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UHU Glue Adhesion (Read 454 times)
Reply #13 - Dec 7th, 2018 at 9:10pm

alfakilo   Offline
Senior Member
Retired USAF and TWA.
St Louis, MO

Posts: 521
****
 
I can't say that I've prepped the frame prior to covering in every instance. In any case, I've seen a significant improvement in my last few builds by using a different adhesive technique than before.

I dissolved an Elmers purple glue stick in alcohol and then used it to glue the tissue to an unprepped balsa frame with a small paint brush. The tissue joints were considerably less obvious than before. Significant reduction in the "dark" look of the tissue joints. The tissue was applied both dry or damp depending on the location.
 
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Reply #12 - Dec 2nd, 2018 at 11:07pm

Sky9pilot   Online
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Stick & Tissue
Kelso, WA 98626 USA

Posts: 10050
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That's the way I've always done the tissue work, gluestick on bare balsa.  Just finished sanded!
Tom
 

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Reply #11 - Dec 2nd, 2018 at 10:23pm

MKelly   Offline
Senior Member
Helotes, TX

Posts: 580
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You might be on to something there - I also have been using the glue stick on bare balsa for covering.

Mike
 
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Reply #10 - Dec 2nd, 2018 at 7:25am

Bargle   Offline
Full Member
Oh crumbs
East Tennessee

Posts: 129
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alfakilo wrote on Nov 19th, 2018 at 10:49am:
Usually I've used a thinned Aleens Tacky Glue to stick the tissue down. It dries clear and seemed to give a better finish than thinned Elmers.

Lately, having read comments here, I've given the Uhu glue stick a try. I have both blue and clear Uhu versions. In both cases, I've had problems with the tissue coming loose.

First, I used thinned EZDope to prep the frame and sanded that down after drying. Then I used the Uhu to coat the outline of the frame and followed that by applying dampened tissue. Initially all seemed normal. If needed, I resprayed the tissue to complete sticking it down (I use a 50/50 water/alcohol mix and it dries quickly). I set the piece to dry normally (no heat gun).

Later, I could see that the piece (bottom wing, for example) was wrinkled and parts of the leading or training edge had come loose. Sometimes a water repray would let me reattach the tissue and sometimes I've had to remove and replace.

When using an Elmers blue glue stick in the past, I don't think I had this problem. Any suggestions?

Not sure, but the problem might be using the EZ-Dope before covering. I always apply the glue stick to bare wood. It's also important to let it dry for a good while (5 hours or more) before adding finish.
 

Sure it's a wrinkly mess, but it flies.
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Reply #9 - Nov 23rd, 2018 at 7:42pm

MKelly   Offline
Senior Member
Helotes, TX

Posts: 580
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My luck with the clear UHU has improved as I've been using it more - I think I'm getting used to its quirks.  I used UHU exclusively when I re-covered the Tempest (previously I had used UHU to tack the tissue down, then followed up with thinned white glue to seal the seams).  Two things seem to help getting the tissue to stick down well:  apply a fairly thick layer of glue stick (I've taken to about three passes over the outer framework), and press the tissue down firmly by running a fingertip or fingernail over the tissue once applied to the glue-covered framework.  The only areas that gave me any trouble on the Tempest were where I had chalked the back of the invasion stripes - I had to flow a little rubbing alcohol into the tissue in a couple areas to get the glue to bite on the tissue instead of the chalk.

The only other suggestion I can offer is don't wait too long to dope the model.  On the Navion I glue-sticked some of the markings to the undoped silver esaki.  For various reasons I didn't get around to doping it until a week or so later, and the markings had started to lift off in several places.  I stuck them back down by flowing alcohol through them, then doped it within a day and all was well.

Hope this helps,

Mike
 
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Reply #8 - Nov 23rd, 2018 at 1:36pm

Kerak   Offline
Senior Member
I Love YaBB 2.5 AE!
Roy, Utah

Posts: 1676
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I might as well throw my two cents into this topic.... Cool  I've built models in various locations on this planet...dry, humid, cold, hot...and for me, the environment has always been a factor.  I've even built in an environment so humid that water droplets were condensing on my model's doped surfaces! 

Around here, I can build inside...then take the model outside...and immediately detect an effect on things.  That's just the nature of our hobby's materials (basically wood...be it balsa or tissue)...plain and simple as that.  Sooooo...build accordingly...moisture and humidity dictate materials (adhesives/finishes) impervious to H2O...like dope/oil base, etc.  If one wants to test their efforts by leaving it all inside of a 100plus F car...well, don't be surprised.  Try that with an unopened can of soda...check out the mess that'll make.  Don't ask how I KNOW.

That being said...all of these adhesives work...when used sensibly...and we're all in tune with that, right?  The key phrase is...WHATEVER WORKS!

This spring I discovered a baseball under some shrubs in the backyard.  I wedged it firmly up in the fork of a tree.  Every week whenever I'd cut the grass...that baseball was lying on the ground!  I'd wedge it back into the fork again.  Point:  Train your tree and shrubs properly and they'll give up your models willingly.  Wink Grin Grin Grin

I come to bury Caesar, not to praise him!  Smiley

Neal
 
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Reply #7 - Nov 19th, 2018 at 9:56pm

subvet   Offline

I Love YaBB 2.5 AE!
Colorado

Posts: 10
 
When I tried purple Uhu to tissue a Piper Cub model I had nothing but trouble with adhesion if I got too far ahead in applying it and problems with loss of adhesion when I sprayed the model with Krylon Clear coat.  Not surprised to hear glue stick adhesive is heat sensitive.  I've gone back to the tried and true thinned white glue for tissue and I'll dope Silkspan.
 
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Reply #6 - Nov 19th, 2018 at 11:46am

pb_guy   Offline
Senior Member
So I'm just a kid at heart.
Youbou, BC, Vancouver Island

Posts: 1252
****
 
I use thinned Gorilla Carpenter's glue for all construction. When applying tissue, I mix up about 60:40 glue water and apply a layer to the structure, go over it a second time, and then lay the tissue down. I cut the edges for overlap and apply the glue mix with a brush to the edges and use a finger to seal the tissue to the structure. Never had any come loose after it dried. I also used the same technique with Weldbond and Titebond.
YMMV
ian
 
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Reply #5 - Nov 19th, 2018 at 10:49am

alfakilo   Offline
Senior Member
Retired USAF and TWA.
St Louis, MO

Posts: 521
****
 
Usually I've used a thinned Aleens Tacky Glue to stick the tissue down. It dries clear and seemed to give a better finish than thinned Elmers.

Lately, having read comments here, I've given the Uhu glue stick a try. I have both blue and clear Uhu versions. In both cases, I've had problems with the tissue coming loose.

First, I used thinned EZDope to prep the frame and sanded that down after drying. Then I used the Uhu to coat the outline of the frame and followed that by applying dampened tissue. Initially all seemed normal. If needed, I resprayed the tissue to complete sticking it down (I use a 50/50 water/alcohol mix and it dries quickly). I set the piece to dry normally (no heat gun).

Later, I could see that the piece (bottom wing, for example) was wrinkled and parts of the leading or training edge had come loose. Sometimes a water repray would let me reattach the tissue and sometimes I've had to remove and replace.

When using an Elmers blue glue stick in the past, I don't think I had this problem. Any suggestions?
 
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Reply #4 - Sep 3rd, 2018 at 12:54pm

Riehlflyer   Offline

It Flies ...... ?
Upstate , SC

Posts: 28
 
Update: I recovered the tail and built a new fuse which promptly got stuck in a tree. It blew down in pieces 2 weeks later after 2 or 3 summer thunderstorms. The only pieces that stuck had tissue were covered with white glue. I think I will stick Smiley with white glue and use uhu for markings.
 

A.R.
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Reply #3 - Jul 14th, 2018 at 4:15pm

Sky9pilot   Online
Administrator
Stick & Tissue
Kelso, WA 98626 USA

Posts: 10050
*****
 
Heat and Stick and Tissue airplanes don't play well together...I've seen where some modelers put their models in a large Coleman type ice chest with a dry blue ice frozen brick to avoid the high temps. 

I remember as a kid we moved from Missouri to So Cal and without thinking my plastic model of the Wasp aircraft carrier was placed in the back window shelf.  When we arrived in CA  the deck of the carrier was curled up almost into a circle.  All those poor little Hellcats dispersed all over the back window shelf!!! Roll Eyes Shocked Cheesy Wink
 

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Reply #2 - Jul 14th, 2018 at 12:43pm

Riehlflyer   Offline

It Flies ...... ?
Upstate , SC

Posts: 28
 
I may not have put it on thick enough, but it was 100 degrees or so and the car was in the sun.
 

A.R.
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Reply #1 - Jul 14th, 2018 at 12:13pm

MKelly   Offline
Senior Member
Helotes, TX

Posts: 580
****
 
I've been using the yellow-label UHU clear glue stick.  Has been fine for attaching tissue to balsa, no problems with the base tissue on the half-dozen models I've used it on.  All were sealed with thinned Nitrate dope.

However, trim applied over doped tissue or on canopies is another story.  The canopy framing in my Tigercat was applied with glue stick and subsequently peeled up in the heat at WESTFAC.  Solved that by applying canopy trim using thinned canopy glue.  On my Navion I used the UHU to tack down lettering on the wings - it was about two weeks before I got around to doping over the lettering and it had started peeling up.  I now tack lettering in place with a few spots of glue stick, then immediately flow nitrate thinner onto the markings, which locks it down to the doped tissue much better.

Hope this helps...

Mike.
 
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Jul 13th, 2018 at 10:33pm

Riehlflyer   Offline

It Flies ...... ?
Upstate , SC

Posts: 28
 
I recently purchased some UHU glue sticks and covered a tail with it. After a few days in a hot car the tissue had come off. Is this the heat or am I doing something else wrong? I usually use thinned white glue and have never had any problems before.
 

A.R.
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