|Jun 28, 2002, 10:04 PM|
18 cell Hawker Typhoon flies!
Back before HobbyHangar changed hands in January 2000, the previous proprietor and I started a project that up-sized my 1/12 scale Typhooon to 1/8 scale size. That's a 61.5" span.
We cut a prototype, and I framed it up. As we used a lot of light ply in the fuselage, it came out far to tail heavy for the FX 46 it was originally supposed to be powered by.
Last year was a wash out for progress on this project, as all of my modelling time went to up-sizing the 1/12 Tempests to be able to carry 10 2400's comfortably.
Well, as you can see in this recent family photo, I finally got the Typhoon done enough to test-fly (it still needs guns,and some other details). It's the big one in the back with a baseball bat for a wing.
Power is MaxCim 13y 3:1, new Superbox, 18 X 2400 NiCd. Robarts mechanical retracts.
My first test flight session was unsuccessful.
The motor would start, rev-up part way, and then coast down. Eventually, it would rev out to full. At 1/2 throttle, the radio jittered at about 15 paces, where 30 was fine with the motor off. Top RPM seemed a bit down. I tried taxi tests, but it would not accelerate past a fast walk. I noted that the rolling resisitance was quite high.
I took, it home a called Max Cim. Tom very quickly got back to me and suggested that my symptoms could be a bad cell. I checked, and, sure enough, one cell was bad. Repalce bad cell - motor/radio problems solved!
For the rolling resistance, I more carefully selected wheels. I went from 2 3/4 Du-bro TL, to treaded Dave Brown 3" foamies. I want to go to the square profile 3" foamies, as they float on grass better, but my LHS does not have them in right now. I also canted the gear legs slightly forward, as the Tiffy had shown a mild tendency to flip. 3" is maximum current wheel wells will allow.
It still would not taxi well on my lawn.
I then did my ultra-scientific static thrust test. I tied a bunch of elastics between the tail wheel and my charging battery. I then gave full throttle and marked the main gear position on my garage floor. Much to my surprize, the APC 12 X 10 glow prop won out on both pitch speed (RPM X pitch) and on static thrust. I really expected the APC 13 X 10 E prop to win on static thrust, even though it revs about 1400 rpm lower. The Zinger 12 x 10 gives just a little less revs and thrust than the APC glow prop.
Thus armed, I then taxied the Typhoon accross my yard.
Back to the field. My wife came, to fly my BP 50 E and help out with the Typhoon flying (not realizing it hadn't flown before...)
On the first attempt it started accelerating well, but flipped when I relased up elevator.
Hold full elevator longer next time. Relax elevator after about 20 mph, allow to build a little more speed, and then gentle back pressure. No correction for torque needed with smallish prop turning 8000 RPM.
About 150 ft of grass was needed, so the run was quite scale.
But the Typhoon is porposing badly. Down with the nose and up with the gear. Immediately, the Typhoon accelerates up to flying speed, smoothens out, and climbs out with authority. Prop wanted to climb airplane, but wing needed to be flying, too!
Elevator is very, very sensitive, as are ailerons. Roll rate is about 450º/second. After about 2 minutes flat out, I am trimmed well enough, and familiar enough with controls to thottle back to half.
Roll rate is still substantial, and elevator too responsive, but there is no pitch oscillations. I am quite familiar with the habits of a Typhoon from my smaller ones, and I recognize this as tail heavy. At high speeds, the only evidence of tail heavy in a Typhoon is a sensitive elvator, and tendancy to climb during the inverted portion of a roll. At low speeds, it gets a bit nasty. The tail plane will stall before the main plane, and the resulting very high angle of attack will blanket the fin with turbulence. The result is a sudden stall with no yaw control. Not really a tip stall, but the same result......
As it was cruising nicely, I had lots of juice (up to 15 minutes at 1/2 throttle, if only 30 seconds of full used), and I wasn't sure that I'd be able to land it without totalling it, I decided to make the most of the flight.
The Typhoon is fairly fast with the wheels up. Even tail heavy and over-travelled, it was quite smooth at speed. There is only prop and airframe noise audible, and it is quite quiet. My wife commented that it had a "heavy" presence in the air. She really liked the whooshing whistling sound made by the air going in the chin-scoop, around the motor controller, and the out under the wing.
It has a very strong climb at speed, and a medium sized loop from level flight at 1/2 throttle showed very little loss of speed and no mush. Rolls were too fast, but slow rolls, with the tail heavy situation, actually climbed a bit with no correction. Strafing runs were smooth, solid and frightening for the ones on the ground. Very Typhoon!
Landing was, shall we say, invigorating.
After about 6 minutes of playing, I throttled back to 1/4, dropped the gear, let the nose drop and brought it around in a large approach. Having planted tail-heavy, wheeled Typhoons before on landing, I kept it up a bit, and didn't throttle back too early. Overshoot....WAY overshoot. Throttle up, raise gear, go around.
Lower approach, drop throttle later, looking good, balloon, go around.
Go around again, never go over 30'. Touch down, too fast, bounce , start go-around. Oh Oh! Stalling, porpoising. Raise gear, do half circuit at low altitude. Legs shaking.
My wife says "go around - you're downwind". I say "I'm shaking too badly".
Downwind landing, nice flare, just shy of 3-point. Suddenly plane stops and flips quickly, but not too hard. Wheel is seen bouncing away.
We get up to plane and realize that there is no damage. The wheel spun off of the hub (Sullivan wheel clips used in place of usual solder until wheel choice final). When the axle caught, it flipped.
This was the scariest, and yet most fun test-flight that I've ever had with one of my Hawkers. It exhibited all sorts of signs of bad set-up, and gave me many firm warnings (at low speeds), but never bit me.
It needed aobut 1/16" down trim, but rudder and aileron were not touched.
I think when I get the C/G forward, the gear forward a bit more to match, and the control settings dialed in, I will really, really enjoy this plane! I will also enjoy flying a Typhoon for 12 minutes, rather than my first e-Tiffy's 2 1/2. I may add another 2 cells in the chin scoop to give just a little more oomph for take-off. Better cells than lead!
BTW, tonight was my wife's first time flying electric. She hates cleaning off airplanes. She thinks she likes electric!
I need to thank Tom Cimato for helping me to very quickly sort out my problems. He knows his product inside-out, and gives support in a very timely fashion.
I also want to thank my friend George for trusting me with HIS MaxCim (and, for that matter, a Typhoon that is pretty much half his, as well). I was hoping George could fly it at Ann Arbour, but he will be away that weekend.
|Jun 29, 2002, 01:04 PM|
Ron, your accounts made me feel like I was there, neat stuff. I'm glad you have the beginnings of a winner in your hangar. A few extra cells because you "need" them for balance is a good thing, your ability to throttle back will really help keep the flight times up!
Very cool pictuire of the fleet. I'm also flat out jelous your wife likes to fly with you!
|Jun 29, 2002, 06:29 PM|
That's a veeery nice fleet! I loved your detailed account. It felt like I was right there with you. I've had some knee shaking test flights too - but when those darn thumbs start shaking too - yeow! My Dad built a ten foot wingspan 1/4 scale Cessna 310 with twin 0.60's. I was the test pilot at age 17 (about 26 ago!).
I'm now starting all over, but in electrics. I don't miss the cleanup of the oil at all!
|Jul 02, 2002, 11:12 AM|
After giving it some thought, and thinking my charger only goes to 18, I'm going to just move a few of my current cells, rather than add more. I just don't want to tie up my charger charging two packs, rather than one big one.
I have enough trouble slowing for landing right now, without adding more weight. If I do another one of these, I don't think that I'll use much "lite" ply.
I hope to get the battery move done this week, and get some good photos by next week. I'm sure that I'll be very comfortable throwing this plane around, as soon as the C/G is right.
|Jul 03, 2002, 08:19 AM|
United States, VA, Arlington
Joined Dec 1996
Good stuff - sounds like you have a show stopper on your hands once you get the beast tamed a little.
A buddy of mine built the Brian Taylor Tempest to about the same size years back. As I recall, it had a 60 up front and the cowl was about lead lined to achieve balance. At least you have the option to line the cowl with ni-cad instead
Good luck with your new warbird - any chance we'll at least see the plan become available ?
|Jul 03, 2002, 12:02 PM|
I don't intend to put out any plan in the near future.
I am not happy with the weight with the construction that I used, and would want to revise it significantly before releasing it (It's one thing to do that to yourself, but quite another to have other guys pay you for your mistake.....).
I have a new fuselage construction technique that I'm prototyping on a 44" Chipmunk, but that project is very delayed. If it works out, I may adapt it to the 1/8 Typhoon. It should be much lighter than the current one, without putting the cost "through the roof".
Before I get to that, I have quite a few projects to finish up, and this is going fairly slowly.
Chris McHugh's Tempest is a Brian Taylor at 61". We're hoping to do some flying together some time.
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