I have 1mx1m of 10mm and about 4ft x 6ft 2.5 mm foam from my scouting for depron suppliers in Delhi.
Well finally decieded what to do with the EPP / Bio foam that I purchased. I am going to build a Cub Trainer with electric power.
The build vs buy debate has been going on in my mind for a long time, finally tilted to build. Its going to be a scratch build after almost 20yrs, first RC build and first EPP build at that, so in general its very exciting (provided I get time off from office and kids et all)....

Now the overall specks are something like this

Wingspan = approx 46 inch. I do not know the wing loading thing, but the width of wing is approx 7.5 to 8 inch
Length of plane = approx 33 inch.

control 4 channel.

I am thinking of having 2 part wing with carbon and/or fiber glass rods to strengthen it. Since there would be 2 parts, then I guess I would need 2 servos to control the aileron. So I think I shall settle for 4 of 17gm servos.
I am also looking at battery of about 3C1P with 30-40 C drain and rating of about 4000 - 5000mAH. So the weight of the battery alone should be close  to 400-500gm..... I think taking all materials into consideration the all up weight is going to be in the region of about 1.2 to 1.5kg, so back calculating from there - I need a motor of about 400-500watts (100-150 watts per pound rule), which in turn would require about an 60A ESC

What am I missing here???  what prop to use - but then its a long way off. Lets see if I still have it in me to complete a build.

So began cutting the foam into managable blocks. Posting the photos of cut EPP pcs....

Pankaj

http://tinyurl.com/lazy-bee
Dear Pankaj,
Check this out........... excellent project for depron or biofoam............. light, quick to build and gr8 fun to fly......
Edwin

I second that really looks great never saw this one on RCG.
The plane looks  very nice and the under cambered wing will really make it a great plane.

I think for a foam plane the battery you are considering is too heavy if the set up is a single motor one .
If it were a double motor set up like twin star the capacity you are talking of should be OK

With a 48 " wing span and a 33 " fuse your set up  the battery should   be around  3s 2200 OR 2650  mah  at best .

17 gms servos seem OK for this size of a foamy .

The motor could be a 2217/8 1000 to 1100 KV

Prop : 10 to 11 inch.

If I were to build it as trainer I would  go for rudder elevator with under cambered wing  rather than aileron to start with .
After I got it right in terms of flying  , I will then make another KFM or Aerofoiled wing  for the same fuse as version 2 with aileron's  .

sai

Sai

Hi Pankaj,

I sure would like to see how your model evolves. I am also into Depron quite a bit in 6mm and 3mm thickness of sheets. I think the 10mm will be too thick and heavy.

I use hotmelt  glue and it works very well as hinges and for sticking but adds the weight.

I wish you success in your venture and look forward to the finished article images.

Where abouts in Delhi do you fly? Did you buy your foam in Pahar Ganj area? Please will you let the other modellors know the where they can get the DEPRON sheets (Actual producer's name of Bio Foam).


Do you know Kuldip who is also into scratch building and flies a few miles out from DLF.

You know what.. you just reminded me of my childhood days in Delhi...

Looking at images of the Bio Foam gave me a glimpse of your floor. I grew up in Delhi's Darya Ganj area and had the same floor in my room... Now this is going back 35 to 40 years.. Good old days.
I have had a few PICO STICKS for over 10 years and have enjoyed it very much in the past years from time to time. In fact I am on my 3rd one now as the power system that it comes with used to cost half the price of kits so I always used to buy another kit when my motor burnt out or broke. Here is a thought based on slow stick and Pico stick..
To get the curves on the wings like lazy bee what if you were to make bows out of BAMBOO SKEWER STICK and wrap it with bio foam or Depron sheet 2 or 3 mm thick. The second option would be Depron warped over ribs in balsa  It does bend to shape when you blow it with hair dryer, but will it keep the shape when the bows are removed

Good Luck

Deepak

Well managed to cut some formers with the 10mm foam. Like with any other foam material, the edges are not smooth, but still the formers seem to be fitting nicely even without sanding

Pankaj

I took the hard copies of this beauty .....and will start working on this today itself... canopy and other will made by Balsa, the only problem i may face is fabricating the wing   , i have 6 mm depron   ........But......

Use a heat gun to get the under-camber

pankaj
where did you source the depron from in  delhi???

I tried , but it require a lot of patience to make an under-camber out of 6 mm depron, and that too on a wing with 30" or more length. major difficulty come when bending the depron and simultaneously holding the heat gun or hair drier  . for easiness i have to make a hot water tub along with some weight to bend. i hope you understand what i mean.
Sandeep

Wings contruction started....

I am thinking like this...
Thick foam base reinforced with carbon/fiberglass rods, foam ribs and then covering the top with a thin foam... wonder if it will work

images of a rib....

Pankaj

Will not the pull of the foam bend the rib out of shape. I would think it better to use use Coro as a rib. Otherwise, why dont you think of coro for the whole under-cambered wing. Would be easy to construct but a little heavier, but also more durable.

Saju

Not sure about bending, I had been planning a thick foam (remember i am using 10mm foam) for ribs and the base of wing with about 2-3 rods for strength. Then again, I could use coro for base and ribs....

I am not able to understand, how to cut and make the monoblock. the sketch of monoblock is not clearly understandable. Please help.
SAndeep

If you could post the sketch, perhaps we could try to work it out..........
Edwin

Sai,

How does one determine the max battery aH - is it weight or something else? What would (most likely) to happen if I were to use a higher aH rating battery - say a 4000aH?

Pankaj

The sketch is available at
http://tinyurl.com/lazy-bee
Sandeep

SORRY buddy, never realised u were workin on the link that I had posted. As far as the lazy bee is concerned, just get the wings correct. thats all that matters. As for the fuse, trust ur intution and keep it as light as possible. make the tail also very light. dont pay too much attention to detail.......... (bad advice probably, but thats how i did mine)
Edwin

hey guys beware of the link posted above the plane just doesn't have enough vertical stabilization so increase the rudders length and you are all set

subbu

What started off as a build thread for one, has now turned into a log for two scratch builds ( one with Sandeep as well) 

loading images of tail assembly. The problem is I am not getting the proper finish (check the closeup image) ... I think I would need to apply some sort of a coat on top and then sand the bits. On its own, the fins look too fiberous. Was thinking of covering the model with areldite - but then a) its too thick for a thin layer b) not sure about the increase in weight.

Pankaj

Building this cubs wing is real challenge for me. i have build fuse and monoblock (i dont know how correct it is), will post the pictures tomorrow.
to build the wing with under-camber, first i am cutting the long wing into 10 small pieces. then each small piece is sliced into 3mm approx.
all 10 small piece is then hot aired and given the shape of the required wing shape, after completing, all wing pieces are hot glued to form the complete wing. although shape of wing is slightly ugly, but i hope it will give proper lift to the cub.
Will post the pictures tomorrow.
Sandeep
 

Well Sandeep, I am using ribs for the aerofoil, what I did was that I cut out a number of them using a coro sheet rib as a template and them sanded them together. Next challenge is to actually fit it.....

Here are the Pic of my Built:








Please don't ask how i build the mono block  , it was the toughest time for me to think the mono block design

Looking great..........

Pankaj