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Author Topic: Curly BBO build along  (Read 31127 times)

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Offline bobnewboy

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Curly BBO build along
« on: July 23, 2009, 06:59:08 pm »
Hi All.

Its been some time since I did any making, bows or arrows, but once the bug has taken hold it is difficult to shake off  8) . Especially with all you guys posting pictures of such fantastic pieces of work.

I've made two BBO bows (both posted on here), and both have worked out really well, so I thought I'd try something different, and perhaps a little more technical.  I decided that I would make a short reflex-deflex BBO bow, like a horse bow, which should be well suited to field archery here in the UK.  I'm hoping for 50-55lb at 28 inches, but I know from reading posts on this forum that reflex bows are very difficult to tiller well, and can be rather deceptive during tillering.  So fingers crossed, and here goes....

First job is to make a former around which I'll bend the recurves.  I have a mildly shaped former for setting back the handle area on my previous bows, but this is not nearly tight enough to make the recurved limb tips I want.  So I bought a large piece of 2x4, and drew a natural tightening curve on it.  I cut it out and added some clamping holes.  I then cut the curved end off, and screwed and glued it to the remaining piece of the 2x4, making a step upon which I could rest the limb being bent, hopefully keeping the bent section in line with the rest of the bow.

I then tried bending an example piece of 0.25" seasoned osage with dry heat from a hot air gun.  This went well, but I noted that wood scorched a little, and that any loose fibres burnt and discoloured rather easily.  See the first pictures:



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Offline bobnewboy

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Re: Curly BBO build along
« Reply #1 on: July 23, 2009, 07:08:34 pm »
Okay, so having read some more on the forum about bending osage, I decided that it would be worth going ahead, but using some kind of natural oil to avoid the scorching of the wood - I chose olive oil as I already have some.  I also got the belly piece to a floor tiller with a good thickness taper, and made sure that all edges and surfaces were rubbed down with sandpaper.  I did not taper the sides of the limbs, so that while bending the tips I could be sure that I didnt pull the limbs to one side or the other, since it seems that limb tip aligment is a common thing to have to correct during or after tillering. 

When cooled down and released from the former, the osage sprang back a little, but not much.  There was still a little scorching, but this was no real problem as the affected wood would be removed when tapering the limbs.  Here are the pics of the limbs being bent on the former:



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"The Englishman takes great pride in his liberty. He values this gift more than all the joys of life, and would sacrifice everything to retain it. The populace would have you understand there is no country in the world where such perfect freedom can be enjoyed, as in England!" Frenchman, London 1719

Offline bobnewboy

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Re: Curly BBO build along
« Reply #2 on: July 23, 2009, 07:16:31 pm »
Having bent the osage belly piece, I found that the bamboo backing piece was fairly unwilling to bend into the tight recurve at the end of the limb tips.  This is a nice piece of bamboo, with a good distance between the nodes (12" or so), so I wanted to use it.  More reading on the PA forum...... ;D.

Ah, ok, bamboo bends with dry heat too!  So I began by thinning the backing strip as much as I dared on my belt sander.  The handle area of the backing strip is now around 3/16" thick, but the tips are around 1/16" - very thin but still seems strong.  Then I used the former again, and gently heated the backing strip into the same curve.  The bamboo sprang back a fair bit more than the much thicker osage belly, but it was now possible to fit the two together.

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Offline bobnewboy

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Re: Curly BBO build along
« Reply #3 on: July 23, 2009, 07:22:13 pm »
So now I had the belly piece bent back into recurves at the ends, and the backing piece gently recurved.  In order to make a R/D curly bow I needed to introduce some deflex in the handle area.  I did this by dry heating (with olive oil) the handle area over a block with the good ol' heat gun, while tying down the limbs to the back of my recurve former.  It makes for a nice shape.

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Offline bobnewboy

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Re: Curly BBO build along
« Reply #4 on: July 23, 2009, 07:44:38 pm »
Now  that I had the parts ready, it was time for the glue up.  I prepared the wood surfaces by sanding with 80 grit sandpaper to give a fresh wood surface and a little surface key, and then wiped the surfaces down with plenty of acetone.  This draws the oils out of the wood surfaces, especially the osage.  I protect the backing piece by covering the waxy outer surface of the bamboo with self adhesive paper masking tape - makes cleanup after gluing much easier.

The glue I use is a resourcinol resin two pack type, originally known in the UK as Humbrol Extraphen, but now sold as "Polyproof Waterproof Glue".  I measure it out by volume, and mix it using a piece of hooked wire in a hand drill.  Its nasty stuff, so keep it off your hands and clothes.  There is no solvent for this stuff once it starts to set!  :o

I buttered both pieces of wood with glue, and then held the pieces together at the handle area using a g-clamp.  I wrap the whole thing in cling film to avoid too much spillage.  I then checked the alignment of the pieces, and then when all is OK, I begin the binding by tightly wrapping pieces of split bicycle innertube round and round the pieces.  I start wrapping from the handle area outwards towards the limb tips.  A good tip for UK-based bowyers - Tesco sell 26" wheel innertubes of reasonable quality for £1.86 each right now - I bought a few extra for the toolbox....The inner tubes provide constant even clamping pressure all along the glue line, and hopefully this avoids any dry spots or overclamping.  At this point I set the bow aside to dry in my shed for a few days - it is nice and warm/dry in there at this time of year.

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"The Englishman takes great pride in his liberty. He values this gift more than all the joys of life, and would sacrifice everything to retain it. The populace would have you understand there is no country in the world where such perfect freedom can be enjoyed, as in England!" Frenchman, London 1719

Offline bobnewboy

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Re: Curly BBO build along
« Reply #5 on: July 23, 2009, 07:54:55 pm »
Tick tock, tick tock.  A couple of days later, I retrieve the bow from the shed.  I peeled off the masking tape and cling film wraps, and the set to with my favourite scraper, a sami knife.  Everything is looking OK, so I begin to taper the limb tips, but only down to around 1" wide at each end.  Hopefully tip aligment will not be too much of a problem during tillering.....

A bit of flexing, or attempts to flex the bow show that it has gained a lot of draw weight.  I think I will need to do some more floor tillering before any long string work.  There's still plenty to do before that.


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"The Englishman takes great pride in his liberty. He values this gift more than all the joys of life, and would sacrifice everything to retain it. The populace would have you understand there is no country in the world where such perfect freedom can be enjoyed, as in England!" Frenchman, London 1719

Offline bobnewboy

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Re: Curly BBO build along
« Reply #6 on: July 23, 2009, 08:07:23 pm »
The next job is to cut out and fit a thickening piece in the handle and flare area.  I made this out of osage too.  Getting a good fit takes some time, because the handle area is now curved due to the introduction of the deflex in the bow.  I thin the ends of the thickening piece in the area of the flares / fades to an edge, since it is far easier to do before fitting.  These edges will be blended into the belly piece during tillering, otherwise the thickening piece is likely to pop off later.  Good thing the bow is now very strong  ;)

The last job for now is to glue the thickening piece into the curved handle area, using the same glue type and process described earlier.

That's all for now!  I hope to have another look at the bow during the weekend.


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"The Englishman takes great pride in his liberty. He values this gift more than all the joys of life, and would sacrifice everything to retain it. The populace would have you understand there is no country in the world where such perfect freedom can be enjoyed, as in England!" Frenchman, London 1719

Offline hedgeapple

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Re: Curly BBO build along
« Reply #7 on: July 24, 2009, 01:50:26 am »
wow! I can't wait to se how this bow turns out.
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Dave   Richmond, KY
26" draw

Offline backgardenbowyer

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Re: Curly BBO build along
« Reply #8 on: July 26, 2009, 06:38:43 pm »
Nice one Bob!  Looking forward to seeing this bow shoot.  Don't tell me you are going to place it in Primitive Class though - something this sophisticated has to go with the other curly bows in Hunting Tackle class!

I've just glued up some ipe and hickorybut I'm not quite sure what style it will end up in.

Keep us posted!

Stan
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radius

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Re: Curly BBO build along
« Reply #9 on: July 28, 2009, 12:11:31 am »
excuse me,

when you heated in the deflex at the handle, do you mean you just propped it on that block, clamped down the ends (creating the deflex) and then just heated it and it held that shape?
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Offline bobnewboy

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Re: Curly BBO build along
« Reply #10 on: July 28, 2009, 07:00:30 am »
Hi Radius,

Yep, that was pretty much it.  As many others have posted in the PA forum, osage bends well with heat.  The wood springs back a certain amount once cooled, so the resulting deflex is not as pronounced as in the picture, but it is there.  If the blocks are symmetically organised, the wood forms into a natural curve around the blocks when heat is applied evenly in the handle area.  I did not include any glued-in Perry reflex in this bow, since the wood and backing will be stressed enough as it is.

I should point out that I'm making this up as I go along - it is my first piece of seriously bent wood.  I am going on info gleaned from this forum, TBB1-4 etc etc.  Half the fun is wondering what the bow will come out like.

Stan, the bow still meets the PV rules, even the proposed new set.  >:D  But we will have to see.  Maybe I'll add siyahs to make it more primitive  ;D

On Sunday I began a lot more floor tillering, because the bow as it came from glue-up out was probably at 100+ lbs at what would be a low brace height.  Waaay too much osage for the intended draw weight, but it is always easier to lose weight than gain it.  I think that this is also partly due to the fact that osage is edge grain from belly to back (??). I've been scraping like mad, and although the bow now bends by hand  :o , it is still too much weight, probably about 60lbs at brace.

More scraping, bending, pics and text to come.  Fingers crossed.
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"The Englishman takes great pride in his liberty. He values this gift more than all the joys of life, and would sacrifice everything to retain it. The populace would have you understand there is no country in the world where such perfect freedom can be enjoyed, as in England!" Frenchman, London 1719

radius

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Re: Curly BBO build along
« Reply #11 on: July 28, 2009, 11:07:27 am »
i've bent osage before, too, but only by cutting it into bendable thicknesses and lamming them together in different forms.  I just didn't think of pre-bending it, then adding the heat to make it stay.  You really are making this up on the fly!  That's how i roll too...
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Offline backgardenbowyer

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Re: Curly BBO build along
« Reply #12 on: July 28, 2009, 07:35:24 pm »
Bob,

Whatever class we call it, this is going to be a first class bow if it all holds up (and I sincerely hope it does)!  What weight are you aiming for?  I'm assuming nothing too high as there are going to be a lot of stresses and strains in there....

Stan
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Offline bobnewboy

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Re: Curly BBO build along
« Reply #13 on: July 29, 2009, 06:58:13 am »
Hi Stan,

I hope it does hold up, but wont be too upset if it doesnt - that's the learning process isnt it   ;)  There has been a little creaking when working on it, but I'm unsure if that's my old bones or the bow - I've worked my way up to stringing at a low brace, but even that is difficult to achieve without both arms, both legs and a table right now......

I'm hoping for 50lb @ 28".  That seems to be a reasonable limit for me and our field archery - no ribcages to burst through in the UK.  Thus far I've left the limb tips quite thick, and instead of thinning them I hope to be able to use them (narrowed) as sort of integrated siyahs.  I havent had much opportunity to work on the bow recently, because of the wonderful Engllish summer we are getting (I'm a back garden bowyer too!), but I will post more when weather and work allow.
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"The Englishman takes great pride in his liberty. He values this gift more than all the joys of life, and would sacrifice everything to retain it. The populace would have you understand there is no country in the world where such perfect freedom can be enjoyed, as in England!" Frenchman, London 1719

Offline bobnewboy

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Re: Curly BBO build along
« Reply #14 on: August 01, 2009, 12:04:09 pm »
Hi All,

Managed to get a little time in working on the bow last night.  After a load more scraping, the bow is bending a little at last  ;D  The osage shavings are up to my ankles!

The following pictures are the bow finally braced (gasp!) at a low brace of about 3".  The other shot is the bow bending on the pulley tiller.  It is pulled to 52lb at about 17" right now, so going in the right direction, but still a long way to go yet.

I'm hoping to get some more scraping done tomorrow, but as always I'm hoping for better weather than today  :-\



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"The Englishman takes great pride in his liberty. He values this gift more than all the joys of life, and would sacrifice everything to retain it. The populace would have you understand there is no country in the world where such perfect freedom can be enjoyed, as in England!" Frenchman, London 1719
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