Board Bows - Minimums & Maximums

[YosemiteSam]

I'm looking to make a couple more board bows.  I picked up some good, straight red oak and some decent maple (sorry, no hickory out here -- not even for backing strips).

Can somebody give me some guidelines about minimum and maximum widths for basic pyramid designs?  I have a leftover strip of red oak that is 67" x 1.25".  Is this too narrow for anything?  Can it still make a safe 30-35# @ 28" bow?  40#?  Or should I keep it mind for something under 30#?

I'd also like to make something in the low 50# range.  The red oak and maple I picked up are 2.5" wide & I was thinking about something around 66" long.  I've heard on this forum that board bows top out at about 55# @ 28" (as a safe weight).  I'll just be doing a paper backing (2 strips of brown rolled paper).  Is there any benefit to overbuilding on the width to the full 2.5" at the fades?  Or is this just going to add extra weight with negligible benefit in strength?

[BMorv]

The 2 major things to consider when making a bow as efficient as possible for a given design is to minimize set and reduce limb mass.
A wide limb will help you make a bow with minimal set but will increase mass, so it's a balancing act to get the width just right.  As I've seen suggested before, maybe tiller it out to 20" or so at full width, then reduce width until you notice the bow taking set.    
I haven't made a pyramid bow as you are describing so I won't comment on exact dimensions.

[Wolftrail]

Personally I would use a 1/8" backing strip of white oak, not red oak.  I dont go over 1 5/8" never had any luck with wide bows.  Most of my bows end up been 1 3/8" after clean up using 1 1/2" stock. Some guys go down to 1 1/8", more of a round profile.  Limb twisting can be a big concern with narrow limbs.

55# @ 28" I guess its doable,  never have gone over 44# making a laminated bow anyway.

[passion for knowledge]

I've made 2 successful red oak board bows - #30 & #42 at 28" and 2 successful maple bows #51 & #54 at 28"

The maple ones were based on an old Trad Gang link

 http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=print_topic;f=125;t=002204

I didn't do the heat treating part.

Here's a link to pics of the @54

It's now had a couple of thousand arrows through it and still shoots very nicely.

[George Tsoukalas]

The straightness of the grain and the width determine the poundage possible.

More on my site.

There is a buildalong there and you can change the width to 1 3/8" for 45-50# possible if you tiller well.

This is for bend in the handle bows where the handle is the widest point.

 http://traditionalarchery101.com/

Jawge

[monterey]

Speaking ONLY of pyramid designs, I don't think you handicap the bow by going full width (2.5") on a board.  You keep most of that mass near the fades which is where set hurts the most.  Go wide at the fades and straight out to extremely narrow tips.  Keep your limb thickness even for the length of the limb except for the first couple inches beyond the fades.  Use just a hair of extra thickness their for additional insurance against set.  Kinda the equivalent of a power lam in a glass bow.

[passion for knowledge]

Here's the link I meant to paste into my previous comment.

 http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=013702;p=1#000004

[YosemiteSam]

Originally posted by monterey:
Speaking ONLY of pyramid designs, I don't think you handicap the bow by going full width (2.5") on a board.  You keep most of that mass near the fades which is where set hurts the most.  Go wide at the fades and straight out to extremely narrow tips.  Keep your limb thickness even for the length of the limb except for the first couple inches beyond the fades.  Use just a hair of extra thickness their for additional insurance against set.  Kinda the equivalent of a power lam in a glass bow.

Thank you!  I've done tips that narrow to about 1/2" in the past.  By the time I round everything off, it's a little less but not much less than that.  Would you advise going more narrow than this?

[YosemiteSam]

Originally posted by passion for knowledge:
Here's the link I meant to paste into my previous comment.

  http://tradgang.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=125;t=013702;p=1#000004  

Nice looking bow!  Am I correct to assume that the more narrow portion of the limb is non-working?

[mikkekeswick]

Yes you are! Narrowed outer limbs should be stiff.
The first and most important thing is that the grain of your boards is straight.
If it is then great - carry on.
If not then you need to back with something. A really easy option is a fairly heavy cotton,silk or similar material. Rawhide is fairly easy too. Many options other than hickory.
i see no real need to go wider than 2 inches and the advice Monterey gave for pyramids is spot on.
Both of your woods are tension strong and would benefit from having the backs trapped (even if you back them). Keep your tips at 1/2 wide minimum to start with. You can narrow later when you have the bows braced and can see how the string is tracking.
Another tip is to leave the handle full width (same as the widest point at the fades) until the bow is braced again to see how the string tracks. Another plus is that you can really clamp it whilst roughing out with no worries about denting the handle area with vice jaws etc
Good luck.

[monterey]

Thank you! I've done tips that narrow to about 1/2" in the past. By the time I round everything off, it's a little less but not much less than that. Would you advise going more narrow than this?

Once again, speaking ONLY of pyramid designs, yes, narrower than 1/2".  You can go so narrow as to exclude string grooves on the sides of the limb.  Glue on a tip overlay and put the groove in it.

Have some broken pyramids under my belt but none that broke at the tips.

[monterey]

Here is an example.  This bow DID break but near the fades due to a faulty glue up of the riser.

   

[YosemiteSam]

Monterey - I have done overlays -- I like the added insurance.  About how wide & thick are those tips?

[monterey]

Just a hair over 1/4" wide and 3/8" thick.