Birch Holmegaard Bow

[bushman]

First off I would like to thank everyone for their generosity, especially RobWiden for the birch stave and everything else that he has done for me. It always surprises me for the generosity of the PA members.
Here is a few pictures of the birch stave with the layout on it for a holmegaard bow. Its 74 inches long, 3 inches wide till the fades at 2/3 the length of the limbs. I drew two sets of lines on it, the inner set are for the finished shape and the outer set are 1/4 inch away from the inner set, those are my cutting lines. This bow is going to take me a will to make but I will keep you all posted on its progress. I'm hoping to get around 55# to 60# at 28 inch draw. Thanks for looking.
Bushman

[mikekeswick]

Birch is very tension strong. Trap the back a good amount as it will really make a difference to any set you get.

[blackhawk]

Birch is very tension strong. Trap the back a good amount as it will really make a difference to any set you get.

Ditto,n it will take some force off the belly as birch is a lil compression weak...it will help ya keep from getting frets because the lever bows are more stressed than a normal flatbow...i.e. shorter working limbs

[RobWiden]

    Bushman - I think that stave has enough crown that it is naturally trapped, so you shouldn't have to worry about that. Do be sure to make a flat belly to absorb all the compression possible. Hope you enjoy the process and end up with a great bow.

[bushman]

Progress report:
Well I got the profile sawed out. Took me almost two hours to do, not bad for the saw I was usin. I really need a good rip saw (hand rip saw that is). Here is two pictures of what it looks like, and the saw I used. I have to draw the side profile on it now.





What did you guys mean by "trap the back"?
Thanks for looking.
Bushman

[blackhawk]

Trapping refers to the cross section of the bow and shaping it into a trapezoid cross section....meaning the back is not as wide as the belly

And there is much easier means to reduce your profiles than that handsaw...a hatchet,machete,or draw knife will go 4 times faster

[Moose]

That's a nice lookin piece of birch, hopefully mine turn out that nice. How long was it dried for?

[Slackbunny]

Wow, you are far more determined than me to carve out that stave with that little saw. But your profile looks good. Can't wait to see more pics, I love the look of that style.  A holmegaard bow is definitely on my bucket list, but its a little advanced for me yet I think. Good luck.

[bushman]

Progress report:
Well I finally got some more time to work on my bow. It was too big and awkward at 74" so I shortened it down to 68" ttt. It is 2 1/2" at the fades straight for two thirds the length of the limb then it starts to narrow down for the last third for the tips which are 3/4" at the moment but I'm planning on takin them right down to 3/8 or less with a tip over lay of ether raw hide or hard wood. The picture of it being tillered is with a long tillering string and it is only being pulled 4" and it is #120. A little on the heavy side, and a lot heaver then I thought it was goin to be. I had read somewhere that for the Holmegaard you only want a working limb from fades to mid limb, to minimize stacking. That was a mistake with this one. I had been removing wood (at times I thought it was a lot of wood but the poundage of the bow wasn't dropping that much) and drawing it repeatedly to 4" then 4" and a bit and so on. Well I had it down to #100 at 6" and it fretted. Not really bad but enough for me to go crazy with a rasp and take off lots of wood on the upper limb portions above the frets to thin it down more then where it was at the fret sight. I thought the bow was goin to be only #30 by the time I was down with it. But when everything was said and done it is #79.5 at 28", it still needs to be sanded smooth so will be around #65 when I'm done.

I did some reading and found out that one of the causes of fretting is having the would too thick on the knock side of the fret, which was exactly what I had. Also frets is caused by over straining the fibers, which also happened I belief since it was pulling so many pounds. I read that to try and fix frettes is to sand it smooth and then with a strong needle push a series of wholes along the length of the fret and if the fibers don't raise any more when the bow is drawn then the problem is solved. Well I did that then drew it to 28" a few times, seemed to be ok, no more fibers raised up.  Since then I have shot it about 80 times and have drawin it back to 28" 500 times in a row and it seems to be ok. The pictures of the frets is from right after I draw it back those 500 times. The last two pictures are of the same section of frets on the lower limb. The frets occurred at about 4" from fades on upper limb and 5" from the fades on the lower limb.

It has a 1 7/8" set on the lower limb and 2" of set on the upper limb. I had heat treated the belly of it and had induced an inch of reflex. The heat treating was to stop the birch from fretting which it is prone to do, but from the weight of the bow at initially tillering I think that the limbs were too thick and the heat treating never penetrated the limbs. Any ideas on that one? I will measure the thickness of the limbs sometime when I get a chance but they aren't much more the a 1/4" in the thinnest place. I don't have any pictures of it at full draw yet. But there is no hinges in it that I could tell anyways. Do you guys think it was survive?
Bushman

[adb]

Those short little thick tips are not what a Holmegaard bow was intended to be. I think they're just going to cause you a bunch of grief. A classic Holmie has stiff non-bending outer limbs which usually occupy at least a third of the outer limb, and they act as levers.

[randman]

So do you have this thing braced or are you still using the long string. If so, do you have a braced pic? and a full draw to 28" pic? It's much easier for us to assess your tiller if you do. It looks like you have a bit of set in it. The set and the frets you have are probably because you were pulling it to 120# which is way over what you wanted to end up with. If you wanted a 60# bow you should never pull it more than 60# at any time during the tillering process. Then you just keep removing wood until the 60# pull gives you 28" of bend (or whatever you want your draw to be).
At this point if it is still 79# then you can still remove a little wood and maybe get below those frets by the time you are at 60# (depends on how deep they are). Then you can heat treat it again and MAYBE save a little of the performance you might have crushed out of it by pulling too heavy.

adb, the bow you are describing is a Molly (unbending levers). The Mollegabet (sp?) and the Holmegaard artifacts are 2 different bows. Bushman's bow is actually resembles the true holmegaard artifact more in back shape (although a little more pyramidal) and the outer limbs are bending (unlike stiff levers) but I'm guessing Bushboy was actually thinking of the molly also by making those tips way too thick so they'd act as levers but they are too short to be levers so reducing them down so they are just stiff enough to not bend much at all would give the best performance at this point.

[mikekeswick]

To be brutally honest I would take what you've learnt from this bow and make another 
When you get a fret it isn't just because there is a thick spot tipward it also means that the spot where it fretted is too thin....
So if it's already too thin and bending too much sanding it will not help.
The only real way to fix a fret (without turning it into a kids bow) is too grind out the fretted section and glue in a new patch. Go to Dean Torges website and have a look on there he has a great article on the method.
As for the tiller on holmguaard bows, the ones i've made have had the best performance when the outer limbs bend a touch. The width profile of the original calls for a mildly elliptical tiller with the last third bending less. The outer limbs only need to be a shade thicker than the 'working limb' to achieve this.
I think the original holmguaard bow is one of the best designs out there and was very well thought out.

[bushman]

Thanks for the info. I thought it fretted because of the strain of pulling #120. I had no idea that it was goin to be that heavy when I drew it to 4 inches. At the moment I don't have any more pictures of it but I will take some soon. I'm still usin the long tillering string but I shorted it down with a timber hitch to get the bow to brace height. I was still goin to thin down the tips and the handle section. Where it fretted is now thicker then the wood on the knock side of it so the strain is taken off of that portion of wood.
Bushman

[blackhawk]

Why were you pulling it to 120# when you were aiming for only 55-60#?....NEVER pull past your intended weight....that wasn't even close to being ready to be braced IMHO. Also never past any little imperfection in the tiller(especially with a "softer" whitewood)...these two violated rules is why it fretted....live n learn. Start another.