HalfSheet Spitfire

[eagle4]

Hey gang, I was impressed with the half sheet racer that Springer made over on RCGroups.
http://www.rcgroups.com/forums/showthread.php?t=1565081

I thought I'd take my hand at making a half sheet plane too. My plans are based off his. although there are a couple of tweaks.

I modeled my spitfire in 3dsmax to get the shape right. i dont have small electronics, so everything is bigger than what he uses in his racer. so this should be intersting. I will use my blue wonder motor i have from having built a bloody wonder, also i'll be using the small 500mah 2s battery. its much bigger than whats needed for this small plane, but hopefully its not too heavy. also the smallest esc i have is a 20A, so that'll have to do, and 9gram servos, would have prefered to use 5gram ones, but i'm wanting to build this out of parts i have already.

The plan is to build this from elmers foamboard (its like adams readiboard, but its all i can get here in montreal) with the paper removed from most of the pieces. as the paper adds a bunch of weight, i am hoping to get this as light as possible, hoping it'll be a fairly slow flyer. i plan to keep the paper on the inside of the nose cavity, so the nose will have some extra strength for when i'll likely high five the earth. also maybe keep the foam on the top side of the wings. should provide a smoother surface and a bit of strength. if i cant bend the wings enough i may just have to glue on a bbq skewer under the wing for strength. but we'll have to see how it goes.








you can get my plans here from my dropbox, I dont know how to attach a pdf to a post
https://dl.dropboxusercontent.com/u/11372149/plane designs/HalfSheetSpitfireFinal.pdf

 

[MEGAjig]

Looks awesome. Can't wait to see it in the air.

I'd like to build one but I only have 450 size and bigger motors with 30-40A ESCs.

If you can recommend a prop, motor, esc, servo combo for this plane from HobbyKing maybe I can build one over the winter.

Thanks!

 

[eagle4]

Hey MEGAjig, unfortunately i cannot recommend a prop, motor, esc, servo combo for this. im completely flying blind here mate.

well I just had one awesome afternoon of building. i stated and just was on a roll!!!

I tried to take pictures at all the important steps i took in building this.

















With all the electronics stuck in there i was truly surprised to find that the CG was pretty much where it needs to be. i did a couple of short glide tests in my living room (throwing and catching) and it seemed to glide pretty well. if it fly's well i might put this up as an article on the front page detailing all my steps. what do you think?

 

[eagle4]

The wing on its own weighed 14 grams
whole plane put together, just the foam was 34 grams

total all up weight, with everything included was 179 grams. I think with different electronics you could probably get the weight down quite a bit.

 

[kingbee]

Hi Eagle

wow looks good thumb up .. when you fly it try and get someone to take a video of you flying it . i really would like to see it fly .

 

[eagle4]

i might take it up tomorrow if there isnt too much wind.
kingbee, if you're up for it would you wanna come down to the island to have a fly?

 

[Craftydan]

Eagle, she looks nice!

Curious to see how she treats you -- looks like she might even survive indoor flight at a fair sized venue.

 

[eagle4]

That was what i was aiming for Dan, especially with trying to make it as light as possible. if i kept the paper on the foam it would have been a lot stronger, but also plenty more weight.

problem is i dont have a venue here where i can fly indoors, i am also limited in my flying areas as i don't have a car

 

[eagle4]

I took my Spitfire for its maiden flight, and unfortunately it ended pretty abruptly,

the 6x3 prop was a bit underpowered on the 1300kv motor, although i think it could keep it in the air, just slowly, but it also torque rolled its self to the left and then into the ground.

thankfully, as it was so light i only broke the prop, but i didnt take any other props with me to the park (i'm a goose. always take extra props!!)

i tried it at home with an 8x4 and it has power to climb vertically, i was holding the plane while throttling up, just to feel the strength it had. i also felt it was generating quite a bit of torque roll to the left. i then found i had a 6x4 prop and it had much more power than the 6x3, but obviously not like the 8x4, anyway, it also was generating quite a bit of torque roll, a bit less than the 8x4 actually. Not really sure how I can counteract this torque roll, i could try trimming it to the right quite a bit, but as its only rudder i dont know... any sugestions?

 

[eagle4]

I don't like calling it a crash, its just High Fiveing the earth!

 

[Craftydan]

Three things that will help tame your torque roll:

- right rudder will still generate a bit of right roll. it's not a symmetrical rudder so expect both yaw and pitch coupling from it.
- a touch of right thrust angle will help counter the left roll. Put two thin washers under screws on the left side, between the X mount and the firewall.
- airspeed. For takeoff, it's your friend. More wind over the wings will tame the torque roll. Either ease into the launch (toss at half throttle and ease it up while picking up speed) or chuck it with all your might.

Keep in mind, the real spit was atrocious about tip stalls -- a lot of elliptical wings are guilty of this. David's spit has undercambered tips to counter this, but this wing is fully undercambered. the reason I bring this up? A torque roll can couple wit a tip stall non launch and be wicked to counter -- again, for takeoff, airspeed is your friend.

Crazy idea: Fill in the undercamber along the inner 2/3 of the wing using packing tape (stuck to the wing top, but not touching the wing as it spans the undercambered gap). If it works, that'll give you more lift out on the undercambered tips at low speed, and make the wing root stall first -- a lot easier to control and recover from.