help with stack dimension on a hill style bow???

[DelawareDave]

Need some help with a stack thickness and limb contour for a hill style bow.  If possible I wanted to make it all wood no glass 68-70" long hickory back, red oak or maple core and ipe belly.  I would like it around 60lbs at 28".  Is this even possible??? Any help would be great.  Thanks

[DelawareDave]

Also how much tapper??? I have a .002" sled so im kind of stuck with .002 or .004  

[jsweka]

I've built quite a few with glass and would have a good recommendation to get you close, but without glass in there, I have no clue.

Given that it will be all wood, I don't know that the taper rate will matter much since you will be scraping the belly to get the limbs bending the way you want them to anyway.  Pre-tapering would speed the process up some, but probably not necessary.  I should shut up though since I really don't know squat about all-wood bows.

[LittleBen]

This is definately possible. If you want more comments from the wood bow guys put something about wood or Ipe or HBI in the title.

I made a bamboo backed ipe for a buddy, it was 67" long, maybe 1.125" wide, tapering to 1/4" tips ... I mean this thing is skinny, and it draws around 60#@28". Actually I think it's a bit overbuilt ... I prtobably woudl have been ok going shorter (harder to go much narrower).

Do you plan on running the belly lam up the fades like a glass bow? or are you using a glue on handle like most board bows? Either will work.

If you wanna run the ipe up the fades it will need to be fairly thin, So I'd actually probably make it 4 lams. In that case I'd probably taper the backing .002, taper the core .002, taper an ipe (or maple) core lam .002 (put all three of those in front of the riser, then add a parallel ipe belly lam up the fades. This probably can't be any thicker than 1/8" (.125") to make the bend and even that you'll need to steam probably. The reason I wouldn't just use 3 lams, and taper the belly lam, is that when you put a .002" taper on a .125" ipe belly lam, it will only be like .060" at the tips, you just dont have alot to work with, so if your tapers arent't prefect or your stack thickness is too thick, you' could be screwed.


If you're just gluing on a handle, I'd probably taper the backing, core and belly, each .002.

Total stack thickness ... I'd say you probably need just over 1/2" thickness ... maybe 5/8" or so.

I'd probably go with like 3/16" hickory back, 3/16" hard maple core, and then for a glue on handle bow I'd use a single ipe slat of 1/2"+. You'll end up thinning it down quite a bit out of the fades, but that'll keep the handle portion nice and stiff and prevent any glued on handle from popping off.

For a bow where you run the ipe up the fades, I'd probably use an ipe parallel belly lam of around .125"-.1875", depending on what you can get to bend up the fades. You're going to need a final stack of probably .625" and a taper of about .006" total, maybe even a tiny bit more. So chhose your other lam thicknesses and tapers accordingly. I like to make all my lams roughly even in thickness ... I just think it looks better.

Some others may have better advice on a precise stack thickness. But persoanlly I'd go with 68" and 1.5" wide at .625" stack. then you can shorten to 66" to go up in wieght, or you can narrow the width to go down in weight, or do both to stay roughly the same and maybe go up a bit in cast. But you'd have some room to maneuver. Worst case scenario you have to add another thin belly lam ... 1/16" or so ... not a big deal really. I'd recommend leaving the belly prefectly flat until you're done tillering and are happy with the weight just in case you need to add another lam.

Good luck.

[DelawareDave]

Little ben: thanks for the info!!! I do plan to run the belly lam up the fades, so I will be making a few thin strips of Ipe.  Being all wood and knowing it will take some set, would it be better to make a flat bow like a Hill or should I add some recurve to the bow??? I havent made the form up yet so ether would be good with me  

[LittleBen]

I remember seeing a bow that Canopyboy made, similar to what you're talking about and he started with 2" of reflex along the entire length of the limb. It ended up having a very slight r/d profile because most of the set was in the inner half of the limb.

Personally I'd start with around 1.5" of reflex. It'll probably end up basically straight once it takes some set, and if you get it bending very evenly, it should look like a straight hill style bow when you're done.

[jporter@work]

Never used ipe on the belly over oak or maple.  Wonder if it would compress the core.  I'd at least use hickory as the core.  It could probably take the ipe belly lamination.  If you use a bamboo backing, if I remember correctly, the stack would be close to what a glass backed bow would be.  Migh be food for thought.

[DelawareDave]

My thinking was like a fiberglass bow the core wood would not matter as much with a strong back and belly.  But I'm definitely no expert  

[7 Lakes]

Once you've committed yourself to thin, belly laminations you better be almost perfect on the other lams.  You won't be able to tiller the bow or drop weight except by removing material from each side.

[LittleBen]

x2 what 7 lakes said. As I mentioned thats why I'd aim for 68" and a little wide, and be willing to pike the bow to 66" or narrow as necessary.

But 7 lakes is right, your taper better be dead on because otherwise you wont be able to tiller it to what you need. my last lam bow used a .004-,005 total taper for a stack of .420", and the one before that was liek .006 or .007 total taper for a stack of .520 IIRC.

As I said I think you need .006" taper, that shoudl be close enough that you can tiller to perfection.

Lastly regardign the maple core ... if a glass bow doesn't compress the maple, nothing will. I've done white oak backed ipe, and hickory backed jatoba with maple core and have had no problems with the core at all.

[DelawareDave]

Any suggestions on limb profile? Should it go strait from 1.5" wide to 1/2" or should the first 12-15" be 1.5" before tapering to 1/2" tips?

[LittleBen]

with a relatively straight limb (not alot of reflex, i.e. 1" or less) I think a straight taper to the tips is fine.

I typically only use a wider limb profile to mid limb if I need to get some more torsional stability like in the case of a recurve or pronounced R/D bow where limb twist can be an issue. Straight limb bows are much less prone to twist.

I will say though, ipe is so dense that a bow with 1/2" tips is likely to be a dog. I'd go 3/8" wide at absolute maximum and probably 1/4" if you can stomach it.

What you can always do is do a straight taper to 1/2" tips, then once you're confident thatthe tips are aligned and you dont have any twist to deal with, you can taper the last 10" or so down to 1/4" at the tips .... thenj I just smooth out the transition between the two tapers so it's not angular and that works well for me.

[DelawareDave]

I was just thinking.... is there any reason all the laminates couldnt be ipe and just back it with hickory??? Instead of an oak or maple core.