Thinking of tooling up for a Hill bow

[Xander]

As I am getting my paying customer's shop projects done, I am finally beginning to foresee building my own bow.  First few will be board bows just to gain some experiance, but I am still lusting after building a Hill style longbow.  So I have been reading, searching, reading, pricing and more reading.

The overall concept is easy to grasp, but I am wonering if there is a thread or page that covers the tooling (form, fire hose, hotbox, etc) process a bit more.  My ideal bow will first be 40#, and later variants would be nice.  I'm having a hard time finding airhose for compression right now, and wondering also, what are common variants of form building?  I'm thinking 3 lams of 3/4 ply for rigidity, but what other options are there?

This is a reasonably long term goal for me, so stuff will be acquired over the next year or so.  For tools, I have a well stocked metal shop, my father has a wood shop and my brother has a mechanics shop, so access to most all tool is covered.  I also have plenty of experiance with laminating FRC on my race boats, so th usual issues with glueing to the mold and stuff is front and foremost in my mind already.

Any help on this would be greatly appreciated!  Oh, and when I do get started on it, I promise to do a build-along.


Cheers!

[JamesV]

Xander............

Have you considered building a simple rubber-band form? They work great, especially for straight limb hill bows, cheap and easy to build. You don't even need a hot box if you use E40 Smooth-on epoxy.

James

[rockkiller]

In my very limited experience,I have had better luck using trilam(don't know if that is spelled right) over plywood.I get a piece of 2"x12"x6ft.Its 1"3/4 thick so you need to plane down to 1"1/2.The stuff is always straight.
You can get the firehose at bringhams.

[Xander]

Originally posted by JamesV:
Xander............

Have you considered building a simple rubber-band form? They work great, especially for straight limb hill bows, cheap and easy to build. You don't even need a hot box if you use E40 Smooth-on epoxy.

James

James, no I have not considered a rubber-band form, so my next question is, what is a rubber-band form?  I have no objections to building a hot box, but I guess if it isn't completely necesary it is one less thing to worry about.  I do plan on using E40 smooth-on, seems to be the tried and true standard for bowyers.

I have been looking at stack recipes as well, seems that 2 layers of glass, 2 parallels and one taper is the basic for a 66 or 68 inch flat bow.  Now, is that with a .002/in taper or with a .001/in taper?  


Thanx!

[Xander]

Ok, I did a search for rubberbnd forms and it looks like a simple method.  I have piles of old bicycle innertubes already (used to manage bike shops and was a collector).

This may be what I actually go for, deffinetly looks doable or me.


Thanx!

[kennym]

Normally 1 or 2 tapers and a couple parallels along with 2 glass in straight longbows.

For 40# , you might be able to do 3 wood lams, but the heavier bows usually have 4 woods.

Some folks use .002 worth of taper, some up to .004 . The tapers can be one  .002 or one fellow used 4 - .001s with great results.

The narrow bows , like 1.25 " at fades, need more taper in the lams because you have less room to taper on limb edges when you profile the limb.

The taper controls where the limb bends, more lam taper(or edge ) makes it bend more at tips.

This is the fun of bow building for me, figuring what I can do with different components.

I like to heat my EA-40 for 5-6 hours at 160 - 180* , started that way and haven't changed. Supposed to stand more heat without delamming, but have never not cooked one, so don't know.

Good luck and have fun!!

[Xander]

Now, when you refer to edge taper, you are speaking of profile, like a pyramid bow, correct?  Due to the fact that the lam taper is accounted for with stack recipe?

For the sake of room for error, I will go for a 1.5" wide bow and the shelf cut to 1/8" short of center.  Sound about right?

Ideally, I would like to keep cost as low as possible (who doesn't, lol), so if I could get away with one set of tapers, two parallels and two glass that would be ideal.  Not really concerned about wood figure or anything on my first, plus I have plenty of nice woods for risers.

And, here's another question, I have about 60sq/ft of carbon fiber twill, 48"x96" sheets, already cured and roughly .020" thick (iirc), could I foreseeably use this in replace of standard glass lams?  Say two layers back and belly?

This would save me considerable money if I could use it.


Thanx!

[kennym]

By edge taper, I mean tapering from 1.5 at fades or just past, to say, 1/2 at tips.

Either tapering limb sides or lams will make it bend where you want it to. I would go with a .002 taper , 2 parallels and 2 glass for the first to get a shooter, and then tweak from there on the next. (You can't build just one)

I haven't messed with carbon, seen too many reports of blow ups.  I know a lot of bowyers use it with success, but I think it took some bows to figure out how to make it reliable.....

[JamesV]

If this works it might help

[JamesV]

[JamesV]

[JamesV]

[JamesV]

Zander.................

Go to the end of your street and pull up the stop sign, then get a straight 2X4 and bolt to the sign post with lag bolts. Drill a few holes and your, straight limb, form is built.

James

[Xander]

Thanx Kenny.  This carbon I have was aerospace skin material, I have data sheets on its specs somewhere.  I think it might go best with a wood that takes high compression well, bois d'ark I think would be good.

James - thanx for the pics!  Although I don't think I'm gonna pull the stop sign, lol!  Tip taken, though.

You guys are mking this too easy for me, my wallet is already cowering in fear!

Cheers!

[Barry Winner]

There's an article in the June/July 2013 issue of TBM you may want to check out.  It pretty much details exactly what you want to do.

[Xander]

Id love to check it out, but I can't find that rag locally.  B&N doesn't carry it and the other places I checked don't have it either.  My local pro shop doesn't have as well.

If there is an online article that would be cool, I don't feel right askin for a scan from anyone, copyright and all that.


I'll keep looking around though.