Plywood base for a form


WCHA member #8947
I know I saw on the forum some time ago a posting about starting a new form with a plywood base (I believe it was from a post by Mr. Doug Ingram). As I'll be starting a new form in a little while, I wanted to get a little more description on how this is done - I realize it's because of the predictability/stability of plywood as a medium, yes? Do you laminate several pieces together? Run some vertically as well as horizontally? Just trying to go about this the correct way. My apologies if this has been discussed ad nauseam here. I check this forum almost every day and can't remember seeing a whole lot about it in the past few years... Thanks in advance. You all are the best.
I'll chip in

but don't weigh my opinion too heavily. I've built one form with help. My station molds are 3/4" birch plywood. My base, or strongback is a straight grained 2" x 6" plank. It has a dado down the length and a 3/4" x 5" plywood edge glued/screwed into it to form an upside down 'T'. The station molds are notched to fit over the 3/4" vertical part of the T. Once everything is square and plumb it is then braced with small pieces of 3/4" ply. I see no reason why you could not use a plywood strongback for mounting the station molds, similar to strip construction. Once it's braced and the strips fastened, everything ends up pretty solid. Very solid.
I don't remember how I built my strongback, I think it was a pair of 2x10s with a layer of 3/4 ply screwed to the top acting as a plate to hold the two 2x10s together.
I think you may be referring to a post with a torsion box as a strong back. A lot of strength for weight. May be over kill or not. Torsion boxes are pretty cool and fairly easy to build, just be sure that you build it on a flat surface or you will build a curve into the box.

While I say easy, I leave out time consuming and tedious as compared to taking a couple of 2x10s and screwing them together. You can adjust your stations as you attach them to the strongback to compensate for any irregularities in your strongback.
Yeah, I thought the initial reference was to something a little different than the strip-built style of "box" strongback... But perhaps you're right, and I don't necessarily think that will be warranted in this case. As long as you get the strongback straight, maybe it doesn't matter how you make it....
Hi Nick,

I don't remember the string you are referring, but assuming you are meaning "form" as in build new W/C, I would check out a few of the pro's sites, maybe one of them has info on building the form. And I believe Alex Comb even has a video of building one.

But, if most of the pros are like Alex, then the forms are a solid "plug" that he sets on stands of some sort, saw horse, table, dedicated stand, something.
The form or plug is rigid unto it's self. (He keeps 6 or 8 of them in a lean to.)

With that said, I see no reason way you couldn't or shouldn't start with a plywood torsion box as the main inner structure for a form.

On the long shot that you are thinking beam to build one, I could be talked out of mine, but it's very heavy and will take some work to get it out of the basement. :( (I don't believe I'll ever make another striper.)

Hey Dan - do you mean in your basement here, or in Michigan? Ha - I'm only kidding. Hope you're doing well with all your "transitioning."

I've built a wood/canvas form already, so I know roughly how to do it. I just thought I remembered seeing something about starting one a little differently than I had built my other one.

Thanks for all your help, and sorry to be too ambiguous to begin any meaningful discussion. I'll keep you posed with pics as I progress, if you're interested. I'm planning on building a smaller boat - 13-14' - that my wife can haul down to the lake relatively unassisted. Should be fun...
Morning Nick,

Yes, here in MN, I'm back in MN for a while on a temp basis.

And yes, please do keep us posted on your progress.

Are you going to make this weekend? If so, we'll get to put faces on names, as Barry "talked" me into going.

Welcome back, temporarily, then. Alas, I'm not going to make the paddle this weekend - I am scheduled to work. It's especially unfortunate since I met my wife working at a summer camp where we both led canoe trips on that section of the Namekagon/St. Croix. It's a lovely piece of river, and I'm sure you'll all have a great time. Raise a glass post-paddle for me, and say hi to everyone.