Bow advice

[Blundstoned Love]

This will, I hope be a sensible question.

I have been looking at a few sites on how to make a simple bow, for a bit of fun.

There are a few that are similar to this one:

http://www.wildernesscollege.com/bow-making-instructions.html

My question is about the way the site in the link "finds the belly of the bow".

I appreciate that this is to find the natural curve of the wood and use that to inform the shape of the bow.

My question is this - Wouldn't you get a more powerful bow if you used the wood the other way as this would put the wood under compression?

The example I have in my head is that if you wanted to make a big crossbow from a set of leaf springs off a lorry, you would use it so the the ends arched away from you (if you were stood behind it), not towards you.

Does that make some kind of sense?

Thanks

Boots

 

[Jamie B]

not for all woods or bows/designs.

think of it as a living branch.
during its life span it has weathered all wind,storms and season in that particualr slight downward bend or arc.
if the tree could not support the weight of the branch it would bend over and break.
the tree constantly seeks the most photo synthesis during the day, stretching twords the sunlight.
the natural curvature of the bow will be a slightly set back profile and have the belly of the bow the underneith side of the branch, and the back of the bow under natural tension
and it bieng the top of said branch.
When you are removing wood, let the wood dictate how it wants to be built. if your wood removal tool is having difficulties, pulling slivers, chattering or dipping and diving..change up position or the way you are working the stave. maybe even change to different tools to make the bow.
If you want to increase the speed/performance you can always heat bend,steam bend,induce reflex etc afterwards.

start simple.
even if you do not find the perfect stave or sappling or even branch...you can string it.
it may not look pretty but it will show you many things.
it will tell you if the bow will snap under tension.
it will tell you when you draw it if it will meet your compression needs.
it will tell you where to remove wood from any stiff non bending spots.
it will tell you when unstrung if it will take setback, or spring back to life withing reason.

all this can be achievd by simply following a few guidelines.
any fruit wood,hard wood, or nut bearing trees are good choices.

find a stave,sappling, or branch that is a little smaller in diamater than yoru wrist, for a heavy weight hunting bow for instance.

cut it man tall

never pull the bow back further than 1/2 of its overall length, unless its backed or properly tillered and is made from a resilient wood

apply fats or wax for sealents

burnish the bow after every wood removal process. i use antler or glass, what ever is at hand

the outer thirds of the limbs need to be narrow and fast. but not weak enough to crumble under draw tension.

i hope this helps.
just get out and string up a small branch.
its just a branch! if it breaks you will have learned something i promise!
then make another, and another.
i working bow does not need to be a warbow in poundage/strength.
start small, work yoru way up.
never overdraw the bows you make. keep full draw at or at least 1/2 of teh overall length of the piece.
have fun.~jlb

 

[chas brookes]

Hi
lots of info already on forum

http://www.bushcraftuk.com/forum/content.php?r=136-diy_crafts_skills

or have a look at Seoras site

www.Bushcraftdays.com

 

[dwardo]

You can make a bow from a uniform, person tall sapling. String it and your good to go.
Whittle it some more to even the stress and it might perform a little better. Let it dry properly before bending it and it will perform better still and may add some longevity.
Reduce the weight at the tips and it will perform a little better again. Heat reflex into the limbs and you will increase performance some more but also increase the stress on the bow meaning your tiller and wood must be able to handle it.
Make a bow much longer and it will be more forgiving of form and tiller, shorter and it will show all your flaws but be easier in the woods and feel much snappier to shoot.

If its something you just want to play with then just cut some wood and play. If you want to go a little further then but the "Bowyers Bibles" books and read read. Then join upto Primitive archer and read some more.
I have been making bows for about 7 years now and put a lot of regular hours into the craft and I would say that I am just starting to get my head around some of it. Give me another ten years and I will be starting to get good at it,.

Like chess, minutes to learn the basics lifetime to master.

Just be aware its very very consuming and addictive.

 

[Blundstoned Love]

Thanks guys - lots to think about and learn from there.

The flexing/growing bits are things I have some experinece of horticulturally am I'm palming my forehead for thinking about metally-type physics rather than the wonderousness of trees.

 

[dwardo]

Thanks guys - lots to think about and learn from there.

The flexing/growing bits are things I have some experinece of horticulturally am I'm palming my forehead for thinking about metally-type physics rather than the wonderousness of trees.

It is very physics when it gets down to the nuts and bolts of it.
Over all Mass will predict the bows optimum outcome every time. Too much mass at a lower draw weight will end up in a sluggish bow. Too light a mass at given draw weight, length and draw-length will end up in a failed or slowly failing bow. Where to place that mass optimally is the key.

Add to this the different properties of different woods. Some are better in elasticity and some better in compression and you are best adjusting the design and cross section of the bow to suit these properties. Then also adjust for the density of the wood and place the mass accordingly.

Its bonkers in the end but at the end of the day a roughed out sapling bow in the right hands will catch the same animal as the next if need be.

Then there is within that given mass the elasticity

 

[Blundstoned Love]

Another question if I may.

When I cut a trunk/branch should I let it stand for a period of time to let it dry out a bit?

And also does the season you harvest the wood have any impact on that? ie longer in spring when the sap is rising.

Thanks guys

 

[dwardo]

Its a toss up between ruining the wood and having something to work with now.
Faster drying - working green wood down to near bow dimensions then letting it dry indoors for a month or so it will dry quicker. But you run the risk of it cracking warping and deforming.
Slower - less chance of damage but you need to be ahead of your self with wood at various dry stages so you have something to work on all the time. Plus enough to account for flaws in the wood and missing tiller, generally screwing things up, which i do often by pushing my luck and limits.

White woods seem to be happier when dried quickly, more dense woods like yew less so. Its all a gamble. Less mass less time to dry. Foot thick log with the bark on is an inch per year. Roughed out bow of white wood indoors low MC month plus.

White woods I find best to harvest end of summer so they have a good back ring. Some say its easier to remove the bark in early spring as the sap it up. I dont find it hard to remove bark at any time with enough patience.
Yew and the likes harvest whenever. In short when ever you get chance.

I am very behind on timber so there wont be many bows any time soon from me, just not had the time.

 

[Blundstoned Love]

Thanks Dwardo - lots to think about there.

And fun to be had working some of it out.