Red Oak bows keep taking too much set. Druid's bow

[willie]

With the profile mostly parallel and then narowing to tips you should have a more elliptical tiller imo

bubby- i have always had a hard time understanding profile vs tiller shape recommendations.

are you saying that....with a constant thickness taper..... the tiller shape will turn out more elliptical with that back profile?

or perhaps

with that back profile, that he should tiller thickness accordingly, to achieve a more eliptical shape?

or something else ?

willie

[Dictionary]

Willie, we're turning bowmaking into rocket science it seems like.

Okay. Decided to whip another one up. Here was another board that was half finished, I tillered and shot in today. I didn't touch the handle area. It was left as thick as the board was. This one appears only slightly more flat in the handle. Still a lot of set taken, little more from midlimb towards the outer limbs now.

62 in ntn. 48#28 in

[willie]

that seems evenly tillered, a touch less in the center. If you want less set with that red oak, your going to have to go longer or wider I guess.

btw, how do you determine your weight goal, before you start tillering?

[bubby]

Have you tried putting one on a caul with 2" of reflex and heat treating it?

[Dictionary]

Shotgun Willie- I think you and a few others are right. I think longer and wider is the only way to go or drive a few hours to find some real bow wood. For these boards, the grain usually dictates what weight I'll shoot for. If the grain is decent, I'll shoot anywhere from 45-55#. If it's bad, 40-45#.

Bubby- A caul? I just googled that and got some really disgusting images. I've never bothered heat treating. Only reflexed one or two bows in the past. But if I have to stick to Red Oak, I may have to start.

I may have to snag some of these ornamental planted trees in the night.

[loon]

I think it's a form, a thick board so you can clamp the red oak into reflex while heating it.

Or I guess you could maybe reverse brace instead? but it'd warp the wood while you heat it i think

[bubby]

A caul is a form with the desired shape that you are trying to achieve, i will see if i have a pic

[bubby]

This is a caul or form, i use the piece i cut out for heat treating

[loon]

but you'd only have the back exposed in that one..

[bubby]

Yeah like i said i use the piece i cut out, the negative pc that exposes the belly for heat treat

[bubby]

Here's one

[loon]

OH doh
thanks

[JoJoDapyro]

Just my .02. If you are tillering by stringing the bow, and pulling with a mirror, how can you be certain that you aren't stressing the bow beyond the desired draw weight? Also, What is the weight of the bow at brace, if the bow is at the highest tension at brace, then you could be getting all of the set from bracing it alone. I by no means have the experience that these other guys have, but I feel I have a basic understanding of how to do things, even if i don't translate that knowledge to action.

[mikekeswick]

It's quite simple really! I'm surprised nobody has mentioned it.
Yes your tiller was incorrect for the bow design before and you still need to work on a proper elliptical tiller. The reason being that any wood at any given thickness can only bend so far before taking set when released. Make it thinner - it can bend further before taking set. Make it thicker and it can now bend less before taking set. Your bow has a thickness taper - any bow that tapers in thickness along its length MUST bend progressively further as it gets thinner. This concept is absolutely key and especially so when you start using woods that can't shrug off tiller mistakes like osage  etc....
The 'problem' with red oak and why it takes set like it does is that it is much stronger in tension than it is in compression. Think of tension and compression properties as two weights on a seesaw - you want the weights equal for both to get a fun ride! Same with a bow - when it is bent the wood gets stretched and it gets compressed - the kicker being that most woods are stronger in tension than compression. So the stronger (actually it isn't 'strength' it is resistance to bending) tension side throws excess stress onto the compression side. As the resistance to compression isn't as great as its resistance to being stretched. Therefore you get set. Set is overstrained bellywood cells that have been crushed past their elastic limit and can therefore no longer spring back.
the way to get around this mismatch of properties is to make the working surfaces proportional to the particular woods set of properties. You can do a simple bend test before starting to work out how your wood behaves and use the information accordingly.
Red oak can make fast, durable, low set bows.
I bought a couple of boards of it years ago and made a whole bunch of pyramid bows and gave them to my friends. They are all still shooting very well. Don't be down on red oak! Just learn how to use its inbuilt properites to your advantage I made the back 60% of the width of the belly.

[loon]

Thanks for the advice & info!