Main Discussion Area > English Warbow

Ipe and Bamboo

<< < (3/9) > >>

Rich Saffold:
Looks like yer good for around 100#'s, Ideally these bows will gain a touch of reflex when removing belly wood, which means your net loss after shooting in remains at zero so it will go back to reflex when unstrung..Humidity permitting..Thick bamboo can suck up more moisture than thin bamboo..trade-offs..

Keep the pics coming..

Rich

markinengland:
Looks like there is a good if big bow in there.
If it was me this is what I would do (others may do different).
Shape is on the back and belly using good sharp rasps ands files so it looks like a bow, giving it whatever profile you like. Make sure the tapers are good and even. Give it a fine finish with fine sanp paper or a very fine file.
Put temporary nocks on.
Use a long tiller string, accurate scales and pulley to pull no more than brace height and no more than final desired draw weight. Adjust as necessary to get a good even bend with somewhat stiff tips. I like to use a bowyers edge for this. A simple scraper is also good, used with the fine file. After each wood removal pull at least 20 times to exercise the bow and see what effect the wood removal has had. Keep a very close eye out for hinges and very stiff sections. At this stage don't worry about the draw weight, just go for good braced shape.
The bow will probably be way over the weight you want and trying to floor tillering it will feel like leaning against a tree, hence use of a long tillering string.
As soon as you feel the basic shape is about right put on a good thick and non-stretch tillering string. Non-stretch is very important as it is quite painfull when your monster bow and stretchy string traps your hand.
Pull the bow on the tiller a few inches 20 times or so and check the draw weight. This may be quite high. I once had an Ipe/Hickory bow pulling 120lbs at 3 inches (a little too much reflex!).
You now have two choices.
Finish the monster bow to the draw weight it wants to be.
Do a fairly large amount of wood removal, a lot of pulling until the bow pulls what you want at your draw length.
I have found that an Ipe bow like this can increase in reflex as you remove wood from the belly and the weight will stay high with a tendancy to develop hinges as parts of the bow do come to weight. Small amounts of wood removal can make a big difference so you may find yourself chasing hinges after hinges until eventually they even out, hopefully somewhere near your desired draw weight with a good shape, but maybe at 15 inches!
Now I like to go carefull, trying for an even amount of removal or each limb, and even off each side, exercising a lot each inch of increased draw, never pulling over the final draw weight. This is the stage at which you can bring the string over a little to the side you will shoot from. If the bow is made symetrically you can decide which way is up at the end and pretend the string lays off a little on purpose. I would be using the finse files and scraper, keeping the bow looking almost polished and ready to use as this help me go careful. Some may say this is too careful but I like to pull 50 times per inch. For me at least, it takes this kind of repetition for me to be able to see the effect of the wood removal. Sometimes it will take a fair amount of this to get the weight you want and the shape you want at the draw length you have got to. The frustrating thing is that you then need to pull it a little more, have to take off some more wood, pull it lots more times to get it to once again pull the final weight you want with the tiller shape you want but an inch further towards the draw length you want.
Now is the time you could get fed up and rush things and suddenly find you have a hinged underweight bow, or a broken bow.
From bitter experience I go slow and eventually find I have a bow that is about what I was after.
One big lesson I have learnt with Ipe is that a little wood makes a lot of bow, so very little less wood can make a much weaker bow. Changes can be sudden and unexpected to keep checking the variables.
Have fun making this one. Hope it works out good,
Mark in England


backgardenbowyer:
Hi Mark - I think we met at SPTA St. George's Day shoot.

I'm not going for real war bow weight as I only shoot about 50lbs at present so this is a "step up" to give about 65-70lbs, to learn how to tiller a compass bow and give me something with which I can shoot roving marks.  Started tillering today and I'm finding that the somewhat variable thickness of the the boo backing between different nodes makes it quite tricky.  I think there may be a slight hinge developing on the right hand limb (nominally the bottom one but still time to change that) which you can see more easily in the pic of the bow at low brace height - so I won't draw it any further till I'm sure that is evened out.  On the other hand it is definitely bending through the handle which is good as I'm aiming for that. Brace height is about 4" and the bow is drawn to a nominal 16", but when set at normal brace height at which the string is shorter I think it represents only a real draw of about 14".  I'm finding it difficult to check the weight using this set up as I need both hands to pull the bow back on the tiller which is tricky using one of those bow scales designed to be used in a normal draw position. It's probably around 50-55lbs at this draw length.  The tillering nocks are about 73" apart and though I intend the finished bow to be about 71" which should be plenty at the target weight.

If the weather holds off tomorrow I'll do some more.  I've always found if you can get the tiller just right at normal brace height the rest is just patience and elbow grease.

Comments and advice very welcome.

[attachment deleted by admin]

markinengland:
BGB,
Yes we did meet at the SPTA shoot.
Bow looks good.
One method I use for looking for hinges is a walky-talky stick. Have you tried this?
I made mine from an off cut or Ipe, about six inches long and an inch wide. I drilled a hole through the centre and screw in a bolt. I can run this along the belly of the braced bow and look at the arc of air between the bow and walky-talky stick. Where the bow is bending less the arc is less, where it is bending more or hinged the gap is greater. By screwing the bolt out slightly you cans get it to just touch the bow at the point of greatest bend (hinge). As you run the WTS along the bow it will rock on the bolt where the bend is less. This can be quite usefull for getting an even bend. Yours looks about spot on from what I can see. It is hard to see the shape against the background.
A pulley set up will be much easier to tiller with if you have somewhere to fit it. I have mine attached to the wall of my garden too shed, made with bits from B&Q. A bit of timber and ply, pulleys, ropes, a few carabiner type clips are easy and cheap to get hold of. The scales may take a bit more looking for. I started off with some simple cheap spring scales but these weren't accurate. I then got some heavy fishing scales with a clock type face from Ebay which were cheap, easier to read but not really accurate and broke. I  and finally invested in a set of accurate commercial scales again off ebay. These are good and I know they are accurate up to 100kgs or 220lbs which should be enough!
Shame about the weather today. Home and can't do any bow making!
Have you heard of the ETAS Batsford shoot put on by Steve Stratton . Just got back from it. Weather was pants but great to see so many bow makers, warbows, primitive bows, people from as far away as Iceland and Sweden.
Mark in England

backgardenbowyer:
Mark

I picked up something about a shot a Batford on this site - is there is talk of a war bow society as BLBS are changing their rules?

The weather is depressing. I shall have to stay indoors and make a string for the bow (15 strands of dacron B50 3x5 plies sound OK for up to 70lbs, or should it be 16 2x8?).  I can usually get away with working on horn nocks in the kitchen if I keep the door open and extractor fan on.  Strings and nocks are my least favourite part of bow making.  I've been thinking abour fitting a bracket and pulley on the wall, but we don't own the house so it may not be a welcome addition.  No part of our fence or the crumbling lawn mower shed are strong enough to cope.

My bow scale goes up to 90lbs which is fine for now, but its one of those you hook two fingers round and draw the bow, curiously I find I can pull less like this with the bow on the till than I can when holding the bow normally.  As tillering progresses I also use the reflection in the French windows so I can feel how the bow draws as well as see it - but this is much less accurate measure.

Let me know if anyone posts pics of the Batsford event.

Stan

Navigation

[0] Message Index

[#] Next page

[*] Previous page

Go to full version