted portions of the stringers, and splicing them with new pieces. Following this I'll glass them in/over and top with the treated 3/4" decking material. With my plan, to install a back to back lounge seat on the passenger side and use a pedestal seat on the drivers side, what's the best way to secure them to the floor, especially the pedestal? I'm thinking I need to put an additional 1/2" sole under the pedestal, CPES the mounting screws, and epoxy the edges of the raised piece to seal it. I also plan to CPES my transom, more because I don't know much about the level of care taken by any of this boats previous owners and it seems to make good sense to have done with it now while I'm doing everything else.

[TerryKing]

Originally Posted by catman021

(snip)... I'm going to go with exterior plywood treated with CPES(top/bottom).

Before spending money on 'penetrating expoxies' read
http://www.boatdesign.net/wiki/Mater...d_Epoxy_Resins

I've used a Heat Gun / Hair Dryer and gotten what appeared to be very good penetration. I've also used West 105 directly on plywood edge grain and it seemed to penetrate well.. 3 coats before it really gelled.

My prejudice (not everyone agrees) is to use well-scrubbed and well-dried Pressure Treated Plywood. Check out:
http://www.boatdesign.net/wiki/Mater...d_Epoxy_Resins

Your distance-made-good-over-ground may vary