Primitive Archer
Main Discussion Area => Bows => Topic started by: MattZA on October 23, 2018, 04:04:00 am
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*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
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hi matt, I see lots of bend in the handle section. good luck
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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.
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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
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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.
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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.
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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:
(https://yt3.ggpht.com/a-/AN66SAxwXRAMtRmC4_mkvQTSv8OwPXbZL_UG9hjI3Q=s900-mo-c-c0xffffffff-rj-k-no)
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.
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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 ;)
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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
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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!
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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.
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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.
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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.
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Sadly.
It's always been a Stanley Surform for me.
Well I'll let you know how it all goes. Photos coming soon!
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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
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Wow it's looking much better! What did you do? Tore it apart and added a 3rd lam? Or just started over?
What kind of set is it taking? Are the tips wanting to twist to the side at all? Since it's already so narrow, your only option may be to keep bending it more and watch that it takes even set, and not too much. If it seems stable, could do some minimal tillering on the sides. Why not? Also you can kind of train bamboo. If you want one area to bend more, hold the handle in one hand and the tip of the limb in the other, and repeatedly push your knee in to the belly of the limb where you want it to bend more. But it looks like you might end up with a bow with a shorter draw and higher draw weight than you intended. But it might be a bow! Might even be surprisingly fast.
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Well I shot it a bit today.
Brace height of 3". Drawing 20". It was pulling 28# at that length. Bracing the bow requires a stringer because of the force needed.
It's VERY fast, and surprisingly smooth. I was expecting a lot of handshock, but I'm pleasantly surprised.
You're going to be amazed at what I did to fix it... I simply glued another lam onto the belly. Just like that. Tillered to be stiffer in the handle, cut from the same piece of bamboo.
It's taking a pretty unique set. It's straight before stringing (with the siyahs about 3" in front of the straight line). Then it takes about 2" of set immediately after being unstrung. That set returns to zero after about 5 minutes. I put about 50 arrows through it today, and it is currently straight, like I've never strung it before.
The side twist is also quite strange. It pulls a tad sideways on the tillering stick, but when drawn and fired it tracks pretty true. The lower side occasionally ends up a tiny bit to one side, but nowhere near enough to miss the string bridge. Which I'm very happy with, considering they're just 3/16" wide.
I also haven't heat tempered the belly at all. I'm kind of saving that for my trump card as a tiller. I was considering heating the handle section to make it stiffer.
It's such a disaster to look at though. The belly lam that I glued on was a bit too narrow - so it was entirely unbalanced when dry. To remedy it, I simply carved a couple of pieces of thin bamboo and glued them awkwardly onto the edges. They got a small sanding (which is the extent of my artistic skill), and somehow fixed the balance.
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Ha! That's great. Who cares what it looks like as long as it works, right? I'd love to see a pic of this belly lam.
It's good that it returns to straight. Bamboo is very resilient. Out of curiosity, during those minutes when it's still showing set, does that set make an even arc?
It sounds like twist isn't a problem but if you want to perfect it and you feel like your siyahs could stand to be a little thinner, the easiest and most effective way I know to fix alignment on a bow like this is to thin the tips on the appropriate side. Just go slow and string it up and check your progress before you feel like you've done enough.
Be careful with heat. What kind of glue did you use? I've ruined more than one laminated bow by trying heat corrections after glue up. Guess I'm a slow learner.
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I've attached a few artistically disgusting, yet functional pics to have a look at. I don't even really sand a bow after a glue up unless it's going to affect the tiller. That said, this is my first ever attempt at actual lamination (across any kind of woodwork discipline).
The set isn't 100% even. It's a tiiiny but more pronounced at the inner limb area
I'm using South Africa's version of TB3. It's named differently, but is made by the same company, and is identical in its makeup. I'm glad you warned me about this. My total "just wing it" approach would love some guidance in that area.
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A few more, showing overall length and various widths...
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Oh, just to mention the glue...
I mixed it with saw dust from a random other piece of wood (a door needed sanding).
So it's a mix of TB3 and doordust ;D
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About the twist on the tree and not in the hand. I had this with a bow and what it was in my case was a little flat spot on the handle the held the bow slightly leaned over on the tree. This lean started the bow twisting. When it was in my hand the flat spot had no effect. I rounded the handle to let it rock freely on the tree and the problem went away. This may not be your problem but it was a nice thing to find.
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DC, that was exactly what it was. I added some cushioning to the top of the tiller so the bow would stay in the position I want and it's been perfect since.
What are your thoughts on wrapping them? Do you think it's necessary when we're only playing with about 45# all in (including brace tension, which is substantial).
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Wrapping them??
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Sorry,
I mean wrapping the siyahs...
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The only bow I glued siyahs on I used a 3" "V" joint. It was a 40# bow. I didn't wrap them and had no problem. I did notice your joints are short but it's not a heavy bow. Is it a "V" joint or glued on top?
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It's just a straight forward V splice. You'll also notice the temporary string bridges. I'm going to measure the height of them and carve new ones to match the siyah wood. They'll also be stuck onto the v splice showing on the belly. That'll provide a bit more support too.
The bow is going to be around 40-45# in total, if I include pre-brace tension.
You reckon that'll be enough?
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I'll take a guess and say that a 2" "V" joint will take it. If you're worried a few wraps of thread will help. I always use epoxy so I don't have any first hand glue advice.
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Yea I was considering a few sisal twine wraps. They bond very well with simple white PVA glue in my experience.
Then it's just to find a way to wrap the entire bow in felt, and build up a handle of some kind...
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Looking forward to seeing how it turns out. I'm fond of this little bow. :)
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Update:
We have achieved brace height! Put another 50 or so arrows through it at half draw.
There is a problem forming though. When glueing up my belly lam, I somehow managed to make a dent in the belly. After shooting, I've noticed it's starting to lift under compression.
Any ideas? I'm considering a bamboo patch to take the strain off.
Here's a braced photo. I wrapped some cotton thread around the handle, mostly to make it easy to find the damn handle at a glance ;D
It's got a cool shape at brace height, I think.
Thoughts?
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I'm unsure what you mean. A dent is starting to lift? Can you post a close up?
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Ha ha, I was just typing you a PM!
Unfortunately it isn't really visible unless braced - and I don't want to do that again until I've fixed it.
Picture it like a small knife slash across the belly (about 1/4" wide). It's not very deep, but you can imagine how it'll behave under compression. It isn't lifting, per se. It's more compressing the affected fibres, which is causing them to lift about 1/2" down from the cut (in the handle direction) I think it was caused by a shim sitting awkwardly during glue up.
Put your hand flat palm down on a surface. Keep your hand on the surface and try to slide your index finger towards your hand. The cut is at the end of your finger nail, with the lifted knuckle where the fibres are lifting.
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Hands up who else just tried the finger thing... ;D ;D ;D
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*hand up*
Ok I understand. Huh. Interesting. Can't say I've had that problem before. Under the lifted part, is it the glue line that failed?
I would try to get some thin CA glue in there. Super glue could work if you can get it in the right places, but the water thin stuff would be ideal to really soak in and saturate the area. Then I'd wrap it tight with string, and soak the string with glue too.
Since bamboo varies in density so much from the inside of the culm to the outside, your 3 lam bow has an interesting layer cake of different densities throughout its thickness, If you tried to do any kind of patch where you cut out a chunk from the belly and insert a new chunk of material, I might worry about some eventual problems stemming from unmatched densities.
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Did you scrape the outside of the boo where ever it was going to be glued? Boo has a waxy outer coating that I'd bet glue won't stick to.
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*Edit* If you zoom into the photo until about 350-400% you can see a slightly raised dark spot on the right hand side of the handle.
Halfbow: No unfortunately it's not the glue line that failed. The cut effectively severed some of the top fibers on the belly. The resulting weakness effectively allowed the cut fibres to start lifting at the depth of the cut. Almost like when peeling a banana - the skin and fruit separate along the grain lines where the original 'break' was made.
Hmm, I'll give CA a shot. I don't have very high hopes, because I tried a similar thing with TB3 when I first saw the cut and fibres just hinting at lifting. They got covered in TB3, clamped closed, and left overnight. All seemed fine, until I noticed the fibres now lifting closer to the handle, but still in line with the grain from the original cut.
It's almost as though the TB3 prevented them from lifting there, so the force simply carried on down the grain until it could find a place weak enough to actually separate the fibres within the lam.
I like your idea of soaking the whole bastard in CA, though. The CA weight shouldn't affect bow efficiency much, since the cut is about an inch above the handle.
DC: I did scrape the waxy layer off. It didn't break along the glue line, though. It's only lifting as deep as the cut (which is very shallow. We're talking maybe three sheets of standard A4 printing paper, here).
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Ok I see. So you're basically dealing with a running crack. Definitely don't want to be chasing it incrementally across the whole bow, but I'd think that if you can stabilize it all the way to the end of the crack, that should stop it from spreading more. Maybe the first time it went farther than you realized.
I've used CA as a finish before, and you may not know what you'd be getting yourself in to. >< If you try to cover your whole bow, you better get what you want in a few quick long smooth swipes. Otherwise it will quickly devolve in to a fumey sticky mess that gets worse the more you mess with it. It's a great covering for smaller things, but it's difficult to execute well on bigger things. Of course if you'll be wrapping your bow with felt.. that gives a lot more leeway on how it looks.
Just to mention, tb3 doesn't stick to its cured self very well. It may not matter much in this context, but in case you're thinking of using it again to try to fix it, it could be unideal to use it again where it's already been.
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This is becoming a build along! If any admins read this, feel free to move the post over there if it's annoying y'all :)
Well I very liberally applied CA to the crack area last night. Not that it needs to set overnight, but I only looked at it again this morning. It does seem to have stabilised the area well.
I'll only know for sure at brace/draw though. I'll continue tillering as soon as I finish carving proper string bridges that don't look like a Lego left in the sun.
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Hi all,
Just an update on the little bugger.
I haven't had the time to do much work, but in tillering I noticed a hinge was forming where the aforementioned running crack was.
To remedy this I glued a small bamboo patch onto the belly and then glued and wrapped some silk ribbon around it a few times.
Unfortunately that didn't have the desired effect. It did however cause the opposite limb to bend more evenly with the repaired one. This has given a unique appearing set, because the cotton I used as a temporary handle (photo above) actually prevented any set in the handle.
I have since removed all the wrapping. I spent the day sanding down my belly patch to as flat as possible, and preparing another whole lam for the inner half of the bow (mid limb to mid limb, through the handle). I'm hoping that'll sort out my issue of the outer limbs not bending enough, as well as support the hinge enough to prevent it getting any worse.
Glue is currently setting. I'll post a photo tomorrow when it's had enough time in the clamps.
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There comes a point where it's quicker, easier and better to make a new bow. I know there's a challenge to "make it work" but just sayin'
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I agree with you DC, if something is not right I just make a new bow. Just saving something that will fling an arrow is not worth the effort in my eyes.
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Oh I know it would be quicker to make another bow. I roughed out and floor tillered a long bow in about 45 minutes this week, and I'm sure you guys could do that in 10 (and undoubtedly much more elegantly and efficiently)
This is just me challenging the laws of physics. I have no real reason to succeed with this bow apart from principle. I don't hunt, I don't 3D hunt. Hell I barely even shoot at targets. I build and experiment with bows because it's damn good fun ;D
To quote the excellent Tim Baker - "A Bow is Still a Bow Until it's Back Breaks".