Maple Board Bow Tiller Review

[mmattockx]

So, I'm at the tillering stage on my maple board Mollegabet style bow. First one ever for me and I am trying to go super deliberate and not screw it up. 68" NTN, target weight is 30lb @ 28". I currently have it drawing 30lb at 5" or so on a long string at and spent well over an hour this afternoon slowly scraping my way to that point. Slow work!

The tillering tree is dead vertical and the bow is level at the start, the shelves are not true. Tell me what you all see:







So, do I just keep taking wood off and reducing weight until I get a few more inches of draw then low brace it and keep going from there with a real string or something else?


Thanks,
Mark

[willie]

Hi Mark,
deliberate is good! nice looking workmanship in the lam job, A pic of the back would help others get an overall view.

Before anyone offers an opinion, I would like to ask you what you see! where does the bow appear to bend the most in the second pic? The acquired skill of tillering is all about judging bend.

[mmattockx]

I don't have a good pic of the back, this is the best one while the tip overlays are being glued on. After this picture I backed the board with fabric from an old bed sheet and Titebond III.




What I see on the right limb is it is a bit stiff out of the fade, then maybe a slight hinge a few inches up and then stiff towards the end of the working limb. On the left limb it looks weak out of the fade, then stiff in the mid portion of the limb and the end bending not too badly.


Mark

[willie]

Hi Mark,

I'm seeing the most bend right above the florescent tube ends peeking out of the box behind. as for the right limb being a bit stiff outof the fade, I dunno, but I am just looking at a single pic and you have the advantage of looking at it from all angles and as you pull. Personally, I would concentrate on getting the mid limbs bending evenly, and hold off on revisiting the fades for a while.
Do you intend to have the tips bend slightly?

One thing I like to do is have a good idea what the design (in a well tillered example) looks like at brace. Luckily there are lots of nice examples to view here at PA, and then try to get my bow looking similar before I draw it further than that with the long string.

[Del the cat]

Not really enough bend to see much (it's mostly at the fade as the others have stated), but what strikes me is that the bending portion of the limb (between grip and lever) appears to be thicker at the lever end (could just be an optical illusion where the camera can see a hint of belly as well as the edge)
I'd measure the thickness of those sections every 2 or 3 inches and check that you have some thickness taper.
Alternatively, nip up some verniers at the end nearest the fade and slide them towards the tip, you should be able to see an increasing gap opening up as you slide along. I'd suggest you should have at least 1mm of taper every 6".
Where you have a stiff lever and a short working limb, you have to get the working limb bending very evenly.
Del

[mmattockx]

Personally, I would concentrate on getting the mid limbs bending evenly, and hold off on revisiting the fades for a while.
Do you intend to have the tips bend slightly?

I will keep at the mid limbs, they are certainly stiff on both sides. I was expecting the levers to be stiff with no significant flex.

One thing I like to do is have a good idea what the design (in a well tillered example) looks like at brace. Luckily there are lots of nice examples to view here at PA, and then try to get my bow looking similar before I draw it further than that with the long string.

Yes, all I am trying to do is get to brace height with the long string and decent tiller.

Not really enough bend to see much (it's mostly at the fade as the others have stated), but what strikes me is that the bending portion of the limb (between grip and lever) appears to be thicker at the lever end (could just be an optical illusion where the camera can see a hint of belly as well as the edge)
I'd measure the thickness of those sections every 2 or 3 inches and check that you have some thickness taper.
Alternatively, nip up some verniers at the end nearest the fade and slide them towards the tip, you should be able to see an increasing gap opening up as you slide along. I'd suggest you should have at least 1mm of taper every 6".
Where you have a stiff lever and a short working limb, you have to get the working limb bending very evenly.
Del

They started at the same thickness from fade to lever. I have been taking most of the scraping off towards the levers to get that taper started, but it is nowhere near the 1mm/6" you mention. I will run a set of calipers over it and see what I have now and keep working towards more taper.


Thanks for the input,
Mark

[Del the cat]

Just in the interests of accuracy (as I was sort of guessing  ) I've been and checked my Molle flight bow.
The working limb is about 13" long... measuring at 6" intervals I got varied results due to the natural Yew sapwood back, sometimes less than 1mm sometimes more. So I took measurements over 12" and it was 2.24mm. So 1mm per 6" seems a reasonable start point.
The bow can be seen at full draw here:-
BTW it eventually after a little re-work shot 283 yards, not bad for a 45# bow
https://bowyersdiary.blogspot.com/2015/07/whew.html
Del

[willie]

Hi Mark,

a few thoughts, and of course a question. is the handle area width (as seen from the back) close to finish width? The pic of the bow on the table shows a rather wide handle.

 

do I just keep taking wood off and reducing weight until I get a few more inches of draw then low brace it

yes a few more inches until it bends on the longstring to about what would be brace height were it braced to take a long hard look at it,  but I would actually wait until the bow is reduced further to try to brace it for the first time. 30#@ what would be  20" - 22" if you are shooting for 28" finish draw length.

 see  http://www.primitivearcher.com/smf/index.php/topic,65722.50.html

[mmattockx]

The working limb is about 13" long... measuring at 6" intervals I got varied results due to the natural Yew sapwood back, sometimes less than 1mm sometimes more. So I took measurements over 12" and it was 2.24mm. So 1mm per 6" seems a reasonable start point.

My working limb is longer at 18", with a 12" lever. I will keep at the scraping and working to introduce more taper and see how it works out. I will leave the fades alone completely until I get the mid limbs working more. Once I get there I will post a new picture and get more commentary on it.

a few thoughts, and of course a question. is the handle area width (as seen from the back) close to finish width? The pic of the bow on the table shows a rather wide handle.

The handle has not been worked on yet and is the same 1.5" width as the rest of the working limbs. Since it's to be a stiff handle I figured it wouldn't make any difference to the tillering and this way I can pick which limb is top after seeing how they are bending. I can certainly rough it to finished width before continuing if that matters.

yes a few more inches until it bends on the longstring to about what would be brace height were it braced to take a long hard look at it,  but I would actually wait until the bow is reduced further to try to brace it for the first time. 30#@ what would be  20" - 22" if you are shooting for 28" finish draw length.

Ok, I can do that with no problems.

EDIT - Willie, I just got through reading that thread you linked to on measuring draw weight with a slack long string. That is super useful, many thanks.


Mark

[willie]

I can certainly rough it to finished width before continuing if that matters.

I am not sure if it matters, I might could be done either way, but my own order of operation is to get the fade area to desired depth and width, before tillering. I also take care to make sure that the full limb width (as seen from the back) extends a half inch extra towards the center of the bow from the point where the working thickness of the limb begins. Preventing excessive bending out of the fades is the reason for the precaution.
Many like to leave the fade area a little stiff until later in the tillering process, and get it bending more, if and when, set starts to show as you get close to full draw. 

[bushboy]

Floor tiller!!!.

[mmattockx]

I am not sure if it matters, I might could be done either way, but my own order of operation is to get the fade area to desired depth and width, before tillering.

Because the wood is only 1.5" wide I am not taking very much off handle portion in the fades. The overlap of full width from the fade into the working limb is a bit over an inch, so I am well covered there.

Many like to leave the fade area a little stiff until later in the tillering process, and get it bending more, if and when, set starts to show as you get close to full draw.

I can understand that after some experience with how tillering goes. I spent a while scraping again today and gained another couple inches of draw at 30lb. Up to a bit less than 17" at this point, with at least another 3" to go before bracing it. Things sure move slowly, I now have close to 0.080" of taper on the limbs and they are just beginning to bend a bit and there is a large pile of shavings under my bench. It will be much larger before this thing is bending as it should.


Mark

[willie]

Things sure move slowly

yes it seems that way on the first bow, however things move very fast when taking those last few scrapes as you near full draw. But of course your deliberate progress will pay off at the end.

Bet the guys would like to see a pic at 17"or 20". More pics = more response here at PA

[mmattockx]

yes it seems that way on the first bow, however things move very fast when taking those last few scrapes as you near full draw. 

I expect so. What's killing me is having no experience to know when I'm getting close. I could have rasped off a bunch of this wood but without a feel for the progress I am sure I would just overshoot and end up with a 12lb bow.

Bet the guys would like to see a pic at 17"or 20". More pics = more response here at PA

Fair enough, today's progress shown at 17" draw length:




Mark

[willie]

I guess 17" draw all depends on how much droop you keep in your longstring. This recent thread demonstrates a use for an elastic cord for judging tiller shape, but  I use the same method to also see how far the tips are coming back. I like to see the tips come back 10" or so which would correspond to about a 20" draw with a braced bow, before I brace it for the first time. As for how long a longstring should droop, there are about as many preferences as there is bowyers. Many start with 5"-6" droop and shorten it to slightly slack with no droop as they get closer to the point they decide to first brace.

http://www.primitivearcher.com/smf/index.php/topic,67369.0.html