Fiberglass for Loose Laminate Prods

Thanks for the tip Ken! I have been looking for the chain link rods but so far none of the big box or hardware stores in my area have them.    I agree that these boat bows should work even better. I find them on line but I hate to order one rod because the shipping would be as much or more as the rod.  So I will try the local boat dealers and marine supply.
Have you ever tried gluing them together? I am thinking that two thick ones glued with high strength epoxy might work because there is minimal stress in the center of a bending limb, but with three layers the stress of the glue would be much higher.
I would like to experiment with this once I finish with my current experiment.

Yeah the chainlink Tension Bars can be hard to find.  I found them at a Fence Supply store here in Ft. Myers, and also a Farm & Ranch store down in Naples.  Cheapest online was Wholesale Marine for $18.25.  I'm gonna check at the "boat junk shop" across the river from me next time I'm over there.

I've not tried gluing lams together... sort of negates the advantages of loose lams (ability to change draw weight easily, ease of construction) to me.  I'm not sure even high strength epoxy would hold.... but it might.  Thing is, you'd have to seriously rough up the surfaces of the poltruded fiberglass to give the epoxy something to grab onto.  These things are polished on all sides, not rough on one side liek a bowyer's fiberglass lamination.

I'm with you Ken,I love laminating,it often gets you out of a hole with material,but there are times when I personally would'nt trust it,this is one of them.Different with wood and fibreglass,wood is porous,and will give you a good bond to fibreglass,but glass to glass in a high stress area?.......not for me.
    Hermit.

Good points guys. There may in fact be no real advantage to gluing them together, I was just curious if it had been tried.

On the boat-materials theme, any ideas whether sail battens might be suitable?  I think they are fibreglass (though I stand to be corrected) and seem to be fairly inexpensive.

Stuck

IIRC sail battens are woven fiberglass not unidirectional poltruded 'glass, and would not work as well.  I'll check at West Marine later this morning.

You can phone these guys: http://www.binghamprojects.com/Bingham%20Projects,%20Inc.%20Catalog%2037.pdf

...ask them for a price on a couple Power-Tuff Glass billets (page three bottom right of the product pdf.

I purchased them before and they are not that expensive.  Its the same stuff as used in commercial high end crossbows.

Thanx Hotspur.  I order lots of bow building things from Elmont.  I guess I never checked into what Power-Tuff was.

I did go check out fiberglass sail battens.  They are the Right kind of glass.  Two problems.  First they're tapered.  Second they're as expensive as the boat bow strips.

Well I had to give the boat cover bows a try. But it has not been a great experience.  
I called boat supply places around the Orlando area and located some at Westside Marine, about 45 minutes drive from here. They said they had 3 96"fiberglass ones in stock and they were $15 and change. So I took the bike on a high speed run on my lunch hour with the intent of buying all three. When I got there, only two were left so I grabbed them. But when they rang them up it was $76 for the two!  Turns out they gave me the wrong price over the phone. That price was for 48" wooden ones. But after going all the way over there, I went ahead and bought ONE for an experiment, gambling that I could make a good bow from one. 
My goal was a 34" center shot bow with around 16" pull and was hoping for 150LB or more.
It actually came in at a disappointing 95 lb. Here is what it looks like on my bow test rig:

  To get the weight I wanted I would have had to make it shorter or use two bars. Too much $.
I have been using this bow on my trigger testing and it has worked OK for that but I need to test them at higher weight so I ordered a 150LB Barnett replacement bow.
Another strange thing is that this bow kicks the arrows hard to the left every shot. I have used it with 3 different locks that I am testing and it is always the same. It looks like it bends both limbs even and it is square with the stock and the groove down the center so I am at a loss as to why it kicks them to the left. Like 2 feet at 20 yards. Maybe some of the lams are binding more on one side.   Any ideas?
It doesn't matter much for testing the locks but it would suck for a hunting bow!
Oh, and I just love the color! LOL 

Very interesting.  Sorry to hear you got such a bad quote and that the experience hasn't been that great.  I'd have jumped at $15 each!!  And,  gotten huffy about the 'new' price...being given a quote over the phone...driving across town... etc just to see if they's come around on price.  Glad to see someone try this.  I was going to do so next payday (for me the 16th).  I still will.

What were your lam lengths?  Looks like 34, 30, 28 24????

IMHO a 34" prod is pretty wide.  Of course that's just one opinion.  My 28" is wide enough for me, especially for a hunting weapon.  Again, IMHO I think I'll try 28/24/20/16.  What I DO like about these bars is that they are nice and wide.  Twice the width of my chainlink tension bar prod.  The fiberglass can be colored/dyed/painted so color isn't an issue.  For the price, for a 95# draw weight prod, it's still actually a pretty good deal when you look at steel prod prices and delays in order and receipt...

Can't imagine why it's throwing 2 ft to the left.... What weight/size of bolt?  The only other thing I can think of is that the lams are not constrained to be in line except at the clamp at the center

looks like you could swap your limbs left for right, then see if it shoots 2' to the left

I love the color too!

Good point Anatine!

Ken, you are absolutely right, I should have made it shorter.   I am just a big fan of long power strokes. I would always trade a longer power stroke for higher poundage. But it does make the weapon bulkier.  And in this case I really needed the pounds for a better test of the locks. If I had time I would shorten it and re-do the stock to fit. I just measured and with the 2" gap in the center the overall lengths are actually 36, 30, 24, and 14. I expect that if I shortened them all about 4 " I would get the poundage I am looking for. Also note that the two white lams near the center are PVC and are primarily there for strain relief so I don't break another bow.
Despite my mostly self inflected issues, I think this could make a good and cheap bow. I want to play around with it more when I can.
And yes Anatine, good idea and I thought about doing exactly that, reversing the limbs to see if that gave a clue (it should) but I just ran out of time. I took all three of my prototype locks to my son this morning so he  can work on the CNC programing. So now I don't have any to test with and I am out of time to make another. I have this whole get the motorcycle ready for a 8,000 mile 8 week trip thing going on. I have to be in Albuquerque on the 14th for the first stop. I am looking forward to the trip but I am bummed that I have to put away my toys for the next two months.

IMHO the advantage of these fiberglass loose lam prods is that compared to a steel prod you DO get ridiculously long power strokes.  My tension bar prod draws half the prod length without a problem and I'll bet the boat bars will do the same or better.  That's the same a good self bow.  A steel prod just can't do that, and a wood prod capable of that ratio won't draw anywhere near the same weight.

When you get back, if you can't find fiberglass tension bar up there in Disney, let me know and I can send you one from here.  I KNOW they'll give you significantly heavy draw weights for just a couple bucks.

HOTSPUR -- I looked at the Bingham's Power Tuff.  It's a special order item and I've sent Elmont an email asking for prices.  We'll see what that's like too.

I remembered I had an old stock with a roller nut made of hickory. So I took the band saw to it and made it fit the orange bow. As expected it shot to the left just as it did on the other stock. So I unstrung it and swapped the limbs. So it should shoot to the right now right?. . .NOT! It shoots right down the center. 

Gremlins?

Well I got an email from Bingham Projects regarding the cost of the Bow Tuff which had been mentioned here.  I asked for a price on 1.5" wide x .125 thick strips.  Gordon Composites, the supplier, send these prices for lots of ten strips in each length:

28"  $17.55 each
24"  $15.05 each
20"  $12.54 each
16"  $10.03 each

That's $55 per 4-lam prod, which makes those $25 boat bars look pretty darn inexpensive by comparison!!

Here is a link for the european crowd:

http://www.carbonscout-shop.de/Glasfaser-Flachstaebe.html

These are unidirectional, pulltruded glassfiber bars in various thickness/length. 70% glassfiber and E-module 40.000 N/mm² . 15/16" width x 5/32 thick or 1 17/16 width x 1/8 thick and Relatively inexpensive at 5-6€ per 6 ft.  Have not tried these myself but  seems good material for a loose laminate prod.

Thanks for the tip.
So a product exists and is not too costy. Just need to find more affordable retailer.
Carbonscout gets bit too expensive for cross border small customers.

Ausland: Versandpauschale 29,90 Euro

Mindestbestellwert 30 Euro

For 60 € I could get 2 or 3 pistol crossbows.