Hybird MF14

[Fuzz]

That is going to be pretty

[OrangeQuest]

Very nice!

[Jeff]

Chenier, very nice work!! Jeff

[Chenier]

Bottom panels.

This was a bit of head-scratcher. The MF14 US plans that I’m using assume an 8’x4’ sheet of plywood. However it turned out the marine ply from my local wood junkie is metric. The widths are identical but the lengths aren't - my ply is 250cm long, about 98.5”. I needed to figure out how to correct for the “incorrect” size of my ply.

The MF14 (p.B244/5) uses different offsets from the aft end of a plywood sheet to set out the deck, side, and bottom. (Measurements on the Moonfish start from the transom.) Studying the plans it became apparent that the offset for the deck placed its butt joint (between the fore and aft sheets of ply) right at the front of the cockpit, on Frame B. The bottom has greater offset so its first half is shorter, placing the joint in the cockpit behind Frame B. The side panels have no offset so their joint is somewhere ahead of Frame B. Aha. This staggers the joints so they don’t all line up and create a “Tear Here” line across the boat.

Since the deck and side panels of this particular MF14 are strip-built cedar, they each end up as a continuous panel with no joint in the middle. Therefore I “moved” the bottom joint a few inches ahead of Frame B by using less starting offset. This gets the butt joint bump out from underfoot in the cockpit and hides it under the deck. I won’t need to spend time fairing it out later on.

For what it’s worth, the prior Moonfish builds that have been well-photographed also ended up with a bottom joint ahead of Frame B. I’m not sure why. At least it seems to work OK:
https://forums.bateau2.com/viewtopic.php?f=13&t=20214
https://forums.bateau2.com/viewtopic.php?f=14&t=58206
https://forums.bateau2.com/viewtopic.php?f=13&t=62869

Here are my two bottom panels, stacked and cut. Per walkabout_slp’s recommendation (last thread, above) I cut them slightly wide on the chine side and will trim to fit at installation.

[Jaysen]

Did you consider just cutting off the extra length to make the sheets the size to match the plans?

A bit wasteful but ...

[topwater]

I don't get the problem all the plywood sold here and used to build and design these boats on this web site are metric

[walkabout_slp]

Yes I would recommend cutting the bottom panels slightly outside of the true cut line. Unless you are meticulous your assembled frames and side panels are not going to be perfect. Having the bottom panels at least 1/4 larger enables you to trim them to the exact shape of the assembled frame. I wish I had done this. I did not and had to fill the joints with thickened epoxy in a few sections.

I also do not think it maters where the fg splice falls for the bottom panel as you will be adding a full layer of fg on the hull and in the cockpit once the hull is assembled.

Are you going with a clear coat on the bottom of the hull and in the cockpit? Or is it going to be painted since it is ply and not strips?

[Chenier]

Did you consider just cutting off the extra length to make the sheets the size to match the plans?

Yes, but as you mentioned it's a bit wasteful. Also, once I found the dimensions weren't what I expected my insticnt was to try to understand what was going on before cutting anything. Besides, as topwater says, I might have been wrong.

I don't get the problem all the plywood sold here and used to build and design these boats on this web site are metric

The build notes for the MF14 call for "Standard sheets 4x8 (122 x 244mm)". That should be "cm" BTW.

Are you going with a clear coat on the bottom of the hull and in the cockpit? Or is it going to be painted since it is ply and not strips?

Paint!

[OrangeQuest]

If you measured everything out before cutting should not matter how long the sheet is or am I missing something. If you measure 240cm from point A to point B you either have 4cm left or more/less. But the measurement should still the example 240 cm

[Chenier]

That's true - the Moonfish bottom panels are 174 1/4" long. The plans, though, explicitly say to begin the cut for the transom offset 16 3/4" in from the end of the sheet. Where you start has to make some kind of difference or the plans wouldn't be that specific. So I tried to figure out what I was missing.