Wooden Boat People
By McKenzieDriftBoat.com
"Will this scarf hold?" (I know, I know, but gotta ask)
I'm building a Honky Dory. At it's widest, the bottom panel of the hull is 57", so I need to scarf two small pieces to widen the 16x8 scarfed piece in the center of the boat.
Unfortunately, I screwed up my glue job, so what was going to be an 8:1 scarf is now a 6:1 (maybe a 7:1 in the best spots) scarf with the feathered edges not touching. In other words, using 12mm Okoume plywood, instead of having a 4" glued overlap, I've only got 2.9" of overlap.
So, here's my question: Can I make this work by doing the following:
- Filling in the gaps around the feathered edges with West Systems epoxy and 403 adhesive filler.
- Kevlaring the exterior side of the panel (I was going to do so anyway).
- Fiberglassing the interior side of the panel with 6 oz glass (and possibly adding a second 6" strip over the "weakened" joint.
I know it's a bit of a "what's your gut say?" question and I know the right answer is to redo the entire bottom panel. But financially, I'm sorta hitting that breaking point. And given that this is my first boat, I'm not totally sure I'd get it significantly better redoing the scarfs...
Heck, I know it will add some weight, but I'm tempted just to add a butt joint on the interior face of these joints, as they will be hidden under the rower's seat.
Recommendations? Warnings? (I've read a bunch of threads on scarfing and I know that ideally, I'd have a 12:1 scarf, but I'm at where I'm at.)
Thanks,
Sean
Views: 307
Replies to This Discussion
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Permalink Reply by Eric Loudenslager on
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I believe you will be OK with a 6:1 scarf on the edge material. I built using the MRB instructions, but modified the plans and built a hybrid between the honky dory and beavertail. The bottom is 52 inches, so I only needed to add a 2 inch strip on each side. I butt joined the strips to the 16 x 48 bottom panel, and used kevlar on both the interior and exterior. The butt joint used System 3 Gel Magic epoxy adhesive.
Dynamite Payson had an article where he butt joined plywood and laminated it with epoxy and fiberglass. He argued it was strong enough.
One of the reasons for scarfing is to produce a board or panel that will have a fair surface when bent on a hull. Butt joints would have a hard spot at the joint. Since the edge strips on a 56" bottom are not being bent on the axis perpendicular to the joint, creating a hard spot is not an issue. The scarf you have is probably enough.
Yes, fill any ragged edge with fairing epoxy or fillet - I would used fairing since it will sand easier and you really don't need the strength of a fillet.
Per the MRB instructions, you should plan on two layers of cloth on both sides of the bottom panel. I put one lamination of kevlar on the interior side of the bottom panel before bottom installation. Then did the exterior, and finally, when working on the interior added a second lamination to the interior.
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Permalink Reply by Mike Baker on
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