Reducing draw weight

[DC]

I'm in the process of donating a bunch of bows to my sons SCA group. All my bows are in the 40-45@28 range and the SCA people want them in the 25-35@28 range. I'm thinking I should reduce the width as much as I can before going thinner. Am I right?

[Badger]

   I would mostly go thinner only slight reducing the width, they will be more durable.

[Deerhunter21]

+1

[DC]

OK

[George Tsoukalas]

Both. You might ftnd some limbs getting too thin. Then reduce the width. Jawge

[sleek]

They to keep the same width to thickness ratio. That ratio is why they shoot so well. I'd record how they shoot as they are, then reduce the draw weight, keeping the ratio the same, and then record how they shoot at the new reduced weight. Nothing should change. If a bow has taken set, you can just reduce its thickness, leaving its width, and the set should go away.

[Jim Davis]

Don't  know who can wrap their minds around this, but leaving the width to thickness ratio the  same is a wrong approach. Thinning the limb by 50% will weaken it by 87%.

Narrowing the the limb by 50% will weaken it by 50%.

Which do you think will be easier to hit the desired  weight?

Narrow the limbs by about 30% and you will be home free. (40# x .70=28#)

[DC]

I seem to have opened a can of worms

[bjrogg]

Someone once said. I don't think of it as reducing weight. I think of it as perfecting tiller.

Wherever you take it off

Bjrogg

[sleek]

Don't  know who can wrap their minds around this, but leaving the width to thickness ratio the  same is a wrong approach. Thinning the limb by 50% will weaken it by 87%.

Narrowing the the limb by 50% will weaken it by 50%.

Which do you think will be easier to hit the desired  weight?

Narrow the limbs by about 30% and you will be home free. (40# x .70=28#)

Jim, your reasoning is solid. But for now, I'm going to stand by my opinion until it can be.explained why it wont work. Perhaps however ( as this is still a developing idea for me ) You remove a ration of thickness according to the effect it has. One scrape off the belly is equal to 8 scrapes off the side. So do 8 scrapes off the side, then one off the belly. However, instead of the hard to quantify "scrape" use millimeter instead and calipers.  Yes, its technical, but a very good learning opportunity.

Your idea of narrowing is logical, but if you want to reduce a bow by half its draw weight, you dont cut it in half, or you will have stability issues, where the bow is now more narrow than thick as an extreme example.

[Jim Davis]

I agree with your points Seek. I think, however, that one would only run into the issue of being narrower than thick with bows of the English Long Bow design, which are about as thick at the fades as they are wide.

ASL bows, pyramid bows, paddle bows etc., would be fine. My pyramid bow are about 1-1/2" wide at the fades and a little over 1/2" thick for the whole length of the limb.

Nice to converse  with a thinker.

[Badger]

If his bellies are real flat narrowing to weight would make sense. If they are crowned it won't help all that much. I like the idea mentioned above about roughly keeping the ratio of thickness to width the same. To me if the bows had taken zero set then narrowing would be ideal, if they had taken some set then just thinning them might be best.

[DC]

Well the one I did today was a Molle of sorts so I narrowed the bending section and thinned out the levers. Ended up with an even taper with a circular(sorta) tiller. Kept everyone happy with that one. How diplomatic of me

[bradsmith2010]

yep narrow and thin, so everyone is right,,

[Rākau]

To jump on this wagon I have a suggestion that is in keeping with Sleeks ratio view point, albeit going about it in a different way...

Find the amount that of poundage that needs to be dropped:

To keep the math at my level lets say we are dropping a bow from 45lbs to 35lbs so = 10lbs reduction in weight.

then we find half of this: = 5lbs

then it is a simple matter of reducing the weight by 5 lbs via side scraping only, followed by reducing weight the final 5 lbs by belly scraping only.

This way it accounts for the belly being flat or crowned like Badger mentioned and it drops mass via side tiller.