need some guidance. stringers & transom - Page 4

Starzofchaos · #31 07-13-2014, 05:31 PM

Have you thought of using Divinycell 5lbs or Core Cell 5lbs foam core instead of the wood? Its a little bit more expensive, but the amount of weight you will save and the thought of it never rotting out...

http://www.merrittsupply.com/default.aspx

tartuffe · #32 07-13-2014, 06:43 PM

I used divynicell for my deck. Its a great product but while it is lighter than wood you will use far more fiberglass and resin in such a crucial structural application so the weight savings will be offset and it will be more difficult to use compared to the wood in the stringers. The transom wouldn't be a suitable application either since the foams are crushable.

Starzofchaos · #33 07-13-2014, 06:55 PM

I thought I would ask if it would be a suitable replacement for the wood transom. I've had one boat builder here in Jacksonville tell me that is all he uses in his, around 3~4 inches thick depending on the application. Yet he builds small skiffs. Boggy Creek Boats. (Sorry for taking over the thread, but I had to ask)

brywheat · #34 07-13-2014, 07:09 PM

Quote:

Originally Posted by Starzofchaos

I thought I would ask if it would be a suitable replacement for the wood transom. I've had one boat builder here in Jacksonville tell me that is all he uses in his, around 3~4 inches thick depending on the application. Yet he builds small skiffs. Boggy Creek Boats. (Sorry for taking over the thread, but I had to ask)

No problem Starzofchaos, had the same questions about it myself!

tartuffe · #35 07-13-2014, 08:47 PM

You can absolutely use divynicell in the stringers, especially if you could get it in the full sheets. The cheapest place I found to purchase it cuts the 4'x8' sheets into 2'x4' sections to reduce shipping costs. You will just have to find a layup schedule that will compensate for the loss of strength the wood adds to the stiffness equation. Only problem in short is that it is a little more complicated to use and the expense is higher for marginal weight gains. Probably the largest advantage is being able to say its wood free. If a boat is built with wood taking into consideration how water would get to the wood (screw holes, permeation through the resin where water stands) and eliminating those paths of infiltration, a wood boat will last as long as a composite built boat.

There are also composite materials that can be used in the transom such as coosa bluewater 26. A great site with a lot of technical knowledge is boatdesign.net lots of builders on there versus some of us 1-off project guys.

Earlier I recommended researching vinylester resin. One thing to consider is that epoxy tends to be a better material to encapsulate wood to prevent water infiltration and rot. When you buy your fiberglass, make sure the resin you will use is compatible with that particular fabric. Polyester resin allows the most water intrusion over time and even it lasts multiple decades. I used epoxy and I like epoxy, to me it is more forgiving and CYA to make up for our rookie mistakes. It does cost more but others have had great success (like every successful large scale boat builder) using polyester and vinylester resins.

brywheat · #36 07-15-2014, 07:02 PM

Thanks for the advice
Think I'm going to research about composite and lay up schedules for the transom and stringers. And obviously save up more if I decide to go that route. Decision really seems to be how much glass do I want to lay

brywheat · #37 07-16-2014, 04:09 PM

So Im really considering Coosa board now. I like the idea of zero water penetration & after a nice talk with the a saleperson at coosa Ive learned a few things

You can actually use less glass, full encapsulation isnt needed for stringers. The bottom of the deck wont need to be glassed unless connected over a free floating seam, Ill just add a bulkhead at the seam location.

The guy couldnt give me a straight forward answer about how much flex the coosa bluewater 26 board has. He did say its similar to ply, 1/4' has the same flex as a 1/4" piece of ply? Any input from those who have used it? With the curvature of the transom, I believe going with 1/4" piece first, then 1/2" cuts I'll be able to get the curve I need.

Anybody familar with coosa 26?

Thanks for your help!!