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Old Mar 10, 2011, 02:05 PM
Gary
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USA, CT, Sandy Hook
Joined Dec 2009
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Shorts Skyvan 24 inch - test flight video

I decided that I was spending too much time being a warmonger with all those WWII micros (joke) and thought that a commercial twin would be a pleasant change. One challenge is the toothpick wings you often encounter in these planes. Indoor is my preferred venue at the moment so 24 inch span is my target. I downloaded a plan for the Short Skyvan drawn by Roger Jones for twin 600's that I scaled to my 24 inch target (http://plans.rcmodell.hu/planelect.html). Roger had some interesting comments on the plane. I quote:

ďBuilt by Short Brothers in Northern Ireland in the 60's, the Skyvan was powered by a pair of Pratt & Whitney PT6 turboprops. It had a high-aspect ratio wing which was fully flapped and slotted for short field performance. It was built to be rugged and require little maintenance for use in remote areas. There are several still flying, now mostly owned by parachute clubs for which the rear doors (which can be opened in flight) are especially useful.

The model will take off from the ground but only from a smooth surface. It needs a good heave for a hand-launch. Landings are fun but don't let the speed drop too much on the approach as the stall is quite vicious. "wheeling on" seems to be the best.Ē

Love that talk about the vicious stall! I hate tip stalls! Oh well, onward.

I plan on a mixed construction: dollar tree foam for the fus. and stab/elevator, depron for the wing and fin/rudders. I'm even going to sneak in a piece of balsa. There are reasons for each which I will describe in the next posts.

An AR6400 for controls and that leaves the powerplants. I considered all my options. I have used 2-cell brushless with the AR6400 in my Pitts. But that may be too much power. I settled on two Champ motor/gearboxes, hoping that the built in esc in will handle the power needs.
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Last edited by gklein; Apr 28, 2011 at 08:21 AM.
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Old Mar 10, 2011, 02:34 PM
Flash, AAAAAAAAAAAHhhhhhhhhh
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United States, UT, West Jordan
Joined Dec 2008
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you will want the ar6400t(twin) if your gonna do 2 champ motor/gearboxes. at that point oyu should just go with the black end motors for more power. plane looks really neat though
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Old Mar 10, 2011, 02:36 PM
free flight or micro RC ???
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Greece, Central Macedonia, Thessalonika
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Or how about this ?
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Old Mar 10, 2011, 02:36 PM
Gary
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USA, CT, Sandy Hook
Joined Dec 2009
816 Posts
Dollar tree foam was the choice for the fuselage. I like it's thickness when shaping the corners. I actually made two different fuselage sides as as experiment. One was 1mm depron on a skeleton of dollar tree foam so that I could have enough body to sand the corners, and the second was dt foam on a dt skeleton. I found the difference in weight to be negligable and the depron/dt foam would have shown a different texture along the edges of the fuselage where you round it off. So dt/dt was the direction I went.

The fus. is a simple box with a blue foam nose for fun carving. Right now it weighs 19 grams. Still quite heavy but I have not hollowed out the nose yet.
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Old Mar 10, 2011, 02:37 PM
Gary
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USA, CT, Sandy Hook
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Quote:
Originally Posted by g_kandylakis View Post
Or how about this ?
Nice one!
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Old Mar 10, 2011, 02:44 PM
free flight or micro RC ???
g_kandylakis's Avatar
Greece, Central Macedonia, Thessalonika
Joined May 2006
460 Posts
Two years ago I too played with the idea of a Skyvan...

This is as far as I got, before taking a "short" break to finish other models.

"Traditional" construction, scale 1/36, span ~22", projected weight <40 gr (hoped for...).

Two Champ motors sound too much to me, I would feel ok with two Cub motors-gearboxes, with aprox 40gr thrust they should be enough for a light model.

If you need more pics of the full size, just let me know...

George
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Old Mar 10, 2011, 02:49 PM
Gary
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USA, CT, Sandy Hook
Joined Dec 2009
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Quote:
Originally Posted by akwardflyer View Post
you will want the ar6400t(twin) if your gonna do 2 champ motor/gearboxes. at that point oyu should just go with the black end motors for more power. plane looks really neat though
I don't think that power will be a problem. I will be looking for scale flight, not aerobatics. And I have the 6400L. It is rated a 2amps continuous. I will check the amp draw of the champ setup. Does anyone know it?
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Old Mar 10, 2011, 02:51 PM
Gary
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USA, CT, Sandy Hook
Joined Dec 2009
816 Posts
Quote:
Originally Posted by g_kandylakis View Post
Two years ago I too played with the idea of a Skyvan...

This is as far as I got, before taking a "short" break to finish other models.

"Traditional" construction, scale 1/36, span ~22", projected weight <40 gr (hoped for...).

Two Champ motors sound too much to me, I would feel ok with two Cub motors-gearboxes, with aprox 40gr thrust they should be enough for a light model.

If you need more pics of the full size, just let me know...

George
I'm a recently converted stick builder so I know the effort nice construction like your's represents. Beautiful work. I hope you get a chance to finish it.
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Old Mar 10, 2011, 02:51 PM
I love HAM
Joined Nov 2005
725 Posts
This is going to be neat!

What about putting in rear doors and dropping a (group of) little skydivers?

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Old Mar 10, 2011, 02:54 PM
Gary
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USA, CT, Sandy Hook
Joined Dec 2009
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Quote:
Originally Posted by Schermvlieger View Post
This is going to be neat!

What about putting in rear doors and dropping a (group of) little skydivers?

The rear door is already cut! Powering it will be one of my challenges at this scale. I have a falcon servo that I'm thinking about, the rotary motion will work better for the mechanism I'm thinking of. Has anyone used one of these with a spektrum recvr?
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Old Mar 10, 2011, 02:59 PM
Flash, AAAAAAAAAAAHhhhhhhhhh
flashkick's Avatar
United States, UT, West Jordan
Joined Dec 2008
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im pretty sure the champ motors pull about 1.5 amps each. thats why the ar6400t would be a good option it has 2, 2amp ESCs built in.
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Old Mar 10, 2011, 03:25 PM
I love HAM
Joined Nov 2005
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Quote:
Originally Posted by gklein View Post
The rear door is already cut! [...]
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Old Mar 10, 2011, 04:10 PM
Gary
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USA, CT, Sandy Hook
Joined Dec 2009
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Quote:
Originally Posted by akwardflyer View Post
im pretty sure the champ motors pull about 1.5 amps each. thats why the ar6400t would be a good option it has 2, 2amp ESCs built in.
I don't want to appear stubborn, but buying a new brick is something that I would rather hold off for now. This chart, prepared by Reme, suggests that if I drop to a 4530 prop that the amperage draw will get close to the tolerance of the recvr. Worst case, I put an external esc in place. Additionally, the 4.5 inch props will help my clearance to the fuselage. At this scale I only have a hair less than 2 inch clearance. I planned on deviating from scale and shifting the nacelles outboard and this size prop will help minimize that change. So I will keep my fingers crossed.
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Old Mar 10, 2011, 04:32 PM
Flash, AAAAAAAAAAAHhhhhhhhhh
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ya i would go with the external esc. wouldn't want to risk your brick.
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Old Mar 10, 2011, 07:02 PM
OY-5542
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Denmark, Central Denmark Region, Silkeborg
Joined Nov 2009
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Quote:
Originally Posted by gklein View Post
I don't want to appear stubborn, but buying a new brick is something that I would rather hold off for now. This chart, prepared by Reme, suggests that if I drop to a 4530 prop that the amperage draw will get close to the tolerance of the recvr. Worst case, I put an external esc in place. Additionally, the 4.5 inch props will help my clearance to the fuselage. At this scale I only have a hair less than 2 inch clearance. I planned on deviating from scale and shifting the nacelles outboard and this size prop will help minimize that change. So I will keep my fingers crossed.
Normally the Ultra Micro j-3 Cub's stock motor/gearbox/prop pull less than an amp. Therefore there should be no problem connecting 2 on 1 brick.
I've ordered 2 UM j-3 Cub motor/gearbo/prop to try that, but they haven't arrived yet. It does look like HH aren't able to deliver does here in Belgium right now. When getting them, I'll connect just one and messure the Amp draw... I'll post it to let you know.
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