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prop choice and flap throws????

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prop choice and flap throws????

Old 08-20-2008, 04:58 PM
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ceecrb1
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Default prop choice and flap throws????

Ok, just taken delivery of my new VMAR SA bulldog (see following thread)
http://www.rcuniverse.com/forum/m_7827011/tm.htm
http://www.sussex-model-centre.co.uk...d.asp?id=25010

part A:

Going to power it with a 2str 50-52 motor (probably an OS max).
Box (nothing stated in manual) suggests weight to be 6-7lb/ 2.8 - 3kg.
Wing span: 61.5"/1560mm

The nose is quite large..

roughly what prop should I be looking at.. when I held up an 11x7 (Spare from trainer which also has a 52 size engine) the prop just "looked wrong" most of the prop is infront of the coweling.... (See photo)

Part B:

the manual gives no hints as to flaps throws.
ailerons 6-9mm
elev 8-12mm
rudder 16-25

but flaps... nowt..
whats a good starting point for the flaps???
dont want to give it "lots" and watch it plummet like a brick as it stalls dead.
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Old 08-20-2008, 05:24 PM
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BadSplice
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Default RE: prop choice and flap throws????

I think that prop would be fine. You could also try something more like a 12x5 if that one wasnt giving enough thrust.

As for the flaps, I think 45* is about the point where you start getting more drag than lift out of the flaps, so I wouldnt go any more than that. I would start at more like 25-30* and see how that goes. Or set them up on a knob so you can let them down slowly in the air till they work the best, then see how far down that is after you land and set them to there.
Old 08-20-2008, 05:51 PM
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Default RE: prop choice and flap throws????

Many thanks, I think i'll go try a 12x5, mostly due to the "scale" problem of the 11x7... it just "looks small"

As for the flaps, the problem lies in the futaba 6ex tx which I own, its switched or nothing.... hence I need a "good idea" before trying (however i'll obviously be testing at altitude.

EDIT:
I've just noticed this in another forum:
http://www.modelflying.co.uk/forum/f...12745234937562

an electric version with a 14x10 being used??? is this translatable to me !?
Old 08-20-2008, 08:14 PM
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Default RE: prop choice and flap throws????

It looks like he was actually using that large a prop..... I really dont know much about the electric systems that big though.

Since you only have the switch, I would start with 20-30* on the flaps and work my way up from there, if it even seemed necessary. A lot of smaller scale models that have flaps dont really need them. It seems to me that on most of these planes, using the flaps mostly just looks cool and shortens the approach and rollout, but arent really necessary for a smooth landing.
Old 08-22-2008, 12:07 AM
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Default RE: prop choice and flap throws????

With that radio you can use the flap trim knob on your first flight and do a few slow passes to get a feel for the effect. Then it's a simple matter of remembering how many clicks you used and replicating it on the air brake function. As always, check the travel and use ATV if needed to keep the servo from binding.

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