Author Topic: Help needed with dimensions for laminations on reflex/deflex Bow with BOO  (Read 6864 times)

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Offline Springbuck

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Also not an expert, and it's been a long time, but I learned a few things.

First, flatten the glue surfsce of your belly bamboo, but leave it thicker than finished thickness. Do your toasting/tempering next.  What happens here is that the rind surface shrinks and actually flattens somewhat laterally (removes some of the crown) as a reaction to the heat.   The flat surface you prepared to glue will bulge slightly in response and must be flattened again prior to glue-up.

Yes, you can sand the nodes flatter on the belly side, but don't go crazy.   If you mill the entire surface very st, you are violating some fibers rather steeply.

I went with a consistent thickness back and belly (as near as obtainable with bamboo), of 1/8 on the back and 3/16" on the belly.  I tapered a thin core of vertical bamboo flooring from about 3/16" middle to less than 1/8".   I think I added reverse wedges at the tip, but very thin. 

The handle was two tapered blocks glued together and sandwiched between the rest.  The backing on one side, core and belly on the other.  I glued core to handle, belly to core, and backing to handle and core in stages, sanding transitions each time.

I did not force either bow into a deflex form, but the shape of the handle filler deflexed it slightly, and I reflexed the tips about 2-1/2".   I left the whole thing full width,  just shy of 2" wide, and relied on clamps and shims.   I planned on doing all tillering from the sides.

These bows were very stiff, and had to be narrowed to less than 1-1/2"   They took enough set near the handle that they became R/D bows, but the tips stayed ahead of the handles.

Hope it helps.

Offline leonwood

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Thanks Pat, missed this post somehow!

You can follow Springbucks advice above and that will work for sure but is probably a little harder because once glued up there is not much wiggle room to change your draw weight or tiller.

This is the way I did it a couple of times:
First make a really flat back lamination of bamboo.
Then pick a core lam, you mentioned ash or oak and they will both work fine.
You can leave your core relatively thick at this point but you can also pre-taper it a bit if you like. Mine are usually about 8 mm at the middle tapering to 5 mm at the tips. I don't really measure a lot as I build all my bows by feeling.
Glue the core and the back together with a little deflex and reflex. I do this with just a few blocks under the tips, midlimb and the handle section.
Pick a handle wood and glue that to the core lam. You can pre-saw the tapers but I usually cut them after I glued them up and sand them flat
Now the weird thing, start tillering you bow from the core. This will help you make sure it bends nice and even and prevent surprises after glueing the whole thing in one go.
But don't tiller to full 28 or higher but say tiller to max 18 or 20 inches so you can see it bends even an has nice tiller that conforms to your profile and your reflex.
Now make two really thin bamboo slats for the belly, you can even heat treat them to improve compression resistance and performance but this is optional. I pre-bend the ends with a heat gun so it glues easier up your handle fades

Does this post thing make sense at all? I am not really used to writing howtos O:)

Offline globalmark

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Hi SpringBuck and leon

Thanks so much for all that info - I think I have enough info to actually Make a workable bow Now

Leon you mention make a really Flat Back of Bamboo - any rough thickness as stuff i have bought i planed by hand and could get a good 5-6mm thick out of it - i saw many people mention 1/8" for the back ?
and when you say Thin for the belly what sort of thickness here ???

thanks again guys will post some pics and info when i get around to staring actual build soon hopefully - shop I just tried to Buy glue from was 5 years out of date ..
Thanks Again all
Mark

Offline leonwood

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By thin I mean as thin as possible;-) What I do is I trace the profile of the bow on the bamboo and cut that out with my draw knife (a few mm wider obviously), then I make the bamboo as thin so the edges are sharp and you really can't take off more without losing width. I do this for both the back and belly bamboo.
This also has the benefit of automatically tapering the bamboo a bit in thickness which helps keeping the tiller pretty after glue up

Offline globalmark

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Hi león

Thanks for all that - gives me plenty to be getting on with ..
thanks Mark


Offline Springbuck

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Leon:  "You can follow Springbucks advice above and that will work for sure but is probably a little harder because once glued up there is not much wiggle room to change your draw weight or tiller."

  Whoa, whoa, whoa, wait up a minute!  I think ADVICE" is too strong a word. ;D  ;D  ;)

  These are just memories of how once, long ago, something kind of worked ok..... trying to share what I remember, and hopefully he can cherry pick a bit.

  Results may vary...

Offline globalmark

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Hi Guys
I want to say Thanks for advice - or suggestions so far
I was starting clean up the Bamboo today and just couple questions about the general measurement (not Including Leon's last post)
but

 a question on general Bamboo shaping -
1. also Dimensions given on Bamboo thicknesses are these measured in the edge or the middle of the bamboo as it curves higher (obviously bamboo is thicker in the Middle (so am i trying to get edge knife sharp with a eg a 1/8' in middle or leave edge 1/8" - 1/16" etc ?


2.I Just started to try and taper them -
but due to the Nodes on one side and as its a natural shape when you plain or sand them how do you get it a even Parallel or even Taper - as at looking from the side it looks like waves a bit if you know what i mean ..
do i need to put something in-between the nodes to stop dipping or is it really not that important (being a cabinet maker i like it precise )

Again Cheers Guys

Offline Jesse

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You will never get it precise. The back will stay wavy. Just get the belly flat so it provides a good joint between the lams. Go as thin as possible at the width of your bow leaving a thin edge. Since bamboo is thicker in the center in general you will notice it gets thicker out towards the tips after you cut out the bow. I don't mind the reverse taper look on mine because it actually makes lighter tips due to the fact that I use a heavy belly wood. To avoid this cut out the bow shape and then re-sand to a consistant thin Edge.
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

Offline Dances with squirrels

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I run the bamboo backing piece over the jointer to flatten the underside and get rid of the bulk of the waste. Then cut it out to the front profile, slightly oversized, smooth and straighten the edges, then do the rest of the thinning and tapering by hand with a toothing plane. As I'm doing that, I have it laying on a flat piece of lumber(nodes touching the lumber), with pieces of 1/8" rubber strips supporting the bamboo between the nodes, so they won't push down as the plane travels over that area. It works rather well.

A single clamp holds the bamboo on its end so it doesn't slide around. I work the plane away from that clamp, and when I need to thin the area near the clamp,  I move the clamp to the other end, and work in the opposite direction.

Be careful with that bamboo, as you thin it, the edge can get as sharp as a knife and cut you.

Too bad you can't get Osage over there. I feel for you.
Straight wood may make a better bow, but crooked wood makes a better bowyer

Offline Jesse

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Here is an example of the tip vs. The handle bamboo thickness.
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

Offline Jesse

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Handle
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

Offline Dances with squirrels

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Measured at its crown/highest point, I like the bamboo(backing piece) to be 1/8" thick in the handle area, and 1/16" thick at the tips... or very, very near that.

Coming off the jointer, there may be places that the edges are knife-sharp, but then its cut to profile, which gives you little flat sides again, then thin it with the tooting plane, or whatever, to 1/8 to 1/16 to the crown as noted. If the 'cut to profile' method is used, after its done, there's approximately 1/16" flat sides all the way around... if that makes any sense.

I make my bamboo backed bows with wood lams underneath, and leave the wood full width until after glue up... usually about 1 1/2 to 1 3/4".

This is all explained well in Dean Torges' DVD Hunting the Bamboo Backed Bow.

Straight wood may make a better bow, but crooked wood makes a better bowyer

Offline Jesse

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Another method for thinning the bamboo and flattening it and also the method that I use. Take a long piece of the pink extruded styrofoam like they use on foundations. Put the node side down and press them into the foam. Then run the 2 through a thickness/ drum sander. Comes out flat. I have also just done it by hand eyeballing it on a belt sander and that works well also.
"If you can find a path with no obstacles, it probably doesn't lead anywhere."
    --Frank A. Clark

Offline globalmark

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Hi Guys
Thanks for the replies

I actually Just used a Long no-7 plane (pretty long heavy plane) and can make it pretty smooth and dead flat and straight that took just a few minutes to get flat - just a quick belt sand after that and is perfectly flat and smooth .
I just was not sure if measured from Edges or the Middle - "so seems mainly the middle part" - cheers

Thanks for the suggestions of using Foam or Rubber strips - I actually clamped exactly the same as Dances with Squirrels already and planed it but was thinking best put something under the node spaces .. - but still got to remove more as at moment the sides are that thickness so will do a bit more tomorrow .

- Does anyone know on Tempering Bamboo - heat treatment - how much supposed to do ?? i got my blow torch out and made even as possible the belly - but turns brown pretty quick -
Thanks again Guys Much appreciated .
Mark

Offline DC

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If you do a google search on "tempering bamboo" there is a lot of stuff the fly rod makers have posted.