Need bow formula advice...

OkKeith · February 05, 2011, 01:13:00 PM

I've been talking to Kenny M and we have been discussing my first fiberglass bow build. I am putting this bow together for my wife to use in a blind for turkeys.

He thought I might get some of ya'll's opinions on thickness of lams and tapers for this bow.

Here are my planned specs:

- 56" OAL longbow.

- I first thought about a 14" riser but have now decided to go with a 12" Charcoal Gray Actionwood riser.

- Black glass front and back with Action Boo tapers and lams.

- 1.5" at the fades, with a continous taper to .5" or .375" at the nocks. Black phenolic overlays.

- A mostly flat profile (or set-back slightly at the handle). 40# at 26" of pull.

What we weren't really sure of was thickness of glass and lams, and what sort of tapers I would need.

Any advice would be greatly appreciated!

OkKeith

GREG IN MALAD · February 05, 2011, 02:23:00 PM

I'm finishing a 56" longbow right now. It's a mild R/D design with 3/4" of deflex and the tips even with the front of the riser. It uses an 18" riser and is 1 1/4" wide at the fades with 3/8" wide tips. I'm using .004 total taper, .040 glass, a .322 stack height gave me 35#@26". When I get the sanding finished today I will post some photos.

mater · February 05, 2011, 03:48:00 PM

I have built a bow with almost the same setup, if I can find the notes Ill get them on here. I for sure would not use .004 total taper. Id be more like .001 total and no more than .002. If I remember,I used a 13" riser and it was very smooth. I no longer have the bow so I cant go measure it. Mark

Dick in Seattle · February 05, 2011, 04:00:00 PM

just one opinion, but that's an awful short straight longbow. I have a 25" draw and for hunting shoot 40#. I've built a couple of shorties, 61" or so. They worked fine (got a javie with one) but the shortness makes for a stiff draw. Your short riser will help, but will cost you some speed. If you can possible stretch out to 60 or 62 inches, you should get a more pleasant bow to shoot.

I posted the layups I used. Check out the Big Bad Wolves and Airwolf in my Gallery: http://dickwightman.com/archeryactivity/bowbuilding/gallery/bowsmade.html

Swissbow · February 05, 2011, 06:20:00 PM

I agree with Dick, for a straight longbow 56" is pretty short. If you want to go that short I would opt for a mild r/d-profile.

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Andy

GREG IN MALAD · February 05, 2011, 06:29:00 PM

I built this as a kid's bow but it will draw 26" without stacking. The amount of taper is determined by the design. A straight bow works fine with little to no taper. Because of the reflex in the tip, this one uses more taper, and if there was enough room in the stack for 3 tapers I would have used .006 per inch.

OkKeith · February 05, 2011, 11:10:00 PM

Hey Guys,

Thanks for all your advice!

My thoughts on the specs are; Lisa wants to shoot this bow from a blind, so I was gonna try and keep it short. Also, even though I have built quite a few all wood bows (HBOs, BBOs and other combos and self bows) I have never done a fiberglass bow. I thought a flat profile would be simpler.

I would like to keep it under 60" (hate for the bow to be taller than her) and 40# at 26" of pull. I suppose as long as it doesn't get too complicated, I am open to any design changes.

OkKeith

OkKeith · February 06, 2011, 11:53:00 AM

ttt

Mike Most · February 06, 2011, 02:48:00 PM

I am with Dick and Swissbow, I would opt for the 62 inch variety,

Learn to cant the bow a bit in the blind and have at it. If its too darn long you could always pike it...

mater · February 07, 2011, 08:49:00 AM

I missed the straight limbed part, more taper like Greg has. Gregs bow seems to have a nice bend to it.

Okie 1 · February 08, 2011, 01:58:00 PM

Keith, are you coming to OJAM this year? If so, look me up and we can put our heads together. I've been working on some designs. I've built one FG bow and it worked out great, but I have several different ideas.

OkKeith · February 08, 2011, 07:59:00 PM

Hey John,

I do plan on being at OJAM! Won't be able to roll in until Friday morning, I have a CLEET class until 10pm Thursday night.

I will keep a look out for ya. Where do you plan on camping this year?

OkKeith

Okie 1 · February 08, 2011, 08:51:00 PM

Not sure where I'll camp. Probably try to get by the electric pole again this year.

OkKeith · February 12, 2011, 05:21:00 PM

Based on some great information I received from a few Tradgangers. Here are the formulas I have worked up and need advice on:

It will be a moderate R/D design with the limb tips coming out to even with the front of the riser.

FORMULA 1: 56" NTN with a 13" riser, 1.5" width at the fades going down to .375 at the nocks;.04 glass, .002 taper with a wood stack thickness of .2. This will give an overall thickness of .3. This should yield a 45# bow at 28" of pull.

FORMULA 2: 58" NTN with a 13" riser, 1.5" width at the fades going down to .375 at the nocks;.05 glass, .002 taper with a wood stack thickness of .2. This will give an overall thickness of .3. This should yield a 45# bow at 28" of pull.

My goal is still a bow pulling 40# at a draw length of 26". She would prefer to have the 56" bow, but is willing to accept a 58" if the shorter one will stack too quick ("quick" is relative I know. She only draws about 24.5 actually).

Any advice on these ideas would be great!

Thanks,
OkKeith

OkKeith · February 12, 2011, 07:08:00 PM

ttt

OkKeith · February 12, 2011, 11:12:00 PM

I'm hoping that some of you folks that have built bows will take a look at these two ideas and give me a little advice.

Thanks,
OkKeith