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scratch built problems - 6/30/2002 10:54:24 PM   
ZoomZoom-RCU



Posts: 471
Joined: 6/30/2002
From: Louisa, VA, USA
Status: offline
> Hello, I'm not sure if this is the right way to go about posting a
> question, but here goes. I have a scratch built foam Fokker DVIII that
> Ive finished and been trying to get off the ground. Problem is I've
> bashed it up so much on attempted takeoffs that I'm not sure it ever
> will. Its still flyable, but just doesn't seem to have the ummmmph to
> get off the field. It wieghs a little over 3 pounds total, and is
> powered by an O.S. La 25 engine, swinging a 10x5 prop. Wingspan is
> about 37 inches. Root chord about 7.5 inches. The length is
> proportionally smaller, but I can provide the details if thats
> necessary. The wierd thing is on taxi out I feed in full up elevator,
> and a little right rudder, then let go some elevator to bring the tail
> up, and also reduce or just release the rudder. Its a small carriage
> and a grass field so I suppose the undercarriage naturally gets a
> little swervy if you dont watch the steering. But after it seems to be
> skipping along I hit up elevator. The wingtips seem to climb, one side
> and then the next, then a wheel catches and its all over and back to
> the shop for another repair after an ugly tumble. Any
> ideas...suggestions!? They would be MUCH appreciated, as I'm about to
> set a match to this thing!! Is it too heavy? Underpowered? I've tried
> everything. Please help! Thanks.
>
> Samuel [email]Orion@louisa.net[/email]
       Post #: 1

scratch built problems - 7/1/2002 5:05:35 AM   
MAJSteve


 

Posts: 322
Joined: 1/26/2002
From: Baghdad, USA
Status: offline 		Try going down to a 9x6 and letting the engine rev up more. I had one of these and it was great with an 8x6 or a 9x6 but a 10x6 is way too much prop for it.

(in reply to ZoomZoom-RCU)
       Post #: 2

scratch built problems - 7/1/2002 7:15:30 AM   
nIgHthAwK17



Posts: 71
Joined: 4/28/2002
From: Starkville, MS, USA
Status: offline 		You stated that shortly after takeoff that it tends to rock back and forth. Is this in the roll axis? If so, then the tips of your wings might have a few degrees of wash-in in the tips rather than wash-out. Wash-in is when the tip chord is of a greater angle of attack than the root chord. When this happens, as I've seen before in minor cases, one wing creates more lift at the tip, making the plane roll to the opposite side. Then, for some reason, the effect stops and reverses direction - in both cases that I've seen, for the entire duration of every flight. If the wing is built up with Monokote or similar covering, then it may be possible to reverse the wash-in and make the wing have wash-out. To do this, you will have to physically twist the wing and hit it with a heat gun. This has been known to cure such mild cases. Hope that helps, and good luck to you.

(in reply to ZoomZoom-RCU)
       Post #: 3

scratch built problems - 7/1/2002 9:28:14 AM   
ZoomZoom-RCU



Posts: 471
Joined: 6/30/2002
From: Louisa, VA, USA
Status: offline 		Thanks fella's. You've been most helpfull. I'll keep you posted as to which of these suggestions helped, and maybe if I'm lucky, include a picture of the plane itself. Gotta borrow a digi cam to do so. I'll probably start with the simplest suggestion first. A different prop. But if that fails, let the wing warping begin. I was leaning towards the 9x6 being the culprit anyway. And of course its a simple solution. Who doesn't love those!? Anyway, if anyone out there has any other additional solutions, please fire away, and thanks again to the two kind gentlemen who provided the first suggestions I'm pursuing.

Peace. : )

(in reply to ZoomZoom-RCU)
       Post #: 4

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