Epoxying the Transom

Well, this was nearly a disaster.

I had dry-joined the planks numerous times to ensure that the join was close to perfect.

The splines were a little tight, so I did a couple of fine runs with a plane until they were a slip fit. Then, as advised by JB and West Systems, I planed a little more off the back of the splines to leave room for the required epoxy bed.

But thinning the splines down from a tight fit allowed the two planks to come together with one just proud of the other. However, I found with judicious placing of wedges, clamps and heavy straight edges, everything came back flush.

So I donned the biological warfare gear again and mixed the epoxy. I had watched my fibre-glass-boat-renovating son mix the epoxy for the laminated stems and so imitating Tim’s technique, all went well. You taught me well Tim.

With a brush I wetted out the spline groove and faces. 

I then added the filler and saw dust to the epoxy to get a good peanut butter viscosity. I found a putty knife easy to get the epoxy into the spline grooves. A test run showed that I didn’t get complete squeeze out, so I removed the splines and added more epoxy. A lot more. Squeeze out is good, so I’m told. I then refitted the splines into the groove, but found I could only push them a little way into the groove by hand, (because you can’t have to much epoxy) but never mind the clamps would pull the planks together and there would be fabulous squeeze out.

So with the two planks pushed together flat on the bench I started winding up my new Veritas Surface Clamps. Well, the planks just would not go together. This was when I realised that verities surface clamps are for holding pieces on the bench while you work on them. Not for clamping transoms. Wind as hard as I could, there was still a 2-3mm gap between the planks. But there was no need to panic, as the epoxy wouldn’t go off for another 20 minutes. Not enough time to rush out and buy some decent clamps, the ones I discounted as not being needed.

Fiddling and winding, the epoxy slowly, very slowly, oozed out of the end of the splines and a mist from between the faces. More clamping and then . . . the two planks started to pop up off the bench at the join. This was looking like a disaster in the making and I could see myself having to saw the joint section off my precious Huon and start again.

But then I noticed that as the planks rose, the epoxy started to find an escape route between them and I could wind the clamps in a little more. So I Clamped a section of aluminium square tube across the planks, spaced so that it would stop them rising more than about one cm, and wound the clamps in until the planks rose to just touched the aluminium square tube. I then clamped the aluminium square tube down to push the planks back flat on the bench. The surface clamps held. The tremendous leverage applied by the aluminium square tube pushed the planks down and they slowly came together . . . with a huge squeeze out from the end of the splines. Yes. I did put a lot of epoxy in there.

Repeating the procedure I finally had the planks snugged up tight.

A couple of more bits of square tube across the planks ensured the result would be a nice flat transom.

The rest was a breeze, watching the squeeze, which got me thinking about the advice, “do not over tighten the clamps, so as to leave some epoxy on the faces.” But if you leave a bed on epoxy on the faces, you you will have a gap and not a flush tight join. Hmmmm.

So I adopted the rationale that the space I left around the splines for the epoxy would do the ‘adhesive’ job and the thin epoxy between the visible face edges was only cosmetic.

I think I need a single malt.