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Nov 21, 2013, 10:38 AM
Designer/Builder
Jim Young's Avatar
Contest

Scale Build-Off 3: Jim Young Mig-17


Hi,

I've been playing around with a GP Phazer (I know, and ARF) and the power system is pretty nice. The Hyperflow fan unit is 56mm and paired with the Ammo 24-45-3790 on 4S LiPo propells the Phazer around 90mph while drawing ~32A. The price is pretty reasonable, and I picked up a second fan and motor for $50 in the classified forums.

So, what to put it in? I liked the simplicity of the Mig-15, but it has been done a lot so Keith talked me into the Mig-17. While it is very similar to the -15, there are enough differences to set it apart. I also, liked the fact that there were several Mig-17's pulling airshow duty, so there are some pretty interesting color schemes.

Inital specs are:

Wing Span: 28"
Length: 33"
Target AUW: 30oz.
Wing Area: 208 sq. in.
Wing Loading: 20oz/ sq.ft.

It will be a "one piece" plane, fully sheeted. The Phazer has a brother called the Evader which is a more conventional plane. I'm targeting my Mig to have a bit more wing area and similar weight. This should keep the wing loading down and make it a nice flyer. No landing gear, and it will have a built in hook for a bungee launcher.

One of my goals was to not have a cheater hole like the Phazer. When I starting designing Keith thought this may be a problem. As the inlet length increases, it is harder to get air to the fan. It is like trying to suck a milk shake through too small of a straw. So I put together a test stand to at least measure the static thrust of the fan with different length inlet tubes. My thinking is that if the static thrust is not significantly affected, the dynamic thrust should be fine. My Mig will have an 18" long inlet. I tested the fan unit with just an inlet lip, a 6" tube, and a 19" tube. For all cases, the static thrust was within an ounce, and there was no significant difference in the current draw. So, I'm proceeding with no cheater hole.

Some side notes on my testing, a proper inlet lip makes a big difference in static thrust (20% decrease without one) and the inlet tube must be properly supported and free from cracks or it will be crushed like a straw!

Anyhow, the plans are complete and I just received the first two sets of prototype parts. So stay tuned as the build progresses.

-Jim
T&J Models
Last edited by Jim Young; Jan 03, 2014 at 09:24 AM. Reason: Entering contest
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Nov 21, 2013, 10:46 AM
Registered User
Ken Myers's Avatar
I'll be watching closely.

No a huge Jet Fan, but I do like this one a lot!
Nov 21, 2013, 11:40 AM
Pro Hoarder
turbonut's Avatar
Ooooo Nice....I am on board...The long intake will only shorten your take off run..but at this size I assume it will be hand launch so no biggy
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Nov 21, 2013, 11:41 AM
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Dennis Sumner's Avatar
I'll be watching too....the plans looked great!
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Nov 21, 2013, 08:53 PM
Gravity sucks.
mrittinger's Avatar
Knowing you Jim, it'll be a keeper. I'd love to do one in bare metal and NVAF colors...
Did Keith say anything about exhaust duct taper ratio? I've heard 5 to 10%?

Mark
Nov 21, 2013, 09:55 PM
Designer/Builder
Jim Young's Avatar
Hi Mark,

I'm using the same outlet diameter as the Phaser which is 42mm. It flies pretty good, so why mess with it.

-Jim
Last edited by Jim Young; Nov 21, 2013 at 10:04 PM.
Nov 22, 2013, 07:53 AM
killickb
killickb's Avatar
But I never got around to the Meteor ! Don't know if its worth anything but I built the MJT Saab J-29 which is also 28inch span. It is a tube in tube fuse construction so the ONLY item in the air flow is the fan itself -- straight thru ducting. The inlet is 14 inches long of rolled acetate sheeting and when stuck to each former shows no signs of being sucked in. The efflux is 5 inches of same. Of course the J-29 is a high wing so getting a clean straight thru duct is simpler than your Mig.

The J-29 is is powered by a Wicked driven Alpha 5 blade fan so smaller than yours but it goes way, way to fast for my old eyes so is rarely flown these days -- it is also silver !

Are you doing retracts ? Mine, being a high wing just takes off from the ground, no gear but only off grass of course, never did trust a hand launch though for you younger guys should be a breeze.

Am sure your Mig will be a great success, as all your designs have been. Happy landings.
Nov 22, 2013, 08:15 AM
Designer/Builder
Jim Young's Avatar
Hi Barry,

Nice to hear from you. I've got a couple of Meteor kits in stock, just in case.

My ducting is straight through, you can see by the main former above I'm using some of the engineering from the Meteor to support the wing. The duct will be 1/64" ply rolled and glued to all of the formers. I've also laser cut a jig to help hold it in place while you glue it. On one of my fan tests, I was switching out the tubes and I cracked the plywood. I taped it up, and when I got to half throttle the whole thing collapsed, flat as a pancake. Luckily, nothing got ingested by the fan.

I'm hoping for similar performance as the Phazer, which would be around 90mph. This is pretty fast for such a small plane. I can't believe there are guys pushing that plane to 150+mph! I've gotten into speed this last year with a Habu 32, the Phazer, and a hopped up version of my Hughes H-1. I figured I better do it now before my eyes and reflexes can't handle it.

No retracts on this one, although my new club does have a paved runway. I've been pretty impressed with the simple bungee launcher that came with the Phazer. A little surgical tubing and some string, can't get any simpler. The Phazer has the advantage of being a delta wing, so it is near impossible to stall it. A simple underhand toss and I can get my hands on the sticks to throttle up by the time it is off the bungee. The Mig will be tossed overhand.

I've got the Mig fuselage designed with some stiffeners behind the wing so you can grip it for launching. With 20oz/sq.ft. it may not need the bungee.

-Jim
T&J Models
Last edited by Jim Young; Nov 22, 2013 at 08:25 AM.
Nov 22, 2013, 10:31 AM
Registered User
Steve Merrill's Avatar
OH no, I may have found my next plane... Spent some time fooling around with a small EDF this fall, was dissapointed in the performance. But there is a learning curve, like anything else. Im sure yours will be top notch!
Nov 22, 2013, 02:54 PM
Gravity sucks.
mrittinger's Avatar
New club,paved runway...do tell!
Nov 22, 2013, 03:19 PM
Designer/Builder
Jim Young's Avatar
Hi Mark,

I joined the Hamburg Flyers RC Club. The field is about 5 minutes from my home, paved runway, solar charging station, permanent canopies, and a nice bunch of guys. Also, we just started flying at the Legacy Center (105,000 sq.ft. dome) which is literally across the street from my house, I don't have to go far to fly.

You need to bring your Stinson out sometime, we fly indoors every Saturday night from 9pm to 11pm.

-Jim
Nov 22, 2013, 06:40 PM
Gravity sucks.
mrittinger's Avatar
Interesting, I might do that!
Nov 22, 2013, 08:51 PM
Designer/Builder
Jim Young's Avatar

Working on the shark fin


A little more progress tonight. Framed up the fin. Pretty typical 1/16" balsa ribs with 1/4" balsa leading and trailing edges. There are a few pieces to make a channel for the fuselage formers to fit in. This should make it easy to get it aligned and support it. The elevator control is all internal. A sullivan flex cable and dubro micro ball links should make it slop free.

Excuse me now while I run around the house making jet noises!

-Jim
Nov 23, 2013, 11:20 AM
Registered User
Steve Merrill's Avatar
This will be a short kit I hope? Any plans for magazine pub?


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