RC India

Its been long time since I post anything on RCI!!!!!

Was building bigger Alula so thought of making it my entry for sweepstake!!! (:|~

After enjoying night flying with my earlier 50” Alula, I decided to make bigger one.
http://www.rcindia.org/electric-planes/biofoam-50%27-alula-powered-swept-forward-flying-wing/ (http://www.rcindia.org/electric-planes/biofoam-50%27-alula-powered-swept-forward-flying-wing/)
Last one was KfM2 airfoil, and now wanted to make full airfoil, MH45. So decided to do hotwire Cut with HD thermocol.
It is actually swept forward wing having really good flying characteristics. Planning for completed 66” wingspan this time…
Hotwire cut was totally unexplored area for me, so started building bow…
But thanks to Rahul Roy, I borrowed is Bow and his complete setup for hotwire cutting…
Bought few HD and normal Thermocol, wasted almost 4-5 sheets while practicing, u need 2 people to operate it!!!  :banghead: :banghead:

Draw scale diagram of airfoil in Corel Draw and then Laser cut airfoil on 3mm veneer Ply, as u can see it in picture!!!!
Used my earlier plan as guideline for the new bird.
Using HD thermocol, after cut both wings are weighing only 170gms

Some wastage and finally was able to succeed

SOme more

Finally was able to cut it

Here is 2 piece wing

awesome work on the wings!! keep it up!

Beautiful!

Very good .... thats a huge wing. how are you planning to strengthening it ? covering with glass fiber? or paper ....

Very beautiful {:)} {:)}

lovely log of the construction..... Have loved the Alula a lot for sometime..but am at a loss of how to build it.... can you please share your drawings and methods with us here please....

Look at the cross section of those wings!!! This guy is a master cutter.

A tip for hot wire cutting... i am sure you must be having issues at the trailing edge.. it must have been too thin....

Keep the trailing edge of the template little out if the HD foam, say 1/2 centimeter... you will get very clean trailing edge.

Yes VC.... I too saw this and am happy that there is someone who can teach at least me how to cut HD thermocol...  I stopped cutting HD Thermocol when I spoiled 2 wings.  I am back to sanding out HD thermocol...

AshJR.... do let us know how do you cut thermocol.... detailed pictures and a tutorial on how to do it... it will be of great help to many of us including me...

Thanks guys!!!

Hey VC, thanks for the complement, seems like u forgot me, was away for sometime!!  :giggle:

@rastsaurabh, I am planning to use aluminum C channel as spar and also planning to make it detachable 2 pieces, let see how it goes   :headscratch:
@shobhit17, about drawing it is posted in my earlier thread, link mentioned in the 1st post. you can use it to make your own bird. full PDF and A4 also attached in that thread.
These wings are cut using hotwire cut and believe me I wasted almost 3 HD sheets and 4 Normal Thermocol sheets while practicing... :banghead: :banghead:
lekin Kida mara nahi....i wanted to do it.....no matter what!!  >:D >:D

For hot wire cutting, I think Rahul Roy has created some good thread..let me check

found it:  :hatsoff:
http://www.rcindia.org/electric-planes/my-experiment-with-a-scratchbuilt/ (http://www.rcindia.org/electric-planes/my-experiment-with-a-scratchbuilt/)

Fellow modelers have a look here ....... a tutorial for hot wire cutting ...

http://www.rcindia.org/for-sale/wing-core-made-of-high-density-thermacol/msg154985/#msg154985 (http://www.rcindia.org/for-sale/wing-core-made-of-high-density-thermacol/msg154985/#msg154985)

Ashish what are the plans for the tail? I honestly hope you up-size it by atleast 20% compared to the last build.

Good to see you Ashish back posting here

Great wings ..... Good going ... All the best

Hey Rooster thanks!!! how u doing man...long time!!!! any boat for Sweepstake!!!
@SLS, ya i can try that!!! but chances are, that it might look out of proportion!!!! if i increase surface, can also put rudder.... can think of it!!!! but as per our discussion earlier, I need to figure out how to make airfoil on tail....will that really help!!!

Thanks Ash... guess I reverted back to good old sanding block and gave up the hot wire cutter... I was using a bamboo bow with the Guitar E string and my inverter battery as power source. Lets see how it goes the next time.... But still you please give ur expert tips on the issue of hotwire cutting to us... Thanks for the info on the plans.. Will surely look at them.
regards
Shobhit

Ash, I did some searching but was not able to find anything that supports the theory of having a symmetrical airfoil on a vertical stabilizer would be of any significance. So i guess a simple strong tail with a smoothed out leading edge should be fine.

Well... dear SunLikeStar.... the symetrical aerofoil on the fin is given so that it has equal forces from both the directions... of you give semi symetrical it will produce a directional force (lifting force) from that side of the aerofoil... well all aeroplanes have a strictly symetrical aerofoil.... For you if you wish you can just keep the fin straight and round off the edges.....  This way it though it will not be an aerofoil but will give the desired stabilising effect.  This may have higher skin friction drag but it is OK for a model...... for an aeroplane it will be terrible.

nicely done !

We already know that we require fully symmetrical or a flat surface. And I'm pretty sure no one would want to use a semi symmetrical airfoli as a vertical stab. But what we were actually interested in is the kind of airfoil (as in which fully symmetrical airfoil) used and the impact of different airfoils on flying characteristic. Not to mention the a flat surface with rounded edges is also a fully symmetrical airfoil. Even better is a rounded leading edge and a tapering sharp trailing edge. And after all I have a couple of very good gliders and both have vertical stabs with rounded leading edge a slightly thinner trialling edge. I wonder if there is a name to this airfoil.

"No one would want to use a semi symmetrical airfoli as a vertical stab."

I'm using one!

A little more detail please. Can you please explain why are you using a semi symmetrical airfoli on a vertical stabilizer? We are talking about a performance glider here. Which kind of model are you using this on?  I hope you are not talking about a control line model. A picture would be really helpful. Can you help me with the other questions in my earlier post.

@sunlikestar
Posted in a lighter vein, as i saw your post just when i was sanding asymmetry into a fin. (FF HLG)
But you are right. Doubt if any aircraft had asymmetrical aerofoil fin. Not even BV 141B.
On models i doubt if there is any gain over a flat plate fin. After all we are flying flat plate wings...

Edit: apologies for diverting a lovely thread.

(a) Asymmetrical vertical fins are used to counter torque and propwash in larger Prop & TurboProp aeroplanes (Apart from the fact that these fins are cantered too). Changing the thrust line caters to one one set of power and configuration, outside this changes thrust line aeroplane will behave differently, in model aeroplane it is fine, however in real life aeroplane, asymmetrical & a cantered fin is preferred as it adjusts to the propwash and forward speed (Not to say that it doesn't have a skewed thrust line, it does)

(b) About Flatplate aerodynamics, read my earlier posts on the subject, suffice to say

   (1) Unlike cambered aerofoil where the centre of pressure moves with the angle of attack, in flatplate the centre of pressure does not move,

   (2) Flatplate has much more predictable rise of lift, and the lift rise is linear until stall

   (3) Stall is abrubt though, which means at high angles of slip (Like in a low speed Knife Edge), if the fin stalls, she will imdtly spiral into ground

  (4) there is a factor called MCdr or critical drag rise mach number, for flatplate it is high however super sonic drag is lowest of them all. for which reason it is used in most missiles


so much for assymetrical fin and flatplate aerodynamics

Very interesting! Now I know why my coro mig was not able to do knife edge properly.

@K K Iyer All the best for the glider. I'm also planning to build a 1 meter HLG :thumbsup:

@Ash, for starter I think just go with a flat fin with rounded edges. Do bring the wing core with you if you are coming to the field tomorrow.

Awesome wing seeing others builds I can't stop the keeda inside me for building so after my exams which are ending at 26 of this month are over some thing is coming out for sure.
What software are you using for creating the airfoil templates. Can I use gimp for this purpose.

Wing tips, to give wing proper shape

with wings

servo slots, and Aluminum 10mm U channel as spar

Cut out control surface so that later on can put it using hinges.

being 66" WS, wanted to make it 2 pieces wing for ease carrying it. but at the same time wanted dehydral of around 4-5 dgr. so there was challenge and making detachable as well as dehydral.....
Since had 8mm solid CF rod as joiner, was searching for 8 mm inner dia, CF tube so that can make proper arrangement. but could not find. so decided to make 8 mm ID tube out of newspaper.
Mixed 2 portion water and one portion fevicol and rolled newspaper over CF rod while applying fevicol water using brush. before doing this i applied few drops of oil over CF rod so that paper should not stick to rod. after rolling paper on rod, i let it dry for few hrs and slip out rood from news paper, as u can see u get perfect tube hard enough.
then stick this new paper tube to Aluminum U channel while giving slight angle, used little balsa for support.

spar and tube

cut slot in the wing to push complete assembly inside and stick it

Awesome build Ashish. All the best!

Lovely workmanship. Congrats

Wonderfull work...
Keep up waiting for the maiden

@Ash. great idea for newspaper rolling  :thumbsup:

Thanks guys!!! finally put spar and same arrangement to other wing as well, now both wings are ready, hav dehydral and detachable.
also fixed servos...now preparing to cover these wings with newspaper and fevicol!!!

Spar installed...

Paper Wrapping....
Last yr i built Plank wing, CHINOOK-2, you can see its fuse in these pictures, it is made up of core...for test flight i am planning to use that fuse...
and after successful maiden will make new fuse for this bird...control surface are yet to be attached

few more..with dehydral.....

@ashjr7202
Looking very nice.
Why do the wings look droopy (anhedral) in some of the pics?

Beautiful. looking lovely.  :thumbsup: :thumbsup:

Airbrush it to bright pattern

@KK, that might be bcoz underneath, I stick Nargis Fakiri!!!!!!! just kidding..... after applying paper, i checked wing regularly till it is dry....it is straight, and have around 5-7 dgr of dehydral at center/joint.... may be bcoz of weight it must be dropping at tips....will check it!!!

@Sundaram: thanks for suggestion!!! i have few acrylic spray cans will try it!!!!!

swept farward wings do look "droopy"... do not worry Ash.... keep going full steem ahead.....
Happy and safe flying
Shobhit

Correct. I forgot that it has a forward sweep.

Ash.... you done it.... I am soon going to build my own alula from your earlier drawings.... a 50" span one.  Well I will be using thermocol and guess aerofoil MH 45 should be ok.....  I am sure the weight would be around 700 gms when ready...  not this month but will start it in may 1st week as am on a month long outstation trip....

OK.... I use fevicryl colours for painting my foam models which have been covered with paper or not.... or else I use vinyl sheet as it is easily available and is cheap.

Do please tell me if the aerofoil will be OK and if there is any other tip you have.....

Regards
Shobhit

2 weeks back finished this and had awesome maiden......was busy in office so could not post build pics earlier....
here are rest of the pics....
for Aileron used 3mm Balsa, stick 2 sheets together, for strength and to give thickness...
after that covered them with RED packaging tape and it looks stunning

Fuse in making

more

finally its completed
Video to follow

Here is the video, taken 2 weeks back...
was busy so could not upload it, sorry for delay

http://www.youtube.com/watch?v=-8TYqcQUTgo#ws (http://www.youtube.com/watch?v=-8TYqcQUTgo#ws)