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SEMFF Combat Jets
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
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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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Quote:
Quote:
Ken
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Latest blog entry: MPF M6 Mermaid Scratch and Kit Built
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Quote:
![]() http://www.rcgroups.com/forums/showthread.php?t=1188648 |
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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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Latest blog entry: Quick Stick
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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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Latest blog entry: MPF M6 Mermaid Scratch and Kit Built
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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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Latest blog entry: MPF M6 Mermaid Scratch and Kit Built
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