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July 09, 2020, 14:52:52 pm

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Wot4 Classic C of G

Started by British Victory, May 18, 2020, 09:55:02 am

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British Victory

Help, I've lost my bit of Chris Foss paper that specifies the C of G for the Classic or straight winged version of the wottie.
Ithink it's 3.5" + or - 0.25" but can't be sure, can someone confirm please.
At present it's 3.25" from the LE but landing speed is a bit high.
there's only one f in RCMF,
               John

PDR

Quote from: British Victory on May 18, 2020, 09:55:02 amAt present it's 3.25" from the LE but landing speed is a bit high.

CG won't change the landing speed - that's determined by the eye-stick interface.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

pooh

Quote from: PDR on May 18, 2020, 10:10:08 amCG won't change the landing speed - that's determined by the eye-stick interface.

PDR

love it !
Confucious he say "more than one aircraft in the same airspace leads to structural failure"

FlyinBrian

My Wot4 was built from a plan and the CG is just on the main spar.
Basic Research is what I do - when I don't know what I'm doing!.

The Saint. (Owen)

Quote from: FlyinBrian on May 18, 2020, 12:21:32 pmMy Wot4 was built from a plan and the CG is just on the main spar.

Let's just hope that the main spar is in the right place then. :''
Electrickery is the work of the devil.
Proper aeroplanes are powered by engines.

British Victory

there's only one f in RCMF,
               John

FlyinBrian

Quote from: The Saint. (Owen) on May 18, 2020, 14:23:02 pmLet's just hope that the main spar is in the right place then. :''

As Mr Foss drew the plan I can only assume it is!
Basic Research is what I do - when I don't know what I'm doing!.

pooh

I think the issue is whether the designer's c of g and the plane's actual c of g coincide

It's down to the builder to make that happen  :''
Confucious he say "more than one aircraft in the same airspace leads to structural failure"

PDR

I think Owen was hoping that the designer had indeed placed the spar at the optimum CG location.

But seriously - why are we even having this conversation? The aeroplane is clearly flyable, so that means the owner can tune the CG to individual taste using the simple, well-publicised methods.  eg:

Trim for straight & level at cruise power, push the nose down 20 degrees, release the stick and observe the response. If the nose rises again more quickly than desired then move the CG back. If the nose stays down or rises slower than desired (and you want more stability) then move the CG forward.

and/or

Trim for straight & level at cruise power, roll to inverted and note how much down elevator is needed to sustain level flight. If it is more than you would like then move the CG back. If it is less than you would like then move the CG forwards. There should always be SOME trim change (unless you have an autostabiliser fitted) but how much is up to you.

There is no "correct" answer - these things are a matter of personal taste. With a wottie my personal preference is for "neutral" (push the nose down and it stays down), but not everyone shares this taste.

€0.000000772 supplied, YMMV, E&OE, GTBoS, HAND,

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

British Victory

Got the c of g back to 3.75" from LE, stance of plane much better in the air and was able to dial out all the up trim.
It's interesting pdr suggests 20 degrees, I'd always used a 45 degree power off dive.
Had a little hesitation flying yesterday, only have 20% liquid gold fuel for my YS, OS and saito engines, the engine here is an ASP 52 2 stroke.
FWIW they run OK on 20%, good vertical with an apc 11x8. It's propped like that to keep the noise down as our secretary doesn't want to wind up our neighbour after months of silence.
So for future reference the Wot 4 Classic flies pretty good with the c of g back at 3.75" from the LE.
there's only one f in RCMF,
               John