1:20 scale (3.1m wingspan) Martin Mars - RC Groups
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May 02, 2006, 08:40 PM
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alexcmag's Avatar

1:20 scale (3.1m wingspan) Martin Mars

This is my all foam MartinMars, movie taken this weekend on a farm.

Original thread in https://www.rcgroups.com/forums/showthread.php?t=400557
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May 02, 2006, 09:16 PM
Yep I got another one.
mohillbilly's Avatar
Very nice
May 02, 2006, 09:25 PM
What a horse!!!! What's the weight?
May 03, 2006, 07:22 AM
Lori, hey, you're home early
CarreraGTSCS's Avatar
Nice! Impressive flyer. More info please.
May 03, 2006, 01:33 PM
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alexcmag's Avatar
It is not heavy (2.4Kg / 5.35lb), in fact it is lighter then most glow trainers.

- Scale: 1:20
- Wingspan: 3.1m (120 in)
- length: 1.79m (70.5 in)
- Weight: 2400g (85.7 oz)
- Motors: 4*GWS EPS400C-DS with GWS 10x6 props
- Battery pack: 9.6V 1900mAh Kan (8s2P NiMh)
- Wing area: 100dm2 (10.76 sq ft)
- Wing load: 24g/dm2 (7.96 oz/sq ft)
- Wingspan of stab+elevator: 1.05m (41 in)

The tail alone is a mid-size parkflyer... Stab looks like a GWS Zero wing!!!

Some pictures...
May 03, 2006, 02:36 PM
iumop ap!sdn w,I
G.P.'s Avatar
Very nice! Even sounds good.

Do you have any landing footage? Or even some ROW (rotate off water) footage?

May 03, 2006, 05:50 PM
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alexcmag's Avatar
Unfortunately, no...

In fact landings are not so beaultifull...

In the first flight one cell of my 10S2P Kan 950mAh failed, making it fly underpowered. When the failed cell short-circuited due to overheating it made a chain-reaction of cells melting the plastic insulation and shorting too. Result was a sudden voltage fall, I noted the lack of power and get it back with low power, but when I would flare for landing left motors quit (separate ESCs, separate cutoff levels for a few millivolts) and it made a tight turn and landed out of sight.

Second flight was with LiPo, good flight, good landing but only recorded in VHS.

Third flight was with Lipo too, but battery connector melted while flying, making the giant to make a long spiral until land softly on glass.

Connector was replaced and fourth flight was made. After 5 minutes of flight left ESC burn out while flying far away (300m horizontally over the farm's swimming pool). I noted a tendency for turns and got it back with differential throttle all right (giving me 50% power on right motors) and rudder almost all right, Nice landing but with no video.

After landing I noted a small hole on the foam bottom, the MOSfet of melted ESC overheated and fall from PCB, making a hole on foam... It was amazing, but it is not so difficult to fly with only a pair of motors running.

Due to these problems with battery/connector/ESC (40A, 480W is a lot of power), and the not so large lake, I did't tried ROW.
May 04, 2006, 07:50 AM
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Airboatflyingshp's Avatar
Sounds like you need a heat sink and or some ventilation, ALL that foam is too much insulation for a warm climate, that or you'l have to move somewhere a bit cooler like Antartica

Alex you or Eric Payen have to have a go at doing a Saro Princess foamy one day .

PS If this is too much of a distraction from your thread I will happily edit it down Clive.
Last edited by Airboatflyingshp; May 04, 2006 at 08:09 AM.
May 04, 2006, 05:47 PM
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alexcmag's Avatar
Actually sounds like I need better ESCs, battery and connectors... And a bigger car...

Nice seaplane, but I need to buy a truck first
Jun 04, 2006, 09:21 PM
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rockbus's Avatar
Fantastic plane. Thanks for Sharing. Got any more Video?
Jun 04, 2006, 11:17 PM
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alexcmag's Avatar
Originally Posted by rockbus
Fantastic plane. Thanks for Sharing. Got any more Video?

Unfortunatelly, don't have a better video. Several friends recorded the same flight from near places, this is not so usefull.

The better part, when I replaced the battery pack by a 3S3P LiPo, was not recorded on video.

With 3S it made loops, hummerheads, tight turns, very funny, byt there was nobody with a camera.

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