Well....here she goes.
I built this form a couple of weeks ago and have been chomping at the bit to give it a try. I was planning on using the firehose method but haven't chased down a hose yet. So...I decided to put some holes in it for clamps and just do a glue up with clamp pressure. I used Titebond III for the glue and let it dry for about 24 hrs.
The lams are hickory/jatoba/hickory and a purple heart wedge. The riser is walnut/purple heart/padauk.
I had read that hickory isn't good under compression, but I had a couple of thin lams that worked out well for the belly so I tried them anyway.
Here it is in the form -
(http://i78.photobucket.com/albums/j96/AKmud/motorhome055.jpg)
(http://i78.photobucket.com/albums/j96/AKmud/motorhome057.jpg)
Out of the form things were looking good, it was straight and had a great R/D.
(http://i78.photobucket.com/albums/j96/AKmud/lam5.jpg)
(http://i78.photobucket.com/albums/j96/AKmud/lam.jpg)
(http://i78.photobucket.com/albums/j96/AKmud/lam4.jpg)
I measured 10" out from center and then tapered the limbs down to 1/2" with the band saw. Floor tillering showed that it was still quite heavy...
I cut in some string grooves and put a long string on it. With 9" of pull, I was showing 50#. I'm looking to end up in the low 50's.
I started to do some scraping and shaping of the limbs and got her to a low brace (about 4"). Eventually I was able to get 50# at 23" then the inevitable happened....
(http://i78.photobucket.com/albums/j96/AKmud/IMAG0396.jpg)
My love of hickory took a hit last night... Soooo...I ended up sanding off the hickory belly lam and finished roughing out the handle and sight window/shelf. When I put it away it was 30# @ 29" and I put about 20 arrows through it. It had a good cast for the low poundage but I still want to get into the mid 40's if possible so I am contemplating gluing another belly lam on but I am limited on my wood choices.
Would ash or red oak be a decent choice for a belly lam?? I was wanting a light color for contrast so how about white (paper) birch?
I think hickory would be the better choice of your options and it failed. Maybe a little less aggressive profile? Can you get an osage slat? It would have less contrast be still be pretty.
Well, I found a site that said oak was fairly good under compression and I just happened to have a 1x2 of it. I just ground out a lam and have it glued up. Hopefully it will work.
how thick is the belly lam?
You need a compression strong wood for your belly lam like osage, ipe or yew. Hickory just doesn't have the compression strength for the job.IMO It is a great backing material!
That's a whole lot of R/D for your first. Use ipe or osage for the belly next time.
Aznboi, the lam was cut at 1/8" on my table saw then sanded a little to true it up.
Pat, I read about hickory not being the best for compression, but I had these two lams laying around so I threw them in the pot (against my better judgment...). I love hickory for self bows and backing though.
Apex, being in Alaska, I don't have access to many exotic woods (ipe and osage are exotics up here in the land of birch/spruce). I'm keeping my eyes open for a bigger variety but I haven't found a supplier for them yet.
The form was built with 3" deflex (measured from the back of the bow) coming back to just about even with the back. Originally the form ended up 1" positive but it was 72" long. When I shortened it up to 64" it ended up being just shy of even with the back.
I have more materials I picked up yesterday for a couple new forms so I will be playing with the shape on these. I'll probably go a little more relaxed on the next one, this one is pretty radical but I have learned quite a bit.
Annnnnd........back to the drawing board!
I pulled the clamps off this morning and did some sanding. I got things looking pretty good and braced it at 6". I put it on the tillering wall and was exercising the new lams when she came apart. Nothing real dramatic, but the jatoba separated at the top of the sight window I cut in. I'm guessing I got a little carried away with the window even though I stopped short of a center shot. 1 1/2" wide is too narrow to cut in a deep window.
Anyway...off to the lumber yard for another try!
Keep at it! It will be a fantastic bow when it comes together.
Here are a few pictures of the sudden dis-assembly (it had a nice profile till this point...)
(http://i78.photobucket.com/albums/j96/AKmud/archery/lambow001.jpg)
(http://i78.photobucket.com/albums/j96/AKmud/archery/lambow005.jpg)
(http://i78.photobucket.com/albums/j96/AKmud/archery/lambow003.jpg)
cut too deep...arrow pass should have widen to fade width about where the red meets purple on the handle.