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Archive for August, 2017
Posted by burkefj | Aug 29, 2017 @ 02:25 PM | 5,044 Views
Here are a pair that I did in parallel, both using the 3" tubing I had and depron surfaces. I tried to style the wing and tail like a Mig 15 shape with a little stub T tail but use elevons for control for simplicity. The rocket glider came out at 10.75 oz rtf with a 24mm E-6 motor. The pusher came out at just over 14 oz rtf with a grayson microjet V-3 and apc 6x4 prop and venom 800mah 3s pack with grayson esc. The grayson esc is heavy and overkill at 1.125 oz and 30 amps but it was super cheap. I flew the rocket glider first to determine max rearward CG.

specs: 28" wingspan, 23" length, 3" diameter.

For the pusher version, I had to make a few modifications compared to the rocket glider. I had to move the motor mount from the center to the bottom of the tube so that the prop would clear the tail. I added a keel which along with skids helps give a bit of clearance for the motor/prop when landing, and gives a nice handhold for launching. Since the battery/electric motor are heavier than the rocket motor and 1s battery, I taped the wing to the top of the fuse before mounting it to allow me to place the required CG right where the natural balance point of the model was, and then cut the wing slot. This location meant the wing had to be about 1.5" further forward than on the rocket glider version. The actual model required 1/4 oz of tail weight for perfect trim.
I've since moved the receiver and esc back so that I don't need any tail...Continue Reading
Posted by burkefj | Aug 29, 2017 @ 02:04 PM | 4,904 Views
In my recent SPEV(spare parts eliminationv vehicle) mode, I have some more 3" psII tubes that are 21.5" long, I'm thinking of doing a mig 19 using one....wing won't be very big so may glide like a stone. A quick mass model I did playing with wing sweep to minimize required nose weight with components placed looks like a rtf weight of 10.5 oz and a wing area of 108 sq inches....
I'm going to use a fully movable elevator which means I'll have to mount the motor higher in the tube so that the pivot rod won't interfere with the motor mount. That should compensate for the assymetric drag of the vertical stab and maybe avoid any boost trim.

Did the wing drawing and frameup this morning, just about everything that could go wrong during building did, just a string of stupidity...Fortunately nothing that ruined the model, just my attitude.....

I played with the wing sweep and tail surfaces till I got something as large and swept as possible while still looking like a mig 19. I mid mounted the horiz stab for simplicity which meant I had to put the motor tube up above the carbon pivot rod. In fact this was helpful to offset the vertical stab drag by having the thrust line above the wing, at least that was my thought.

I inserted the motor mount backwards, realizing it just before the CA set, pulled it out and tried to clean up and redo it. Made the canopy from laminated foam and decided it was taking too long to shape by hand so used the belt sander and it grabbed...Continue Reading
Posted by burkefj | Aug 15, 2017 @ 01:03 PM | 5,408 Views
I was trying to find a use for some 3" pro series tubing I had that was pre-cut to 21.5" long, I decided I wanted to try to do something similar to the Mig 21i Analog, which was a testbed for the TU-144 supersonic aircraft wing. I was limited to how much wing I could use by both the length of the tube and the spare depron I had left in large enough pieces. I made a nose insert using a paper cone soaked in CA glued to a .03 styrene disk with a shoulder made from some strips of body tube reduced in diameter to fit the inside.

Wingspan is 20", single 3mm carbon spar wtih elevon controls. Back edge of the wing has a cutout for the motor tube, and the vertical fin goes through the tube and glues to the top of the motor tube to help align it in place. Exposed wing area is approx 1.29 sq foot, so about 7.75 oz/sq foot wing loading compared to 5.5-6 for my kits.

Rail buttons are offset to the side so they don't get damaged by landing and I put some skids on the bottom of the tube. Did some quick indoor glide tests which gave me a conservative starting point for launch. Came out at 10 oz rtf with E-6 motor and battery and 3/4 oz of nose weight.

I did six test flights this afternoon, nice straight boost, glide was not bad, not as good as my kit planes since the wing is about 3/4 of the area of my kits and the nose is fairly draggy. It was fairly windy but did some nice near vertical touchdowns in a headwind.

I went home and added a cockpit/spine tunnel with...Continue Reading
Posted by burkefj | Aug 04, 2017 @ 06:48 PM | 4,985 Views
I've been having a lot of fun flying these models, built with 6mm depron for surfaces, I built three with hand rolled double thickness 2mm depron tubes and one that uses a lightweight cardboard tube. The cardboard tube adds an extra 3/4 ounce but allowed a much straighter/rounder fuse. The tube is completely open except for the vertical fin tab, and the thrustline is about 1/2" above the top of the wing but parallel with the wing. The horzontal stab is parallel with the wing but just for looks.

The receiver and esc are just velcrod to the bottom inside of the tube near the front, the battery velcro's right at the front bottom of the inside of the tube. Air just flows straight through, wiring is taped down so it doesn't flop around. No nose weight was required.

I'm running these with grayson microjet V3 motors with 18 amp tbird esc with 800mah 3s eflite 35c batteries and apc 6x4e prop for 4 minutes of runtime. They fly great in high wind, will do high alpha slow flight, and are pretty neutral with a fairly axial roll. I re-worked the one I did in US markings to a pseudo german winter eastern front camo pattern, along with a Navy version in pax river test pilot school colors, and a huckebein camo version and a russian mig style version. Easy to hand launch with the keel and are just a lot of fun. I find myself flying these more and more. 21.5" long, 32" wingspan, 12.5-13.25 oz rtf with just two servo elevon control. They have a generic enough look to look good in a variety of schemes.

I used to do kits of these set up as rocket gliders, however I find myself now flying them just as pushers since they are so much fun.

Dynasoar rocketry Mach 2 kit flying with electric motor adapter (4 min 23 sec)

Dynasoar rocketry Mach 2 kit flying with electric motor adapter (4 min 28 sec)