Stubborn Ft Versa

[Instru(mental)]

Hey guys.

I'm new to the hobby, and made an ft versa from 5mm foam board. 40a turnigy 1450kv brushless outrunner, pusher configuration, 30a (I'm so sorry, but due to budget this was needed, and I never go above 3/4 throttle for more than 3 seconds) ESC, and a 2800mah 3s. I have 9x7.5 and 9x4 props.

All up weight is 1.28kg. I've balanced the cg slightly in front of the marks, and needed to add 250grams of lead... With the cg slightly behind (haven't tested any other) and 300 grams worth of landing gear, it wouldn't get off the ground. Please list everything I'm doing wrong.

 

[Jugsy]

That sounds ridiculously heavy! The plans show 300g without battery, if your landing gear is 300g by itself you'll definitely have problems.

 

[PsyBorg]

Seems added weight from several places. The recommended battery is a 2250. That 2800 has to add a nice chunk of weight as well.
So between the landing gear, the battery and the 250 grams of ballast you have easily doubled the weight of the design.

Just for giggles lose the ballast, try front mounting the motor and lose the landing gear. see what all up weight is then and see where that puts you for CG. If it looks respectable try a glide test before trying to re-maiden it.

 

[Instru(mental)]

So between the landing gear, the battery and the 250 grams of ballast you have easily doubled the weight of the design.

Sorry, I didn't explain very well. The ballast is only needed when the landing gear is on. I don't have time to remove the motor etc.

How would I go about doing a glide test?

 

[JimCR120]

As much as possible/practical I try to balance my planes with existing essential components. Some must go in certain places (motor) of course but others can vary enough to make all the difference (battery).

 

[Jugsy]

A glide test just means a brief unpowered flight. Hand launch it (preferably over some nice squishy grass in case things go wrong) and just control it down to the ground. This'll just show you if anything's majorly wrong before you get speed and altitude happening.

If you need that much ballast you may need to consider forgetting about the landing gear and only hand launching/belly landing. I know it's hard to find the time to do major changes like moving the motor but ultimately its worth it to get a model dialled in perfect.

 

[Instru(mental)]

The battery is all the way up the front. The motor I'm using is http://www.hobbyking.com/mobile/viewproduct.asp?idproduct=18226

Threads I've real day that if the motor is big enough, go for it. I think the foam board is causing my woes...

 

[Jugsy]

I doubt it, unless it's absurdly dense stuff. Could you tell us the weight WITHOUT landing gear, ballast, and battery?

 

[quorneng]

Instru(mental)
I don't know why but it is so over weight I really wouldn't even try to fly it.
I think it is already trying to tell you this!

As Jugsy pointed out it:-
Weight - 10.6 oz (300 g) without battery
Wingspan - 38 inches (965 mm)

The Versa is not intended to use an undercarriage and if it is at anything like the correct weight you don't need one.
Just search "FT Versa" on YouTube for some videos to see it being launched.

 

[Instru(mental)]

I doubt it, unless it's absurdly dense stuff. Could you tell us the weight WITHOUT landing gear, ballast, and battery?

Approx 600 grams. Nothing but foam, reciever and servos etc (no battery, motor, landing gear or ballast)

 

[Jugsy]

What's the brand of foamboard? Do you have an intact sheet to tell us the weight of? 600g still sounds high especially without the motor. Did you use hot glue or another adhesive?

 

[Instru(mental)]

What's the brand of foamboard? Do you have an intact sheet to tell us the weight of?

The foam board is Jasart brand.

I'll tell you the weight of the foam board in 6 hours (I'm in NZ)

I used hot glue, EVA glue...

Hold on. I printed the designs onto a massive sheet of 200gsm paper... If someone could find me the whole area of the versa, multiply that square meter measurement by 200, and that's the weight I've added to the plane, in grams...

I also used an epoxy adhesive to bind the two halves, and sprayed the plane with general purpose spray paint.

 

[Jugsy]

Ah, you left the plans attached to the foamboard? Luckily I was warned off it before I made that mistake, but I've heard it's caused weight issues for other people. Sounds like there's nothing majorly wrong with what you've done, just a whole bunch of the little things spray paint adds a surprising amount of weight.

You'll probably need to work at cutting it down, start with the big stuff and get more and more granular as you go. A smaller battery is your easiest and best bet, a 2800 is pretty big. Take off as much of that extra paper as you can get to. This might mean taking back some paint but that might be beneficial too if there's a lot of coats. Scrap the landing gear and ballast all together. Any additions you've made to the guts (zip ties, extra skewers, etc. etc.) try and minimize if at all possible. If there's excess servo/esc/motor leads cut them right back and resolder them. If it's still really heavy and there's nothing else you can take off, cut some speed holes. Quite seriously, just be very careful with placement so you don't compromise structure or aerodynamics too much.

 

[Instru(mental)]

Ah, you left the plans attached to the foamboard

Thanks for pointing the issue out .

Ill Get that off as soon as I can, and then think about other things. Probably a good 150 grams of paper there.

The battery is actually needed to balance it out (using a lower weight battery will just require more lead), and anyway, I've added all this ballast, most of which will need to stay due to CG.

The plane is for a High school competition, the criteria of which is yet to be announced (flight time? speed? etc) so the Versa seemed like an obvious choice.

Thanks for the help. Ill ask back if need be, but for now, the paper is priority.

The landing gear has already been completely stripped. since it's a pusher, no power pod.

PS: how much weight can spraypaint actually add to something like the versa?

 

[Bricks]

With all the weight are you adding Reflex to the elevons I built an over weight Versaout of Bordens Foam board and had to add 5/16 of an inch of Reflex to get it to fly it flies heavy but does fly.

 

[PsyBorg]

Well I'm afraid you wont be winning any competitions if it will not fly mate. You would be surprised how much weight painting something can add. It wont seem like much in real world weights but the difference of a few grams can have drastic effects like on something as light as a foam air frame.

Remember the Flite Test planes have been designed and tested. They DO fly and the DO perform well IF you built them according to designs. Any changes outside their build designs can and will probably (as you are learning) have adverse effects.

 

[Instru(mental)]

Scrapped

I've stripped the versa of its servos and ESC, and managed it put together an ft flyer within two hours. Test flight tomorrow when I buy the motor.

Funnily enough, if I get any powered plane to fly, I win, because there is no one else in my category...

 

[PsyBorg]

Cool!!! Hope you have better luck with the new build. At the very least you learned some serious lessens in scratch building and the physics of all things that fly.