Help with dimensions? Hickory and Maple board bows

[Jefficus]

Hey everyone, first time posting here!  I'd just like to get a little advice for some options that you guys know already work besides a pyramid design?  I have some nice pieces of Hickory and Maple, split with the bandsaw from two original boards.  The Hickory pieces are 70'' and the Maple are 72'', with both having plenty of width--about 3'' across for the whole length, an they're both 3/4'' thick.  I know some of you more traditional fellas won't like this, but i'd like to put a sturdy riser block on them and cut a center-or-close-to-center shelf on them.  The thing is I don't know how much working limb length I need on both of these kinds of wood, so I don't want to make the stiff riser too long or too short.  Can I go to 8''? Can I go to 14''? Also I know a pyramid limb design would work, but I'm not sure I like the sharp slope and I'm curious what other options are out there.

Also, the boards have a slight curve, and I'm having trouble deciding if i should choose the belly such that it has a natural reflex, or the other way and then flip the tips with some steam bending.  And I have a feeling this could be different between the two wood species.  Any advice and tried-and-true dimensions would be nice!  I'd like at least two of the bows to come out at around the 30# range at 26-28'' for my girlfriend and her sister, but i'd be open to building the others a bit heavier.

From lurking these forums, I have a feeling a lot of you will say, "do whatever you want, if it works write it down."  I know the only difference between science and screwing around is writing it down, and many of you have notebooks filled with successful and failed builds to draw from.  I'm just hoping you won't mind sharing a little!

Of course, I promise to post pictures as I go 

[mikekeswick]

At 3/4 thick you won't need much in the way of wood to build up your handle area. I would say another piece 3/4 thick to give a total of 1 1/2 inches is plenty. I definitely wouldn't be cutting your bow to center - to do that you need to strengthen your riser/handle area significantly by adding ideally glass/phenolic/carbon eg. something very stiff that will eliminate any flex there. You have to realise that when you cut a shelf out you are violating the grain and making a weak spot - wooden bows don't like this sort of thing! You can cut a shelf in but keep it shallow and if you want to build it up more then glue some thick leather soaked in superglue to the side of the bow (or a piece of wood) and shape that piece to effectively make your shelf bigger.
You can use any width taper you want - it will make little difference to the finished bow. What does matter is that you link the tiller shape to the limb width taper. A pyramid is the same thickness (give or take) along the length of the limb and woods thickness determines how far it can bend. so if your limb is the same thickness along its length then every part of it should be bending the same amount eg. arc of a circle tiller. If you keep the width of the limb constant out to the near the tips and then taper into the nock then your limb has to taper somewhere so it will taper in thickness. So the tiller shape for a limb like this should be an ellipse eg. bending only a little ear the fades and progressively more as you travel along the limb to the tip. Elliptical tiller.
Getting a grasp of matching limb taper to tiller shape is the key to making wooden bows.
If you don't already have them I strongly recommend reading the Traditional Bowyers Bibles.

[Jefficus]

How about relationship between riser and limb length--how much working limb do I need?  I would think since I see a lot of people on here making 60-62'' bows with 4''handles that with 70-72'' bows I would be okay with 10-14'' to make big decorative riser sections.  Is that accurate, or are there other factors?

[bubby]

At the weight you want go 68" ttt 1-3/4"wide to mid limb then taper to 1/2" tips make the riser 12" including fades and and I'd glue up some 1/8" thick wood of contrasting color for that, also glue one of those on the back area of the riser about ten inches long and have at it you should be able to go almost centershot, almost

[Jefficus]

Thanks bubby! Would that work for the hickory as well as the hard maple?

[Wooden Spring]

Here's a GIF of how I do it. In this page I also document a number of successful bows. I recently started using a thickness jig to get a uniform thickness drawn as a starting point for floor-tillering. It works like a charm and saves SO much work. Good luck!

[bubby]

Thanks bubby! Would that work for the hickory as well as the hard maple?


Yes it should work with both at that draw weight