2021 what did you do today?

[Shredd]

   Mark...  How thick are your lams going up the ramp on the belly side??

   Where are they not going down??  Is it the last inch or whole ramp area??

[Longcruise]

I've been thinking about alternative riser layouts and designs for my lam bow. While the first one eventually worked out, I wasn't really happy with the force required to get the belly lams into place, even after pre-forming them with steam. I learned a bunch in the first attempt and am sure I could get things to go more smoothly on a second run but I would prefer to design a better riser layout to eliminate the issues from the start.

I have been thinking that a riser more like Kenny's last FHLB would make more sense in that it lets me use larger radius bends for the belly lams, which should ease the glue up forces.

In the attached sketch my first riser is shown on the right with the FHLB styled riser on the left. In both sketches the belly and back lams are hatched to highlight them. The sketches are accurately drawn to scale, so all proportions are correct.

Let me know what you all think about the alternative design as compared to the first one.


Thanks,
Mark

I think the alternative design solves your problem AND will be more attractive.  I might even "borrow" your design.   However,  I'm also thinking that the problem you had was more about form fit than the angles.

[Mad Max]

   Mark...  How thick are your lams going up the ramp on the belly side??

   Where are they not going down??  Is it the last inch or whole ramp area??

x2
How long is the riser??
What is the radius??
How thick are the lams at the riser??

[Roy from Pa]

Fixed the bore for ya, Mike.

You can edit your post ya know?

[mmattockx]

   Mark...  How thick are your lams going up the ramp on the belly side??

   Where are they not going down??  Is it the last inch or whole ramp area??

x2
How long is the riser??
What is the radius??
How thick are the lams at the riser??

Sort of in order:

The lams were ~0.150" where they went up the ramps. This is pretty thick and was a result of following Dan Perry's suggestion on the proportion of belly wood to back wood for same wood bows that use Perry reflex. One the next one I will be using thinner belly lams, more like 0.125"-0.130", with a thicker core.

It wasn't one spot as such that was a problem, it was more how hard I had to clamp them to get them on everywhere. I was worried about squeezing all the glue out. I boiled them and clamped them in place to pre-bend them but it still took a lot of force.

The riser block was 9.5" long and the lam I put under it to smooth the fades was 14" long. The riser ramp radius was just over 6.25". The alternative design uses a bend radius of 10.375" for both bends.

I think the alternative design solves your problem AND will be more attractive.  I might even "borrow" your design.   However,  I'm also thinking that the problem you had was more about form fit than the angles.

I think it will look good, too. You may be correct on the fit versus angles. This is all new to me so I am dealing with things on the fly with no previous experience to fall back on. Even doing the same thing again will go better because I have one attempt under my belt now, but I would prefer to have a better design to start with.


Mark

[Longcruise]

Fixed the bore for ya, Mike.

You can edit your post ya know?

Whaaaa!!!

Just kidding, I know that.  It's harder to do on my phone so I just clarified. 

But, I sure am learning a lot from you this week, Roy!   

[Shredd]

  As a rule of thumb I was always was told not to go over .120"...  6" radius sounds way too tight, especially for .150"...  10" radius still sounds way too tight...  But then it might work with the new design if you go down to .120"... I use a 18" to 22" radius and a thicker lam may still be stubborn to push down...  The riser sounds short also... 

Is this a glass bow??  How long is the bow, nock to nock??  Are you using a air hose??  It sounds like you are not and clamping it...

   

[mmattockx]

  As a rule of thumb I was always was told not to go over .120"...  6" radius sounds way too tight, especially for .150"...  10" radius still sounds way too tight...  But then it might work with the new design if you go down to .120"... I use a 18" to 22" radius and a thicker lam may still be stubborn to push down...  The riser sounds short also... 

Is this a glass bow??  How long is the bow, nock to nock??  Are you using a air hose??  It sounds like you are not and clamping it...

Again, somewhat in order:

6" radius with 0.150" lams is far too tight for a dry bend but not when the lams are boiled and formed. It is a larger radius than guys typically bend recurve tips to on selfbows.

10.375" radius isn't too bad for a 0.125" lam, that works out to a strain of 0.6%. Wood selfbows are routinely bent to higher strain amounts than that. I will likely steam and pre-bend the belly lam on this design as well, just to reduce the clamping force required during the glue up.

It is an all wood lam bow, no glass involved. Bow is 67" NTN, target weight is 40-42# @ 28". No air hose, I am indeed clamping it.

The riser length is really 14" from end to end of the fades with the lam added in. It can't be nearly as long as a glass bow riser because I need the working limb length to not over stress the wood.


Mark

[williwaw]

mm,
Will riser-2 have a full length lam, or 2 half length lams with a joint mid-handle?
Have you considered tillering a wood pressure strip for the difficult areas?

[mmattockx]

mm,
Will riser-2 have a full length lam, or 2 half length lams with a joint mid-handle?
Have you considered tillering a wood pressure strip for the difficult areas?

For the belly lam? I am going to try to do it in one piece. The back lam will remain one piece.

I am going to try using TBIII one more time, with aluminum pressure strips for the bulk of the limb length and shaped blocks for the riser portion, like I did with the first one. I have no complaints with the blocks, it was in other places I had the issues.


Mark

[flyonline]

Thought about going outside for a bit of work on my latest (osage selfbow).

Looked at tomorrows forecast.

Decided against it 

Mind, that's down from a forecast the other day that had 45C/113F

[wood carver 2]

Too hot for me! I’ll take your nighttime temps any time though...
Dave.

[Roy from Pa]

20 degrees here and snowing.

Warm temps would feel good about now...

[kennym]

14 here this morn 

[Roy from Pa]

Good day for shed hunting:)

[kennym]

I know where my shed is and it’s 58 in there , thank you!

[Roy from Pa]

 

[Longcruise]

Not today but yesterday I took the spousal unit for her first round of the vax.  Getting mine next Tuesday.   

[Roy from Pa]

 

[Robyn Hode]

I started an HBO bow then hurt my shoulder then got COVID-19. I am currently in physical therapy and hoping to start back on my bow. I used Roy’s form set up but removed the mid blocks. The glue up came out great but when I was removing wood for better tiller I hit a bad piece of grain. It tore out at the tip. I am going to cut off two inches and continue. I will send pics when I can. I hope everyone is doing well.