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Old Sep 28, 2012, 05:56 PM
Slipping the Surly Bonds
dz1sfb's Avatar
Attica, MI
Joined Dec 2006
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Yippee!
SEMFF Combat Jets with plans and video

The time has come to start this thread. There has been some interest in creating combat jets in the same vein as the series of WWII fighters. This will be somewhat of a learning curve as the process for designing simple, great flying, and good looking models is developed.

Design Criteria:
1. Wing area - 150 sq. in. This is calculated by extending the leading and trailing edges to the centerline. The area of one wing panel then would equal 75 sq. in. Keeping to this size is more likely to allow the design to fit on one sheet of MPF (24" x 48" x 6mm). Tail surfaces will be enlarged 10% from scale for stability purposes. This has served well throughout the WWII series.

Typically jets are longer than their wingspan, so I may have to revise the wing area down to allow the use of one sheet.

2. Flight Controls - Pimarily aileron/elevator designs. However some will include rudder/flaperon options. In this case there will be dual aileron servos and a rudder servo. Some setups may be four channel with a single aileron servo, or even as simple as tailerons or elevons.

3. Construction Style - This will vary between VLF (vertically laminated fuselage), and PLF (perpendicularliy laminated fuselage), and or a mix of the two.

4. Power System - I want to go with the 1700 Kv 24g motor again, but this time it will be set up for 3s. We found on the WWII models that the motor/esc/prop combo that they handled 3s just fine. Since these are models of jets, I want to see a more jet like performance. Batteries in the 1000 mAh + 200 mAh. Sticking with the 7x6 prop as well. These may be tractor, prop in slot, or pusher setups.

5. Servos - Sticking with the low cost 9 or 10g servos. You will be able to opt in 5g servos easily. The opening is close enough to hold the smaller ones as well.

The WWII thread sat somewhat idle for a year until I was able to turn my attention to the idea. Hopefully this will not be the case and we will have several models to build this winter and be ready for the spring or even some indoor venues.

I already have some projects on the burner. Feel free to post 3 views of projects you would like to see.

Ken

Plans list:

DH100 Vampire

F-22 Raptor

Su-27 Flanker

MiG 29 Fulcrum

F-15 Eagle
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Last edited by dz1sfb; Oct 10, 2014 at 10:45 AM. Reason: Added links to plans in thread
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Old Sep 28, 2012, 06:07 PM
Slipping the Surly Bonds
dz1sfb's Avatar
Attica, MI
Joined Dec 2006
10,699 Posts
Hawker Hunter

Here is the starter. It is a tractor mounted motor with that is already motion. I should be cutting the prototype this weekend. Plans will eventually be placed in this post.

I am fond of the T7 varient, but this is the Mk9 (I believe).

Hawker Hunter

Wingspan - 21.6"
Foam weight - 72.6g

Have a great weekend,
Ken

Edit 03-OCT-2012: Maiden flight report
1. I put three batteries through this model today. Adjusting the battery aft until finding what seems like the optimum CG, which was at the rear of the aileron servo case (not the mounting tab). I will be repositioning the elevator and rudder servos aft so that the battery can sit on the CG.
2.Pitch response was acceptable once the CG was found. May add some TE to the elevators.
3. Roll response was super sensitive. I had to put the pushrod in the 3rd hole from the end on the servo horn to tone it down, and rate was set to 50% on the radio with 60% expo. Still a bit twitchy. Truncating the ailerons and fixing the tips should slow this down to a more docile rate and allow full use of servo travel. I will try this once the CG has been tuned for the battery at the CG.
4. The rudder was mildly effective. A little more throw and it will hold knife edge flight. May add some TE to this surface as well.
5. Flaperons were causing serious nose down pitching. This effect was so pronounced that at one point I reset up the radio for elevons and flew it without the elevator. It not the most responsive this way, but the throws were way down. Then I plugged the elevator servo into the aux1 channel on the rx and mixed the the elevator to aux1. Then the pitch response was super sensitive. I used +100 so there was full deflection. This may have merit if it is tuned down.
6. Power system performance was more than adequate with unlimited vertical on 3s.

Summary
Some tuning and adjustments to the design will make this more fun to fly. Right now its kind of a handful.

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Last edited by dz1sfb; Oct 03, 2012 at 11:11 PM. Reason: added pictures
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Old Sep 28, 2012, 06:07 PM
wrong descision, wrong time
United States, WA, Maple Valley
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Are these going to be setup with propeller in front? It would be hard to cut streamers any other way. Of course, these could be made to be full contact combat planes ...
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Old Sep 28, 2012, 06:12 PM
Slipping the Surly Bonds
dz1sfb's Avatar
Attica, MI
Joined Dec 2006
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Quote:
Originally Posted by dumb_thumbs View Post
Are these going to be setup with propeller in front? It would be hard to cut streamers any other way. Of course, these could be made to be full contact combat planes ...
Quote:
These may be tractor, prop in slot, or pusher setups.
Going to do what seems best for any given design.

Ken
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Old Sep 28, 2012, 06:18 PM
wrong descision, wrong time
United States, WA, Maple Valley
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One jet that might work well for combat is the Vampire. There are also quite a few other early jets that would work well, like the meteor, f-86 mig-3 etc.

-Heath
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Old Sep 28, 2012, 09:23 PM
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Canada
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I'm thinking that your Avatar Photo would make a Very Good Candidate for a prop driven "jet' ?
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Old Sep 28, 2012, 10:46 PM
Watts is life...
rcjetpilot's Avatar
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Excellent thread.... will be following along, and perhaps I may even add a design as well.
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Old Sep 28, 2012, 11:24 PM
You sabotaged my plane.
eliworm's Avatar
Arizona
Joined Jun 2002
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Quote:
Originally Posted by Bare View Post
I'm thinking that your Avatar Photo would make a Very Good Candidate for a prop driven "jet' ?
It does.

http://www.rcgroups.com/forums/showthread.php?t=1188648
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Old Sep 29, 2012, 12:42 AM
Gone Fly'n
planecrazy1969's Avatar
USA, NV, Las Vegas
Joined Jan 2007
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I'm in Ken...been thinking about designing jets like this for a while...glad to see you got it started...I'll certainly contribute some designs
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Old Sep 29, 2012, 03:57 AM
Allways the hard way!
georgy's Avatar
South Africa, GP, Germiston
Joined Jan 2012
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I think "North-American" designers knew this thread was coming 30 years (edit!) ago when they designed this "dog"...

EDIT: Just checked... it's 62years ago!! 1st flight Dec 1949!

George
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Last edited by georgy; Sep 29, 2012 at 04:05 AM. Reason: History lesson
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Old Sep 29, 2012, 09:09 AM
Winging it >
leadfeather's Avatar
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Good idea Ken.

I think an F-86 and Mig-15 dog fight would be great fun!
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Old Sep 30, 2012, 09:40 AM
Slipping the Surly Bonds
dz1sfb's Avatar
Attica, MI
Joined Dec 2006
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More progress on the Hawker Hunter in post #2. This is turning out to be a great looking bird.

Also want to thank all for the suggestions. There are so many choices out there and your input helps me decide what will interest the broadest spectrum.

Excited,
Ken
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Last edited by dz1sfb; Sep 30, 2012 at 09:54 AM.
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Old Sep 30, 2012, 09:57 AM
Slipping the Surly Bonds
dz1sfb's Avatar
Attica, MI
Joined Dec 2006
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George,
That F-86D is a great candidate for a tractor mount with spinner, while the earlier F-86 and Mig 15 may get a mid mount setup ala Eliworm's BD-5J. It really depends on the fuselage cross section hieght.

Ken :
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Old Sep 30, 2012, 10:28 AM
Allways the hard way!
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South Africa, GP, Germiston
Joined Jan 2012
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Hi Ken,

Donno if you ever saw my Mig-15 slot jet. It Had a very hi Kv motor (mid mount) to allow using a 4x2 apc. Although very heavy, it flew really nice. 1000ma 3cell, 18A esc. Had about 5 to 6min duration. Problem is that this set-up will suit few flyers... sounds like a dentist drill! & it is not really off-the-shelf. I had to convert the mounting set-up & shaft of the motor from heli to pusher-airy set-up.

I don't have nice pics, but in essence the fuse hight covered the prop diameter & i used bamboo scewers as bracing top & bottom to ensure fuse stiffness.

One of these days i wanna build it again. Much lighter & make sure the CG is designed forward. That huge T-Tail weighs a ton

see pics... Like I said before, I'm the last modeler to give you advice but i did learn a few lessons forcing that Mig into the air...

George
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Old Sep 30, 2012, 07:44 PM
Slipping the Surly Bonds
dz1sfb's Avatar
Attica, MI
Joined Dec 2006
10,699 Posts
George,
I appreciate you sharing your experience. Your Mig 15 is similar to what I may try. If you get a chance to check Eliworms thread he posted here. To use a more standard power set up, I would go with a 3 point strategy. and allow the prop to extend through the bottom of the airframe.

I got the Hunter nearly ready to maiden. Right now its a bit on the nose heavy side, and I will likely move the elevator and rudder servos aft a bit to balance it out better. Probably mount them as in the wings. Much cleaner profile that way. Oh well, sometimes you have to do something to see where you should have gone.

I really like the long lean looks of the Hunter. More pics in post #2.

Ken
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