Extreme Measures - ive cut my bow down...(UPDATE)

[g_r]

Hi,

i have (had) an Mohican LB with 68" and 42#@my30";
The laminations on the lower tip overlays started to break, and as the bow was a bit on the light side for my liking and i was in experimental mood i decided to cut it down to get more poundage.

ve meassured 1" down from the tips, marked where the new string groves should be, marked the tips to come and took the saw:


then ive taken the old overlays off with knife and rasp:



this is how the "tips" looked:


Next ive glued micarta on, rasped and filed the string groves and the tips in shape and sanded it down.

This is how it looks now:

Upper limp:




lower limb:



Tomorow i will polish it and pu the first layers of finish on. On the weekend it gets a string and ill see if this worked.

Im really curious if it will work...or if it will break and fail or stack like hell. Ive all goes well it should come out with 66" and about 50#.

And for those that now think im an idiot and ruined a bow...well maybe but it was great fun.

To be continued...

[longbow steve]

Well done Axel, it should work fine. Just check the tiller is correct and your good to go.

[Stickbow Hunter]

It looks like you have done a good job on the string grooves and tips, well done.

I'm not as confident as Steve that all should be fine though. I can't recall the design of your bow to say for sure, but 30" is a long draw and stack may become a problem. I think you will immediately feel the bow is a little less stable also; yes it is only two inches shorter but I think you will notice that; I certainly did going back to a 66" bow from 68" ones.

Jeff

[g_r]

Jeff, thats my main concern,too.
The bow desin:

Thats a 31" draw in the pic if i recall right.

And about the tiller, do i have to build me a tillering device? I hope not

[longbow steve]

Jeff, thats my main concern,too.
The bow desin:

Thats a 31" draw in the pic if i recall right.

And about the tiller, do i have to build me a tillering device? I hope not

No tiller device is needed, just a measurement from a point on the limbs to the string. The top limb should be a greater distance unless it is tillered even for 3 under shooting.
I didn't realise your drawlength was so long, the bow in the pic is just about at the point where it could be stacking and it is working extremly off the fadeouts. Steve

[g_r]

OK, ill measure it.

I dont know if it says anything, but before starting i drew the original bow back to 32" without stacking, thats what gibves ma hope.

[longbow steve]

You may not notice the stack being a light bow and you a burley lad . You would probably have to plot a Force/Draw curve.
When the string to limb angle exeeds 90 degrees it would be fair to say it would be stacking. Steve

[Stickbow Hunter]

When the string to limb angle exeeds 90 degrees it would be fair to say it would be stacking. Steve

Absolutely!

Axel, It will be interesting to see what you think once you have drawn the bow back now that you have shortened it. Let us know how it goes and perhaps post a photo of you holding it at full draw.

Jeff

[Steven J]

Seems like a good experiment. I'll be keeping my ear to the ground on this one.

I agree with Steve, in that the limb is working pretty hard in the fades. You could narrow the limb too and drop the weight in the outer third. It seems overbuilt there anyway.

Steve

[rodlonq]

Nice job on the repair and new overlays Axel, a whole new bow will be next maybe?

I dont have much experience but I have a few of observations/questions to put out for discussion.

It seems the way Axel's bow is designed with the stiff outer limbs may be the one thing that saves the string angle from exceeding 90 degrees when it is shortened?

If it had more flex in the outer limbs, would there be more chance that the string angle would exceed 90 degrees even though it may not stack as much?

Obviously the draw weight would not increase as much if the outer limbs were refined to bend more. Would the stack be much bother considering Axel can probably pull a lot more than it will ask of him?

Cheers......... Rod

[Stickbow Hunter]

If it had more flex in the outer limbs, would there be more chance that the string angle would exceed 90 degrees even though it may not stack as much?

If the limbs bent more towards the tips the string angle would probably exceed 90 degrees and that would cause the bow to stack more.

Jeff

[hazard]

When it comes to extreme measured, if it pinches too much why dont you cut it in half and make it a take down? Make sure you add a spacer so the bow is longer knock to knock.
Havent done it myself, cant vouch for its success but I have seen it done before (except for the spacer) and the bow works fine! Apparently there is a special hinge you can get from the states.


Hazard

[g_r]

It worked!

Ive sanded the tips a bit smaller for less weight and then finished it.
Now ive put a string on and it didnt crack .

Now it has 65"

at 28" draw it has 42#
at 29" draw it has 44,5#
at my 30" it has 47#

So no Stacking, as far as i can feel less handshock then before and still absolutely quiet.

The relatively low increase in draw weight and the non existent stacking are i.m.h.o. due to the fact of the bow working mostly after the fade outs and not in the limb tips.

I like it!
Now its a keeper, and will be my bow for tournaments where you need that classic D-shape and woodies to get into the Longbow class. Ill build some bamboo arrowsfor it.

My camera is in the car, so pics will come later.

[g_r]

[Stickbow Hunter]

Congrats mate it looks like it is fine. Going by the full draw photos the string angle looks less with you drawing the bow now than in the photo of the other fella drawing it previously. Be aware that it may feel a bit more unstable when you first shoot it because it is shorter as those couple of inches you cut off does make a difference. I'm sure you will get used to it though.

Jeff

[g_r]

Thanks Jeff;
Well the other guy draws one inch more.

I dont think i will notice any difference in stability as i didnt shoot it with the lower poundage often (maybe 100 arrows three months ago). Ive bought it when i had some shoulder issues and wanted a light bow, after that it just collected dust.

[rodlonq]

If it had more flex in the outer limbs, would there be more chance that the string angle would exceed 90 degrees even though it may not stack as much?

If the limbs bent more towards the tips the string angle would probably exceed 90 degrees and that would cause the bow to stack more.

Jeff

Hi Jeff, I didn't articulate what I meant very well. I wasn't considering the amount of stack after the string angle went past 90 degrees because I thought allowing the string angle to exceed 90 degrees would be unadvisable (is it OK to do this?). What I was saying/asking is if the outer limbs were weakened to bend more, would the amount of stack be less as the string angle approaches 90 degrees? Would the trade off would be that the string angle would reach 90 degrees earlier and the maximum draw length and weight reduced? It appears this would not suit Axel very well, which is why I was hedging toward not weakening the outer limbs to bend more. I should be just asking straight out questions instead of making statements and looking for answers (just trying to learn the most from a very interesting topic). Am I on the right track yet?

Sorry about highjacking your thread Axel. The new tips look good mate.

Cheers........ Rod

[g_r]

no prob rod, very interesting indeed, but i cant help you with that anyhow.

[Stickbow Hunter]

What I was saying/asking is if the outer limbs were weakened to bend more, would the amount of stack be less as the string angle approaches 90 degrees? Would the trade off would be that the string angle would reach 90 degrees earlier and the maximum draw length and weight reduced? It appears this would not suit Axel very well, which is why I was hedging toward not weakening the outer limbs to bend more.

I can't say for sure regarding your first question. I agree you are correct with the rest of your thinking though.

Jeff

[rodlonq]

Thanks Jeff.

[Dennis La Varenne]

g-r,

your last picture with you drawing your bow shows that the string angle is pretty close to 112.3 degrees between the upper and lower sting halves which means it has another 22.3 degrees to go before it reaches the stack area as some current theory would have it.

The problem would be whether or not your limbs give out beforehand. To get your string angle to 90 degrees, you would have to draw the bow another 20 to 30 cm as the attached pictures show.

In Photoshop, I have drawn two ways in which the 90 degrees can be measured. You have to allow a bit of a margin for error because of the amount of cant at which you hold your bow. However, I believe that very many trad bows would run into problems with materials integrity well before they achieved the theoretical 90 degrees string angle.

Also, your picture which I have used shows pretty clearly that the outer limb reflex is starting to come out with your long draw and there probably is not anything beneficial you could do to reduce any apparent stacking which clearly by your f-d figures, does not exist anyway.

[Dennis La Varenne]

Also,

Just in case anybody was wondering where I got the 112.3 degrees of string angle on g-r's bow at full draw, look at the pic below.

I don't think many of us actually realise how far one must draw a bow to get the string angle to 90 degrees where Tim Baker considers that stack begins. I must say that his thesis on the 90 degrees business which he describes in TBB Vol. 1 has always caused me a lot of bemusement.

It has always been far from clear to me in his description just how he measures the 90 degrees. My guess is that it is done at the limbtip/string junction as in the first of the pics in my post immediately above, but as one can see very clearly, this still necessitates in a prodigiously long draw of which even the Warbow blokes and blokesses would be impressed.

My only consideration in support of Baker's thesis would apply to very short bows, and they would need to be VERY short indeed. In the pic below, g-r would need to take something like 25cm from each limb to achieve a 90 degree string angle even at his long draw.

This is where I contend above that to achieve a full draw string angle approaching 90 degrees, materials integrity would be almost certainly be compromised because of the severe bending loads applied. String pinch would be a very minor issue in this instance.