Red Oak backing on a RO bow to up the weight--How thick?

[Jefficus]

Hey everyone, I made a very snappy but light weight Red Oak board bow a while back that shoots great, but I'd like to increase the draw weight a little and maybe add just a little glued-in reflex to it.  It currently is a 72'' bow that only pulls about 20#.  I have some really straight quartersawn Red Oak that I'm thinking of ripping the backing from to keep the overall look of the bow(rather than using Hickory or something else), but I'm wondering how thick to make it. 

Any thoughts as to whether 1/8'' or 1/16'' would be better with Red Oak, or how much each of those might increase the draw weight?  I know if I glue in any reflex that will add more than if I just left it straight and applied the backing (Somewhere I read 10#/inch, is that true??).  If anybody has done something like this before with Red Oak or a similar wood, I'd appreciate the input!  Also I'm probably just going to use TBIII, should be fine right?

[Pat B]

I don't think red oak is a good candidate for a bow backing unless maybe you could chase a ring and get a good, clear backing strip. Maple, hickory or elm would be a better choice for a backing strip.

[Jefficus]

I was worried about that, I could always use the RO I have for another bow altogether (though I could probably do that even after I ripped a backing off).  I'll use Hickory or Maple or something If I absolutely have to, but the bow is performing great right now unbacked, so I thought it might be possible to add more RO?

[willie]

quarter sawn might help out some if you are going with the RO

if you state how wide the bow is and how much weight you want to add it, I could do a quick calc for you. also how much handle (non working) is in that 72" bow?

[Jefficus]

It's 2" at the fades and tapers straight from there to 1/2" at the tips, with I think a 10 or 12" handle section, I don't have it with me right now. I was thinking 5 or 10lbs maybe to add, but I wasn't sure what a realistic range is.

[willie]

it seems to me that you could remake the bow into anything you want up to 50lbs + if it is 72 inches long. I could figure that for you, if you like.

just curious, though. Is this a red oak experiment kind of thing, or are you just wanting to raise poundage to 25-30 and improve the bow with out too much trouble? Piking might be easier than gluing a lam. the bow as is, seems under worked, or overbuilt as they say (for 20#)

[joachimM]

How thick is the bow currently in the most bending part? I'm guessing it's 12-12.5 mm thick right now (1/2")?

You could add a wood backing, but a fiber backing would be much easier to apply. With wood, you'd need 2 mm to get to about 32#
Linen canvas of 1.5 mm thickness would up the draw weight to at least 30#, maybe 35.

Shortening the bow: if you want to get to 30# you'd need to remove 9" in total, to a bow of 63". That may be a bit short for a red oak bow, although I think it would stay together at that thickness of 12.5 mm if the back is good.

Joachim

[Jefficus]

Willie- what are you using for these calculations, if I may ask? Sounds like something I could use! It's definitely more wanting to raise the poundage than anything, if it were more for experiment I'd just go for it haha.  I'd agree that it's overbuilt, it was one of my very first bows and I wanted something that would work haha

Joachim- it's definitely closer to 3/8" or 1/4" than 1/2", that's for sure.  I can't say exactly cause I'm at work right now. I was under the impression that linen as a backing doesn't do work and wouldn't really affect the poundage, would it really change it that much? Still, I'd prefer wood.  I've thought about shortening it, but I don't want to put the bow in any real danger...plus I'm fond of the tips.  I guess I could steam those off and reapply them, and smooth it together...But it's not first choice.

[Jefficus]

Its possible the handle section is even 14", haha. I remember being really nervous and overbuilding it because iy was center-shot.

[bubby]

what's the draw length

[Jefficus]

26"

[willie]

a spreadsheet that lets me plug in some basic dimensions and bending strains.

a rough calc confirms Joachims number of 2 mm additional thickness would be alls that necessary to raise 10# with 58" working limbs. I do not like to rip less than 3/16 with my saw though. you could tiller from the back if its vertical grain though, and have some extra for a cushion........

Maybe just re- working the handle some, and some piking would get you where you want to go. if the existing back is not flat, you will have to deal with that before you cut and glue the new strip

why not post a pic, and ask "what would you do" you might get lots of advice, and if you are like most of us, will do what you want to do in the end, anyways 

[Jefficus]

I have access to really good saws at the Kansas City Woodworker's Guild, and a thickness sander, so getting the right thickness is definitely doable.  I think I will post some pics later, and more after I do...whatever ends up happening haha.

[bubby]

Well if you have a 70" ntn bow and a 12" riser if the tiller is good you can cut the bow to an overall length of 68" and 66" ntn retaper the bow to 1/2" tips and this will raise the draw weight at least 12#