23' seacraft

[chrisvazquez1]

i was warned against certain types of plywood though because the laminate will not last. douglas fir is a cheaper source for a trustable transom im assuming? or what would anyone recommend if i did decide to go with the plywood core? and also i was told i should consider a 2" transom if i plan on drastically increasing the hp. has anyone ever heard of a 2" transom before ? backk to the greenwood product, i take it there hasnt been much experimentation due to the prices?

[bigeasy1]

I used marine fir plywood for my transom,and have no regrets.I used two 4x8 sheets of marine fir glued together with thickened epoxy resin.No way it will ever come apart.

By the way,as for thickness,my transom now measures 2-3/16" thick including the core,and inner and outer glass skins.(it's an I/O).
The original was much thinner,around 1-3/4".I laid up two layers of 1708 on the inner side of the outside transom skin,before i put in the core.
If you use high quality materials,resins, plywood,etc,and do it properly with good craftsmanship it should outlast you,or at least until your too old to ride in a boat.

Ok,
now all of you can throw rotten tomatoes,and tin cans at me,because,may I dare say that I used,oh my god,Polyester Resin.
I know,I know, epoxy is a stronger resin,and does make a stronger secondary bond,but in every glass boat that I've owned(10)it was never the resin system that failed.
It was usually poor workmanship,like resin starved glass,or uncoated wood,no drain or limber holes,and just plain sloppiness,and that included a couple high end brands.

I work for a friend in the glass and resin business,and could have bought epoxy from him at a very good price,but i decided to stay with a high grade polyester.Yes it smells,and it may be not as strong as epoxy in a secondary bond,but it wets out material better,and for me it is just easier,as I am very comfortable working with it.


Whichever one you use,make sure you use a high quality resin.be wary of some of the cheap stuff no matter if it's epoxy or polyester.
Remember quality is remembered long after cost is forgotten.

Here's a couple pictures of the transom glued together,and a piece showing the glue joint.

[chrisvazquez1]

im not questioning your method in any way but i was also recommended when gluing two sheets together or using the "sandwich" method, that i should drill holes occasionaly throughout the transom to release air pockets which you would of course later fill. did you do this when makign your transom or is it not necessary if done the right way? also where could i acquire "marine' fir plywood assumign there is a difference from douglas fir plywood? you say your transom is over 2' thick but is this because you used 1" sheeets or just due to the glass etc.?

[McGillicuddy]

Marine plywood comes in many species. Douglas fir is the most common in the boat building industry. There is, however, a huge difference between "Douglas fir" ply from Lowes, Home Depot or whatever and "Marine" plywood.
Marine ply is a much higher quality or grade for a number of reasons. Look at the picture John123 posted showing the edge of the plywood. The plys are of consistent thickness, the glue - a waterproof aliphatic resin of some kind also is consistent in thickness. There a few if any voids in the plys, and the plys are all heartwood (the center of the tree trunk). No where for water to begin the decay process, in fact the only void I see in that foto is in his glue line. Go to the lumberyard and check out exterior grade (waterproof)doug fir plys, you'll find voids in the wood, air pockets in the glue, inconsistent ply thicknesses and glue line and low grade wood in the plys including knots, and sapwood (both weak points). The marine grade plys for decks and especially for transoms are worth every penny, and as you've probably already seen, they cost at least twice as much.

Regarding the Greenwood XL panels, it is heavily used by the boat building industry, but if you're finding no input it is likely because lumber yards just don't move enough of it to carry in stock and people move on to the more available products. Call a few boat builders and ask what they know about it. Boat Builder Central and Jamestown Distributing may have a lead on it. Good luck with the project.

Don't know where you are located so no clue where to shop, but good lumber yards or wood stores will have it or can get it. Unlikely at home improvement centers. These guys have good selection and their prices are about par. It's the shipping that gets you.

http://marine-plywood.us/

[chrisvazquez1]

sounds good. im going to try getting some prices on the xl panels to be delivered to me. im all the way in gainesville,fl so the wood may cost as much considering its comign from ohio. im definately going to keep the douglas fir in mind. if i do decide to use the doug. fir for the transom could i use the pressure treated type or will that not laminate well?

[chrisvazquez1]

called diab products today who are over in texas. they gave me a price on some renicell e 240 which is actually 15 lbs/ft whereas the divinycell h130 is only 8 lbs/ft. its 2" thickness and 4 by 8 sheet for under $400. im not sure if this is correct but it sounds like a good deal. does that sound strong enough for a transom core? im sure the shipping isnt goin to be cheap either though.

[Bushwacker]

The professional fiberglass guy that advised Skip & Carla on their 21 restoration recommended drilling vent holes to allow air pockets and excess cabosil to escape from back of core, so we did that. I've also seen that recommendation elsewhere, maybe on the Coosa web site. Some bubbles and cabosil did ooze out of most of the holes, so I believe it's a good idea. Using a serrated edge tile trowel on the cabosil before installing core may provide a similar benefit by providing space for the putty to move around when the core is clamped against transom, but we did both. Holes were drilled in a random pattern with fairly large spacing; since they do add a potential weak spot you don't want them lined up so as to create a "tear-along-the-dotted-line" scenario! I believe Carla posted some pics after we installed core, so you can search her posts to see what it looked like.

[gofastsandman]

The original transom on my `89 20 is 2 3/8" thick total.

Before you buy marine ply, call the manufacturer to be sure the glue used is NOT oil based, as poly will not bond well at all! As suggested go to a quality yard to buy. I paid 60 for a 1/2" sheet.

[bigeasy1]

I bought my marine grade fir from a plywood wholesaler,who knows what they are talking about.
I've used them several times on several project boats,and it's top notch stuff.It's regular marine Fir,from an American mill.No oil base glues or coatings.

You can see from my pictures,that there's no voids.

As for drilling holes,i didn't do that,although i can see the reasoning behind it.After doing four other transoms,and having no problems,i did it the same as always.Thickend epoxy,and a flat floor and lots of weight.I should mention,that i always prime both faces with a coat of epoxy resin,and let it kick,before I apply the thickened glue coat.
It seals and primes the wood,and keeps the glue coat from being sucked in to the wood too far leaving too little glue,which would make a weaker bond.
Don't let it cure too long,just till it's cured to the touch,but young enough for the glue coat to chemically bond to it.

You can see the glue joint is solid,and the same thickness throughout.All the excess that i cut off was the same as the picture.


If you are going to use plywood,do yourself a favor,and stay away from Lowe's And Home Depot.I know it's not all of them,but lots of the employees at these stores have no idea of what they're talking about,and their product knowledge is poor at best.
Go to a specialty plywood distributor,or a quality independent lumber yard,who can order it for you from a specialty plywood wholesaler.

A few weeks ago,i went to Lowe's, only because it was sunday.I wanted a sheet of 3/4" AC Fir.Of course i couldn't find it,They had some weird type of plywood with odd grade stamps.
So i ask a clerk in the lumber department,Do you have any AC Fir? His answer was, "No you won't find that anywhere locally".
This idiot had no idea,.I went to a local yard on Monday,and got what i wanted without a problem."Enough said.

[chrisvazquez1]

john123, where did you come across that template for your transom? im thinking up a strategy for converting my transom to a closed style but have figured out how to "arch" the top of the transom. any suggestions?