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Dec 29, 2015, 03:42 PM
Thermal Junkie
Warren's Avatar
Thread OP
Build Log

My Prairie Bird - Coming along nicely...


Having a blast putting her together and learning a lot!

Yesterday I went out and bought a pair of magnifying goggles to help with the next one.

Almost ready to cover!

I am finding I like building with the Duco cement thinned 50/50 better than the thinned white glue, but will still experiment more...
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Dec 29, 2015, 07:50 PM
Registered User
Pat Daily's Avatar
Looks good--good luck with the covering Warren!
Dec 30, 2015, 04:57 PM
Kansas is windy.
pburress's Avatar
Looking good.

IMO thinned cement is the way to go on these smaller models. It's strong enough, sets very quickly, is light weight, sands well, and you can quickly undo any joint with some acetone.

My Prairie Bird is a great and consistent flyer. I had a 5 minute thermal-assisted flight a couple of years ago with it. Very light breeze that day and I only had to chase it a short distance across the field.
Dec 31, 2015, 12:49 AM
Registered User
Have to agree with the thinned cement. I'm a recent convert myself and really liking it.
Dec 31, 2015, 06:51 AM
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Gluehand's Avatar
Yes, water based or cellulose, thinned glue is the way to go.

Tip on covering: These delicate structures really need to be pinned down when drying, after water shrinking, AND after each coat of dope.

HERE are a few pics from my build, some years ago.
And, here's my PB:

Good luck..!
Dec 31, 2015, 12:07 PM
Thermal Junkie
Warren's Avatar
Thread OP
That for the all the support and advice!

Gluehand very nice!

HAPPY NEW YEAR TO ALL!

-- Warren
AMA 19909
Dec 31, 2015, 12:55 PM
B for Bruce
BMatthews's Avatar
It's huge fun putting these together, isn't it? The focus on detail really shuts out all one's other day to day issues.

On the thinned glue idea if you are using one of the cellulose glues keep in mind that acetone is the thinner of choice.

There's a fellow that was on Small Flying Arts back when it was growing that used nothing but thinned Ambroid on his stick and tissue models. He thinned it down so much that he applied it like thin CA to pre-set joints. It was so thin that he used one of the small glue bottles that came with a hypodermic needle applicator as used for applying solvent in working with acrylic plastic. He used a three minute egg timer so after the last joint was wetted he flipped the timer. When done he'd go over all the joints with a second wetting to fill in the small "pores". I won't call them gaps because this method would call for a little more fitting than that. If you're not that good a third bit of glue on the slightly open ones would likely be wise. The timer gets flipped after the second applications is done. And when the timer is done the glue is dry and the frame can be lifted. That makes for pretty quick work and would be much faster than waiting for something like thinned down Titebond to dry.
Dec 31, 2015, 01:27 PM
Thermal Junkie
Warren's Avatar
Thread OP
I found these bottles at Rockler - They are awesome and I thin the Duco 50/50 with acetone:

Needle Point Glue Injector
Item #: 63297

http://www.rockler.com/glue-bottles-...nd-applicators

-- Warren
AMA 19909
Jan 01, 2016, 05:54 PM
B for Bruce
BMatthews's Avatar
I've got some Duco I bought in the Fall but have yet to try it in the thinned format. Be sure to let us know if the 50-50 in this case is the right ratio as well as if that three minute double coating trick works for the Duco.
Jan 01, 2016, 08:11 PM
Registered User
SteveSw's Avatar
Coming along great, Warren! It's a nice little flyer.

As for working with Duco:

Starting to use thinned Duco right now on a Flyline Veli Monocoupe I’m putting together as my supply of Ambroid is starting to wane. Strength seems to be good but I am finding myself thinning a lot more than 50/50 as it seems to be drying too fast for me. Seems thicker than Amodroid straight out of the tube which is probably the reason. Tried using it as I did Ambroid which was to apply a thinned coat to each surface and after it tacks up apply a second coat to one surface and then assemble. Just wasn’t working for me.

In my case, Duco thinned 50/50 didn’t have enough open time to penetrate into the grain. I found thinning more like 25/75 did the trick. Still comes out of the needle applicator bottle thicker than Ambroid but seem to be holding just fine. One plus is that instead of using straight Ambroid for the second coat, a second coat of thinned Duco from the bottle to both surfaces seems to work. Actually like using it better than Sig-ment.
Curious to hear others experiences.
Last edited by SteveSw; Jan 03, 2016 at 12:14 AM.
Jan 02, 2016, 11:44 AM
Registered User
Are you using a brush Steve?
Jan 03, 2016, 12:13 AM
Registered User
SteveSw's Avatar
Quote:
Originally Posted by TRuss
Are you using a brush Steve?
No. I tried to use the Duco the same way as I did with Ambroid with little success. It was drying too fast to get a good joint.

With Ambroid, I would prime both surfaces with Ambroid thinned with acetone and let almost dry. Then apply a full strength second coat to only one surface with a scrap stick of thin bamboo or basswood. Attach the parts immediately and let dry.

What seems to be working for me with the Duco is thinning it more than the Ambroid. Just to get it to flow out the same needle tipped bottle I was using with the Ambroid it seems to be around a 25/75 dilution ratio. Then as it starts to tack up, give both surfaces a second coat of the thinned Duco and assemble and let dry.
Jan 04, 2016, 12:06 PM
Thermal Junkie
Warren's Avatar
Thread OP
Getting closer!

-- Warren
AMA 19909
LSF 9170 Lvl IV
Jan 04, 2016, 08:36 PM
Diesel Danny
danny mz's Avatar

Glue Joint Strength


G'day people.

This test was done many years ago, but I think that the results are still valid - and they do work for me using thinned Aeroflyte C23 (Balsa cement).

Anyway, I think that some of you might find it of interest

Regards * Danny M *
Jan 05, 2016, 10:54 AM
B for Bruce
BMatthews's Avatar
It most certainly is still valid. It simply needs updating to include information on more of the glues we use these days. And I'd love to see it expanded to include a couple or three different balsa densities. I think it would be an eye opener to many.

Model builders are no strangers to end to side grain joints. It's hard to avoid them. We use joints like that in our stick built fuselages universally. It's rather fussy work to produce multiple mortise and tenon joints in 3/32 square stock after all.... Yet any traditional cabinet maker would cringe at using such a joint. It's a recipe for disaster in any sort of cabinet or other fine joinery work. So we really are relying on the strength of the glue to carry the day.

At the very least we can work towards avoiding any end to end grain joints. It's not that hard to produce a 4:1 length scarf joint. In 1/8 stock that's only 1/2 an inch. For 1/16 we're talking about 1/4 inch. With any care at all this can be done by hand and eye with a good razor blade. And a 4:1 scarf joint has an angle of 14 which puts it well up the strength scale for our sort of use.

Steve, thanks for the note on the Duco cement. Something you might try with a small sample is to thin it with cheap hardware/paint store lacquer thinner. The stuff is a soup of other solvents but the primary one, because it's fairly cheap, is acetone. And the smaller amounts of the toluene, xylene and likely a few other 'tones, 'lenes and retarders helps to slow down the evaporation rate by a little compared to straight acetone. I've used it instead of straight acetone in thinning Ambroid over the years with good results.


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