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Mar 12, 2018, 06:35 AM
I Look, Listen, and Learn
Timbo383's Avatar
Quote:
Originally Posted by portablevcb
So why do you need the polycrylic if the titebond II is waterproof? Can you not just sand the titebond/paper and paint directly?
I'm assuming just for extra protection, the poly has more ding resistance than the Titebond. Best example I can think of is waxing the car, the paint protects the metal, the wax protects the paint.
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Mar 12, 2018, 09:18 AM
The Junk Man
Quote:
Originally Posted by warhead_71
Mod-podge dries soft and rubbery--
Nope. It dries to a fairly hard shell. About like polycrylic. I've used a lot of it lately and it works fine.

The regular Mod-Podge is not water proof although it will slightly resist water. Better, say, than doped tissue which will sag on a humid morning. But not much.

Mod-podge comes in several flavors though. One being rated for "outdoors" and one even "dishwasher safe".

But I just use the regular and if needed top coat it with spray clear coat.

Tom
Mar 12, 2018, 09:33 AM
Always Ready!
warhead_71's Avatar
I quit using Mod Podge because I could easily dig my thumbnail into it and could even peel paper off the plane "dry" once getting it started... it's actually quite stretchy stuff. Also had a seaplane where the entire bottom of the plane turned to soup after being in the water for more than 10 minutes. I have not tried "dishwasher safe" Mod Podge but might be worth checking it out. But after 5+ years of flying off water, I've had no such problems with TB-II and masking paper. Very difficult to remove actually.
Last edited by warhead_71; Mar 12, 2018 at 10:21 AM.
Mar 12, 2018, 09:47 AM
Space Coast USA
hoppy's Avatar
Quote:
Originally Posted by ruff1
I believe this is to allow just about any kind of paint to be applied. Hoppy, can you confirm that please?
It's an optional step with the glue/paper.

With bare foam it allows the use of most any paint. With masking tape designs, using PolyC on the masking tape edge/foam area prevents weeping of the paint under the masking tape.
Mar 12, 2018, 06:55 PM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
Quote:
Originally Posted by hoppy
It's an optional step with the glue/paper.

With bare foam it allows the use of most any paint. With masking tape designs, using PolyC on the masking tape edge/foam area prevents weeping of the paint under the masking tape.
Thanks Hoppy, that is very useful. I will be using masking tape for some edging, so I will continue applying Polycrylic. I will test masking on the FFF piece.
Mar 17, 2018, 08:16 AM
A Day @ a Time - Matt. 6:25-34
ruff1's Avatar
I tested the masking on the FFF piece, it came out good. Foam was eaten away where I did not have covering. Used a very old rattle can of Valspar, barely could push out the paint. I got sloppy on one piece of tape and got some bleeding under it. Used some sandpaper to take down the ridge of paint, overdid that a bit.

I applied polycrylic to the flap, that went on well and weight gain was very little. I'll weigh the second flap and report back.

I'm sold on the tb / water and coffee filters, I'll go this route.

Thanks for the thread Hoppy!
Mar 17, 2018, 10:49 AM
Space Coast USA
hoppy's Avatar
Good luck
Apr 26, 2018, 09:22 PM
Scratch builder
I'd like to try this (standard Hoppy technique) on a wing for strength.

However, my wings are a single thickness $ tree sheet bent into an airfoil curve with a rib here and there.

I know Hoppy has suggested many times, "cover both sides at the same time!" to prevent warping.

What difficulties/challenges can I expect as far as warping with this type of undercamber wing?

I am most interested in increasing the torsional stiffness.

I have also thought about using 45 criss cross strips of paper spaced apart, top and bottom to reduce weight.

Any thoughts/advice?
Apr 26, 2018, 09:58 PM
Space Coast USA
hoppy's Avatar
Foam, water, and glue are cheap which is the beauty of the method and one can experiment to their heart' s delight.

To my knowledge, no one has tried 45deg spaced strips. IMO, it will be significantly less strong than a fully paper covered wing. Give it a try and then give it the load test shown in the first post. If you try it, let us know how it turned out.

A preformed under cambered wing should be no problem with the covering of both sides at the same time. I've done it.
Apr 27, 2018, 10:37 AM
Registered User
As you want an under cambered wing in the first place, why not cover one side, let it warp to see how much of an under camber it gets you. Make that the bottom, then glue your ribs in and then cover the top?

You could also put it on just ever so damp. Mix up the water and glue, let it dry hanging in the wind. Spray the foam with a squirt battle, just enough to mist the surface. Place the all ready shrunk paper in place. Should be enough to wet the glue on the paper, but not enough to soak the paper through.

Buzz.
Apr 27, 2018, 11:34 AM
Space Coast USA
hoppy's Avatar
The shrinking is what helps makes it strong, how much more than pre-shrunk, ??
That would make an interesting experiment.
Last edited by hoppy; Apr 27, 2018 at 12:57 PM.
Apr 27, 2018, 10:43 PM
Registered User
Once you put water to it, it does expand a bit, but is does not shrink as much compared to when you soak it the first time.

Way back when, I was shown the pre shrink trick because I was crushing the structure of the peanut scale planes I was building. He sprayed the tissue laid out on the table, let it dry. Put a coat of thinned dope, layed the tissue down, after the dope was dry, he misted the tissue. It shrank enough to get the wrinkles out but not enough to bend or twist the structure. So, thought it might work here as he did not want a lot of tension in the paper.


Buzz.
Apr 28, 2018, 06:32 PM
Scratch builder
Preshrunk.... hmmm...very interesting as Artie Johnson used to say.

I was thinking of adding a 2" strip of paper, lengthwise across the wing, top and bottom, starting at the center of the wing, and allowing to dry.

The next session would entail two more strips on top, either side of the first, followed by two on the bottom, again, allowed to dry.

Continue towards the leading and trailing edges until the wing is covered.

Another thought: When removing $ tree paper, I use alcohol.

It does not make the paper mushy like water does.

Does alcohol mix with Titebond II?
Apr 29, 2018, 07:51 AM
Registered User
psychedvike's Avatar
Does alcohol mix with Titebond II?[/QUOTE]

I don't think so. Titebong is a water soluble glue. You could test a little on a crap piece to try it but I'm not sure the results would be what our looking for. Let us know if you do try it and have good results.
Apr 29, 2018, 02:03 PM
Registered User
Captain Dunsel's Avatar
Which type of alcohol? Rubbing may work (although I did find it turned latex spackle into a nasty jelly). Don't know about methanol (methyl), though. How about giving it a test and telling us what happens?

BTW, I got a chuckle out of 'Titebong', psychedvike.

CD


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