Hickory Backed Mulberry Buildalong

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9/9/06 - Thinning the Hickory

Today I took the mulberry off the form. Tips are mostly aligned as seen in the pic. I thinned the hickory down on the belt sander, which took a while. The backing was 3/16 when I got it and I wanted it 3/32 at the handle. I eventually got there and then tapered it out to 1/16 at the base of the recurves. Though I've read that it isn't critical with hickory, I still only tapered the glue side so that most of the grain violations will not be on the back.

Apologies for the dark picture. The tips are mostly aligned. I just clamped it flat to a board and put dry heat on the handle and they are perfect now.
I should have taken a few more pictures of this, but I'll describe it. I'm thinning the back down with a 50 grit belt. I flattened the bottom of that block smooth so that the backing would slide easily under it while I was pressing down and pulling the backing from handle to tip. When I had it almost to size, I would hold the block at 90 degrees to the backing, so as I pulled it out from under the block I could feel the peaks and valleys. Finally after it was smoothly tapered I made marks every 5 inches and took a caliper to each side until they matched.

9/10/06 - Prep for glue

Getting ready for glue! I decided to put an extra strip in between the backing and mulberry. If nothing else it will help stiffen it up and look cool at the same time. Looking again at how short this thing has become, it makes me wish I had set the curves farther towards the tips. I will likely be cutting off at least an inch anyway, as they look too long to be stable. Ah well, learn more on every build.

I'm hoping to have everything ready for a glue up tomorrow.

Here are all the parts.

9/11/06 - Mid lamination and Form

Well, the glue up didn't happen today. I made that middle lam to go between the backing and belly. It started as 1/4 inch in the center but ended up 3/16. It is 17 inches long. I used the basic dimensions of JD's form. The ends and center post is two 2x4's high (3 inches) and the midlimb is 1-1/2 inches high. The midlimb posts are 13 inches out, and the ends are 26 inches out. I may put something about 1/2 inch on top of the midlimb, the 1-1/2 inch deflex looks pretty intense. I'll decide tomorrow after trying a dry run.

Ain't it pretty? I guess other than that this picture has no point.
Here's a pic of how I worked the taper. I also took the pic because I was lacking a picture above of how I worked the hickory backing down.
... taking caliper measurements for every 2 inches to make sure the edges and sides match.
Finished. The edges are paper thin.
Ok, the form. It will be built in 2 tiers of 2x4's. I want all edges to be square with the centerline, because the bow will be resting on edges during glue up. I drew center lines across the 2x4's that were square with the cut edges.
Here I'm putting the second tier on the ends and center. I started with the ends and made sure to maintain the centerline, then lined up the center one with the string.
Finished. It may be overkill, but I like having the centerline marked from one end to the other, and knowing that all edges are 90 to the centerline. It eliminates the chance of the limb being torqued by sitting on an edge that isn't straight. I'd hate for this to go wrong because I didn't spend the extra hour lining it all up.

9/12/06 - Glue up

Got a late start today, but I managed to glue it up. I marked up the surfaces with 36 grit, then raked my pull saw blade over them. Then after a dry run, I cleaned all surfaces of dust and oil with acetone and glued up with urac. Stacked up the handle and clamped it down, then clamped from the handle out. I don't have very many C-clamps, but I do have a *lot* of spring clamps from building a cedar strip kayak last winter.

Prep stuff, 36 grit, pull saw blade, wood.
I haven't watched anybody prep wood before. Is this about right?

Update: I'm told this was good :)
Buttered up. During the dry run I decided to put 1/4 inch pad over the midlimb so the deflex is only 1-1/4 inch. I'm hoping it will relax to 1 inch. I forgot to do it, but when gluing flat surfaces like this I would normally put an extra bead down the center. That way when it is clamped it will push out towards the sides and eliminate bubbles.
Told you I had a lot of spring clamps ;) I also had a bunch of 1-1/2 inch squares of plywood for padding cut up from when I was building the kayak. I'm not too worried about starving the joint, these clamps aren't the kind that will sever a finger like those industrial strength ones. Anyhow, I clamped the limbs handle to tip first, then clamped the midlimb down for the R/D.
Here's how I did the recurves. Not perfect, but it worked.
Into the hot box. You can see I screwed up the alignment of the backing a little. It was only off by 1/8 inch. It went to the left on this tip and to the right on the other, so I'm going to assume the center is ok and it just rotated a bit. I don't think it's worth unclamping and putting more glue on to reclamp. I should have clamped the tips before working down the limbs, in retrospect.

Those are 2 parallel wired stovetop elements wired in series with a light bulb to limit current. I'm poor, so I have to work with what I can find in the basement ;)

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