Batboat Rebuild: Day 23 June 4, 2009

This is the day I had been waiting for since last October. Nothing had to be thought over because I had been rehearsing everything in my mind all winter. It was time to put in the transom.

I woke up, had breakfast, suited up, grabbed all the materials, and got to work with no hesitation.

Here is the 1708 biaxial fiberglass cloth I cut from the template last year. I mixed up a large batch of tooling resin and wetted it all down and squeezed out all the bubbles with the fiberglass roller.

I let it cure for a little bit as I got the plywood ready. I wanted that fiberglass cloth to be a little rigid before dropping the transom in fearing it would ooze around while adjusting the wood to fit in place and from the pressure from using the drill, clamps and bolts.

While it stiffened I rehearsed exactly where every clamp was suppose to go. I did this the evening before but one final run through couldn't hurt. :)

Once the resin was tacky and cloth had stiffened a little I mixed up a large batch of "Peanut Butter." This is what boat restorers use as a low cost adhesive and filler.

Here's how to make it. Blend polyester resin and its MEKP activator good then add a lot of wood flower (fine saw dust) and mix. What you'll end up with should have a peanut butter consistency, depending on how much wood flower is added.

The idea is to permanently bond the new plywood to the hull. The fluid-ness of the peanut butter will fill in the voids created by surface inconsistencies between the ply and fiberglass hull when clamped together. The excess peanut butter will ooze out from the corners of the ply as pressure from the clamps increase, thus filling in those spaces, as seen in the below images.

Moving quickly, I spackled a generous amount of peanut butter along the parameter of the transom.

Then I spread on a thick layer of the peanut butter to the plywood. The thickness of the brown goop ranged from around 1/8 - 1/4 inch.

I ran out of it and hurriedly mixed up some more.

There is no room for messing this up. If the transom was bonded in wrong I'd have to start all over again from scratch by grinding down the hull and buying new marine grade wood.

For some reason peanut butter does not seem to harden as quickly as plain old resin but I had to work and move fast. Everything had to go in perfect. After a few adjustments it slimed in superbly.


Having the ply in place I clamped it in at the center then drilled holes where the splashwell and bilge holes are to tightly fasten it in with scrap wood and a couple of nuts and bolts.

Starting from the center, the various clamps where mounted and screwed tight. A good deal of peanut butter oozed from every corner exactly like it supposed to do.

I think 10 clamps were used. Several were bought at Harbor Freight the night before but I really could have used a couple more.

The rear of the structurally unstable fiberglass hull had spread under its own weight after I cut off the splash well last year. I put the well back in temporarily to bring it back to its proper shape while the peanut butter cured. When hardened it is not flexible.


No stone was left unturned because there was no room for error. This had been thoroughly rehearsed for months.

As it cured, I smoothed the peanut butter down and used some to fill in spaces.

Looking down in to the hull

It oozed out from the pressure of the clamps perfectly. No evidence of voids or air pockets between the new plywood and hull.

A couple hours later the peanut butter was hard and I took off the splash well.

The outside of the transom was hot to the touch for hours from the curing of all that polyester resin.

When I started out I had a useless Batboat with a rotted transom. It was cut out with a grinder but I went too deep and took out most of the original fiberglass down to the gel coat and had to rebuild the hull. For that 1.5 chopped strand mat was glassed in. Later, peanut butter was spackled in and sanded down to make the surface smooth and another layer of 1.5 oz was laminated on top of that. 1.5 oz was added to the transom plywood and today 1708 biaxial was laminated into the hull. Both were bonded with peanut butter.

The result is a transom that is better built and much more structurally stronger than when it came out of the factory 40 years ago.

BEFORE
(red outline shows the original transom area)

AFTER