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Old Oct 14, 2008, 05:42 PM
Sopwith Camel's Cousin
Between my tx and crashed aircraft
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Quote:
Originally Posted by davereap
... on my 30" verson with the slot moved back a bit I was still having problems with getting the COG back far enough. I only just managed to get it good, but I still felt that it could have gone back some more.
I believe that the KF steps like a more rearward COG
...
Another possible factor in your COG difficulties: your 2 oz. undercarriage will probably shift the COG forward.
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Old Oct 15, 2008, 05:22 AM
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Quote:
Originally Posted by davereap
here are the dimensions and some pics

LOOKING GOOD
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Old Oct 15, 2008, 05:35 AM
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You are correct in that the UC does take the COG forward a bit. With the UC in place ive still positioned the COG further back than the reccomended superfly spot, and even though it is flying great, it would benefit from going just a touch further back.
I could easily fly without the UC and get that COG back a bit..But I prefer to use the UC..thats why on the new 38" version I am again moving the motor back that bit more.

I also wonder how you can easily get the cog correct on the real thing. It is obviously no trouble as the design is succesfull and has been going for quite a while ..and they fly so well

On my first clone I moved the motor/prop slot back to avoid the KF steps and still have slight problems with getting the COG correct.

cheers jeff..
I have now got the elevons in place with their tape covering and started on
the motor mount...the weight is up now to 6+3/4 oz
Still need the fins, motor mount, decor, to finish the airframe... then on to the radio fitting...

looks like its going to be a touch heavier than I wanted .. but not too much
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Old Oct 15, 2008, 10:45 AM
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Fairplay, South Park, CO
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Dave,

looking good! I'm backed up with work for several weeks right now, but hope to get some building time before too long, so this design is one I'm strongly considering building

My thought for your consideration: what about adding a pair of underside vertical fins that act as the rear landing skids, and installing a mono-wheel under the nose?

Think of the IFO, or take a look at the Manta ACE for a very functional application of this approach :

http://www.rcgroups.com/forums/showt...=618548&page=6

Post # 85

I actually mount a single ski on the gear for winter / snow flying, & a wheel for bare-ground flying; there are a couple of photos below to give you an idea which could be adapted for this design.

The setup is very light weight, adds minimal drag compared to three gear legs, and the underside vertical fins / tailskids add stabilization affects- especially in high-alpha maneuvers. You could then reduce the height of the top surface vertical stabilizers.

The Fun continues!!

VIKING
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Old Oct 15, 2008, 11:26 AM
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worth considering ...especially on a light weight version
post your UC solutions here
http://www.rcgroups.com/forums/showthread.php?t=937395
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Old Oct 15, 2008, 09:49 PM
Onward through the fog.
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Looks really good Dave. I'm so tempted to put a slot in mine and move the motor forward. It would help to balance it out quite a bit. I'd have to re do the elevons but that's not a big deal. Hmm..... Prop wash on the control surfaces is a good idea for low speed control.

You do nice work. I enjoy following your exploits.

Steve.
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Old Oct 16, 2008, 04:26 AM
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Have you tried Google sketchup..its free and does an excellent job for various modelling aplications...it takes only a couple of seconds to resize any model to a desired wingspan.

heres the dimensions for the 38" SF clone..load into sketchup,use the tapemeasure tool across the span..enter the value you want..ie 30"..OK the resize..done..
All the dimensions are recalculated

more info on sketchup here...
http://www.rcgroups.com/forums/showthread.php?t=920416
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Old Oct 16, 2008, 10:46 AM
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The 38 superfly clone flew today.... no problems..heres the decor.

It was too windy today,, but I had to try it..
AUW with a big battery and the UC was 22+1/2oz.
This gives a wing loading of 5 ozsqft..
It has a much floatier feel than the 30 inch version which was flying at 6.4 oz sqft.
The only problem encountered was the prop catching the ground on rotation at take off.. Due to a revised geometry with the engine being further back, the prop came too low as the plane did its rotation.. Bending the UC legs down a bit and moving the UC back will cure this.
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Old Oct 16, 2008, 11:37 AM
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Nice looking bird, Dave.
How are you attaching the undercarriage to the fly? Velcro?

thanks...arniep
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Old Oct 19, 2008, 07:04 AM
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It fixes well and strongly with just two velcro strips..the ply plate is 2" wide the velcro about 3/4" so 2 strips line up nicely.
you can see the strips on the yellow area on the above pic...
Slightly modded now, the strips go further back ..to the end of the yellow section. I position the uc so that its cog lines up with the planes cog.
I bent the legs down as well as moving the uc rearwards, and now the prop well clears the ground, and there are no problems with the take off..no more broken props
I had a good session with the 38" delta and it flys really well, from slow high alpha to pretty fast, with unlimited verticals,and it has absolutly no vices. I have adjusted the cog just a bit (1/2")behind the superflys spot, (scaled for this larger size) and glides now are slow and flat, just a touch of left and right and it will land itself.
It goes inverted with hardly any down required, which makes life easier..

note....with the cog at this spot there is no self righting, it will go where you point it and going faster downhill it will not pull its nose up at all...If you want some self righting just take the cog forward and have a couple of degrees of reflex to hold the nose up..

I tried the discus launch and at 1/2 power with a slight arm swing and with the nose slightly up, it floats away rock steady.
The lower wing loading makes much lower slow speed no problem.
All in all I am very pleased with both sizes
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Old Oct 22, 2008, 08:58 AM
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Another good flight today with the 38" for the purposes of a video.

I had a bad crash at the end when I tried to get clever with a fast low pass....too low..

It shows how tough the tape reinforcing makes the plane. The crash was hard enough to snap the motor shaft, it ripped the UC off, (not a problem as only held with velcro, the prop made some minor damage to the slot area, and the nose got some creases.


video here

Depron Superfly 38 clone KFm4 (4 min 46 sec)



.
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Last edited by davereap; Mar 14, 2009 at 11:42 AM.
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Old Oct 24, 2008, 04:05 PM
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dave, im building one of these, but was wondering where the cg is?
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Old Oct 25, 2008, 04:41 AM
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On the 38 size go 12 1/2" back from nose....the pic from sketchup shows the absolute rearward cog.... start slightly more forward for first flights..
Are you using the sketchup program?
Because you can resize so easy from that and make any size you like..makes life easier..

Note when fixing the step layers skin get the rear edge down first onto the balsa step...then the depron step..then push the skin down at the nose..then use both hands and work outwards fron the nose getting left and right sides of the layer down evenly.

the depron step see pic in post 21...no rule for its position..its a spacer to further support the skin...I position it so its front edge is about half way back from the rear of the glued area used to fix the leading edges together..I only take it out about 3/4 of the wing because the wing tips will not need it

I do my laminating on a flat glass surface which gives less chance of building in any warps..

As you finish the one layer you will notice a slight spring back as the skin pulls the main layer up a bit...dont worry cause this will pull back when you fix the other layer...

the main thing is start to stick at the nose then work out evenly
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Last edited by davereap; Oct 25, 2008 at 05:07 AM.
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Old Oct 27, 2008, 06:02 AM
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thanks dave for the tips! cant wait to see how she flies!
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Old Oct 29, 2008, 01:28 PM
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You wont be dissapointed..my two favorite planes are... the nutball and this 38" clone
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