RC India

Just built this pusher slowflyer with ingenious plans

Build time : 3 hrs

Materials : 3mm foamboard and 15mm PVC pipe for spar and booms

Electronics to be fitted..

Length : 950mm
Span : 960mm
Chord : 210mm ( A/R almost 5)
Airfoil : Flat bottomed with slight undercamber
Airfoil thickness : 25mm
Total unladen weight : 750gms

Planning electronics

1000kv Out runner with 1045 Pusher prop
30A ESC
3 9g servos for Airelons and Elevator
3S 2200 mAh Lipo
2.4ghz Tx/Rx

Any suggestions pls comment...

Thx

drone.....thats a nice looking plane....by unladen, you mean w/o any electronics? (you mentioned the gear you intend to use below)

.....its less than a meter....any chance you can cut down on some weight....seems quite heavy, unless its a typo ;)

what are your desired flying behavior from this plane?

.....your wing area is about 2.17 sft. and the plane as is weighs 750 g(assuming no typo)

some estimates....

1. Motor - 50g
2. ESC - 25g
3. Rx-10
4. Servo - 30g
5. 3S, 2200 = 190g
6, Prop & pushrods = 15g

Total electronics = 320 g

Plus plane weight (750g) =320+750=1070 g = 37.80 oz

So, wingloading = AUW(oz)/Area(sft) = 37.80/2.17 = 17.42 z/sft

WAY TOO HEAVY.....unless there are typos(or errors in my calculations).

....at this weight, the motor you intend to use should ideally be a 200-250 w.

....glad to hear other comments..

good luck !

Thx so much..

That helps me think about what options I can use to get this bird up..

Also wanted to discuss about the motor required.. I have read in several forums that about 50w per pound is a good way to calculate for the power to weight ratio and the motor I have is rated at 180w max throttle and 120w at medium throttle... Shouldn't that suffice as my plane would only weigh a little over 2 pounds.

Also the motor is capable of 750-850gms thrust as I have seen in a few YouTube videos

Any recommendations and advice will be appreciated..

Thx again for the feedback!

Cheerz

Just to shed light, this is the motor i have..

Just to shed light, this is the motor i have..

.....as you say it, the motor's s'posed to deliver 180W at full throttle and 120W at half throttle.

a popular thumb rule for power to weight ratio of the motor is for every watt, the motor should pull about 4 grams of AUW. So at 180x4=720g and at 120x4=480g.

....this plane can be 'made' to fly with the setup you have, but I sense this will be with some struggle provided it structurally withstands WOT performance.

...my chavanni(0.25 Rs) is a plane should be built with the intent of achieving pleasurable flying experience (define: pleasurable? simply put, it should meet your design and performance objective {broken down into sub parameters} ....once you have decided this, the design of the plane MUST comply with parameters thus arrived that will help achieve the desired performance).

the only way to check is to try it.... ;D.....so, give it a shot  :thumbsup:

1. PVC is heavy ! have you weighed it before using it? replace it with an alternative? bamboo if CF is not avbl.
2. The airfoil looks quite healthy - so that's a +

3. I dont recall(as I type this note) a dihedral....if its there, good: else build/introduce wing tips/lets - this will increase wing area and reduce WL marginally.

finally, whatever changes you make and irrespective of the outcome, let us folks know how it flew....thats the essence of it  :hatsoff:

.....here are some suggestions you could consider:

1. Do away with the 'fins' at the rear, replace them with ONE conventional fin+rudder. This way, you reduce one servo (10g) and one fin, whatever the weight.

2. Add wing tips(just saw the pic) about 9 in on either side with the same chord. reinforce it adequately. This will increase your wing area and reduce wing loading. Make ailerons non-functional using tape.

3. Do away with two booms, provided you have enough vertical clearance for the prop if you were to mount the motor on the pod as a pusher config.

4. Convert this into a RET plane  :(

......I know the plane with the two fins looks good, but its better to have a not-so good looker that flies well, than have a pretty looking brick.

...keep us posted.

EDIT: ....saw your other build....the black one, did it fly? just curious !

Wow! That's some good piece of advice

Thanks so much, I will be trying to reduce the weight the best way I can without comprising on aesthetics as far as possible but if push comes to shove then as u rightly said.. A bad lookin plane is better than a good lookin brick

I will be fitting the electronics and doing a couple of ground tests before I take it out to fly

Attaching some pics of the build..

Cheerz

Build pics.. And final product after painting..

Cheerz

Assembly and final product

Cheerz

drone.....I am curious to know if the black one flew. It appears to be a bit smaller and from your other post, i recall it weighing 1kg+

black and yellow is a great combo...your final result looks good. What is the weight with taping?

*** you are aware what happens when kinetic energy meets the ground! your nose looks impressive but I suggest you pack it up with foam as snugly as possible and then make room for the batt - this may help in cushioning in case KE meets the ground too often.

** If you can share how your black one flew, maybe we could use the learning to ensure the yellow one performs as desired.

* finally, its not necessary to have a power to weight ratio of 1:1. However, the WL here is on a much heavier side, hence my thoughts. For planes such as this one, a max WL should be under 10 oz/sft (ideal would be 6-8 oz/sft).

go for it  :thumbsup: and update your experience here. I would build one of these, the plane actually looks quite good.

I have t flown the black one yet and I doubt a good flight on it as its grossly underpowered..

The build was more of an experiment with this type of aircraft design cos the new prototype was always on my mind but I wanted to build a rough cut scratch first..

I was to test it last weekend but it rained.. Also I impulsively constructed this one as I had a free day and that doesn't come by too often. Will test both these together over the coming weekend.. Will test the black one first as I can afford to crash it as much as it will..

Will keep u updated..

Cheerz

Comparative sizes of both aircraft..

Cheerz