Double glue joints with pinhole method.

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LW Bercini

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I've been using yellow glues and the double glue method on my LPR birds since the Dead Sea was only sick. On tubes with a glassine covering, I remove a strip of the glassine from the alignment line on thetube. The resultant double glue joint is surprisingly strong.

With the white "craft" tubes (if they have a proper name, I don't know it), there is no glassine to remove. In that case I put pin holes in the alignment line to enhance adhesion.

Now, here is my question:
Do people do the traditional double glue process with pin holes, allowing the saturated pin holes to dry completely before doing the second glue application? Or do you do only one glue application on the alignment line and attach the fin before allowing the pin holes to dry?

I've heard of both ways.

Thanks.
 
I've been using yellow glues and the double glue method on my LPR birds since the Dead Sea was only sick. On tubes with a glassine covering, I remove a strip of the glassine from the alignment line on thetube. The resultant double glue joint is surprisingly strong.

With the white "craft" tubes (if they have a proper name, I don't know it), there is no glassine to remove. In that case I put pin holes in the alignment line to enhance adhesion.

Now, here is my question:
Do people do the traditional double glue process with pin holes, allowing the saturated pin holes to dry completely before doing the second glue application? Or do you do only one glue application on the alignment line and attach the fin before allowing the pin holes to dry?

I've heard of both ways.

Thanks.

LW That is a GREAT Opening Line ROTFL! Since the Dead Sea was only Sick LOL!!!

I've been a big fan of the Epoxy rivet method since first discovering it back in the very early 70's. It is the after runner of the Pin Hole-Double glue joint method I learned from G.H. Stines book in 63.
Personally i've always used the pin holes with the traditional double glue method. Mark the alignment lines, I do not remove glassine, just rough it up with 120grit sandpaper, punch the holes with a Needle in a pin-vise. Apply the first application of glue, Let dry completely. Reactivate with second Glue application line on the fin root and apply. I've always also stuck the pin in the root edge of each fin before the first glue application also. Glue's used either Elmer's white glue or Carpenters yellow glue, both seem to have about the same DRY strength. White glue does take longer to tac and set up.
 
LW That is a GREAT Opening Line ROTFL! Since the Dead Sea was only Sick LOL!!!

I've been a big fan of the Epoxy rivet method since first discovering it back in the very early 70's. It is the after runner of the Pin Hole-Double glue joint method I learned from G.H. Stines book in 63.
Personally i've always used the pin holes with the traditional double glue method. Mark the alignment lines, I do not remove glassine, just rough it up with 120grit sandpaper, punch the holes with a Needle in a pin-vise. Apply the first application of glue, Let dry completely. Reactivate with second Glue application line on the fin root and apply. I've always also stuck the pin in the root edge of each fin before the first glue application also. Glue's used either Elmer's white glue or Carpenters yellow glue, both seem to have about the same DRY strength. White glue does take longer to tac and set up.

Can you explain what the epoxy rivet method is, and how to do it? This is the first time I've heard of it.
 
Can you explain what the epoxy rivet method is, and how to do it? This is the first time I've heard of it.

Sure: I can do much better then that: If you'll visit www.narhams.org look in the left hand menu for the Library. got to Tech-Tips, download Tech Tip-017 and the photo suppliment.
Epoxy rivet attachment method is one of several subjects contained in Tech Tip-017 "Working with Plastics". The photo suppliment shows many different material combinations using the Epoxy Rivet method.
This attachment method is as strong or stronger then TTW fin attachment without having to slot (weakening) the body tube.

Plastics-6b_Polycarbonate-Polyproplene epoxy rivet fin_01-02-10.JPG

Plastics-6c_Styrene-Polypropylene epoxy rivet fin_01-02-10.JPG

Plastics-6d_Acrylic-Polypropylene epoxy rivet fin_01-02-10.JPG

Plastics-6e1_Best polycarb-anything epoxy rivet joint_01-02-10.jpg

Plastics-6e2_Polycarb-cardboard epoxy rivet & fillet joint_01-02-10.JPG

Plastics-8a_Polypropylene & Epxoy Rivit fins_01-02-10.JPG
 
I first became aware of the double glue method working with my father in his shoe repair shop in the 60's (he was a mender of soles) and I have used it ever since. As for pin holes. I occasionally us them, mostly on MPR birds and I have good luck with the fins staying on. Let the glue completely dry, then apply a lighter second coat and use what ever fin guide or method you prefer.
 
Sure: I can do much better then that: If you'll visit www.narhams.org look in the left hand menu for the Library. got to Tech-Tips, download Tech Tip-017 and the photo suppliment.
Epoxy rivet attachment method is one of several subjects contained in Tech Tip-017 "Working with Plastics". The photo suppliment shows many different material combinations using the Epoxy Rivet method.
This attachment method is as strong or stronger then TTW fin attachment without having to slot (weakening) the body tube.

That's great! I've seen people do that for the roots of TTW fins - I guess it hadn't occurred to me that it was possible on external fins as well. I might have tried that on my recent Quest Big Dog build if I'd seen this post before I started.
 
Is there any standard “density” for pinholes? Like, “x per inch”? I’m assuming the more, the better, but at what point might you weaken the body tube?
 
I do mine about 1/4" apart - basically, TLAR

I do 1/4" to 1/2" depending on the Size of the model. alternating down both sides of the fin alignement line. the trick is to have enough rivets to stiffen the butt joint, enhanced by the small Radii epoxy fillets added to cover and Hide the holes in the Root edge fin side holes. I'm sure for the majority of LPR and MPR models 1"OC per line (1/2" stagered centers) is more then enough for anything up to the 1500g Model limit;)
The Up-Scale models below All have Epoxy rivet attached fins on 1/2" stagered centers. To date haven't had a single broken or cracked fin/body joint in countless clustered flights:)

077a-sm_Maxi Bomarc 3D 13.25 scale_10-12-90.jpg

100a-sm_ Brighthawk 5D_03-04-91.jpg

150-a-sm_Hobby Goblin on Pad_05-14-94.jpg

171a-sm_Crayon 5D_Clu Odd-Roc_08-14-95.jpg
 
Great info, thanks! I was thinking that 1/8" spacing would start playing havoc with the body tube integrity/strength; the idea of 1/4" spacing, and to stagger off the center line is great, and likely all a medium power rocket would need.
 
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