Getting ready to Tiller--3 Questions

[bubby]

http://www.primitivearcher.com/smf/index.php/topic,35312.0.html
this is how I do a lot of pyramid board bows

[Comancheria]

Thanks, DC.  Good info.  When the time comes, I will
Give that a try.

Clint, what a nice offer.  I will accept gladly on this first bow.  I hit a snag (quite literally) tonight when I noticed for the first time that one tip has a large chunk come out of the SIDE--must have happened when I was taking wood off the belly near that tip to work in some thickness taper.  So I have one tip at a little over 1/2 inch wide, and the other right at 5/16.  I will look it over tomorrow and before cutting in the nocks, I may have to shorten the tips about an inch and a half each, bringing the NTN length down from 70 " to more like 67 or 68 inches.  May be a while before I get it to brace height (I am thinking 5-6 inches?  I am working at the speed of a mole in solid granite!  I will
Let you know, and thanks again. 

Ah, the trials and tribulations of a master bowyer. 😄

Russ

[Comancheria]

Bubby,

Thanks.  That is looks like a great build-along.  I actually followed a very similar procedure, though I wish I had taken a look at your build-along first.  Lacking a band saw, I used a hand saw in to my width lines every inch or so, then chiseled out the material.  The main difference between your bow and mine is that I have not--yet at least--glued on any additional handle material.  May regret that if I decide to later on, given that I have already cut in the fades with just the 3/4" thick handle.

Russ

[Jim Davis]

The bow will be unbacked and 70" long, NTN, is from a 72" red oak board with a handle 3/4" thick and the rest of the bow, right now, at about a uniform 5/8 inch.  The handle is 7" long from where one fade levels off with the belly--to the same spot on the other limb.  It is a pyramid, tapering from 1.5" wide at the fades to .5" at the tips.  I am hoping for around 50# @ 28"
(...)

This is a perfectly fine lay-out. But you should be warned that there has to be some thickness taper. A pyramid bow starting at 1½" wide will not result in an even thickness throughout the limbs. Taper the limbs about 1/8" to start with. So 7/8" at the handle, tapering evenly to 5/8" tips. Proceed tillering from there.

Dark Soul, you have prescribed 1/4" of taper, not 1/8". That's WAY too much for a pyramid style bow. If laid out as described in the thread about tillering from the edges, no thickness taper is needed. BUT, laid out as proposed in this thread some taper in the mid-to-tip area is needed. But certainly not 1/4", which would result in a decided whip tiller.

[bubby]

You don't need to glue a piece on 3/4 is thick enough, you can build it up with cork or leather or rawhide to fill your hand, go ahead and cut it down you have plenty of wood

[mikekeswick]

3/4 inch thick handle...70 ntn   -  I don't think so.
I would make your handle 1 inch thick now. Better to have and not need.

[DarkSoul]

Dark Soul, you have prescribed 1/4" of taper, not 1/8". That's WAY too much for a pyramid style bow. If laid out as described in the thread about tillering from the edges, no thickness taper is needed. BUT, laid out as proposed in this thread some taper in the mid-to-tip area is needed. But certainly not 1/4", which would result in a decided whip tiller.

Whoops! You're right! Stupid emperial system... I actually meant 1/8" thickness taper, from 7/8" to 3/4" preferably. If the board was only 3/4" thick to begin with, then taper from 3/4" at the handle to 5/8" at the tips. Remember to not narrow the handle as you go, but to leave it full width.

[bubby]

3/4 inch thick handle...70 ntn   -  I don't think so.
I would make your handle 1 inch thick now. Better to have and not need


Yeah mike 3/4" thick not wide, he already stated he's going to pike it to 67-68", plenty thick plus if it does flex a tad it won't hurt anything I bet the limbs at the fades are around 1/2" thick when finished

[Comancheria]

Bubby,

(As a side note, every time I type in "Bubby", the iPhone tries to substitute "bunny"! 😳)

I am glad to hear your opinion as to the thickness of handle.  Right now, at a more-or-less uniform 5/8 inch, the stave is still fairly stiff against the floor, so you may well be right about the near-handle thickness having to drop to 1/2".  Right now, As might be expected, most of the bend is in that area, so my current plans are to try to work in some taper, starting by removing wood from the belly, mid limb, and seeing how that looks.  Actually, it would not hurt my feelings if this first bow came in fairly light.  50 would be great, but I am a little leery of not having started with a wider board--say 2 inches instead of 1 1/2--and now having to shorten the bow somewhat.

Russ

[bubby]

With that width shortening it will help you reach you're draw weight with less mass, I was texting a buddy about my little duck decoy, you can guess what the phone changed that too

[Comancheria]

I can only imagine!😊

Hmmm, maybe I ought to try narrowing the width of the wider tip and stay with 70 inches as a first try?

[Springbuck]

  Most of us are refering to tip movement, not the notch numbers, and that will vary with the long string length.  I like to tie the long string as tight as I can w/o bending the bow.

Also, without a scale, get a weight of some sort, equal to what you want the final draw weight to be.  Old dumbell plates, or a bucket of rocks, etc..   When you go to make a correction, hang the bucket on the string, either freehanding it, or actually hang it on the string while the bow sits on the cradle.  Watch the tips move.  If they move 3", take it off the bucket, and pull the string until the tips move 3", and NO FARTHER until you make a correction.

This method of never pulling the bow beyond desired draw weight has GREATLY increased my success rate.  These days, if I get a bow roughed out without screwing up, I usually finish it.

[Comancheria]

Thanks, Springbuck. Sounds like a good alternative.

OK, progress, but not sure how much.  Sorry I still cannot post pictures yet.  I went ahead and kept the length at 70", thinned both tips down to 1/2" wide.  I cut nocks in and installed a string with timber hitch at the bottom, just able to have the loop slip over the top and hang loose.  I exercised the limbs repeatedly down to 10, 11, 12...and eventually to 15 inches.  I pulled weight on a bathroom scale which showed 21 pounds at 15 inch draw with the loose string.

Not sure how to proceed and am open to advice--(understanding as I do that this is difficult without pictures).  The bow bends a little in the handle and near handle area.  It bends somewhat less at mid-limb and not at all in the last 10 inches.  To my imexperienced eye, the limbs are bending equally and both curve smoothly, and without visible hinges at this point.

I am wondering what the likely weight would be at 28 inches given 21# @ 15".  Any guesses?  (I promise not to sue!😀)

I am a little uncertain whether to remove more wood at this point at mid limb and within a few inches of the tip--OR--go ahead and keep exercising the limbs and pulling down further and checking tiller as I go.

I may have screwed up by cutting the nocks not only diagonally, but across the BACK of the tip.  Does that constitute violation of the back?  (Remember that this is a board bow not following one ring anyway). 

Also, the knotted end of the string holds on quite well to the nock channels but the loop end hangs onto the back, but comes out of the side channels on top.  Do I need to re-file these at a different angle or is the string likely to change direction
Imto the channels as the draw increases?

Thanks,

Russ

[bubby]

almost impossible without pics to help with tillering, you can make a simple tillering gizmo with a 6" block and run a sheet rock screw in so the tip sticks out just a little, hold it against the limbs belly and find the spot with the biggest gap and run the screw out till it almost touches there, now run it back and forth the length of the limb it will scratch where you need to remove wood, scrape the wood of where the scratches are, exercise the limbs 20 times , repeat
as far as draw weight figure 3# an inch but don't worry much about that till you get to low brace

[Comancheria]

Thanks, Bubby.  Understood with regard to tillering.  And with all my reading, I had not heard of that gizmo.  May give it a try.

If the formula you suggests holds in this case, I would theoretically end up at 60 pounds.  Sounds about right for the amount of wood I still have left on the belly. 

Let me ask you (and anyone else for that matter), this: assuming I am correct that tiller is equal and smooth, does it appear safe for the bow at this point to keep drawing down and visually checking for hinges, or differential tiller?  (Hope that question ales sense.)

Russ