Guidance request for Walk through Tiller in progress. Long HHB.

[Don W]

This stave was the small half split off a HHB 4-5" diameter tree. The stave wasn't quit big enough for two complete staves, so this became a bend through the handle design for lack of enough material in the center for a better handle.

I decided to use it and do some experimenting and learning

This stave had a hook that made the sting center outside the handle. I heat treated just the center section while drawing it back into form. I figured this would allow the string to be closer to the handle center (although not really centered) and would stiffen the handle section of the bow

Here is a walk through of my notes. I'm looking for any thoughts or guidance, especially around why it has such bad handshake.


I quickly roughed it out and had a good floor tiller when I got to the long string. I tillered normally and was working pretty quick. At 72" i figured I had room to pike if I made a mistake. I was shooting for 60#@28"
Being quick I hit 60#@28" before I expected and full draw looked like this:
 
 



 
 
Spec's at this point look like this
1 1/2" at widest to about mid limb then tapers to .5"
72" tip to tip
60#@28"
it has some fairly significant handshake
1 3/4" string follow (most of that is set, although some may be soft set)
I did some trapping to cut the weight and hoped to improve the fps. It didn't help the speed. I've also narrowed and lighten the tips hoping to improve the handshake. It hasn't helped much yet.

At this stage it's shooting at about 145fps
Then I Did some tillering with the gizmo. That helped the tillering but still has significant handshake.



 
Now 55# (i may pike it but waiting to improve the handshake)

After some testing i found if I shot the arrow of my knuckle at bow center I get 158fps. If I raise the arrow to 1 1/4" above center I loose 5 fps to 153fps (this is with 10 shots of arrows ave 650gr) if I shot the arrow of my knuckle at bow 1 1/4" below center 157fps

So the bow definitely wants the top limb to be longer(or I assume the lower limb stiffer)
Still a 1/8" positive tiller


I then narrowed the tips down to .38" atthe nock. This was tapered to about mid limb as before.

draw weight is still reading about 55.3#@28" Narrowing the tips brought the speed back up to 152fps. The handshake might be slightly better, but still uncomfortable.

[Don W]

Yesterday I glues some leather on the handle to make it more comfortable.
I formed that into a handle

I cut 1 1/2" off each end and recut the knocks.
Did some minor tillering and weight reduction back to just over 60#
63.8#@28" now shooting about 159fps
still using 10 shots of arrows ave 650gr
Second set 63.9#@28" now shooting about 161fps
1/4"positive tiller and most if not all of the hand shake is gone.


Did some more trapping and weight reduction from the sides
switched to a lighter string
3/16"positive tiller
No handshake
61.5#@28"  161fps  156fps   158fps
About 2 3/8" string follow (some of which is soft set. After about an hour or so it had reduced to 1 7/8")

Did sanding, removed tools marks etc. Sanded to 320 grit

Shot about 60-70 arrows and still 150fps and reading 60#@28"   

It's turned into a reasonably pleasure to shot. It's a little heavy for me, but I can still hold a reasonable group up to 30 yards

Final dimensions
66 1/2" tip to tip
1 1/2" at widest to about mid limb
tip .49"
Bow thickness starting at 3" from center

dimensions:

[BowEd]

You've figured out the reduction of handshake on your own there.It's the extra mass the bow had on it's limbs at 72".By piking you've eliminated a lot of it
Nice bow by the way.

[Don W]

I think I'll try and see what happens with a little shorter.
I'm not sure what the most efficient length would be, but I guess there is only one way to find out!

 It also seems HHB likes a trapped back.

[Don W]

I cut another 1" of each end bringing it down to 66 1\2" tip to tip.
Tillered it back to just under 58#@28".
Current average speed with my 650gr arrows is 158fps.
It's a little more powerful than I will take hunting. I loose accuracy after about 53#, but I like to shot a heavier bow once in a while, and this one is fun to shot, and as with all I've built so far, it was a learning experience.

I will add some pictures when its finished.

[BowEd]

That's very good speed from that bow.

[bownarra]

Simple reason for the handshock - it is bending too much in the handle/innerlimbs.
At that length the tiller should've been highly elliptical with virtually no bend in the middle. 1/3rd.
As you have shortened it you have effectively reduced the bend in the handle/inner limbs.
Narrow tips will help reduce handshock on a bow that suffers with it. However your tips are not the reason you have handshock. You can leave the tips 3/4" wide and have zero handshock IF and its a big IF........the bow is tillered correctly. Handshock is your bow telling you that it is out of tiller. Either limb balance relative one to the other is out or the tiller is wrong for your width taper.
I suggest you buy the TBB (vol 4 I think specifically for the design and performance chapter) series of books. They will explain the answers to all your questions.

[BowEd]

Correct observation by bownarra and should have mentioned it but I don't make too many bendy handled bows myself.Making that thickness of .84 extend out a few more inches either way from the handle for a more eliptical tiller.
Shooting heavier arrows does reduce handshock a bit too making the bow more efficient with bows 5.5' in length.To really see if a bow has no handshock shooting an 8 grain arrow will show you too.Right now your shooting around a 11.5 grain arrow.

[Don W]

That's all good to know. I have all 4 volumes and have read it several times. I guess it's time to read it again. Maybe now it will sink in

I usually let the bow bend a little, but I made this handle ad big as I had wood for. I planned to shorten the bow all along, but wanted to see what it would do, and I learned a little more.

It's shooting pretty nice now, so I'm not going to experiment any more on this one.

Thanks for the responses. They always help me and hopefully will help others as well.

[Don W]

I Cut another 1" off each end to finish at 66 1/2" tip to tip
I retillered it and shot it over a week or two.
It Finished up with 57#@28" shooting around 158fps for my 650gr arrows

[PaSteve]

Looking good Don. It's good to figure things out through experimentation. Thanks for posting your results.

[Selfbowman]

Well done Don! That’s good speed with that heavy arrow. Probably has no shock either. I like it.

[superdav95]

That’s decent speed out of that bow for the gpp you are shooting.  I’d be happy with it if you can hit what your intending.  Hhb is strong bow wood.  Well done don!   

[Allyn T]

This was a cool walk through Don thanks for bringing us along.