Saturday, 19 August 2017

Messing with Bamboo

I've been reading around heat treating bamboo, and like a lot of stuff it's all rather confused and poorly defined with conclusions ranging from, it makes it worse, to it makes it better.
Well I have an off cut from my crossbow prod making which is planed to a nice flat one side with the outer surface intact on the other. So I cut this diagonally to make two tapered limbs I did some bend tests with the limbs up either way and messed with some heat treatment, but it was all rather inconclusive.
One problem I think is that simply  hanging a 2# weight on the tip wasn't giving enough bend to be significant. Anyhow here's the question:-
If you were to make a bamboo bow from one piece, would you have the back of the bow as the flat planed inner bamboo or the hard, shiny outer surface?
The received wisdom is that the strength of Bamboo is mostly in the outer fibres and that most materials like wood and bamboo are stronger in tension than compression. Now this would suggest that you's want the stronger side on the belly.
Of course I could just look at a Youtube video of how a Batak native guy makes a bamboo bow, but I do like to check out stuff for myself.

So, I glued and bound the two pieces together to form a bow flat faces meeting together for a few inches in the middle, made simple nocks by binding thread round the tip and letting low viscosity superglue soak in (V quick and effective). I put a string on and pulled it which immediately showed it as much stiffer in one limb than the other. The hard glossy outer bamboo to the belly was the stiffer limb. The preference for having it this way round is also shown by the fact that the other limb (glossy outer as the back of the bow) took a bit of set.
Now, here's the supplementary question for a bonus point:- How will the flat planed bamboo surface hold up as the back? Will it splinter at the nodes?
What is the point of all this?
Well if you have a bamboo slat and want to make a V quick simple boo bow maybe the counter-intuitive shiny side as the belly is the way to go.
Just in case you didn't watch the video, yup, that's the way he did it :-)

Still dunno if the heat treating made any difference... so many experiments, so little time, and the kitchen still isn't decorated. Slow and steady wins the day ;-)

Monday, 14 August 2017

Coarse Grained Yew Test Shots

I got some video this evening of my mate JT shooting the coarse grained Yew. It seems to shoot pretty crisply, and I left it with JT so he can give it a more thorough work out at his leisure.
Meanwhile I'd been tidying up the garage, finishing some new arrows and spending the day doing my yearly batch of cider 12L this time.
 Once I've got the cider making kit cleaned and put away I can get on with some bows. I had a visitor last week who brought a partly finished bow from a friend of his to be finished and one from a well known bowyer that was a bit stiff in the lower limb. I rasped a little off the belly while he was here and had it up and down on the tiller a few times to check it was better.
I took care not to over do it, he can shoot a good load of arrows and see ho it settles down. It's always better to proceed with caution else you can take off too much and next thing you know you've gone from a 80# bow to a 40# bow!
I like to do small jobs immediately rather than have a stack of jobs which can easily get forgotten amongst the clutter of the garage.

Friday, 11 August 2017

Coarse Grained Yew gets to Full Draw

It's back to nearly 100# at 30" still at a slightly low brace, but I'll let it get shot in rather than stress it on the tiller.
It looks very weird but that's a reflection of the unbraced shape. The wood certainly looks handsome and I can't wait to see how it shoots at the weekend.

It's looking good now, I don't know if it will loose weight or take set but it's pretty much felt like almost any other bit of Yew, silky smooth in places, grain tearing in others and needing the rasp, creamy waxy sapwood. Almost no knots or problems except a few pins and one small dark patch in one ring which didn't seem to go very far.
The waggle is a bit extreme and I used heat to take some of the bend out, but one can't expect to completely straighten something that severe. The heat was also used to stiffen that area a bit as the bend tends to be a weak point.

Monday, 7 August 2017

Coarse Grained Yew Warbow

I've started on a warbow using the Yew harvested in July last year, the ring count is as low as 3 or 4 rings per inch in places. It's often stated that fast grown Yew is "unsuitable"for bows, but I'm of the opinion that there is a huge variation in Yew that can't be directly attributed to where it was grown, altitude it was grown at, ring count, colour appearance of the bark or age of the tree.
I've had good Yew and poorer Yew in all shades and from all sorts of places.
This Yew certainly disproves any idea that fast grown lowland Yew is pale with poor heartwood/sapwood definition. I have 3 billets, so I roughed them all down and picked the best two to splice into a warbow, (I don't feel the world is ready for the three limbed warbow, but I expect some wag has made a 3 limbed bow!) I'm aiming for a fairly modest 100# at 31".
You'll see there is a nice waggle in the further limb.
I've also been sorting out my old arrows and making some new ones. The old ones have been mended so many times and I had more with broken off point than whole ones. I've turned all the old ones into a set of slightly shorter arrows and won't bother to repair any further breakages.

Friday, 4 August 2017

Fun Day

The crossbow project has wound it's way to a conclusion. The prod was a bit weak in one limb as demonstrated by the sting not being at right angles to the stock at brace. I eased off the other limb by removing a little from it's lower edge especially from the glass fibre lamination. Finally plucking up courage to cock and shoot it first with the 100gn point on the bolt 141fps and finally with the 70 gn point 151.7 fps . Excellent!After a couple more shots the nock partially sheared off one limb, this adequately demonstrates the problem of searching for greater and greater projectile speed, it simply leaves more energy in the limbs and thus modern compounds and crossbows and up being noisy brutes with shock absorbing buffers built in.
I could go back to the Boo/Yew prod, but I'm not that fussed about shooting, the best speed I got was 244fps from the natural materials and 251 with the glass belly. I've learned a lot and I now have a good design for a shoot through prod mounting and a usable crossbow prod test bed.

Shock horror probe! Del buys a bow! Well I couldn't resist, its a 1950s Accles and Pollock take down steel bow, it's a bit scruffy but for £25 quid i had to have it. I've put a string on it at low brace and drawn it. The lower limb looks weak, but maybe just needs a little judicious bending. I'll probably make a decent string and try shooting it, I can't imagine it will fail as it's steel.
Update:- I've had many people on Facebook warning me that these have a reputation for breaking and rusting from the inside. I'll probably draw it to full draw on the tiller, don't know if I'll make a proper string for it.

Talking of Facebook, there are some odious idiots on there.
A nice woman archer who I know posted her new English Longbow on there... then some bloke asks "what makes it an English Longbow"
I (and the woman in question) replied at some length in good faith assuming he doesn't know that there are various definitions and a difference between a Victorian target bow and a warbow.
Anyhow it turns out he's well aware of the differences and was just Trolling for an argument, complete tosser.
He tried to sucker me in by saying "don't you want to discuss things with people who have different opinions?"
What...? No I don't!
a) He didn't offer any opinion.
b) He asked a question under false pretenses as he already knew the answer.
c) He accused me of arguing, when I was merely answering the question which was originally posed.

My pet hate is people who ask questions when they don't actually want the answer and are aren't interested in it...

Wednesday, 2 August 2017

Bottle Job

I rasped the Yew belly on the crossbow prod down to about half its original thickness and glued on the fibreglass lamination. Gut feel and experience being used rather than extensive computer simulations and calculations!
The first limb went fine, but the second somehow contrived to be a dodgy glue up, not sure how as I'm pretty meticulous, anyhow the excess fibreglass at the tip got snagged on the bench and popped the glue line at the tip... hmm I was V irritated, but I got it all cleaned up and did it again. It seems ok this time, but is very stiff so I've taken about 4mm off the lower edge of each limb and I'm slowly working it towards full brace and being cocked.
Note I'm using the longest string of the 3 that have been made for the various versions of this prod, which is looped through the string adjuster.
 I'll add the string catchers too as there will be a lot of energy in this bow and I don't want to risk it going over center.
It's hard work to cock it, gotta be about 100# .The actual numbers are a bit irrelevant, but if it settles down to be a reliable prod I'll doubtless measure it on the tiller at some point. The pictures show low brace and cocked, I was hoping to see if the tiller looked even but it's hard to see without carefully lining up the camera, it's also tricky with a crossbow as it's possible to pull the string back off centre forcing it to be on the skew, similarly you can force it back dead straight and it will look true as the string won't slip sideways on the latch.
Dunno if that makes sense... on the tiller rig, the string is being pulled buy a long rope and hook, and the bow is supported so that it can rock, this lets you see how it settles under tension, it's not being forced one way or the other. In comparison, on the crossbow, the prod is tightly clamped and the string catches solidly onto the latch.
Just had it on the tiller, still hard to see how even it is, maybe a hint stiff on the right limb, but that looks contrary to the pic above, I took it to 90# and it wasn't full draw, so I reckon it is pretty much 100#
Anyhow I'm basically rather scared of getting to full brace and cocked without making sure everything is as good as possible. I'm even considering some linen binding at a few strategic points along the limb in case it shatters. What worries me is that now the belly is stronger than the back the failure mode could be an explosion of bamboo splinters which would be at eye level (it will be  a safety glasses job). With the previous configuration the likely failure mode would be a graceful collapse of the Yew belly with chrysals and a deterioration of performance.
I am getting a tad jaded as well as scared but do want to see it through, I'm pining to make a longbow or warbow, and there's decorating to do and we want to put some small windows in the summer house as it's a tad dark in there (good for a crafty cat nap tho' !)
Could also do with a holiday, but that will wait until the school holidays are over.
August already, and we've had blackberry and apple pie, the woman next door is leaving me her windfalls for cider making... the year is rolling by, seems like the Summer months all only have about 15 days.