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Old Jan 01, 2012, 09:01 AM
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Idea
Hover Jet, a Stryker VTOL, flight video

My latest project is coming to completion pretty quickly. The Hover Jet is a cross between a trciopter and an X-Raycer. The X-Raycer is a very good delta with both excellent high speed and low speed capabilities. I think it is a good choice for a VTOL craft.

I'm going to try to incorporate everything I've learned so far about VTOL to make an easy to fly and fun VTOL craft.

I'm also going to push things a little as far as top speed goes. I'm using high kV motors and smaller props. They should have enough thrust for hover, and will really move this thing quickly in forward flight. I left room to swap in lower kV/bigger prop main fans if required or better.

I should be able to try hovering by the end of the day today.
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Old Jan 01, 2012, 04:33 PM
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First hops

I haven't put on the fuselage or the fins yet but I did my first hovering in the basement.

The first couple of hops were with 4.5 x 4.5 EMP props. Plenty of lift to hover, but I think the amps were a little too high and the esc would cut out sporadically.

I switched over to a APC 4.5 x 4.1 and it seems to be OK now, plenty of thrust to hover. The MiniWii flight controller is from the F-35. Hovering is very smooth and easy so far.
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Old Jan 02, 2012, 07:05 PM
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ready for maiden flight

The fuse is on as far as needed for the maiden flight. I'll finish it off after the maiden flight checks out OK.

The weather forecast looks good for a first flight after work on Wednesday.
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Old Jan 03, 2012, 08:07 PM
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I just finished making the removable landing gear. Sticks on with Velcro.

Fired it up and no trouble lifting off with the added fuse, fins and lg but the stuttering problem I had in the beginning with the right motor is back. Propped down to 4.1 x 4.1 but still stuttering bad and the motor is getting hot. I think the stuttering might be due to a short in the motor and the esc is shutting off on high current. The left motor is fine and does not get hot at all.

I think the right side motor is on it's way out (dying). Decision time. I have a 3000kV HXT motor on my speed pbf that I could swap in or I could swap in two 1500 kV motors.

The forecast is looking excellent for tomorrow afternoon so one way or another I want to get some test flying in.
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Last edited by leadfeather; Jan 04, 2012 at 01:21 PM.
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Old Jan 04, 2012, 08:23 PM
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First try

We had an amazing evening for test flying, Fairly warm for this time of year and almost no wind.

I had swapped in the 1500 kV motors for the 3000 kVs. During testing in the basement all 3 of the 25 amp esc's died one by one. I think the stuttering of the 3000 kV motor previously reported was due to the esc and not the motor. I replaced the 25 amp esc's with the 12 amp Mystery esc's I had used on the F-35.

Went out to the flying site for the first forward flight test. During the take off run I noticed it was pulling to the left a little. I should have stopped and trimmed the motors to pull evenly but I was in a big hurry and wasn't thinking. Rotation and lift off was exactly as expected, cg seemed very good; but immediately it started to roll left. It happened to quick and rolled over and crashed. It wasn't too bad but there was a little damage I couldn't fix at the field and not enough day light to fix and go back to the field.

All fixed now. Will do a better job equalizing thrust before take off next time. Tomorrow should be good enough weather for another try.
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Old Jan 05, 2012, 05:11 PM
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but I was in a big hurry and wasn't thinking

Boy... do I know that saying all to well .... hope all goes well in the next test
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Old Jan 07, 2012, 11:00 AM
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The next test couple of tests didn't go well. But this AM I finally got a really good flight. In forward flight there is no gyro input at all.

I had two problems to overcome that were mutually problematic. The left motor just doesn't pull nearly as hard as the right and the fins were too small. I put on larger fins and adjusted the motors with tonnnnns of sub trim to get the motors pulling evenly.

With these adjustments the flying was really good. The wind was blowing about 10 mph. Top speed was just OK. The 1500kV Blue Wonder motors with an 8x4 prop have good thrust but are not great for tops speed.

I had scaled the design up a little from the original X-Raycer to make sure it was floaty for landings. The idea was to build a VTOL craft that was very easy to fly plus has really good speed capability.

The flying characteristic "on the wing" are better than my tandem Hover EZ. I'm going to stick with this delta configuration and see if I can better meet my goal of easy to fly yet fast.
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Old Jan 07, 2012, 11:01 AM
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***duplicate post***
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Old Jan 08, 2012, 08:27 AM
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I'm thinking about re-making the airframe. This one (26" span) is nice and floaty but it just got too heavy for what I wanted to accomplish. It is heavy in hover and the low kV motors don't provide much speed.

Here is a non-intuitive finding ( at least non-intuitive to me). I've done testing on the same Blue Wonder motor but at different kV's. As expected the lower kV motors were the most efficient in terms of thrust/watts, but they also produced the lowest maximum thrust. As kV increases; efficiency decreases ( a lot to do with smaller props); but (surprisingly) max thrust increases ... along with the risk of burning the motor out (not surprisingly).

I have a pusher F-16 with a rewound motor of about 2100 kV. It is a very good combination of thrust and speed and efficiency. I prefer to use "off the shelf" motors, but I might rewind a couple similar to the 2100kV specifically for the HoverJet.
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Old Jan 08, 2012, 09:31 AM
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Hi lead,

I'm using this calculator for my Tri/Quad/Vtol design (thread in multirotor on rcgroup too)

http://www.ecalc.ch/xcoptercalc_e.htm?ecalc

It could give a global idea about your motor/prop/frame config.
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Old Jan 08, 2012, 07:20 PM
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Originally Posted by leadfeather View Post
I'm thinking about re-making the airframe. This one (26" span) is nice and floaty but it just got too heavy for what I wanted to accomplish...
Having similar problems. Fast FF and hovering don't seam to like each other on these things.
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Old Jan 08, 2012, 07:59 PM
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Having similar problems. Fast FF and hovering don't seam to like each other on these things.
I think that is that state of the art right now...finding the sweet spots that allow good hovering and good forward flight.

For the Hover Jet, I'm gong to make a new, somewhat smaller, lighter airframe, and use special wound motors for good thrust and speed and a lighter higher C battery. I think this will get me reasonable hovering and very good flying speed I want. I'm guessing this will take a couple of weeks by the time I get new esc's in.
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Old Jan 09, 2012, 02:12 PM
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I think that moving the fins outboard in the front prop wake would allow to use the smaller fins of the conventional setup too
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Old Jan 10, 2012, 07:35 AM
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I started the new , lighter airframe last night.

There is a TV show called "The Bachelor". My wife watches it, I get build time. 2 hour show.

The elevons are pinned slightly up and a temporary fin is added for the glide test.
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Last edited by leadfeather; Jan 10, 2012 at 07:49 AM.
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Old Jan 17, 2012, 05:28 AM
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I rewound a couple of blue wonder motors last night. Two slightly different winds. One is about 2150 kV ( 8 turns, 23 ga, Y) 1810 kV, and the other; more difficult (9 turns, 23 ga, Y).

I'm planning on testing both motors tonight on the test stand and compare thrust vs power consumption. I'm expecting an actual required operating point of between 200 and 300 grams of thrust in hover for each motor for the Hover Jet (and F-35, Flying Monkey, Hover EZ) so I'll be focusing the testing in this general range.
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Last edited by leadfeather; Jan 17, 2012 at 10:30 PM.
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