Author Topic: Narrowing the limbs on recurve.  (Read 438 times)

Offline matt_w

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Narrowing the limbs on recurve.
« on: June 25, 2012, 10:35:00 AM »
I am building a bow and was shooting for 60 pounds and ended up getting 70 instead. The veneers were thicker than I thought and now I am wondering how I can drop the weight down a little on the bow. It's a 50s style recurve with 1.5 inch limb width. I am worried if the limbs get too narrow I might have some issues. Would it be alright to narrow it by 1/8 inch or so and how much weight would you guess that would drop it? Also, can I sand down the fiberglass a little to reduce the weight? I used .043 ULS glass. I'm pretty new to building and any advice is greatly appreciated.

Offline David Flanrey

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Re: Narrowing the limbs on recurve.
« Reply #1 on: June 25, 2012, 03:30:00 PM »
Matt,
I would start by trapping the back a little.  I have never tried it on a recurve but I trap all my d/r longbows. I would try trapping about 3/32 on each side of the limb with a file and smoothing it out with a sanding block.  Go nice and slow so you don't pull any glass splinters.

If this doesn't take enough weight off all you have to do is sand the trap flat which is essentially narrowing the limbs.

David

Offline strungstick

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Re: Narrowing the limbs on recurve.
« Reply #2 on: June 25, 2012, 07:38:00 PM »
I'd make sure your limb edges are rounded over like David suggest but don't hesitate to sand glass off both back and belly.  You have .043 on both sides to play with.  You can drop pounds on a recurve pretty quick sanding glass.  Sand evenly so you don't get any weak spots (usually with a rigid block) drop both sides glass down to .040 (if need be)and check draw weight as you go.  Narrowing the limbs can cause issues with stabitly especially if you are new to bow building.

Offline Robertfishes

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Re: Narrowing the limbs on recurve.
« Reply #3 on: June 25, 2012, 09:34:00 PM »
I had good luck reducing bow weight (4-6 lbs) by using emory cloth to "round trap" the belly glass. I started by securing the bow to my bench with one limb out where I could work on it..then I put on my respirator..Then with a piece of 120 grit 1 inch wide and about 16 inches long, I began using a "shoe shine" motion to remove glass from both sides (L and R) of the belly glass, make sure both hands are pulling at the same angle, stop and check your work often, once I get close to where I need to be I switch to 240 grit emory cloth. You will need to check tiller and may need to spend some more time with the 240 to get the limbs pulling straight and even, I have only done this during the build and before shaping the grip. I sanded belly glass with a sanding block on a couple of bows and maybe reduced weight by 2 lbs at most. I didn't want to remove too much glass on belly since I use 040 glass and I'm no expert on reducing weight. I don't know if you can reduce 10 lbs off of your bow. if you sand belly and back glass like strung stick suggested I think you would loose about 3/4 lb(?) for each .001 you sand off

Offline strungstick

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Re: Narrowing the limbs on recurve.
« Reply #4 on: June 25, 2012, 10:03:00 PM »
By my rule of thumb if you sand the glass to .040 back and belly you should drop about 6 lbs.  I start with .040 glass on my TDs in the 55-70 lb range.  I've had a couple over the years where I was shooting for  62 lbs and they  rough sanded closer to 75#.  I got them to 65# without any problem.

Offline Robertfishes

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Re: Narrowing the limbs on recurve.
« Reply #5 on: June 25, 2012, 10:45:00 PM »
With my 1 3/4" wide recurve I would also lose 1 lb for each 001 of thickness. I was thinking since the bow in question was an 1 1/2" wide design maybe the weight loss per 001 would be less than than 1 lb/001. When I sanded the belly glass I only sanded about 4 inches from end of fades and up to 8 inches from string tips and that might be why I didn't get too much weight reduction. I have been thinking about building a 50's style recurve similar to a 1959 Bear Kodiak..

Offline matt_w

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Re: Narrowing the limbs on recurve.
« Reply #6 on: June 26, 2012, 07:29:00 AM »
Hey guys thanks for all the help. I rounded the edges and dropped 5 pounds. I think I should be able to get the rest with sanding the glass like you guys have mentioned. Thanks for all the replies and the advice.

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