MiG 17?

[contenderguy]

I am planning/hoping to scratchbuild a MiG 17 EDF, like the "Stoli" MiG aerobatic team. I have been flying glow-powered planes for several years, but I don't know much about electrics. In a perfect world, I'd use a jet engine but the cost is too much. Glow ducted fans are still expensive... and the glow engine sound is a little "incongruous" with the jet. My ideal would be a sport scale model with a wingspan around 50", retracts, and a flying time of around ten minutes with good performance. I'd love to include flaps and speed brakes as well, and have the ability to take off and land from a grass field. So that's the dream... I understand that in reality compromises will have to be made. The cost of the ducted fan, motor and batteries should be <US$400. With this price range in mind, does anyone have any thoughts regarding what I can achieve and what I will have to sacrifice? Any recommendations regarding fan, motor and batteries? Also, I really need to learn the basics of E-flight (for instance: what is a 3S1P battery pack? What are the advantages of an outrunner motor, and in what application? How do I size a battery pack, ESC and motor to suit the application?) and I would be much obliged if someone could point me to a site that will help me out with this.

[watt_the?!]

sorry for no reply.

My ideal would be a sport scale model with a wingspan around 50", retracts, and a flying time of around ten minutes with good performance. I'd love to include flaps and speed brakes as well, and have the ability to take off and land from a grass field.

>>woah there nelly...you could do this, but you'll need a whole lot of power to do so...esp the ROG bit. Might have to hold off your dream for flaps/speedbrakes also..unless you got the dough of course.


So that's the dream... I understand that in reality compromises will have to be made. The cost of the ducted fan, motor and batteries should be <US$400.

>>MiniFan 480, 3s2p 2000mah+ lipos, mega 3t or similar, plus 50A ESC = approx $400US.


With this price range in mind, does anyone have any thoughts regarding what I can achieve and what I will have to sacrifice? Any recommendations regarding fan, motor and batteries? Also, I really need to learn the basics of E-flight (for instance: what is a 3S1P battery pack? What are the advantages of an outrunner motor, and in what application? How do I size a battery pack, ESC and motor to suit the application?) and I would be much obliged if someone could point me to a site that will help me out with this.

>>Checkout Fancalc 1.1 via www.rbckits.com (http://www.rbckits.com)
Any other help just ask here- better to go to the beginner section so others can read your posts for their own benefit also.

[pace_likethesalsa]

Last night I was just thinking "dang, making a ducted MiG would be pimp" I was thinking more like 20" or so haha. let us know how it goes


Main problems I see are squeezing radio equipment in it, espescially one like the 17 where the whole body is used for housing the jet, where as some models lowered the jet a bit.


If I/he/we were to this, would we have to use two ducted fans, one right after the other, spinning in opposite directions? Or is the torque low enough to be fine?

[contenderguy]

Thanks for the reply, Watt The?!

As I said, my dream was to include all of the neat stuff like flaps and retracts. In my ignorance I am guessing that I could maybe keep these, but ROG would be limited to paved fields, otherwise it would be a bungee launch. I downloaded Fancalc and I'm sure that fiddling with it will help me decide what compromises I need to make. I guess this is always how it starts out. Anyway, I'll explore this further and if in the end it looks like the model I can make is one I want to have, I'll post it here.

Regarding Pace (like the Salsa)'s thought about two EDF's in series - I'm no expert in electrics but I have a "reasonable" background in fluid mechanics - my guess is that a configuration like this would cost you more than you would gain, in terms of weight vs. performance. I think that unless the second fan were pitched to operate efficiently in the high velocity exhaust of the first, it would probably consume a lot of power without being able to load the fan for efficient operation.

[watt_the?!]

contender, your fluid mechs are right. flow separators, different diameter and diff pitch are needed for a second fan, and even then it wont yield the gains worth the input.

have you checked out eam.net?

they have the mig17 there.

if you go for the big $ setup, you'll have ROG from belly on grass and plenty for ROG pavement for your retract setup.

Tim.

[RichTheBikeRider]

try these sites
http://kress-jets.com/Outrunnerfans.htm
http://www.kamodels.com/
http://www.rcgroups.com/links/index.php?t=display_link_search&having=250245&cat=156
as for doubble fans a guy built a Skyray never heard how it flew
http://www.parkjets.com/f14-tomcat.html:)
Rich

[Bill G]

contender, your fluid mechs are right. flow separators, different diameter and diff pitch are needed for a second fan, and even then it wont yield the gains worth the input.

have you checked out eam.net?

they have the mig17 there.

if you go for the big $ setup, you'll have ROG from belly on grass and plenty for ROG pavement for your retract setup.

Tim.
Well since a thread is already here on the Mig17, I'll use this one.
Got one of these EAM Mig17 kits from Thomas B. The manufacturer John Dutkowski still has them for sale, I believe.

Making things a bit more interesting, there were no instructions. Found enough online pics (and not many) to answer the few key questions, although most of it is self-explanatory. The sheeted foam core wings have been a good task, as the LE, TE, and endcap stock is HUGE, and requires a lot of sculpting to complete. Makes you feel like you're really building a wing, although it's a simple foam core and not balsa frame design. This is also my first glass kit, which is night/day different from anything I've done before.

The kit was designed in the nicd/nimh days, and with the lipo benefit, I downsized a few mm to a HET 6904 fan and 2W motor. The designer says that the cheater can be eliminated with the smaller fans, which would be nice to to see. Going together pretty well at this point.

[Bill G]

This kit includes a clear canopy. I almost cut off the molded-in fiberglass canopy, thinking it was there just for folks who didn't want to use the clear canopy. Then I looked at some pics and saw that people were cutting the window pillars out from the fiberglass molded canopy, and then inserting the clear canopy underneath.
This is a task that you will want to be 100% steady, clean, and sober to do.:D
Used a thin Dremel metal cutoff wheel to cut out the pillars. They will need the edges cleaned up a bit with sandpaper, but they turned out pretty well. The glass is loosely inserted with the cocpit base in the pic below:

[Bill G]

Well it's about time I got back on this Mig. Pretty much down to painting/covering, and if I ever get bold enough: flying.

The only area of this kit that really concerned me is the ply stubs which glue into the sheeted foam core wings. Since the foam cores are very soft, the stubs really rely on the epoxy gluing to the sheeting to, keep the wings from ripping off. Not good enough in my opinion, so I drilled holes in the LEs of the wings, which CF rod is inserted through the LE and routed along the slots cut into the wings, which epoxy to the ply mounting stubs.

[Bill G]

Finally getting this thing together. A few mostly inconspicuous small sags, but pretty decent, using Monokote paint. Nice blurry picture. :D
Still have the white outline red stars and final asm to go.

[CHELLIE]

Finally getting this thing together. A few mostly inconspicuous small sags, but pretty decent, using Monokote paint. Nice blurry picture. :D
Still have the white outline red stars and final asm to go.

Thats looking very nice Bill :ws: I want to fly it after your done with it :D Take care, Chellie