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Tools & Supplies: Glue and Adhesives
Talk about sticky stuff.
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Metal and Styrene
robertdlipp
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United States
Joined: October 05, 2014
KitMaker: 10 posts
Armorama: 0 posts
Posted: Sunday, February 01, 2015 - 11:42 PM UTC
Hello Again,

Have finally started work on Dragon's DD-421 Benson. Prior to cementing the top and bottom hull sections together, I glued 6-32 nuts to the lower inner hull section. This was to accept 6-32 screws coming up through the wood base (through spacers), through hull and into the nuts. I used 5 minute epoxy to glue the nuts in place. This turned out to be a mistake...after a couple of weeks, one of the nuts broke loose. Had to cut a section out from upper hull to remove the thing.
What type of cement should I use to secure the metal nut to the inner hull section?

Thanks in advance for any suggestions.

Robert
JClapp
#259
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Massachusetts, United States
Joined: October 23, 2011
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Posted: Monday, February 02, 2015 - 03:58 AM UTC
An interesting problem. Epoxy would have been my choice also.

Perhaps the contact area of a standard hex nut is just too small for epoxy to resist a mechanical load.

Perhaps instead of a nut, drilling and tapping a hole in a small square of brass plate, say 3/8" square by .080 thick..? and epoxy that down.
Also, give the styrene around the hole a good scuffing to give the epoxy some traction.
amoz02t
#192
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Kentucky, United States
Joined: November 25, 2009
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Posted: Monday, February 02, 2015 - 04:12 AM UTC
I have beefed up aircraft fuselage halves with milliput epoxy (super fine-white) before drilling a hole for a brass support rod. Perhaps reinforcement around the nut with something solid like the epoxy putty would help?
Blespooky
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Tel Aviv-Yafo, Israel
Joined: June 03, 2014
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Posted: Monday, February 02, 2015 - 04:42 AM UTC
My solution was to glue large pieces of sprue around the nut as shown, it has held up very well so far:



Bryan
Namabiiru
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MODEL SHIPWRIGHTS
#399
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Rhode Island, United States
Joined: March 05, 2014
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Posted: Monday, February 02, 2015 - 05:02 AM UTC
Robert,
I think a big part of the problem was in choosing 5-minute epoxy. My experience has been that the fast-curing stuff tends to fail after a short period of time.

Back when I was making alcohol stoves for backpacking I came across J-B Weld, which is two-part epoxy designed for very high-temperature applications. It takes awhile to set, but I have never had a joint made with J-B Weld fail.

Bryan's suggestion of reinforcing with something to take the torque is a good one, although I personally would use something with a flat side right up against the nut and glue it down with plastic cement.

robertdlipp
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Joined: October 05, 2014
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Posted: Tuesday, February 03, 2015 - 11:37 PM UTC
Hi All,

One thing I failed to mention in my original post was that I did glue pieces of sprue alongside the flats of both 6-32 nuts (first with Tamiya liquid cement and then epoxy). When the aft nut came loose, the sprue remained in place.
As a repair, I replaced the nut and just added more sprue crosswise (again using Tamiya and epoxy), thanks to Bryon's suggestion. Hopefully it will not come loose in the future.

Thanks all for the prompt replies!

Robert
Kennewick, WA
Kevlar06
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Washington, United States
Joined: March 15, 2009
KitMaker: 3,487 posts
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Posted: Wednesday, February 04, 2015 - 02:08 AM UTC
Robert,
I've done many commission builds in 1/350, 1/400 and 1/144 for private customers. I've used many of the suggestions above, and then some, but I keep coming back to the solutions that's worked best for me over the years. I use thick super glue from Bob Smith Industries (BSI). I "tack" the nut in position, carefully avoiding getting any glue on the threads. Then, in several separate applications I build a large "bead" of super glue up around the nut until it reaches the shoulder of the nut, using spray accelerator to harden the glue between applications. All my models are mounted on brass faucet finials from Ace hardware, which are hollow-- the retaining screw goes up through the center of the finial, and the top of the finial fits flush against the hull, providing a secure and elegant tapering effect at the base. The finials are glued into an appropriate wood base drilled to accept them. This method is simple, works extremely well, looks great on the outside and the nut will never move, its a lot stronger than using plastic sprue or epoxy, which sometimes doesn't hold on the plastic surface. Just be sure to use lots of glue around the base of the nut so it cant break free-- also roughen the inside of the hull with a course grit sandpaper. You can find the appropriate nuts, screws and finials at Ace hardware or any good hardware store. Cheers from Gig Harbor. VR, Russ
Removed by original poster on 02/05/15 - 01:25:10 (GMT).
robertdlipp
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United States
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KitMaker: 10 posts
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Posted: Wednesday, February 04, 2015 - 08:23 AM UTC
Russ,

I've used Bob Smith cements before, mostly on my Charles W. Morgan. Wish I'd thought of that when I started the Benson!
Thanks for the idea.

Sincerely,

Bob
Kennewick, WA