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bow swap build-along for catamount (finished pics p10)

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Re: bow swap build-along for catamount

Postby cst » Sun Aug 17, 2008 7:36 pm

Thanks for the very detailed buildalong. There is no such thing as too many pictures. I appreciate all the trouble you are going to with this. I have always suspected that there was more work to this type of bow than I knew and it turns out I was right.
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Re: bow swap build-along for catamount

Postby jwillis » Sat Aug 23, 2008 9:51 pm

I finally got some time in the shop, so I glued up the first limb today. Here are the lams and glass all stacked up in order. Before gluing I always put the back on top and the belly on the bottom in the back of my gluing area. There is nothing special about the way I do this...it is just how I always do it so I don't get confused during the gluing process.
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I swept the lams with my shop vac, then brushed them off with this clean brush. I only use this brush for lams. I'm using the hot box for my gluing table and it warms up the lams and keeps the glue warm and flowing nicely while I put it on. This works really well. The only problem is it's really low and my back starts hurting if I take too long, especially when gluing up one-piece bows because they take so long to put the glue on.
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Then I mixed up about three tablespoons of each part of Smooth-On. I don't weigh it like some guys, but wish I could figure that out sometime, because this was just about two lams too much this time and I hate wasting it.
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So, here's my gluing process. Take the back lam off the top of the stack, flip it over, put glue on it and lay it down in a new stack closest to me. Then put glue on the next one in back, flip it and put it on the front stack, put glue on the other side, then go to the next one in the back. I continue this process until they are all glued and stacked in the opposite order in front of me. Now the stack is back down, belly up. You can see the belly overlays in place. Oh...I wimped out on the osage belly overlays and opted to use these walnut ones. I was just afraid they would look too bright...Catamount might have to wear sunglasses when shooting the bow...lol.
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The forms are prepared and waiting on the work bench. Here's the top half. I put the back of the limb on the top profile so there is a flat smooth surface on the limb back. This is opposite from how the Bingham process does it. I do this because I am also gluing on the belly overlays during glue up and the firehose can conform to the different levels.
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Next, I pick up the lam stack and put it on the top half of the form with plastic on it. (back down, belly up)
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Adjust the lams against the pin and tape it down, starting at the butt and moving towards the tip. I have found that if I keep them aligned and put them on and then immediately tape them down at the butt in a couple of places, they stay right in position, but if I get too retentive about checking them and start moving them around, then they start sliding all over the place and are really hard to get them into position. The line-up washers are in position on the back side, but I put the line-up washers on the front side after the lams are in place. When taping it down, I make sure the belly overlays are in position flush against the ends of the fiberglass.
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OOPS, I forgot to put the metal strip on there. So, I just taped it down over the top of the other tape. Then, I flipped the top half with the lams, put it into the press and tightened it all together. Checked to make sure the hose was aligned and equal on the sides.
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Took it over to the heat box and started pumping it up one stroke at a time, then waited a bit, checked alignment, then pumped it again up to about 20 psi...checked alignment...waited another bit...I have found that pumping it up slowly like this lets the glue squeeze out slowly and everything stays in alignment...
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...then pumped it on up to 60 psi. What the heck, I think I'll pump it on up to 70 this time.
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Put the cap on the valve, then put the form in the hot box. Note that I use one hot box for both full-length one-piece bows as well as these shorter limbs. I just put a divider inside and unscrewed the other light bulbs.
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Plugged in the timer and set it for six hours. Using half the box and two light bulbs, this box will go up to 160 degrees and stay there. When I'm using the entire box with all of the bulbs, it will go up to 180 then shut off...the thermostat will cycle it on at 150 and off at 180.
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Christmas time...time to open the presents...HOLY COW, look what happened! :shock: The bottom of the form broke in freakin two pieces! :x
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SCHWING!...that's a stiff looking hose.
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I guess that extra 10 psi... :idea: ...lol.
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Whew! It broke after the glue cured! It appears to be a perfect limb. :D It only had 10 minutes left to cook when I left tonight to go to church, and I never heard it blow, so it must have been fully cooked and cured. That was lucky.
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It broke clean in half on the bottom. You know, I've got an extra form blank that I can make a new bottom half. I'm going to put 1/4" plywood on the sides of the MDF on the new one. It will strengthen the form and also serve as the spacers for the clamps. Luckily, the limb profile side of the form is still perfect.
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Tomorrow, I'm going to fix the form and glue up the other limb.
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Re: bow swap build-along for catamount

Postby tjdeerslayer37 » Sat Aug 23, 2008 10:13 pm

looking good. did you grind down the brown glass yourself? it looks ground different than any glass ive had.

too bad about the form. good thing the right side blew. :D i use 80 psi on mine. guess i need to reinforce it a little.

i always right back and belly on my glass. and one other thing, i dont tape my pressure strip down with the lams, is it necessary?
Save a tree, shoot a buck

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Re: bow swap build-along for catamount

Postby tjdeerslayer37 » Sat Aug 23, 2008 10:23 pm

oh and did u decide not to put on the osage overlays?? or am i blind and missed em?
Save a tree, shoot a buck

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Re: bow swap build-along for catamount

Postby Crooked Stic » Sat Aug 23, 2008 10:29 pm

Bummer on the form. Where did you get that timer?
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Re: bow swap build-along for catamount

Postby Catamount » Sat Aug 23, 2008 10:55 pm

Sorry about your form Jim. I always use 70 psi and have never had a problem. Can't wait to see those limbs mounted up.
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Re: bow swap build-along for catamount

Postby cst » Sat Aug 23, 2008 11:20 pm

Was that the result of the air looking to expand when it was heated? Or just bad luck?
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Re: bow swap build-along for catamount

Postby VRB » Sun Aug 24, 2008 7:07 am

Looks like you should position the bracket farther forward,it would be stronger there.You might be able to save that form with a couple 1" steel straps, eight " long bolted across the break.
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Re: bow swap build-along for catamount

Postby Kirkll » Sun Aug 24, 2008 8:39 am

cst wrote:Was that the result of the air looking to expand when it was heated? Or just bad luck?


That is a good piont cst, or good question rather....about the preasure increasing as the heat rises....i never have checked how much it does rise actually...

Have you? or anyone else out there?

i have noticed less damage to the bolt holes in the plywood forms i use dropping down to 60 pounds...when running 80 lbs i could see the holes starting to elongate in the plywood at the bolt holes after a couple lay ups....

personally i wouldn't use MDF for forms myself...besides what can and will hapen with Jims form here, the stuff soaks up moisture with time and becomes unstable. maybe in a dryer climate you could get away with it for awhile....but i just don't trust the stuff after years of using it in construction and seeing all the problems associated with the stuff....its only sawdust and glue....

Jim....This is an outstanding build along you are doing here! the details you have gone into here is excellent!....
using a hand pump to seat the hose slowly is a great idea....and sectioning off your heat box is something i'm going to look at doing too....

do you section off your form doing a one piece bow, one limb at a time, like TJ's forms?

the one thing that i noticed here that really has me going ......is how everthing in your shop there is spotless... :? :? even your work bench and forms are clean as a whistle.....how do you do that????? i have to put a new top on my bench once a year, and the old top has 40 pounds of bondo in it usually..... :?
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Re: bow swap build-along for catamount

Postby tjdeerslayer37 » Sun Aug 24, 2008 8:44 am

if jims using the one limb deal hes been keeping it quiet and not telling anyone. :lol:
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