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Author Topic: First attempt - Sweepette 14 Mk 2  (Read 283 times)
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pete_n_pugs
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« on: November 04, 2021, 09:40:08 AM »

I'm a very inexperienced builder, but have attempted a Sweepette 14 mk 2. It is the first time I've really had to shape anything, but I'm quite happy with it so far. I'm planning on testing it indoors tonight. Seems like the stab especially warps very easily. Attached is a photo from before I added thread to the tow hook and leading edge, and a light coat of thinned dope.
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First attempt - Sweepette 14 Mk 2
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dosco
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« Reply #1 on: November 04, 2021, 10:01:01 AM »

Looks nice!

Looks like maybe you have some balsa "fuzzies" on the leading edge(?). May I respectfully suggest you lightly sand those off with "very fine" sandpaper (say 400 grit).

Hope you'll post a flight report!

Best-
Dave
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pete_n_pugs
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« Reply #2 on: November 04, 2021, 01:30:59 PM »

Good spot - I have given the whole ship a gentle going over with 400 then 600 once I had added the thread to the LE, and the light coat of dope.
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pete_n_pugs
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« Reply #3 on: November 05, 2021, 05:25:29 AM »

Well I had a pretty good initial session. Glide was initially dead straight, and I was not able to tweak the surface enough to get a decent turn. I ended up cutting through the rudder to get enough offset. Then I was finding that it would go up, then just stall into a dive. What I finally found was that I was not launching hard enough, and with the harder launch transitioned nicely. I think my initial problem was inaccurate building, as the tailplane was angled, but it still flew straight, so something was counteracting that. Being very thin, the wing was slightly warped at one tip - which I tried to counteract by breathing and tweaking. Here is the link to the video https://youtu.be/vZti-JYPL0w Any suggestions or feedback appreciated!
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dosco
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« Reply #4 on: November 05, 2021, 12:11:08 PM »

What I finally found was that I was not launching hard enough, and with the harder launch transitioned nicely.

This is not surprising.

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I think my initial problem was inaccurate building, as the tailplane was angled, but it still flew straight, so something was counteracting that. Being very thin, the wing was slightly warped at one tip - which I tried to counteract by breathing and tweaking. Here is the link to the video https://youtu.be/vZti-JYPL0w Any suggestions or feedback appreciated!

Not sure what you mean by "the tailplane was angled." If you mean stab tilt ... generally you want some of that in an HLG.

Yes, warps in wings = generally not a good thing.

The flight in your video looked nice, actually.

Best-
Dave

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pete_n_pugs
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« Reply #5 on: November 06, 2021, 12:14:50 PM »

For the record - weight was 12.6g. Wish I had weighed it before adding the dope. That was after a couple of running repairs, where I foolishly tried to catch it, and when the wings split apart at the join following too many stalls onto the nose.

So - how do I avoid the warps to the wings? They were sanded flat, but maybe I went too far and made the TE too thin?
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dosco
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« Reply #6 on: November 06, 2021, 12:19:58 PM »

For the record - weight was 12.6g. Wish I had weighed it before adding the dope. That was after a couple of running repairs, where I foolishly tried to catch it, and when the wings split apart at the join following too many stalls onto the nose.

So - how do I avoid the warps to the wings? They were sanded flat, but maybe I went too far and made the TE too thin?

Putting dope on the wings can do it. What sort of dope? Was it plasticized?

I've gone to spray-on varnish and polyurethane. I had a can of Deft spray lacquer that was nice, however I can't seem to find that stuff at Home Depot or Lowes anymore.

The spray-on stuff allows one to put on the bare minimum. I suppose if you thinned the brush-on stuff, you could probably get a very thin coating ... plasticizing will also help.

Best-
Dave
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pete_n_pugs
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« Reply #7 on: November 09, 2021, 04:32:02 AM »

Thanks Dave. It was not plasticised. I will have a look for spray on varnish, or may a go using an airbrush next time.
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OZPAF
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« Reply #8 on: November 09, 2021, 08:01:06 AM »

I agree with Dosco and just use polyurethane varnish on my CLG's. I use a method i picked up here on HPA - wipe it on with a tissue or paper towel and then use another dry tissue to wipe it off straight away. Rub it in a bit on teh first application but then wipe it as dry as you can.

After leaving it to completely dry (can take a while - I allow a couple of days), finish sand it with 400 grit paper to produce a smooth matt finish, which will also provide a degree of water protection if flying outside. It will still require wiping down though if it does get wet.

Your model is asking to be flown outside and grass is a lot softer than a hard indoor venue floor. It is flying well but needs more height on the launch and a little more trimming.

Good luck - happy flying.

John

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cglynn
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« Reply #9 on: November 10, 2021, 11:33:51 AM »

To increase indoor glider survivability, glue and thread wrap a foam earplug to the nose of the model.  Most of them need nose weight anyway, so no penalty there.  And the foam works surprisingly well as a shock absorber. 

I crashed one of my balsa fused F1N's countless times, and because of the ear plug, damage was almost nonexistent.  Once, the wing pylon popped off, but that was about it.  On prior versions of the same plane, any nose in crash would cause the fuse to break in two (or more).  The foam earplug was the cure.
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