Working on a giant bow to beat Allen Case!

[Badger]

  I am getting started on my giant bow project. 80 ft across. I am going to be forced to use a soft wood for the limbs because of the length. Looks like I will be limited to spruce, western red cedar or Doug fir. I realize I will have to make some serious design modifications but will need a little help from someone who can read the wood property mechanical sheets. What would be the best wood from those choices? I am also wondering how much less bend can I expect for a same thickness as a typical whitewood bow? I do plan to build several scale models and work up but am kind of looking for a starting point.

[osage outlaw]

Just curious, but what kind of draw weight are you looking for?  What will you use for the string?  How are you going to draw it?  I hope you keep us updated with pictures as you go.

[Danzn Bar]

You know you won't get the performance that you would out of osage......
DBar

[avcase]

Steve,
You win!!!!!  Hahaha!

What is the history behind this project?  Does it have to be 80 feet long?  What about 20 feet?  I think it will be really challenging to do with any kind of wood.  I think the procedure required just to string this thing would be enough to kill me. A deflexed design might help in case you find it has to remain strung for long periods of time. Could you splice hardwood laminates together into some kind of mega-bow blank?

I bet the incredible scale of this project will give the neighbors something to talk about.

Alan

[willie]

Steve

this came up earlier in another thread, I cannot recall what was said, but I ran some calcs in wood bears spreasheet on a  doug fir gluelam. you can buy any length up to 60' long at the local lumberyard.

[willie]

strains for the few larch and DF bows I have tillered were about .6 vs .7 for birch, for the same amount of set

[sleek]

You may consider white oak? I know its used as planking for plank on frame ships. They like to get the planks long, so perhaps source boat lumber.

[avcase]

strains for the few larch and DF bows I have tillered were about .6 vs .7 for birch, for the same amount of set

You were able to get the bows to 0.6% strain and live?  That’s pretty impressive. I keep my hardwood bows around 0.5%, depending on species & condition.

Alan

[avcase]

White oak would be great choice!

[Badger]

  If possible I want to make the limbs 1 solid piece. I plan to use 2 timbers about 6" or 7" thick, 2 feet wide and 32 feet long attached to a stationary center piece about 20 ft long. I am open to a stack leaf design if I can get it to work right. I am hoping for a draw weight of about 8 to 10,000 pounds and about a 24 ft draw length. I plan to draw it to destruction going up incrementally until it fails. Hoping for a little over 100,000# stored energy.

[Badger]

White oak would be great choice!

  White oak is my first choice but I doubt I can get that in 1 piece. If I absolutely have to I will cover the backing with FG cloth but I really want to avoid that.

[avcase]

You may need to tightly bind it with rope every few feet to keep it from throwing a 2x4 sized splinter!

[Selfbowman]

Ok Steve why a 80' foot bow? What's the deal. Worlds largest bow? Plywood laminated together. Arvin

[Del the cat]

You will need a very tall archer to avoid the lower limb hitting the ground 
Del

[Badger]

Ok Steve why a 80' foot bow? What's the deal. Worlds largest bow? Plywood laminated together. Arvin

   Da Vinci had drawn up plans for an 80 ft war machine but never built it.