Hi tech redneck flight bow.

[Pappy]

Looking good Arvin, should be a smooth shooter.
 Pappy

[Selfbowman]

Thin it out one more time and heat it again and we should have profile .

[Jim Davis]

Hope I remember  to  watch this all  the way to  the test results. A computer's output is only as  good as its input.

[Selfbowman]

Jim you know me. I don’t like computers . But I’m not a engineer. The design depends on the wood test to be even close. That’s why we are testing scraps from The stave . This is the only way I know to get close to the design. Then It depends on the builder. I also think that I need to ease into the tiller weight. I’m going wider and thicker than the design slightly and work toward the design. The last one I did it came out 10# light. But the sample from the stave was not tested. So we will see how the engineer and the builder does on this One.

[JW_Halverson]

Just gonna drop a throwaway comment here so that this comes up regularly in my new replies listing. I wanna see how this comes along, as well as the finished product.

Crack on, brother.

[Selfbowman]

Lord willing I will give you the chrono  Results in the next three weeks. The crown of in the back is throwing a monkey wrench in the mix.

[Selfbowman]

I have the profile done and need to put my string nocks in the ends. The engineer has been so kind to give me a force draw curve along with brace profile, 18” draw profile, and full draw profile. So I’m going to try to get close to thickness dimensions then follow the profile and force draw at that draw length. I have found that at 20” on a 28” draw the set comes in. So at 18” on this bow if no set and the force draw matches up . Then it will probably hit close to the 50@25”. If the design is correct to the point that no set should happen then I do my part hopefully we will have success. Has any of the computer design guys approached the tiller in such a manner with success?

[mmattockx]

Has any of the computer design guys approached the tiller in such a manner with success?

I haven't. I trusted the design completely and just made the bow(s) to final dimensions as closely as I could, then put them on the tree and worked them out to full draw. IIRC, the maple bow I did this way I did actually do a bit of fine tuning on the tiller in the end, but very little. The red oak lam bow I just exercised out to full draw with no touch ups at all.

The big questions (for me, maybe not you and Alan) are how consistent the wood is in matching the bend test samples over the full length of the bow and how accurately the bow is made to the design dimensions. If these two things are good then you won't need more tillering than very small fine tuning adjustments, if anything at all.

Using laminations helps with the consistency of the material properties, but I don't think you are allowed to do that for your flight bow.


Mark

[Selfbowman]

Mark did you do a force draw before or after or both. If so how accurate was your force draw computer design to  final bow?

[mmattockx]

Mark did you do a force draw before or after or both. If so how accurate was your force draw computer design to  final bow?

No full F-D chart, but the draw weight was bang on for the maple bow I did. I played around with preloading the lam glue ups in the red oak bow and ended up a fair bit heavier than predicted because I had no way to quantify what the preloading effect was going to be.


Mark

[Selfbowman]

Mark part of my problem I think is that you glue up reflex and deflex in your bow and I have to heat the limbs to get mine. The heat may change the woods property’s . That being said if the force draw design and the bend design match up in the end . Could we not tiller to draw weight and bend design no matter what the woods properties are? Also Allen did test on the wood. The density was 85 so my Osage stave is a good grade. The growth rings are even in thickness pretty much through out the length of the stave.

[Selfbowman]

The red line is my design thickness at this time. I got to narrow the width some . Then it will still be heavy but may be able to brace it. Will bracing to heavy cause set?

[Selfbowman]

Pic

[mmattockx]

Could we not tiller to draw weight and bend design no matter what the woods properties are? Also Allen did test on the wood.

Yes, the actual wood properties don't matter much as long as they are consistent throughout the stave. Doing bend tests on the drops should get you close enough to be 98% or better of the design results unless the wood is really inconsistent. Heating it to bend may alter your properties, but osage seems to be super tough and resilient to every sort of abuse, so hopefully it doesn't change too much. With the stiff handle design the heat there shouldn't matter, it's more the recurves that may have a noticeable change.

The red line is my design thickness at this time. I got to narrow the width some . Then it will still be heavy but may be able to brace it. Will bracing to heavy cause set?

If the weight comes from excess width it won't cause set, if it comes from excess thickness it could. When I did my maple bow I used a set of vernier calipers to get the thickness as close as possible to the design amount, measuring down to at least 0.005". Width is more forgiving, because it doesn't cause extra strain in the wood.

Since it's Allan's design I would ask him what he thinks of this, but I would say you want to get the thickness as close as possible to the design value and then do any tillering adjustments on the width if you can. Thickness determines how much strain the wood sees for any given amount of bend, width just adds or subtracts weight without changing the actual strain the wood sees.


Mark

[Selfbowman]

I got the tips all done time to tiller.