need some pointers on laminated bow

[msamn]

After being inspired by the wonderful woodwork and buildalongs by so many here on this forum, I decided to try a fiberglass laminated recurve. I had middling success with a R/D longbow before this. So I got the Binghams instructional book, plans and DVD and built myself a half decent bow.
will try to post photo.

Thanks for all the tips and inspiration.

but I have a few questions and problems I was hoping to get some help with before I try my next bow.
1-the bow came in way over weight at nearly 50#. I decided to try using the rubberband technique for a recurve since I was aiming for a lowish draw weight of 35 #. I was too cheap to do the firehose technique. Tolower the wt., I sanded the belly and back of the bow in attempt to lower the weight, Not enough. I grinded down the sides and made the initially 2 inch limbs down to just over 1-1/2 in. and got it down to about 42 #.
For my next bow,
should I have use  more rubberbands to get more pressure?, should I have tried to warm up the epoxy prior to mixing and using for better(lower) viscosity?
I got the limbs as a set from Binghams- I asked for 35#
what did I do wrong to get such a high draw weight?
2- I had issues with air bubbles under the glass. Any remedies for that? I did use plenty of epoxy, I made sure to be generous with that. Would pre-warming for lower viscosity have helped here too?
3-what do you use guys use to sign bows on dark wood/fibreglass? the pen I used smeared when I sprayed on Deft poly.
4-I tried using CA to try to splice together the two halves of parallels under glass on the back but it was too brittle and kept breaking apart. Am I using the wrong kind of CA? or is there some other technique to keep the two halves from separating with the pressure and the fluidity of the epoxy?

thanks for any help and hints you might be able to provide.

[msamn]

[msamn]

http://s668.photobucket.com/albums/vv43/msamn/?action=view¤t=DSCN1903.jpg" target="_blank">http://i668.photobucket.com/albums/vv43/msamn/DSCN1903.jpg" border="0" alt="bubbles under fiberglass">

[msamn]

coco and bocote riser, with a strip of oak accent


close up of riser


bubbles under the fiberglass

[kennym]

Almost looks like thick glue in the middle of limb to left of bubbles on the bottom pic.

You may have not had enuff pressure on it. Not sure if thick glue lines would up the weight that much,but a possibility.

Binghams are usually close on draw weight,were you measuring at 28"(kinda the norm)?

Good lookin first bow BTW !!

[Apex Predator]

What kind of, and how many, bands did you use for clamping?  I get lots of pressure using rubber band clamps.

[Russell S.]

I am too use rubberbands, i cut the bigest bike intertubes i could find in to 3 bands each.  i started with 5 bike tires i use all of them when i do a full size bow.  until today i didnt have any issues with them.. today while trying to remove the kids bow from the form amlost all the bands broke.  i got 6 bows out of them.. and even the ones that broke in the oven stayed tight on the form, so no complaints.  did you use a pressure strip?  i use 1/8" alum.  pressure strips carefully bent to the contour of the bow.  thwy have rubber on the bottom of them like marty's, the rubber is a 4" tall rubber base board contact cemented on its 2.50 at the home improvment store.  in the flooring section.  then on the back on the pressure strip i put a 3/4" wide strip of the same rubber on. the idea is that the bands do not apply all there pressure to the edge of the pressure strips causing it to crown.  i made a few test bows with out a pressure strip they all crowned...  this last kids bow has fiberglass on it, didn't use strips, and it a bit as well.  

i think you need a healthy pressure strip and some intertube bands.  i am sure i get 100psi or more out of them.

[msamn]

The draw weight of 42 pounds is at 26 inches(my short draw length).
I used old bicycle innertubes for the rubberbands, just as Marty demonstrates. I used 4 bicycle inner tubes, cut into two strips each.
I accidentally left out the pressure strip, despite stewing over how to do this with local material. I guess I was rushing things and starting wrapping the innertubes and was halfway through before I realized that I left out this step. It was getting so messy that I decided to just finish the job. Now I see how important a good pressure strip really is.
I do believe you are correct, Russell. I did suffer from crowning. I had trouble getting the riser overlays on due to the crowning. It was not flat.
Thank you all for your hints and experience and insights. Now I have the confidence and strategy to approach my next recurve bow.

[Apex Predator]

Russel nailed it.  I have never had a bicycle tube clamp fail.  I have torn a few while removing them from the form due to them being glued to the bow.     Some of the ones I use have tears and holes, but still hold up.  I only take my laminating oven to around 140-150 these days, but went as high as 180 without problems.  I normally get 2-3 strips from each tube, and use 7-8 per limb wrapped tightly.  I want to cover as much of my pressure strip as possible.  I have several layers of rubber on the critical fade areas.

[Russell S.]

yea i think my thermostat is acting up, or the little bow just had dif thremodynamics.  the box stayed between 180-190 for 4 hrs this time...

[jess stuart]

I use old truck intertubes usually get then for free at the tire shop.  I think they are thicker than a bicycle tube.  I cut them with a pair of shears about two inches wide, by going around the tube kind of like peeling an apple I get bands than are several feet long.  If you use more than one layer you can get alot of pressure.  A good pressure strip is a must.

There is a thing wrong with the rubberband method.  Yet I have gone mostly to firehose the last few years, go figure.

[Russell S.]

wish i could find some old truck or tractor tubes to cut up!! but too expensive to pay for new.

[BUCK-EYE]

I`m doing a recurve right now that has a air bubble in the lower limb. I wondering is there going to be problem`s with the bow or will it be ok?
Thanks Don

[msamn]

My bow (with about a half dozen little bubbles) shoots just fine, Straight and smooth. I am not the most experienced bowyer obviously, but I think that little bubbles are mostly cosmetic. I can imagine where a bigger bubble might affect durability. A big bubble will be a weak spot since there is no epoxy adherence. With a heavy draw and time, it's a spot waiting to delaminate.
Any other opinions?
And any hints on how to avoid bubbles?
thanks

[Robertfishes]

I use the fire hose method. I start off by using a bicycle air pump pumping the hose up slowly, looking at lams for slippage or movement every couple of pumps/strokes. I do have adjustable washers on my forms to prevent lam movement but I check anyway. I use the bike pump up to 55 -60psi then I use my compressor to fill hose to 65psi. I think starting slow with the bike pump may help push out any bubbles

[pditto613]

The first binghams bow I built I used pallt bands and it did the sme thing, come in about 12# heavy.  Without a pressure strip the bands put most of the pressure on the edges and not the center.  the limbs were convexed or concaved depending on how you look at it and had bubbles under the clear glass. The curved limbs changed the tension surfaces and made the bow stronger.  Turns out that it was similar to the new adcock limb design. I keep sanding the sides until it got to a draw weight I could handle. It shot great. Now I use a fire hose and I set the regulator on the compressor to the pressure I want, 65psi, and leave the air hose connected to the fire hose.  Guaranteed no loss of pressure unless you spring a major leak.