Hi tech redneck flight bow.

[willie]

Arvin,
I think we have the force draw curve covered. I will double check when I get home this weekend.
The thing about full sized bend curve drawings is the special printer need to make 3 foot prints with accuracy.  I am guessing that is something Alan does where he works. And there is also the file type that the bow program generates to feed to the printer....it has to be compatible. I will look at that also when I get Vbow installed on my new laptop.

The wider stave sound like it may make it easy to get the test sample or maybe  more, unless...
Were you hoping to get 2 bows out of it?

Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness.  I will take post some pics of doing it on my saw with a stave I have here and work out some test sample dimensions if you want to move foreward.

The general plan is to rip a thiner slat and make a few test samples, something that can be tapered to a point on each end. A long dimond shaped bend in the handle pyramid mini bow if you will. Then do some bend tests on the tiller tree and use Vbow to reverse design and give us good numbers for the wood.  Actually a bit of time spent on the test sample will be worthwhile. Doing some testing on the sample at the working moisture content and testing again after the sample sees some heat treatment and possibly rounding the slat to approximate the crossection of the finished bow and testing a third time.


Do you have a decent scale for the tiller tree that can read  weights down to ounces?  a digital?

I would really like a thread like that, it would help me understand better how to design a bow specifically for any stave

Take a look at https://www.virtualbow.org/ for its capabilities and for a peek at the visual outputs.
If you have difficulties installing, please post as if I remember correctly, some guys had it working well and some had install issues a few years back when there was a similar discussion.

[Selfbowman]

I’ve got a architect that can print 32”by long as you want. I just need the design in a folder emailed to me and I have the nice lady move email from my phone to the printer. Just need to do it in 1” scale for me. That’s about as high tech as I get.

[mmattockx]

Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness. 

Depending on the thickness you want, a table saw may not be accurate enough. I use a thickness sander to get consistent thickness on my bend test samples and a decent surface finish to prevent lifting splinters during the test.


Mark

[willie]

Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness. 

Depending on the thickness you want, a table saw may not be accurate enough. I use a thickness sander to get consistent thickness on my bend test samples and a decent surface finish to prevent lifting splinters during the test.


Mark

making the thickness of the sample to a given thickness should not be an issue (within reason), as the sample length can be adjusted to fit.  manufacturing the sample to a consistent thickness side to side and end to end will be the most important part, and getting a good measurement of that thickness also.
Hopefully we can make a number of measurements as the build progresses with various conditions of the sample, (at moderate stress levels of course), and if murphy is on vacation when we conduct the final test for set taking, we can get good info to plug into the program.
Having a few test samples on hand will also be nice for various tests.

[willie]

Just need to do it in 1” scale for me.

I got the latest version of the VB downloaded and working.  the latest version does works in pounds and inches etc.  earlier versions only did metric.

It claims to be able to export files in .csv files. I will have to look into that more to see how useful that could be for printing. The latest version of VB also claims to be able to overlay photos on the graphs it makes within the program so one can make comparisions to the results and the predictions sort of like some of the pics guys post here on the forum sometimes.

whether or not full size drawings of bend profiles happens or not is somewhat of a different project.
If we never accomplish generating full size bend profiles, will that be a deal breaker for you?

[Selfbowman]

Willie I can print 1” full scale drawings at my architects office. Bend profile and force draw. It would be nice to have it all on the same page unstrung , strung, and bend profile every 4” of draw. Every other bend profile starts about ten inches from fade as to not blurry up the first ten inches. coming out or the fades.

[willie]

Do you have access to a nice table saw? A shop type table saw with a decent fence will work with care. The important thing is to be able to rip a slat with a uniform thickness. 

Depending on the thickness you want, a table saw may not be accurate enough. I use a thickness sander to get consistent thickness on my bend test samples and a decent surface finish to prevent lifting splinters during the test.


Mark

After measuring some rippings, I see some deviations that would warrant a thickness sander, especially if trying to get a good sample from a stave.
I suppose if you had some sizable stock that didnt make a stave from the same tree, and you had enough to work with squaring, resquaring and re-ripping with decent featherboards it might possible.   

what bend test do you use and how big a sample?

[mmattockx]

what bend test do you use and how big a sample?

I used a simple cantilever bend test where I measured the deflection of the sample slat due to a known weight at a known bending length. The two bows I did this way were made from boards, so I cut one test piece off the board before I did anything else with it. My primary concern was measuring the elastic modulus (Young's modulus) so I could calculate the dimensions to achieve a desired draw weight. I was less concerned with finding the strain where set started, but I did do some of that for the second bow I made from red oak laminations just to get an idea of the strain limit. Because of the imprecise way wood takes set this is pretty approximate and mostly gives you a kind of fuzzy edged range of where set starts to be noticeable.


Mark

[willie]

I did do some of that for the second bow I made from red oak laminations just to get an idea of the strain limit. Because of the imprecise way wood takes set this is pretty approximate and mostly gives you a kind of fuzzy edged range of where set sttarts to be noticeable.


Mark

I wonder if the imprecision is "in the wood" or a better test method could help?
Maybe something that bends a sample to a true arc of a circle can be less fuzzy.

I might do some experimenting with test methods here that Arvin could duplicate at his place. I think he would like to design a bow that just begins to take set at full draw if I understand his needs correctly.

[mmattockx]

I wonder if the imprecision is "in the wood" or a better test method could help?

I expect it is some of both. The biggest problem I had was determining when set had started. I'd put a load on the sample, measure how far it bent and then take the load off to see if it returned to zero or not. Because wood has some hysteresis there is always a little bit of what could be set, depending on how long you allow for it to return to the unloaded position. I would repeat this with increasing load until I clearly had set, then try to determine where set really started by going back through the test results.


Mark

[Selfbowman]

Still fine tuning. I don’t even know how many hours of the heat gun!

[superdav95]

Same bow Arvin?  How many heat sessions you done on it?   

[Selfbowman]

Same bow. I’ve lost count on the heat sessions. Reduced the width on the last 4” getting it to work more not taking any off where the set was. We will know soon if the bow does not take set again. Took .3 oz off.