Trapping

[Crooked Stic]

For performance gain on longbows. better to trap compression or tension side of the limb. And why? I have seen it done both ways. If I have to do it is mostly for weight loss. So need to do it on the side that will benefit.

[kennym]

I've been told both ways, and that it doesn't matter.  Just weight loss.

Yer gonna have to build two alike and do one each way and test...  LOL

I trap to back and like you , only to lose weight.   I think Widow does back too...

[monterey]

I don't trap much but when I do it's on the back.  My reasoning is that the belly is generally weaker in compression by the tension of the back.  This is almost universal for wood but not certain about glass.  With glass I'm concerned about compression and set to the wood lams directly under the belly glass.  Probably not a thing with thin stacks on recurves but on the deep stacks of an ASL the percentage of glass/wood gets into the low percentage range and they can easily take noticeable set.

It's not a bow killer but is a performance robber.

Anyway, that's my take on it.

[Mad Max]

reduce width then Trap 

[PV]

I've not seen any performance gain trapping limbs. Have seen stability issues with trapping to much on the belly side

[Crooked Stic]

Well you are reducing the mass weight of the limb so a little gain can be had there.

[Shredd]

  I have not done any extensive testing on this but I find trapping to lose limb weight to gain performance is that the  performance you gain will be minimal or possibly nothing...  The number one way to gain performance is bow design...  The second is the proper bending of the limbs...  I have had very fast limbs and lost performance because I made the limbs narrower or trapped them...

  I find the only way to make gains in performance through removal of stock on a limb is, One, you have too wide of limbs to begin with and excessive dead weight that should be removed...  Two, If the last third or half of the limb is too stiff you can remove stock and make a significant gain in performance with a better bending limb...

  If you think you are gonna make a gain by trapping or narrowing your limbs you could shoot yourself in the foot by changing the bend in your limbs for the worst...

If I have to trap I usually only trap the last half or third of the limb and I do it from the belly side being that it is easier to do with a convex surface when the bow is unstrung...  I guess the back could be just as easy when the bow is strung when working with a longbow...

 I like the first half of what Monty said...   

I don't trap much but when I do it's on the back.  My reasoning is that the belly is generally weaker in compression by the tension of the back.

                 But I feel you don't have to worry about trapping the belly if you are only trapping the last third of the limb...  There is not nearly as much stress out there as there is just off the fades or mid limb...  If for some reason I had to trap the whole limb to lose weight I would probably trap the back of the bow...

There are always exceptions to the rules...  One being ( it still kinda falls under the rule)  Designing a bow that is expected to be trapped...  Meaning with standard square limb sides and width as narrow as you can go and the last third is on the stiff side, trap the whole length of the limb to lose weight and you might find a gain of 1 or 2, maybe 3  fps  I don't think you will get more than that...  To me I would only do such a thing if I was to enter some kind of contest where speed was involved such as flight shooting or the WTT contest...

  Here is something to think about...  If Trapping were such a sure thing in gaining performance then everyone would be doing it as a standard in building bows...

[Shredd]

I just want to add that removing stock and weight from the tips is way more beneficial than moving it from other areas of the limb...

   There is also something to be said for trapping the whole back of the bow to possibly make the belly a bit more stronger in compression in comparison to the tension of the back of the bow... Which could possibly move the neutral plane more towards the belly of the bow, which could aid in less stacking but still maintaining a good rate of return through the shot cycle...  This is just a theory...

[Crooked Stic]

So just a good thing to get rid of some draw weight. I hate doing it beyond a good corner rounding.

[Pat B]

Doesn't seem to me that there is more than a design consideration for trapping a glass bow. Back tension and belly compression for a wood bow, yes but for a glass bow I think the FG covers both of these characteristics. Simply narrowing the limbs would be more effective in reducing mass weight and draw weight...coming from a wood bow builder and not a glass bow builder.

[Flem]

I think that other than giving an inelegant slab a little visual appeal, the only reason to trap is to scrub some weight off without loosing any width. Which can be important on occasion with a narrow ASL style.
And since most wood is stronger in compression than in tension, it would make sense to trap the compression side to reap the most weight loss.

[Pat B]

Other than gluing surfaces and of course aesthetics does the wood in a glass bow have that much to do with performance?  I guess it could be lighter physically than an all glass bow.

[Flem]

Other than gluing surfaces and of course aesthetics does the wood in a glass bow have that much to do with performance?  I guess it could be lighter physically than an all glass bow.

Yes, but it depends on the particular style of bow made. The wood in an old style glassed longbow, with a deep/thick core is going to be doing a lot of work.

[monterey]

I think that other than giving an inelegant slab a little visual appeal, the only reason to trap is to scrub some weight off without loosing any width. Which can be important on occasion with a narrow ASL style.
And since most wood is stronger in compression than in tension, it would make sense to trap the compression side to reap the most weight loss.

I think the compression vs tension works the opposite of that.   Self bow builders can probably sort that out for us.

[Pat B]

Most woods are stronger in tension than compression. With a glass bow the glass takes care of tension and compression so it seems to me the wood is on a free ride.

[monterey]

A typical ASL will tend to take some set especially at the fades if there's not enough thickness taper.  Otherwise, they are inclined to take a gradual circular set like many self bows.

[Pat B]

The glass in a bow doesn't compress or stretch so it's the wood that is being compressed between the glass lams and near the fades is the most highly stressed area of any bow, glass or wood.
 I don't know what a typical ASL is.

[Shredd]

I believe that Flem is correct in his statement that wood is stronger in compression than tension...

Pat B...   I am not sure that your last statement is correct though...  If the glass did not give the bow would not bend and if it did the wood would shear...

[mmattockx]

And since most wood is stronger in compression than in tension

I believe that Flem is correct in his statement that wood is stronger in compression than tension...

This is backwards. Wood is significantly stronger in tension than compression, sometimes upwards of 3x more in tension.


Mark

[Shredd]

Then why do you reinforce the back of the bow with sinew??  A don't have to reinforce the belly if you choose not to...