LM 18 with Tunnel Build - Texas

[fallguy1000]

One approach is to cut those notches a little bit over depth and then shim them back to level. You won't rely on those notches being the exact right depth when you assembly the boat, you'll be spacing the stringers and frames off the bottom and spacing the stringers and frames from each other to ensure you have gaps everywhere. This ain't shaker furniture.

I supported my transom with a "dead man" to take the weight of the stringers, just a 2X4 clamped on that ran to the floor. I screwed some 2X2 to the back edge of the stringers and then screwed the transom to the 2X2. This worked well for me and required no clamps.

The transom is actually going to be attached to the sides and bottom at this stage so it's position and fit is a little more important than the stringers and frames which are only acting as molds at this point. As long as your panels are fair when they are stitched, the molds are doing their job.

One thing I messed up was over-tightening my side-to-bottom stitches, causing the side panels to flare at the sheer, resulting in a lot of extra effort to get them into proper shape after I flipped. Beware large gaps between your molds and side panels at the sheer and correct before glassing.

That's my .02, worth every penny!

Great post and I learned something, too.

[GrantL]

Thanks everyone again for the great info and help along the way. I have the boat framed up now and fixed to start laying and stitching the panels.

1 questions on the puzzle joints - can you wet with regular epoxy on the grain ends of the joint and then after it kicks it, apply some EZ fillet to the joint? I don't have any wood flour so my only options are either all epoxy resin or a combination of epoxy/resin and EZ fillet to join the puzzle joints. Thanks!!

[fallguy1000]

You cannot bond with all epoxy because you will end up with a bondline flaw. Epoxy bondline is not super strong and subject to limits. Then if you have a void; it is much worse as a weakpoint of up to zero ultimate strength may exist.

Use the ez fillet or some epoxy putty; not sawdust. And after precoating..

A small correction. All epoxy bonds can work if you can be certain no bondline flaw exists. The puzzle joint is also far more forgiving than an end to end bond.. Foam core is often end to end bonded with epoxy only, for example, usually under vacuum.

[GrantL]

Ok thanks!

So do you recommend to wet first with epoxy and then EZ fillet over or just use EZ Fillet only straight on the wood/joint?

[fallguy1000]

Ok thanks!

So do you recommend to wet first with epoxy and then EZ fillet over or just use EZ Fillet only straight on the wood/joint?

Prewet until tacky..takes an hour. Then use putty.

[GrantL]

Thanks, will start doing the puzzle joints this week.

1 more question - there was a small area on the edge of one piece of the plywood (puzzle joint) below that came de-laminated. It looks like some oil or substance was dripped on it and it peeled back at least of of the ply layers. Do you think this is fixable by just sanding out the affected area and filling in with EZ fillet? Or recommend using something else? Or should I get a new CNC piece cut and sent? Thanks and pics below.

[fallguy1000]

Oil is very bad for epoxy work.

If you received it that way, I'd give them a call.

If you did it and don't want it to cost you hundreds of dollars, then you'd need to remove the oil soaked section with a utility knife and sand it out and acetone wash and piece it back in with fiberglass and some thickened resin on the edges which would be tapered to the good wood. If you go this route, measure the cutaway thickness. A piece of db1700 is about 0.035". But a lot of work to repair..unfortunately.. make the glass repair a bit thinner than the original and use some fairing compound prior to your glasswork to make it all fair.. If you do a repair, I can offer you more details if you are confused.