Epoxy Glue-Up Temperature

[PeteDavis]

Dunno if this is taboo but I thought I'd ask here (repeat from LW)

I am getting ready to glue up a Reflex/Deflex bamboo-hickory bow from the Rudder site. I am using the Bowgrip epoxy to lam things up so I have a long work time. Everything will be shrink wrapped, bent over a form and clamped up rigidly.
I plan to make a plywood box, insulated and foil-faced on the inside. I am going to place several incandescent bulbs in parallel to generate heat. What is a good target temperature to go for to get a solid cure? I will test with different bulbs and venting until I get a good consistent temp. Someone told me 140 F. was a good target.

Any opinions on this?

PD

[sailordad]

   hi pete,

imde that exact same bow over the summer last year.nice kit.
i too used bowgrip 100 also bought from jim at rudders.
i glued mine up on july 4th last year,your probably gonna want to keep the epoxy atleat 65 degrees,then get your hotbox(i used mine for this also) temp up to 175 degrees and maintain that temp,put it in the hotbox after glue,wrapping clamping to form etc, for atleast 4 hrs,then shut the hotbox off and let it cool down on its own.

i dont know where you live or what winter is like for you,if your in a climate like me(minnesota) then i wouldnt leave it in an unheated garage while its cooling,may cause
it to cool to quickly.here today it would cool that down in about 10 minutes,-12 degrees outside right now.dont know if cooling to quick would cause any advers effects on the adhesion propertiesor not,but why take the chance.

good luck

                                                                                         peace,
                                                                                              tim

p.s. 
hope you have better luck tilering that bow than i did.r/d bows can be tricky to tiller,i ended up getting some chrysallin on the belly cause thetiller wasnt perfect.
it still shoots fast and hard,but i wont take it hunting.i may pike it and reduce some more draw weight to try and improve the tilering yet.

[dragonman]

I've glued several bamboo backed recurves with epoxy and I now heat them to 120F for 2 1/2 to 3 hrs and this works even with severe recurves. Rudderbows uses much higher temps I tried them  and the glue melted and spoiled the joints. Also it is recommended to find a way of clamping the bows in the heat box, because around 120F the epoxy melts and if the joint is under high  stress it will come apart, i've had this happen a few times so now i made some wooden clamps, I personally dont think you need go over 120F but others do and say the glue becomes harder strengthening the bow , hope this helps

[Pat B]

I would go by the glue manufacturer's recommendations about the curing temps and times. With wood to wood(boo too) glue up, Urac is probably one of the best glue to use. I have also used TBII and TBIII for boo backed hickory, osage, yew and other woods with good results and never had a glue joint fail...and my glue joints leave a lot to be desired.     Pat

[dragonman]

patB  I agree but I could never get this info from the manufacures so I experimented, also it is a bit annoying that you cant buy urac over here I heard it s a good glue ,but i cant find it

[CutNShoot]

I think Birmingham projects sells a T stat for the light bulbs that is 180 for their hot box. You could go to their web site and find out . I have one but I don't know where it is right now and cant remember for sure what temp it is. I think if you set it at 120 and it gets over 120 though it will get loose. It gets over 120 here on my porch a lot in Texas in direct sun. That is why I think it is the higher temp.

[CutNShoot]

sorry I didn't read Dragon man anyway I think your right.

[sulphur]

i'll preface this with that its just my opinion.  i used to use bow grip but i found it very lacking in many respects.  Its too thin so you have to buy thickener too, it has to heat cured, its cost more than it should.    i switched to Urac 185 for all wood to wood and smooth on for fiberglass.  urac is totally cheap and can cured without heat, although i usually bake anyway.  I found it at wood craft stores for $10.00  or order right from Nelsons paints website.  smooth on is expensive but is the absolute best for fiberglass builds (not that it matters on this site since its not paleo authentic).  do yourself a favor and find some Urac for your next build.   But to answer your question i baked bowgrip at 120 degress with no problems, and went as high as 150.  I only had one failure and that was a crappy glue joint (my fault).

[sulphur]

dragon it didn't realize u couldn't get urac in the UK. bummer.  if bowgrip is all you can get it will have to work, right. good luck.

[Pat B]

If you can't find Urac try to find Weldwood Plastic Resin. A member from Italy(Alberto) used it quite often and said it is very similar to Urac. It mixes with water. I have used the Weldwood glue with good results on a few bows. You can also contact the Nelson Company and order directly from them. I don't have any idea what the shipping would be.
   My hot box (from Bingham plans) has a thermostat(from Bingham) that goes to 186deg but I would control the temps by adding or subtracting a light bulb or two. I now use TBIII on just about any glue up I do. It is simple to use and only room temp to deal with and cleans up with warm water.    Pat

[dragonman]

patB thanks for that.          you can definately heat all epoxies up to 180F and they get harder  with more heat, if your climate goes upto 120 then you have to heat the epoxy over that, just be sure you clamp it in the box well without metal clamps, or theres a good chance itll come apart, it never gets to 120 here so I dont take the risk, never thought about hot climates!!!

[sailordad]

why no metal clamps?

i have never had a problem with them and thats all i use for forcing r/d,as far as the glue joint goes i have always just used innertubes wrapped tightly around the wood.

and yes the higher glue up temp i think is essential,if you ever leave your bow in a car or truck in summer months you could have a seperation if you dont cure at higher temps .
on an 80* day sunny outside the interior of your vehicle can exceed 140*,90* day it can exceed 160*,if you doubt it just go to any store and get a meat thermometer and stick it in the panel vent of your car and see what happens.(mechanics call these a/c thermometers).i dont know about the rest of you but my bows do occasionaly sit in a hot car once or twice a year, i personaly dont want a delam when i'm shooting.

[Pat B]

I believe when you heat cure epoxy it will hold until it reaches the temp you cure at. It is a good idea to heat cure to a higher temp(within reason) so, under normal conditions, your bow won't delaminate if left in the direct sun or in your car.
   When I used to do more glue ups I used spring clamps because the screw clamps I had used would loosed(the wood would shrink) as I baked the glue up. The spring clamps stayed tight for me. My last glue up was with bicycle tube bands. I got my best glue line with that...and in summer you can wrap a glue up and place it in the sun for a few hours and the glue will cure because the black tube absorbs the heat and holds everything together as it cures.   Pat

[dragonman]

this country is always cold and damp except for 3 days every year,  and i never leave my bows in hot cars , but you are totally right , better to be safe.
I only mean no metal clamps in the heat box, have you felt how hot theyn get after a few hours!!!!   I forgot to mention, you must wrap the bow in the heat box in srink wrap or you will seriously dry it out. Maybe I'm just paranoid because my bow was ruined in heat box at 180, could have been something else caused that??

[Pat B]

I would let a glue up rest for at least 24 hours and sometimes longer so it has time to rehydrate to a safe M/C after cooking it.  With glues like Urac and the TB glues, that are water based, too much moisture is a problem. Even after gluing a snake skin or rawhide backing with TB glues I wait a week after glue up before I stress the bow because of the added moisture. I have had osage bows loose 10# of draw weight after adding a snake skin and a week later it was back to normal.    Pat