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Nov 14, 2017, 02:03 AM
Dion Patelis
wingfocus's Avatar
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Build Log

Another Gemot V3 build


Body sanded.
Wire paths cut and RC gear glued in with power / charge switch and a bind switch.
Experimental pure foam leading edge coated with Multihesive / Q-Cell bog for strength.
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Nov 15, 2017, 04:22 AM
Dion Patelis
wingfocus's Avatar
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More photos on the WingFocus blog
Nov 16, 2017, 06:05 PM
Dion Patelis
wingfocus's Avatar
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More laminating.

The previous red Gemot is pretty beaten up now. We started messing around with FPV. You can see the grey duct tape on the leading edge where I had the camera internally mounted. It worked fantastically, except we were not really familiar with FPV and ate various rocks, fences, brick walls and just the ground in general at mach 10. So the original Gemot now looks a bit like a boxer after a few fights. Still flies, but it's not so crispy smooth any more.
There was a noticeable difference with the camera in the leading edge as it caused a lot of turbulence. I think we'll keep all future Gemots purely for flying by line of site and I'll design something with the cargo on a separate fuselage well away from the leading edge(s). Like back in the days of slalom windsurfing, when that leading edge gets even the slightest kink in it, the performance seriously dwindles.
Last edited by wingfocus; Nov 16, 2017 at 06:21 PM.
Nov 20, 2017, 02:24 PM
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hmmm. have you tried laminating film?
Nov 20, 2017, 07:33 PM
altitude adjustment
thumbhead's Avatar
Why split the elevator and ailerons only to join them again?

Mark
Nov 21, 2017, 04:37 PM
Dion Patelis
wingfocus's Avatar
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Quote:
Originally Posted by thumbhead View Post
Why split the elevator and ailerons only to join them again?

Mark
I wanted to keep the smooth curved anhedral shape and if I ran the control surfaces dead straight at the hinge point I would have had to dig out up to 8mm into the top surface of the wing. So I split them and the dig out was no more than 2.5mm (from memory).

With Gemot V2 there was only 10mm of anhedral and the control surfaces could be kept in one piece. Then to fix some other issues , I bastardised V2 with a knife and some packing tape to make Gemot V2.5, which worked extremely well. It more or less had flat sections for the anhedral. When V3 was made with the smooth anhedral, this lifted the performance another level. In order to keep the control surface hinge point working well and keep airfoil geometry smooth(ish), I reluctantly broke them into two. It paid dividends though.
Nov 21, 2017, 04:38 PM
Dion Patelis
wingfocus's Avatar
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Quote:
Originally Posted by mr.zagi5c View Post
hmmm. have you tried laminating film?
No, but I'd like to.

Does it work on EPS like EPO?
Nov 21, 2017, 04:40 PM
Dion Patelis
wingfocus's Avatar
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...
Nov 21, 2017, 05:44 PM
Dion Patelis
wingfocus's Avatar
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I was super pumped about taking it for a fly before dark, so that's my excuse for not finishing the paint job.
.
**********************

Like a rabid dog, foaming at the mouth. He sprinted to the edge of the cliff face and released the eagle into the sky. With head held high he let out a Dracula style evil laugh and then pronounced. "It's alive,,,... it's aLiiiiiiVee!!!!" .... and he flew, grunting, snorting and chuckling in deep satisfaction as Gemot whooshed overhead.

**********************
Nov 21, 2017, 05:56 PM
It's time for me to fly
JimZinVT's Avatar
Quote:
Originally Posted by wingfocus View Post
Does [lam. film] work on EPS like EPO?
I've had mixed results with lam. film over XPS (blue or pink) and haven't tried it yet over EPS (white beaded foam). I sometimes get poor adhesion; not sure if that's related to iron temperature or maybe not completely removing sanding dust from the surface before applying the film. I have not used any spray adhesive under the film, and I'd guess that would cure the problem. Going to try that next time I do an XPS wing. It needs to be done in very light mist coats of course, so the solvent doesn't eat your foam. The ones that go on thick and goopy (like 3M #90) would not be a good choice over any PS foam, I think.

The melting temp. of PS foam is not a whole lot higher than the melt temp of the lam. film adhesive, so you have to sneak the temp up until you find the sweet spot. Be sure you get the low-temp lam. film. EPP's higher melting point gives you a much wider margin of error here.

- Jim

( I always confuse the EPS / XPS terminology....if I have it backwards please correct me)
Last edited by JimZinVT; Nov 21, 2017 at 06:06 PM.
Nov 21, 2017, 06:30 PM
Dion Patelis
wingfocus's Avatar
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Quote:
Originally Posted by JimZinVT View Post
I've had mixed results with lam. film over XPS (blue or.......... PS foam, I think.

The melting temp. of PS foam is not a whole lot higher than the melt temp of the lam. film adhesive, so you have to sneak the temp up until you find the sweet spot. Be sure you get the low-temp lam. film. EPP's higher melting point gives you a much wider margin of error here.

- Jim

( I always confuse the EPS / XPS terminology....if I have it backwards please correct me)
Thank you for the info Jim.

EPS and XPS are pretty close except EPS is expanded in a mould and XPS is extruded through a hole which gives it a grain. XPS is strong compressively inline with the grain, but we've found it to be brittle in other axis' as you can see here. EPS is evenly strong in all directions, but not as stiff as XPS and no where near the compressive strength.

Zawlade was made with the same paper coasting system as Gemot except using XPS and it was hand shaped instead of CNC milled.

From your description and the occasional video which I see, I am not so keen on it as we've found EPS melts or distorts really easily. What I am keen on this 25gsm woven fibreglass cloth and epoxy resin I found at Ballina Fibreglass. It should make the planes last a whole lot longer and really it shouldn't be that much more hassle than the Multihesive glue. Well somewhat more, but a far stiffer more durable shell.
Dec 22, 2017, 08:17 AM
Dion Patelis
wingfocus's Avatar
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Some video:

The sea level windspeed was 18-25kts. This slope was at 70m elevation.

Gemot v3 yellow (0 min 45 sec)
Last edited by wingfocus; Dec 22, 2017 at 08:36 AM.
Dec 22, 2017, 05:44 PM
It's time for me to fly
JimZinVT's Avatar
What does she weigh? Looks like you could use a little more weight at the windspeed in the video.
Dec 24, 2017, 06:25 AM
Dion Patelis
wingfocus's Avatar
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Bit over 300 grams.

Will have to try the extra nose weight.

Have put the plane design on this torrent http://wingfocus.com/downloads/wingf...mot_v3.torrent
Last edited by wingfocus; Dec 24, 2017 at 06:31 AM.


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