Another mad project!

[MattZA]

*Edit* Progress photographs on page 2 and 3*

*Edit 2: Bow is no longer a kids bow. New stats show we're looking at around 40# at a full draw of 24". It's still unbacked and now around 43" - there's just a new belly lam which accounts for the weight increase*

Hi all!

Just searching for a bit of tillering advice, but any other advice would be welcome

Inspired by my last short bow, I've decided to make a crazy short kids bow (aiming for around 25# at 23") out of two laminated pieces of bamboo. Then to complete the process, I'm sticking little siyahs on it to give it that faux 'horse bow' appearance.

Numbers: 45" tip to tip including siyahs. Bow is two flattened sections of bamboo, glued into reflex. The belly is heat tempered and given more reflex to add up to 3" in total. It's very narrow, at 3/4" wide across the whole bow. Siyahs are Garapa, spliced in with a V. I'm tillering to a draw length of 24".

The handle is currently just a piece of felt to protect it on the tiller.

Here's a link to the photos. We're still in early tillering, obviously. Where to from here??

https://photos.app.goo.gl/gMtKUpDnxNU3duPXA

[simk]

hi matt, I see lots of bend in the handle section. good luck

[PatM]

Back to the drawing board.  You'll need to pre-tiller your slats better since you can't really tiller after glue up.  That's going to mean a better taper and/or a power lam in the center.

[MattZA]

Hi Pat and Simk

I'm thinking a similar thing, unfortunately. I do however have an infinite supply of free bamboo, so don't mind snapping this and keeping the levers.

Probably being stupid, but could I not put a short 'power lam' on the belly? I suppose it'd effectively be a bending handle, but could it not achieve the objective nonetheless?

Matt

[Pat B]

The problem with working the center 1/3 of the bow is the leverage of the limbs puts all the stress on the center 1/3. I like to get each limb bending and leave the handle area stiff. once the mid limb bends well then I bring the bend back into the handle area. With a bendy handle bow I like to feel the handle area give slightly as I hit full draw.
 If you are going to back the bow put the power lam between the backing and belly.

[MattZA]

Yea it was a two fold mistake. I tend to accidentally make my bows whip ended, so I was trying to avoid that. I also wanted to achieve that Asiatic style curve with the bend close to the handle.

So it seems the only option involves separating the two laminates? Pity. I was hoping to try and keep the two laminates together and add something to the belly or back to reinforce/strengthen the section that's bending too much. I'm still considering a silk backing, but I doubt that will do anything to lessen the bend in the handle?

Thanks for all the advice, guys. This is my first ever attempt at a full laminated bow.

[Halfbow]

I've backed a few bows with silk and it's never made any difference to the tiller or draw weight. The most I ever used was 2 layers of fabric, so perhaps if you used a whole lot of layers.

I'm not sure if this will save it, but you could try gluing and lashing a handle block to the belly. Something like Dave Mead does with his bows:




However I'm assuming the belly is still the curved outer surface of the bamboo? If so, I recommend you don't get rid of the hard power fibers on the outside, which means no planing the surface, which makes a good glue joint difficult.

[MattZA]

That's a really interesting idea, Halfbow. As you say, it might be tough to get a perfect glue joint, but what I like about the handle block idea is adjustability. I could cut some reflex/deflex into the handle area (like a minor Perry reflex), depending on the tiller.

Fortunately I only need a measly 25-30# at around 24".

As for the silk, I've only got it in ribbon form. Which means a weaved thread. Heavier, but I'm hoping it'll pay for it's weight by keeping the limbs from twisting thanks to the perpendicular thread.

I'll update you guys when the doctors finish pulling the bamboo splinters out of my face   

[Bayou Ben]

Hey Matt, just a heads up on your next glue up, in that last picture it looks like there's some gaps in the glue joint.  That can lead to de-lamination issues. Let us know if you need advice on getting better more even clamping pressure.  There's a few ways to do it. 
-Ben

[MattZA]

 Hi Ben,

Thanks for the heads up. The photo makes it look a lot worse than it really is, but you're right, there are a few gaps in the joints.

I've tried a couple of methods. I initially clamped the bow belly up with the few clamps I had, and then used spare pieces of wood as wedges to place under the bows back. That partially worked, but left gaps.

This time round I bought some bandage for muscle injuries, etc. I placed the backing down and wrapped it tightly (although not too much to squeeze all the glue out. The mummified bow was then claimed to a basic form for the reflex.

I'm interested to hear the best ways, though. I tend to use my countries equivalent of TB3.

Any help is always appreciated!

[Bayou Ben]

Matt,
Before I acquired enough c-clamps I used a bike inner tube cut in half length wise and wrapped very tightly with no gaps.  This works ok on simple laminations (just joining two pieces).    C-clamps with pressure strips on the top and bottom work the best imo, but you'll need a few to do it properly ( I use 36 if I remember correctly).
TB3 equivalent should work fine, but there's no gap filling properties in TB3, even more of a reason to have even consistent pressure throughout the glue up.  I haven't tried it, but I imagine bandage wrap could work, but you would have to wrap it very tight, almost to the point of breaking considering it's stretchy nature.  A bike inner tube would work better if you could get your hands on one.  And wrap the entire limb with no gaps in the wrap.
Good luck.

[MattZA]

Yea I still have a loooong way to go before I have that many clamps. My last count was 4. And two of those squeeze clamps, which are useful.

The bandage actually worked out. I honestly believe the issue with this glue up was that the two laminations weren't 100% flush. As much as I tried I just couldn't get them to fit perfectly. Worried about losing thickness, I decided it would be good enough and glued them together.

If you have any secrets about how to get laminates the correct thickness and to fit perfectly against each other, I'm all ears! First up though, the handle block.

Thanks man. I'll let everyone know how it goes.

[Bayou Ben]

Nah, I have no secrets for that, especially using bamboo.  Whether you use a rasp, hand plane, or belt sander, it's a chore to get bamboo flat and down to size.  But a flat surface is a must. 

[MattZA]

Sadly.

It's always been a Stanley Surform for me.

Well I'll let you know how it all goes. Photos coming soon!

[MattZA]

Hi all. Here's an update on this mania. Please shout with any advice.

After a bit of tinkering, it now reads...

Three laminated pieces of bamboo all from the same shoot. Garapa siyahs. 43" nock to nock. 3/4" wide at the handle, reaching 1/2" at the tips. The length includes the 3 1/2" siyahs, which are 3/16" wide.

My original target was just 25-30# at 24" of draw. In this photo it's pulling 28# at 17" with a very low brace height string (2" brace).

Any advice?

Matt