New airframe (again) - Funjet II

[icebear]

Hi all,

My first Gluonpilot installation was a Funjet (OK, I had a GP in 2010 in a trainer too...) and while it flies well and is well trimmed I havent been able to carry a GoPro camera due to the weight of the Ultra (700 grams total with battery including repairs!). It is also a handful to get airborne...

Therefore, I was inspired by Eddis build of the "old" Funjet and I have decided to start a light build that should inculde the Gluonpilot AND a GoPro cam.

Parts have arrived and weigh in as follows;

Wings: 52 grams
Fuselage: 84 grams
Stabilizers: 10 grams
Canopy: 14 grams
Motor mount: 25 grams
Spar: 20 grams
Small parts: 15 grams
TOTAL: 220 grams

I think by just modifying motor mount and exchanging the heavy spar I can save 30 grams or so. On top of that some foam will be removed to allow for the GoPro mount and to give it a clear forward view.

The equipment weighs:

Gluonpilot: 15 grams
XBEE (external): 5 grams
BEC: 5 grams
GPS: 10 grams
Hitec Rx w/o case: 5 grams
Servos HS65HB: 20 grams
TOTAL: 60 grams

Motor/ESC/cables approx 60 grams, and I would go for a light 2S or 3S-LiPO at approx 90 grams.

That means that I could have a complete Funjet @ 190 + 60 + 60 + 90 = 400 grams. Even with the GoPro I could be within 500 grams total...

To be continued...

/Björn

[Tom]

Interesting to see how far (or low) you can push it. My experience tells me my builds are always 10% more than I thought it should have been (glue, ...)

Where would you mount the gopro?

[icebear]

Interesting to see how far (or low) you can push it. My experience tells me my builds are always 10% more than I thought it should have been (glue, ...)

Where would you mount the gopro?

Yes -I totally agree - at least 10%... I still think 500 gr should be doable, but we'll see...

I still havent decided on the place for the GoPro. I am laying out components to see how I can move a lot of weight further aft. Ideally I would want it as far to the front as possible (ie at the fron of the canopy) not to shorten the nice nose too much.

I think I can place the battery directly after the Moto/ESC so in that case I would have eveything in THIS order;

Motor->ESC->Battery->GP->GPS->XBee->GoPro

I will do some trial fitting and post pics here...!

/Björn

[icebear]

This morning I weighed the equipment and as can be seen in the picture, there is 80 grams of electronics excl servos, or 100 grams incl 2xHS65HB servos.

Some weight watching to be done here;

Lighter GPS - 6grams
No case for Rx - 2 grams
Smaller ESC - 5 grams
Smaller servos -10 grams (HS45HB instead of HS65 but questionale if 1kg/cm is enough compared to 1.8 kg/cm for the HS65's)
Shorter cables: - 2 grams
Total saving: 25 grams

The layout in the Funjet seems to work out if I put the battery far aft just behind the CG - good for having options on different packs.

Now the question come regarding the SPAR and motor mount - with a light motor and light wingload - can the Funjet survive WITHOUT a spar at all?
And is 10 grams saving on motor mount worth losing the nice, practical original?

Any thoughts welcome!

/Björn

[Tom]

Hi Bjorn,

I would for sure install the spar. It will allow a more stable flight with for your video . Also, I thight turn with the heavy gopro and without spar is risky. You can also use a small carbon fiber one instead of the big plastic one. Your setup is light, but with the GoPro the total weight can be high. I would decide on the motor mount once you have a view on the balace. If it is nose-heavy you can install the motor mount. It obviouly looks a lot better with one. How would you do it without?

[icebear]

Hi Bjorn,

I would for sure install the spar. It will allow a more stable flight with for your video . Also, I thight turn with the heavy gopro and without spar is risky. You can also use a small carbon fiber one instead of the big plastic one. Your setup is light, but with the GoPro the total weight can be high. I would decide on the motor mount once you have a view on the balace. If it is nose-heavy you can install the motor mount. It obviouly looks a lot better with one. How would you do it without?

I agree - my idea was originall to get a lighter c/f spar but then I read about Jürgen Heligs super light FJ where he left out the spar entirely ...

With the 10% rule I will not hit <500 grams and then for sure spar would be necessary - albeit a lighter one!
I still thing somewhere around 550 grams should be doable!

And yes, I want stable video...

/Björn

[lukasz]

hmmm..goPro itself weights just above 100g, so you have more than 500g.

I would use carbon tube spar - quite light + strong

[Tom]

I see a very nice hyperion motors
Still hoping to receive another one for my broken motor...

You can also wait for gluonpilot2 and save a few more grams

[icebear]

hmmm..goPro itself weights just above 100g, so you have more than 500g.
I would use carbon tube spar - quite light + strong

Agreed! I just ordered a nice hollow c/f tube... BUT I will for sure aim for approx 500 grams - even if I know it will be slightly more...

I see a very nice hyperion motors
Still hoping to receive another one for my broken motor...
You can also wait for gluonpilot2 and save a few more grams

Yep - got another Hyperion from Robotbirds in the UK (out-of-stock in Denmark) and it should be a perfect match for the Funjet - 7x5 prop on 3S or 8x6 prop on 2S - we'll see what is best...

And I am for sure waiting for the GP2 but by then I will have a new project

[icebear]

I did some more work on the Funjet yesterday and decided to use the standard motor mount after all;

- easy to change up/downthrust
- stable and easy to mount
- weighs 20 grams BUT with a rearmounted Hyperion I have to add the mount with screws and a ply-plate so I would only gain 10 grams
- I cut the connectors and shortened the cables between motor/ESC and saved 10 grams(!)

Now time to install the gear in the fuselage...

/Björn