FPV49 KFm Wing

elmattbo · November 18, 2015, 11:30:17 PM

After considering a Z2 but deciding I didn't fancy spending the money on it, I did a bit of research for any scratchbuild plans for something similar and found this http://flitetest.com/articles/fpv49-build
Anyway, I splashed the cash on £25 of depron (enough for 2 wings if the first goes wrong!) and set about cutting...
As you can see in my first pic, the tools leave something to be desired. I don't have a long measure so had to use a tape, the longest straight edge I had was off a Venetian blind and I 'borrowed' my daughters pen!
Anyway, cutting all done, carbon spars glued in to place, the next step is placing the electronics. I'm sticking with 5.8 for video and will use a Frsky x8r receiver as I have one lieing around, but I may also use a L9R. For OSD I've got a cyclops breeze but I could also use the storm that's in my Bix3.

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weavo56 · November 19, 2015, 03:10:49 AM

Hi Matt , I need to ask you , did you use UHU por to glue the layers together ?
If so how did you do it , cover BOTH sheets and let them go off then put them together or cover one sheet and then put the next one on it straight away .
Seen FPV 49 vids but still not sure .
I've cut out all the parts but I'm doing the kfm 3 wing and I'm waiting for carbon strips .

Cheers Graham

Devonian · November 19, 2015, 02:43:52 PM

I've built a couple of KFm wings, like this...
http://www.rcgroups.com/forums/showthread.php?t=1023254
In there somewhere is my 1 metre pdf plans (1 metre is the most common wide depron sheet width)

They will fly real slow and predictable

I use half round wood dowel on the leading edges to stiffen it up and stop it 'flapping' itself to death in a steep dive - don't ask how I know they will snap in half !
UHU Por works well (light coat on each layer).

Nigel.

weavo56 · November 19, 2015, 06:34:28 PM

Thanks for that Nigel . I bought some 1200 x 800 sheets for the fpv49 .

G

elmattbo · November 19, 2015, 08:15:51 PM

Hi graham
I used uhu por initially and then ran out! I put it on one side and by the time I had spread it out it had about 10 mins to cure so just stuck it together and it's fine. The instructions say 10-20 mins but I find if you leave it the full 20 it's really tacky and harder to work with.
Also did a layer with PVA and that's fine too! Someone will probably be along to tell me I'll regret it though...
If you use the carbon strips as in the build video it is absolutely solid, no flappiness there at all! Thanks for the link Nigel although I think you've got a different intended use for your airframe, although I'll certainly be looking for tips as this is my first scratch build.

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English Turbines · November 20, 2015, 12:10:52 AM

Quote from: elmattbo on November 19, 2015, 08:15:51 PM
Hi graham
I used uhu por initially and then ran out! I put it on one side and by the time I had spread it out it had about 10 mins to cure so just stuck it together and it's fine. The instructions say 10-20 mins but I find if you leave it the full 20 it's really tacky and harder to work with.
Also did a layer with PVA and that's fine too! Someone will probably be along to tell me I'll regret it though...
If you use the carbon strips as in the build video it is absolutely solid, no flappiness there at all! Thanks for the link Nigel although I think you've got a different intended use for your airframe, although I'll certainly be looking for tips as this is my first scratch build.

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Why not try this stuff, its loads cheaper and its German..?....Spread a thin layer on one surface only and put together while still wet. Has the consistency of honey. You need to pin it to prevent creep and then use a large flat board to hold it flat while it dries out. It kind of expands as it dries, so you need to use a thin layer and weight it....Dries in about 20 mins....Cheap as chips...:)

http://www.ebay.co.uk/itm/5-Pack-of-Dr-Schenk-Grab-Adhesive-300ml-Cartridge-BIG-SALE-/331580595495?hash=item4d33be5d27:g:jjkAAOSw~OdVeuP8

:vulture:

weavo56 · November 20, 2015, 02:27:36 AM

Thanks Matt and ET .

Good info .

G

elmattbo · November 20, 2015, 10:19:01 AM

Graham, just a tip. Consider how you're going to mount the motor before glueing the sections together; the foam could do with a little reinforcement to spread the load. I'm purposely not using a solid mount as I'd rather the motor break off in a crash than remove a chunk of foam down the middle. Something like a plastic gift card embedded in the layer between the middle sections and top step will probably work fine.

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weavo56 · November 20, 2015, 06:00:16 PM

AH , good idea Matt , I've got some of them . Other one is gift card on top as well and double side tape to motor mount .
Cheers mate .

Graham

elmattbo · November 21, 2015, 01:30:24 AM

Ah yes I think I've seen that online somewhere. Ta

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elmattbo · November 22, 2015, 02:01:29 AM

Spent a few hours on it thins evening, cutting in the servos, GPS and vtx. Also trimmed the elevons, glued on the motor mount and glued on the top step that houses the embedded electronics. Most of the time was spent standing around though and just looking at
it and thinking! I still haven't worked out the layout for cameras, batteries and reciever/cyclops storm. Once I do, I need to make a balsa/plywood box to house everything and then cut into the foam to mount it. My headache is doing this whilst keeping a little room for manoeuvre with the CoG. Regardless, I need to bevel and sand the leading edge so I'll crack on with that whilst I figure it out.
I'm sure some of this seems basic and shoddy to you puritans out there and I think you'd be right! However I thought I'd log it for anybody else trying to do the same. Frankly, the gods of aviation will forgive a lot if the cg is right and that's what I'm counting on!

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FPVSteve · November 22, 2015, 04:05:40 AM

lol, i attempted this once. Total disaster, no plans and no clue :D Yet it "flew" :D So I'm sure yours will be fine ;)

https://www.youtube.com/watch?v=CPJ3alJpf88

elmattbo · November 22, 2015, 09:13:31 AM

Quote from: Steve W on November 22, 2015, 04:05:40 AM
lol, i attempted this once. Total disaster, no plans and no clue :D Yet it "flew" :D So I'm sure yours will be fine ;)

http://www.youtube.com/watch?v=CPJ3alJpf88

Haha! Good effort though! I wouldn't say I have no plans as they are pretty well drawn up. It's just all those cutting errors of 1 or 2mm add up! The other thing is fitting in the bespoke bits for my own set up. It could have been way more complicated though!

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English Turbines · November 22, 2015, 09:56:46 PM

Hey Matt,

It looks fine to me m8....I have about 8 sheets of 6mm Depron in my garage, so I could put one of these together for a Winter hack FPV model...
Keep us posted as you make progress....more pics..!!..... :terrific:

:vulture:

elmattbo · November 22, 2015, 11:28:14 PM

Thanks! No pic but after a bit of head scratching trying to work it out, this evening I bevelled the leading edge whilst watching I'm a celeb! Initially, I couldn't figure out how to get a smooth symmetrical leading edge, top and bottom, on both sides. In the end I drew three lines at 5, 15 and 30mm from the leading edge. Then I cut down to the join at 3, 2 and 1 sheet deep from the lines. Given that it's 6 sheets thick that's given me a near parabolic edge and with a bit of sanding it should work out ok hopefully.

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