All wood takedown limb thickness, solid vs lam vs glass

[chrisgedwards]

what is the difference in thickness of limbs when making fiberglass wood laminated limbs vs all wood? If they are the same length, width and weight, is the difference in thickness between materials as extreme as I'm finding?

To be clear, I'm most interested in making all wood bows, screw fiberglass. I'm trying to make hickory backed 1/8") maple and whit oak limbs right now. They are 1.5" wide (should have gone with 1.75) 25" long (minus 3" for pad area) of consistent thickness, tapering to 5/8" wide starting at 10" from the butt end. I expect the laminated limbs to be around 7/16" thick at completion My riser is 15" long. Im shooting for 50-60lbs.

I recently made a takedown bow, solid hickory riser and solid hickory dry heat bent recurve limbs. I just used limbs from a broken self bow at around 7/16" thick. When I look up laminates limb thickness with fiberglass, I'm finding total limb thickness around .25 inches for bows with similar specs.

QUESTION: are all wood limbs on a takedowns really suppose to be this much thicker than wood fiberglass laminates? Is it possibly because I'm making pyramid style limbs that my limbs are so much thicker? I bought some fiberglass to try as a backing but I rather stick with wood. I already tried .25" thick recurve limbs that were solid hickory, I got between 10-20 lbs of draw weight.

Ideally I'd like to put two pieces of wood through the thickness planer, one at 1/8" the other at 5/16, taper their width to 1/2-5/8, heat bend them for reflex then epoxy them together. With that technique i could make make limbs so much faster and with less chance of mistakes compared to laminating multiple layers with a homemade core taper. Thoughts on this technique?

Sorry for the garbled message, difficult to type on the phone. Thanks for the help!

[aaron]

Yes wood bows are much thicker than FG. How much thicker depends on the wood.

[chrisgedwards]

Sooooo glad to hear this! I thought I was missing something embarrassingly obvious. I'm using hickory "self limbs" and hickory 1/8" backed maple and white oak. 7/16 sounds realistic for Width both thickness tapering  takedown limbs? That's the rough cut thickness before tillering.

I haven't seen many all wood 3 part takedowns, anyone have experience with them?

Thank u again :-)

[Badger]

  I am in the process of building a white oak backed ipe bow. The limbs are right at 7/16 thick for a 50#, my riser is 10" long, and the bow is 66" long. When we buid wood bows we tiller them according to shape and ignore the thickenss. We select a width that is known to be acceptable for certain woods and design and then adjust the bend of the bow by removing wood. I expect your bow would wind up about 3/8 thick but I think you may have too much stress in your design for the width you have to work with.

[PatM]

Glass is not wood so throw your preconceived notions out. Look around for all wood or wood lam take-downs. There is a few on here. Remember there is no need to think of them as much different from any other wood or wood lam one piece bow when it comes to dimensions of the bending limb.

[chrisgedwards]

Your riser is so short! I thought I was going too short with 15". However, taking your guys advice and thinking of this as a backed/self bow, a 15" riser is huge, I usually make mine around 8-9"

I don't understand the appeal of long heavy risers like the 23" that I see with some fiberglass bows.

I'll bump my limb width up to 2", pyramid style with the width tapering at 10" out from the end, 3" for the pad area and a total length of 28" with prior to tiller thickness of 7/16" that should give me a bow with a length of 65" at hopefully 50-60lbs. I'm remaking the limbs right now from solid hickory. I'll consider backing with fiberglass if the limbs seem to stressed, rather stay using primitive materials. Otherwise it's fiberglass weave with smooth on, probably two layers.

My riser has 15 degree angles, no way will that work for non recurves or the brace height would be huge so I'll dry heat bend the hickory for sure. You guys are great thanks for helping out this confused noob.

[PatM]

I don't think Steve is talking about a take-down. Huge risers allow more weight in the hand and spacing short limbs on a longer overall length bow. Glass guys love all those perks.

[joachimM]

Glass bows are so thin because the modulus of elasticity (the stiffness) of GF is so very high. And it can stretch about three to five times more than wood before breaking. Both these properties allow you to make bows with thin limbs. Still, they're about as heavy as wood bows, because GF is about four times as heavy as wood.

As for thickness: there's a cubic power relation between thickness and stiffness. Meaning if you double the thickness (x2) the draw weight will multiply by eight (2 to the power 3).
Now if your original bow weighed 15# at full draw, and it had 0.25" thick limbs, in order to get to 50# it would need to be exactly 3/8" (assuming all else being equal). For 60# it would require some 0.40". That is, if you didn't break down the wood with that particular design. So basically, follow Badger's advice on tillering to get to your target weight. And I'd forget about these three-part-takedowns with long risers. They're just so damn ugly!

[bubby]

ugly? Maybe to some people

[chrisgedwards]

Takedowns are gorgeous, especially the one in the post above, I say God damn! I will admit that I just recently fell in love with them, self bows have that gorgeous ancient history and oneness with nature aspect.

So I went ahead and roughed out my first for realszy takedown. I had made one with spare parts (pine riser good god) but it's not exactly much more than firewood.

The limbs are 28.5 inches long, 2 inches Wide(0.25" wider then the riser oops) 7/16" thick, 3inches on the riser, width tapering starting at 10 inches from the end to 5/8" tips. Riser is 15" with 15 degree pads. I did not reflex the tips, not sure if I will, too nervous that I'll mess it up and I have no hickory at the moment to make new limbs from.

OBVIOUSLY this bow isn't done, I like to make really rough cuts to see if it tillers and shoots fine before polishing it up. I have almost no power tools, this was done completely with a table saw and a sander. The rest was done with chisels hand saws and a crappy rasp. It's time I get a membership to tech shop ($85 a month, I hate being poor).

I plan to stain the riser Cabernet and the limbs oak. If I put 2 sheets of fiberglass on the back of the limbs I'll probably paint the back gloss black.

At 22" it drew 35 lbs. it's 63.5" ntn so I'll be making a continous loop string from b50 tonight (60.5"long)

Only question I have now is if you guys see a problem with the limbs being wider than the riser and if the reflex is necessary with the angled riser. Thanks and sorry for the rambling post. Tiller photos when I've had time to sand everything down.

[chrisgedwards]

Yeah those pics are very smashed vertically, not sure what caused that

[Badger]

 Did you orient the grain on your riser where you see the growth rings on the back and belly side but not on sides? They can pull apart violently if not properly matched up the the grain.

[chrisgedwards]

The riser is one thick piece of hickory with almost vertical growth lines from top to bottom. Not a single knot in it though it is one half heart wood and the other half new growth. I laid it out like it was a bow limb. Not sure why I have to compress my photos so much and why they are being smashed. I'll get better pics up tomorrow when I've sanded and figured all the photo hog wash out.

[bubby]

I would reflex the tips with that much deflex at the riser, and please no f#!;&glass !!!!!!

[bow101]

I would reflex the tips with that much deflex at the riser, and please no f#!;&glass !!!!!!

Same as what Bubby says without the reflex and that angle the bow will stack quickly.  I just finished another 3 piece the limbs turned out fantastic with a few glitches, but my tillering process lasted about 2 minutes.  I put on a short string right away took about 30 pulls on the stick then braced it to a full 6 1/2" incredible only took 1/4" of set tiller is almost 100%.  Will shoot it in soon and take it from there.
The secret in these bows as far as I'm concerned is doing the tapers exact using a long power lam and a 10" wedge.