RC India

RC Models => Self-designed, DIY and College Projects => Topic started by: rahulroy31 on June 28, 2013, 03:37:40 PM



Title: Scratch builds
Post by: rahulroy31 on June 28, 2013, 03:37:40 PM
Hello, here are some aircraft which I have built and not scrapped as yet.  I am a scratch builder who loves building as much as flying. More into the aerodynamics, structure and construction side than electronics. After building a couple of flat wings planes I discovered hotwired wing and since then stuck to hotwire. I do my design calculations and then draw out my designs on news paper  … hence no plans.


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 03:55:28 PM
HIGH WING TRAINER
 
This is one of my earlier planes.. called it the ‘Phantom Flyer’
•   40” span, clarkY airfoil, hotwired, coloured tape covered.. the wing has an aluminium channel spar in the centre
•   Coro box fuse
•   1000KV, 8 X 3.8 prop, 3S
•   Elevator, rudder and throttle
Flies well. Does ROG and glides nicely….. a real trainer, can take on a lot of abuse… flies hands –off  after trimming.


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:03:11 PM
HIGH WINGER
 
Another  high-winger… not given it any name
•   48” span, thick (17%) ClarkY airfoil, , hotwired, coloured tape covered. … after testing the dihedral  proved a bit less (was nearly straight).. hence angled wingtips(not winglets) added…. The wings have no spar
•   Coro triangular fuselage.. tried a triangular fuse to save wt…. worked, wing  and landing gear mounting was easy …
•   1200KV, 9X3.8 prop, 3S
•   Elevator, rudder and throttle
Excellent and rugged  flyer. Initially turns were not well coordinated and lacked authority till the addition of wingtips and increasing the rudder… after that it flies very well… can fly very slow without stalling because of the large cord and thick airfoil ….. cannot do ROG because of skids


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:05:04 PM
F 22
 
•   20” biofoam, KF2 airfoil… one CF spar
•   Semi profile fuse… it is thick foam which has a slot for housing bty
•   1800KV, 6X4.7 prop, 2S
•   Elevons
Flies  ok… glide not too good. Tried a 7 prop but then it has a tendency to torque roll. KF did not have a great impact on flying characteristics..


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:08:43 PM
AEROBATIC  PLANE
 
An aerobatic plane … again not named
•   34” thick (18%) symmetrical airfoil (E 479), aluminium channel spar, coloured tape covered
•   Coro fuse with detachable canopy for access to electronics
•   900KV, 10X4.7 prop, 3S
•   Ailerons, rudder, elevator, throttle
Very responsive in all three axis… fabulous roll rate…. The rudder area was increased later on to enable knife edge.  Glides well for a stunter. … has good stall characteristics (adequate indications by wagging of wings) .. a good aerobatic  aircraft... (that's my son Abhiroop who who does the knife edges)


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:11:05 PM
TWIN BOOMER
 
Wanted to build a ‘boomer’ so tried out this  “so”  design with my own dimensions.
•   34” span, laminar flow airfoil thickness (15%), hotwired, no spar, paper covered.
•   Twin boom fuselage is foam (EPO) covered with paper
•   1100KV, 7X4.7 prop, 3S
•   Aileron, throttle,  elevator… this plane has a single aileron
From a construction side, this was a good build .. flight characteristics did not meet expectations….. there was no significant advantage of using a laminar flow airfoil  .. on hindsight,  a thinner,  high lift conventional airfoil might have worked better. The single aileron was not effective enough at low speeds i.e. in power off mode. The foam covered with paper proved to be very effective in making it strong and rigid… there is no spar or reinforcements either in the wing or in the fuse.  It used a 2200 mah bty which sat in the canopy (the canopy was made of coro (‘C’ section) and was attached with velcro


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:12:53 PM
LARGE POWERED GLIDER
 
A large aircraft made completely out of  coro and PVC pipe
•   72” span, coro wing, Jedelsky airfoil, wooden “patti” spar, detachable wings, no dihedral
•   PVC pipe fuse, wing and tail section mounting plates
•   750KV, 12X4 prop, 3S
•   Aileron, elevator, rudder, throttle
This large plane is made completely out of coro and PVC pipe and a little bit of ply. The wings were two piece and has plug-in aluminium joiners. The tail unit (horizontal and vertical) is one piece which can be bolted on to fuse by four nuts. The whole thing can be assembled in field very quickly. It flies well and can fly very slow. Turns are tight and controled. The jedelsky  airfoil  did provide high amounts of lift.


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:14:40 PM
A Large wing
•   46” span, 12” root cord, 5” tip cord, 22 degree sweep, semi symmetrical airfoil (MH 64), hotwired,  initially covered with coloured  tape but subsequently  paper covered. CF spar
•   1200KV, 8X4.7 prop , 3S
This was my first real (other than flat plates) wing. … and if flies like a dream.  Its glide angle is superb… and so is the roll rate.  With dual rates  it can be a screamer and roll like a drill or trimmed to fly hands-off. Initially it was foam covered with coloured tape but once I discovered paper covering changed over to paper. The paper covering gives it immense strength, stiffness and ease of repairs…  along with very close adherence to airfoil geometry for fantastic performance.  I fly it with a 2200 mah... (that's my son Abhiroop)


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:16:25 PM
SMALL WING
 Small wing…. No name
•   31” span, 5” cord, 25 degree sweep. Semi-symmetrical airfoil (MH 44), hotwired, paper covered….  has  wing fence  at mid span and  winglets which also act as skids
•   Simple coro(2 mm) box fuse
•   2200 KV, 5X5 prop
This is a superb flyer.. both the glide angle and sink rates are superb. …. One of the best I have seen. With a 800 mah bty it can fly for hrs (on a windy day).. controls are effective at all speeds . The aircraft has no nasty characteristics . can be flown very slow and banked without stalling due to the fences. Drag is minimum due to the design (I do not have a folding prop) and winglets and by keeping electronics tucked away. … a very satisfying aircraft to build and a blast to fly.. the only problem is because of its size, orientation becomes an issue, when flown very high or far.


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:17:59 PM
SIMPLE WING
 
Abhiroop’s (my son) build. .. no name
•   20” span, biofoam wing , KF2 airfoil
•   2200 KV, 5X5 prop
This is Abhiroop’s first clean build… flies nicely. To balance the CG a boom had to be added in the nose and some wt put at the tip…  with the CG correctly balances she flies quite well…  sink rate is pretty low … can roll like a drill.


Title: Re: Scratch builds
Post by: Bilal on June 28, 2013, 04:28:09 PM
Great designs sir,
can you please share your secret of hot wiring....am not able to get it right no matter how many times I tried

regards


Title: Re: Scratch builds
Post by: punty on June 28, 2013, 04:51:28 PM
Still Bilal Bhai? Thought you must have got a way out for the hot wire after that computer SMPS thread...


Title: Re: Scratch builds
Post by: rahulroy31 on June 28, 2013, 04:58:50 PM
Hi Bilal... to be honest it was only after many tries did I manage to get my hot wire cutting straight. Some of the things which help are
1. making the templates with very smooth edges and sticking them firmly to the foam (movement during cutting will ruin everything). I cut the templates out of thin 2mm sunmica(formica) with a backing of cardboard and fiber tape on one side  
2. While cutting keep the wire taunt... but DO NOT put too much pressure on the template. it should just float over the template
3. it is very important to move the wire equally at both sides..... i mark out numbers at regular intervals in the template ... having a helper really helps. that way both call out the number they have reached which allows for corrections to be made at either side by going slow or fast
4. cut slowly... by going fast the chances of a kerf will increase
5. temp of the wire is important, but it impacts cutting less than the above points


Title: Re: Scratch builds
Post by: Bilal on June 28, 2013, 05:09:07 PM
:D Punty, I guess am a slow learner then.
Actually am still not able to get the finish in my hot wire cut wings, apart from this, the power supply and other things were sorted out a long ago


Title: Re: Scratch builds
Post by: punty on June 28, 2013, 05:20:19 PM
@Bilal sir.. No offense ment by what I said sir... Not about being a slow/fast learner.

Maybe try adjusting the temp of the wire along with other tips as given by Rahulroy sir for neatness in the cut. Or Maybe heat up a flat knife and try to smooth out the cuts.

Regards
Punty


Title: Re: Scratch builds
Post by: SunLikeStar on June 28, 2013, 05:24:00 PM
Rahul, glad to see your builds on the forum. This thread could very soon become a long one if you keep posting your creations here :thumbsup:


Title: Re: Scratch builds
Post by: Bilal on June 28, 2013, 05:26:02 PM
Punty,  no offence taken dude, and avoid the SIR..... I haven't done anything to be elevated to that status, Bilal is okay
btw, ever tried making a hot knofe by attaching one of the soldering iron elements to a normal pastry knife?...... It works wonders with foam


Title: Re: Scratch builds
Post by: Bilal on June 28, 2013, 05:30:12 PM
Rahul Sir,
please throw some light on that detachable wing concept, seems great..... A build log is really desirable
regards
Bilal


Title: Re: Scratch builds
Post by: kaarthic.r.b on June 28, 2013, 05:33:25 PM
 Great job rahulroy  :hatsoff: :hatsoff:


Title: Re: Scratch builds
Post by: VC on June 28, 2013, 05:38:25 PM
Where were you hiding all these days young man? You should have joined us a loooooooooooong time ago. Superb scratch building.


Title: Re: Scratch builds
Post by: AnjanBabu on June 28, 2013, 05:49:15 PM
Great designs sir,
can you please share your secret of hot wiring....am not able to get it right no matter how many times I tried

regards

Bilal, this video from Flite Test is all i had to absorb before i got hotwiring beautiful aerofoil ribs. hope it helps you too-- http://www.youtube.com/watch?v=fi3CAtpvJJs