Cheers.
A few more words of advice.
It depends a great deal on your tools and skills. A good idea may be to base it on the timber available.
Say you have 1/4" or 3/8" thick material you can choose the width and length to suit.
An AFB and pyramid are not (IMO) the same.
The advantage of a pyramid for a relative newbie is you can keep the limbs at constant thickness and just taper the width from say 2" to 3/16" and you have a bow! Obviously it's not that simple as you will have to build up a riser section to allow you to narrow the grip.
You can experiment with all sorts of sheet material say 3 ply plywood ... I've even made a kids bow from hardboard! Quick experimentation with materials you have to hand can save a lot of time later and indicate the sort of curve you can expect.
Note all the figures above are total guesses, but say you start with 3/8" tapering from 2" to 3/16" and each working limb 30" long. If it's too weak you can take a few inches off the tips... if it's too stiff you can change the taper to 1 1/4" to 3/16"
Like I said WAQAP !
Nearly all bow making is a process of successive approximation!
Del