hornbow project numpty questions

[mikekeswick]

No the stiffest cross section is a rectangle. More material at the surfaces to resist tension and compression. The problem with a rectangular limb is the poission effect. The upturned edges on the bent limb then take more stress. The flat back/round belly cross section pretty much eliminates this problem but is less stiff than a rectangular section.

[bjrogg]

Thanks for sharing this stuckinthemud, someday this is on my bucket list and I really haven't a clue so this is very helpful.
Bjrogg

[stuckinthemud]

Big thanks to all who have/are guiding me along this path! I'm really struggling with the final dressing of the horn plate. I keep trying to tack it down to a base board to be able to perfect it but the centre bellies up when I tack down the ends. Any suggestions?

[mikekeswick]

Steam it flat. Remember that it will spring back if you just clamp it between flat surfaces. I heat the horn then bend it past straight by hand, hold it there and then run cold water over it. It will 'set' very quickly into its new shape.

[stuckinthemud]

Not a question, just an update. Rasped and scraped the plates down to 4.5mm, the hollow section has reduced to 2" length, giving a 13" length 35mm wide plus a 4" taper to the tip. Time to sort the core

[Del the cat]

Great Q and A thread for us armchair, would be hornbow makers.
I'm looking out for local maple... damn council cut down a lovely one about a month back, I got there too late it was cut into stupid short sections  .... grrr.
People with chainsaws who don't know the value of what they are cutting down ... grrr 

Del

[stuckinthemud]

So, these horn plates are quite short, I'm thinking a Magyar style might be the best option?
If I do go with this form, then, is the outside timber of the lath on the back like a Turkish bow, or belly side like a self-bow, and if on the belly, I'm guessing I need to de-crown the core-lath? I was thinking of a three-piece or 5-piece using v-splices throughout.

[BowEd]

Stuck....The outside of your core on a turkish is on the belly for form bending reasons avoiding splinters.An end view look of the core should look slightly oval to avoid the poissen effect.It reduces that extra mass weight off the corners and puts a stress line straight accross through the core from side to side looking at it from the end.
Most times both surfaces of the core are violated getting sinew and horn over it anyway.

[stuckinthemud]

So, does that mean you would slightly hollow the horn plate?

[mikekeswick]

You use either a flat joint or a convex core,concave horn joint. Both work.
There are a few reasons for the convex/concave way. As Beadman mentioned the outside of the tree is the belly of the bow because this is the best way to bend the cores eg. the outer fibers of the lathe are then uncut and able to conform to the bends without excessive splintering. The outer surface of lathes from small trees are naturally convex. Buffalo Horn is naturally concave on its interior. Therefore you can get more length and thickness from your available horn and have to remove less material from the formed and joined core.
However for a first bow it is easier to make flat mating surfaces.
A Magyar style bow is much easier to make than a Turkish bow (from a core point of view) and would be more suited to short horns.

[stuckinthemud]

OK, I have finally sorted out some wood for a core (apple) so its time to make a little progress, and, I have some questions about scrapers.  What do you make them out of and how do you cut the teeth, and, finally, I want to go with non-matching grooves but I'm not sure precisely what that means: does that mean that one scraper has 2mm deep triangular teeth at, say, 16 points per inch, while the other scraper has 2mm deep triangular teeth at, for example,10 points per inch?

[BowEd]

I used a Saws All type blade that I triangular filed the teeth[10 or 12/inch groove over 1.5"width of limb] for flat grooving of horn and core.A concave/convex scraper with the teeth filed into it with a fine triangular file for concave and convex grooving would be needed.Done by hand.Around 2mm or 1/32" deep.
Some prefer to have many more grooves per inch.
Here's my grooving tools.

This did'nt cost much to make.


These I acquired through a trade from a good bow making friend.Both styles will work.

[stuckinthemud]

I give up trying to source green timber for a core!  Just checking, a timber merchant not too far away has acer saccharum in stock.  Assuming its perfect, straight and rift or quarter sawn, am I correct in asking them to mill me some laths to 20mm thickness, or is it OK to go for 12mm for a 45#@25" Magyar-style bow? 

[Bjoern Sofeit]

I bought some material from smith-lumber dot com

Their website seems to be under maintenance atm, but you could write them an email, and get some 2x4 hard maple bow staves. They also ship green wood.

[stuckinthemud]

Time to resurrect this thread,  inspired by the hornbow build along I have pulled my horn plates out of storage and measured them up.  They will give me a 30mm (1 1/8") wide rectangle 30cm (12") in length after which they taper to a point, they are currently 5mm thick to the point where the hollow starts where I have been a bit enthusiastic with the thinning, they are 4mm at this point.  If I hollowed them a little, I might be able to stretch the rectangle out to 33cm (13") .  These are my biggest plates, I have another 2 the same size and another pair that are a little narrower.  I was hoping to build a Magyar style bow - is this viable?