Sister r/d longbows build along and questions

[Jstick87]

Hi! I am a long time lurker of tradgang, and have built three bows previously, but the last bow I built was 7 years ago. I am finally getting back to building and starting off by making two bows at the same time, one for me to shoot and one for a co-worker. I have been taking pictures as I go with the thought that I might do a build along, and now that I am stuck and needing advice I figured I would take the plunge!

The bows are bamboo backed Ipe, one with zebra and bloodwood riser and power lam, the other is the same except it will have maple and bloodwood riser and power lam.

I found the Ipe at a local woodworking shop called called CU woodshop, and they agreed to cut two slats from a nice piece that I found for $20 each. The bamboo was from echo archery, the zebra wood block was from Big Jim's bow company and the bloodwood was from Bell Forest Products. The hard maple was part of a left over box at a local hardwood flooring store, and they gave me it for free. (If sourcing my materials is in violation of the board's promotion policies, please let me know and I will edit it out)

The first step I did was use a friend's table saw to get all my materials as close as possible to the needed size.

I then made a template from posterboard based on dimensions found in Sam Harper's boo backed ipe build along at poorfolkbows.com

   
 

I then took my hand held belt sander and taped the trigger down and attached it to a sawhorse to remove wood and make an even taper.

 
(my humble work bench)

I followed the same process to taper the sides the same way as the belly side of the ipe. I came to the conclusion I would need to taper both before my glue up because I am shooting for an aggressive reflex-deflex profile.

When I was satisfied with my ipe pieces, I clamped them to the pre-flattened bamboo pieces. Then I marked around the edges and went back to the belt sander.

 

 

If you look closely, you can see that I labeled each limb and the corresponding side of the bamboo.

Now, onto the powerlam! I have always been intimidated by powerlams, mostly because the precision required.. and you all saw my "shop" set up    :rolleyes:

After grinding the zebrawood and bloodwood seperately, I glued and clamped them together.

 

   

When glue up was complete, I took them back to the belt sander to ensure that the taper matched on both parts of the lam. With that done (and some prep work to the other riser pieces) I got to this point.

 

[Jstick87]

At this point I slowed down progress and looked at a lot of different r/d build alongs and the resulting limb profiles. The one I liked the best was from a video build along on youtube by DIY sportsman. He did a very detailed job of providing the specs to his form, and followed them closely.

I took a perfectly straight 96" 2x4 and cut it to 70" long. I then screwed in shelfing pieces to ensure that it would not warp over time. I also included feet to provide clearance for clamps, and marked the center line to help keep everything perfectly straight during glue up.

 

At this point I decided I was ready for a dry run. I marked center on all pieces and found my 4" C clamps. This is where I ran into a problem.

 

 

As you can see, the glue line in my power lam has made it very stiff and rigid, and it will not flex at all. This is creating a gap between it and the ipe. If anyone has suggestiongs... please help!

I am considering gluing the power lam to the ipe before the rest of the glue up OR sanding on the ipe under the power lam until it fits.

[BMorv]

I am a little confused by your setup.  Is the power lam already glued to the bamboo?  
You should be able to tighten down on the clamp and lose some of that gap but if that doesn't work I would grind down the power lam.
 
Most power lams are a lot thinner than what you have (1/4" at it's thickest, tapered to a feather edge at the ends).  This would allow the bamboo and ipe to conform to the gradual taper of the power lam.

[Jstick87]

Thanks for the reply! The power lam is not glued to the bamboo, but it appears like it might be because I have it under significant clamping pressure. The lam itself is a strip of bloodwood and zebrawood glued together. I glued them ahead of time because the bloodwood pieces I made had some pretty significant warping. It is tapered to where I can see light at the ends, but I think that the glue line has made the lam a lot more rigid than anticipated (Im using unibond800)

 

That is the thickness at the middle of the 16" powerlam. I made the powerlam a little thicker because I was wanting to try shaping the riser similar to a takedown recurve. (Im not sure if this would even work, since it would be violating the backing?)

 

It would look something like this.. any advice on whether or not to try something like this?

[Bvas]

This may seem silly......but have you tried moving your clamp and wood block closer to the riser.
The edge of your wooden block should be right at the end of the power lam. You are actually bridging the gap with your block in the pic shown.

[Jstick87]

Good idea! I will give that a try.

[BMorv]

That's a nice drawing, but I wouldn't cut through the backing and power lam like that.  You would be putting a lot of pressure on the glue joints where the dips on the back start.  On a take down you are transferring the limb bending stress to the riser via the clamping force of the screw.  You are asking too much from the glue with that setup.    
Maybe someone else can chime in but no way would I try that.  
On the power lam, an easier transition to the feather edge will help you with that gap.  Check out my power lam thickness one inch in from the edge vs yours.    
   

[Jstick87]

Well I grinded down the power lams for a more gradual taper and adjusted the clamp placement, and it helped some. I was about to take a picture when... a loud snap. There is a small section where the grain exits the back on one of the limbs and it went. This will be a one bow build/help along now.

 
 

[BMorv]

That's no good.  Is that the same spot where you were trying to close the gap?

[Jstick87]

Nope, it was further down where I was clamping to induce reflex into the bow limb. And I mis-typed on the previous post, the grain lifted on the belly side of the bow.

At least this happened before I glued anything to the Ipe slat, so I'm only out 20 bucks and time spent on it, and the bamboo, riser and power lam will live to see another bow.

[BMorv]

I've had that happen to me more than once with ipe.  It is strong as can be in compression but it really doesn't like to be put in tension.  I've since made a few adjustments to my procedure and I haven't had a failure at glue up since.
- I get the belly side (especially where you are going to induce r/d) really smooth down to 200 grit or finer sandpaper, and round the edges
-Make sure the thickness is close to final dimensions, as a thinner piece will bend much easier
-clamp a metal band to the belly.  This takes a lot of the tension load.  I use an old aluminum yard stick but any thin metal should work.