My experiment with a scratchbuilt

Started by rahulroy31, August 26, 2013, 05:45:51 PM

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rahulroy31

good question....I sand the fiber tape very lightly (320 sandpaper)...  and then before sticking the paper swipe it throughly ...even after that it does not stick as well on the tape as it does on the foam.... however since the paper is overlapped to the other side it does not make too much difference.

rahulroy31

Right Atul... my previous wing (yellow and black one) had a "A" pattern.... in this one i put a cross cord CF strip on top side of the wing at the apex where the two CFs meet... I could not do a "A" because of shape of the undersurface of the airfoil.. the groove would have to be very deep which i wanted to avoid.. hence had to put it at the apex

rastsaurabh

Where you get the Carbon fiber rods ?

one of my work ... since it was small and thermacol was strong  enough did cover only at the edges with brown paper.

rahulroy31

I get my CFs from Hobbyking / RCBazzar... you are right the paper covering gives great stiffness .. in some of my planes i have used aluminium 'U' channel and some are without spars.. just thermocole reinforced with some spanwise tape and covered with paper

bmblb

rahul.....really cool. looks like you have had a lot of practice on the foam cutter.

"The Flight Of The Bumblebee"

rahulroy31

Sorry for the delay in posting the rest of the details

The fuse pod is a simple box made out of coro.. the wing will be fixed to it using rubber bands.. the RX, and bty will be housed inside it.. planing to keep the ESC outside due to cooling issues... finally went for a pusher config

here are some pics of the fuse under cosntruction

rahulroy31

the wing-tips/winglets are made out of coro.. notice the markings at the base, these help in aligning the elevons and trimming.

the wing is painted with fabric acrylic paint (normal camelin) mixed with fabric medium (camelin) in a 60:40 ratio. this gives it a good water resistant finish

the servos are mounted on the underside of the wing.. this ensures that the top side of the wing is absolutely free of any appendages for more efficiency... a hole is cut in the wing and the servo stuck in with double sided tape and then covered from top with fiber tape which is flush with the surface.. the pushrods and horns are connected

the CG is location is calculated with a online CG calculator .. consider the elevon cord also. at a 47" span, 10.25" Root cord, 7" tip cord (incl elevon cord) and 7.25" sweep, at 20% CG is at 5.14" ... Notice the markings on the LE which are the CG positions at 15%, 20%, 25%.

The wong with the servos, horns, pushrod and wing-tips fitted... the servo wires are taped up and will... completed

rahulroy31

the wing mated with the fuse.. it is tied down with rubberbands

rahulroy31

A closeup of the Rx with the servo leads fitted.... notice the velcro stuck on the topside to correctly position the bty

rahulroy31

Flew her yesterday

weight of airframe with motor, prop and all electronics except bty = 406 g
AUW with 3 cell 1000 mah = 486 g
AUW with 3 cell 2200 mah = 571 g

initially tested it with 1000 mah and at CG at 15%.. was a bit tail heavy.. had to add a dry pencil cell at front  to get the proper balance.. trims OK  .. climbs at 50% throttle.. felt bit vauge in yaw at slow speeds.. the folding prop is not folding during gliding..
next was flew it with 2200 mah...this time with CG at 20%... this confirmed the sweet spot of the CG at 20% ...

It was not a windy day with few thermals, and even under thse conditions and with the heavier bty (2200mah and AUW at 571 g) she could stay up without very very less use of power. In thermals she tracked beautifully and could be flown hands-off when trimmed to circle with the thermals, the reduced sweep helps .. outside a thermal the glide ratio is superb and she retains energy well during penetration..... the additional wt of the 2200 mah below the CG also helped in stability............... a lovely bird and a treat to fly..... the podded design also protected the wings during landing by keeping them off the ground.........only issue is that at large distance orientation is difficult.. not sure how this can be bettered.

One of the design objective of having a good thermalling plane has been successfully met.. looking forward for some sloapsoaring now... attaching a pictue of her in flight.. you would have to zoom to see her... she is a dot in the sky

crazycalvin


shobhit17

Lovely.... Thanks for the great thread...
Well I been into aeromodelling since I was in School....  and then been in the air for over 30 years.  Now looking to be back into aeromodelling full time...