.030 vs .040 glass performance ?

[Forwardhandle]

Does any one have any thoughts on performance difference between using .030 glass vs . O40 or .050 for bows under 50 lb  durability , performance etc  or using different belly/back combos I know there's guys around here grinding off size combos for back & belly ?  Like the idea of lighting the mass but wondering about long term durability ?

[Crooked Stic]

I think there is a ratio of wood to glass but I dont know what it is. But from 40 to 60 I use.040. I have used .030 on the front and .040 belly. Cant say as by eye I could see much difference in performance. I do know of some trying to build Hot Rods put .030 on the belly. But that is not something I would let out the door for someone else.

[Mark R]

Under 50# I'd say 040 is best, 030 is a bit thin, but under 35# could be fine, always trade offs in design, cast, and other specifics. I've made a few with 050 on bows over 55#, I think it works great for heavy arrows but I don't think the cast is that much of an advantage on lighter arrows. Carbon is pricey but seems to work best when comparing weight to cast, I continue to experiment a little in different lay ups to find what I like best. If you use 030 on anything over 40# you might have to make up for it in adding a thicker core lam or another core lam witch means another glue line thus adding dead weight and maybe losing performance unless its uni carbon but then again you could just use a carbon backing. ? jmho 

[Mad Max]

Quote from Kennym last year

"I did a survey many years ago, and on longbows it was in the 20-25% range.  I have no real testing on it tho, but that seems to work."

So
.365 stack on a long bow 50#
25% of .365= .090, so 2 pieces of .045 glass
20%-----------.073-----------.037

[jess stuart]

My understanding is o e benefit of using thinner glass on the belly.  You need a thicker core to get the same weight as with thicker glass.  Thicker core gives better stability.  I built quite a few short takedowns and it can be tough getting into the forty pound range with thicker glass especially clear glass with veneers.

[jess stuart]

Sorry should say on the back not  belly

[Shredd]

   I started building a bow yesterday...  Glued up the riser...  I am planning on a 35# bow...  I am gonna use .030" on the back and .035 on the belly...  Any comments or thoughts on this would be appreciated... My usual standard layup is .040 /.040 from 30# to 50# bows...

[Forwardhandle]

Thanks guys the one I'm finishing up now should be shooting next week end I used .030 back and belly it's a short bow 58" 49lb @31  I'm droping the weight to around 46-47 lb  I will test it out it should be a good test if it holds up at my draw & see what kind of performance difference if any ! 

[Forwardhandle]

I got the .030 bow shooting so far Im liking it pretty light mass wise will be around 17 oz. when done , performance wise it seems about the same as the rest , so durability is the question I will get about 1K arrows before hunting season & report back ! This one seems to be a slight cut above with lighter arrows but not sure if its the shorter limbs !

[Overspined]

I go thin on back and thick on belly. The glass is really good for belly and the bow power compression.  The back just needs something to hold it all together. My normal build is .050 on the belly and .40 on the back. I haven’t chrono tested, but it would be impossible to truly duplicate everything because of the variances. I doubt it’s very noticeable whether it’s .050 for both, or a combo or go thin, but that’s just what I do. I figure also the wood shows better on the back with thinner glass so why not. I would think trapping the limb to the back would lighten the glass load plenty if someone is after a few FPS.

Also, kids bows I go .050 belly & back. Durability is what I’m looking for when my 6 yr old son would literally drag his bow down a gravel road. Bow never failed and a neighbor kid still shoots it.