Primitive Archer
Main Discussion Area => Bows => Topic started by: Aaron H on July 22, 2015, 12:34:40 pm
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So I have decided to embark on my first laminate adventure to see what all the hype is about. Haven't started anything yet, but I thought I would get a solid game plan together first. This last weekend at mojam Bob Barnes let me shoot his 50# reflex / deflex BBO and I was very impressed by it's speed. I picked up a nice piece of bamboo, and I have decided to use it as my back. My questions follow:
In your opinion, what is the better belly material, osage or juniper (virginianas)?
What is the best material for a power lam? I was leaning towards sapele (aesthetics), is this a good option, or would you recommend a different wood? I want speed and performance my main goal, followed by looks.
I was thinking about using bird's eye maple for my riser, thoughts?
How long do I make my power lam?
Thank you for any advice you can offer,
Aaron
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Aaron, osage would be better in my opinion. Any wood can be used for a power lam. It is between the back and belly, in a non working area so any wood should work. It is used to keep the handle area from bending, preventing the handle riser from popping off.
If your belly lam is 5/8" to 3/4" thick a power lam isn't necessary. Just use the full thickness at the handle and reduce the limbs as you tiller. Leaving the handle area thick will prevent the handle area from bending which will prevent the riser from popping off
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Have you got TBB vol4? It has a chapter dealing with lam bows and they make a r/d bow using BBO. I think it's a great bow design to start with.
If you don't have access to the book i'll dig mine out and give you all the specs.
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Despite it's name a powerlam doesn't do anything for performance. It's only purpose is to provide stiffness to the handle.
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Yea I do have vol. 4 Mike. I will look through that chapter tonight. Thanks.
Thanks Gordon and Pat
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Actually, a powerlam can serve another function. I use them to increase the overall thickness of the limb and to create a mild r/d when I glue-up. To explain, I get 4/4 Ipe and will rip it in half so I get 2 pieces,about 7/16 thick. Then with about 1/8 - 3/16 (final thickness) Bamboo I will glue an 1/8" thick "powerlam", deflexing down about 2" (my form is one big arc). The lam extends, 6-8" down each limb plus the handle area and is tapered from full thickness to nothing through the 6-8" area. Then I glue the belly wood (Ipe or other) while reflexing about 2". Then final shaping and tiller as usual.
I do pre-shape all pieces to within about 1/16" of expected finished dimensions before any glueing.
When all done, I often have a mild 1" deflex, 1"+reflex bow.
Ken
PS I pick powerlams mostly for aesthetic reasons, but I do try and use easy to sand, shape tight grained lower density woods. Maple, Paduak, Yellowheart, etc.m It also helps if the local Rockler or Woodcraft has the wood available in 1/8" strips.
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I pretty much agree with all the above posts. I like to use a power lam because it allows me to use a thinner belly lam with no risk of the handle popping off, so it is economical. I prefer at least 3/4" thick before I glue on a handle block, a 3/8 belly lam and a 3/8 thick power lam will give me two slates from one 3/4" board. I also prefer to deflex it through the handle when using a power lam, much nicer design than deflexing out of a straight handle.
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Awfully tough to beat osage for the belly lam. It's always my first choice.
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What about a high quality glue, or do you guys just use tb3?
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As far as glue tight bond is great, but unless your fit is perfect use a bow epoxy like smooth on or similar, plus you will get a lot more work time
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I've used TBIII with good results. I've also used Urac185 with good results. Urac was discontinued a few years ago and was replaced with Unibond. Very similar to Urac and probably one of the best wood/wood glues there is. I've not used Unibond but will when the time comes.
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Unibond 800?
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I've never used it so I don't know about the 800.
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I really like this build along.
http://www.primitivearcher.com/smf/index.php?topic=6916.0
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Yea, thanks Blaflair2. I was reading that yesterday. Unless I missed it though, it didn't say what glue he used, it certainly doesn't look like tb3.
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I use tb3. I think it says he uses smooth on
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All good lam builders know powerlams are where it's at. I make 16-18" long and like others said they allow you to add more deflex, use a thinner core, keep your handle strong even if it works a little, and they look good. I only use smooth on in my lam bows.
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Ok, I did some research and for those of you who are interested it is Smooth On EA-40. It sells for $35 for a 2 pint set. It has gotten great reviews
Or Unibond 800, which sells for $16 for a quart.
Both companies claim they are excellent for laminate bow makers
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Smooth on is bullet proof. Those two little pints will last you for seeeeveral bows and it's what most professional fiberglass lam builders use.
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Yea, from the reviews I read, seems people like the smooth on better
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I've used Unibond and Smooth On to glue up wood lam bows, and they both produce great results. Smooth On seems to have a little slipperier texture but that's the only difference I've noticed. I tape the lams down either way, so it's not an issue.
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I've never used the Smooth-On (...'cause I'm cheap!) but I can report that both Unibond 800 and TB3 work well. Unibond 800 is certainly superior to the TB3, ...but again TB3 is much cheaper and more readily available! ;)
OneBow
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Urac was considered the best wood/wood glue. I think it was used to make wood laminated airplane propellers. Unibond is supposed to be as good. If you have a glue failure using Unibond, Smooth-on or TBIII it is because you didn't do something right. Read and follow the directions with any of these glues and you shouldn't have a glue failure. I've not used Smooth-on but I have used the others and never had a glue failure.
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I use the smooth on if I am using a power lam. I use the tightbond for simple backed d/r bows. When I am backing with tighbond I rub the glue into the wood with my fingers, especially with ipe and some of the tropicals.
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I've used urac for years on splices so naturally I decided to use Unibond 800 recently as I've started making laminated bows. I like it as much as urac no doubt. It seems to have a great shelf life and it's easy to mix by weight. Also it is light colored so if you do have a little glue line showing its not as noticeable. But most of all it doesn't require a hotbox. So for someone just testing the water with lam bows it might be the best option.
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I have used TBIII, and smooth-on, both with good results.
Never had a delamination with either.
I don't recommend TBIII for tri-lam glue ups because the glue is water based and it adds ALOT of moisture to the wood. If you do use TBIII to glue up a tri-lam, treat it like a fresh cut stave and let it dry out for a month or two. It may seem extreme but go and weight your blank every day after glue up and see how long it takes to stabilize. It will shock you. Anything recently glued up with that much TBIII is basically dripping wet.
For this reason I try to limit my use of this glue.
Smooth-on is like liquid gold in bow building. It has long working time, there's no rushing. It doesn't smell too much (it's not roses, but you don't need to be outdoors or anything). The glue is also pretty forgiving of surface prep I find. I have more than one bow where the lams essentially got zero surface prep after being cut on a table saw or jointer with no problems. And let me be clear, you do not need to heat cure it. It cures faster with heat, and maybe stronger, but it just is not necessary in the world of wooden bows. If it's hot out I'll put my glue up in the sun, and that speeds things up a lot, but I've also just let it cure on the form for 24hrs at room temp, maybe 48hra for safety sake.
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I just tried to google Smooth-on, is it the "EpoxAmiteŽ 100" that you use?
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Ea-40 smooth on epoxy