Mustang Fever

My Feedback: (2)

Yeah, I guess I went through all the same considerations. Based on how it behaved during the first attempts, off grass, I had three problems: the nose was too light, the wheels were too small, and the track was too narrow. (It kept wanting to tip over onto a wingtip.)

The contact point on the main tires is about where it was the first time, fore and aft, but the track is much wider, the wheels are much bigger, and there's a lot more weight on the nosewheel simply by raising the tail up even with the nose. (When the nose is high, that engine gets further and further behind the CG, and really takes a lot of pressure off the nosewheel.) I think, once it's fueled, that there won't be any problem rotating as long as I let it get plenty of speed up. That's kinda the secret with "jet" designs anyway, as there's a real temptation to rotate early and lift off before either sufficient flying speed or control speed is reached.

Can't do anything but try it, anyway. No idea when, as the weather here is definitely winter. Snow last night. 75 mph winds knocking power lines down all over the last few days. Northern Michigan s####s. Once the wife retires, we're gonna spend more time in Arizona than she ever imagined.

Strykaas

Hi Bob ! Any recent attempt over there ?

I am now deciding on the powerplant for mine. I hesitate between two engines :

Webra .55 : http://www.webra-austria.at/motor.ph...der=AERO〈=EN
Webra .61 : http://www.webra-austria.at/motor.ph...der=AERO〈=EN

The second one is 445g vs. 360g for the .55. What do you guys think ? Is it a tail heavy bird so that any light engine would be recommended ?
Bob, could you please remind me how heavy yours turned out ? And how heavy is your engine btw ?
thx

Strykaas

MMhh I've checked myself, TH.46 is given for 475g 16.9 oz with muffler. Previously posted Webra weights were without muffler, so I think the .61 may be OK, along with Peter considerations about using a Rossi.

Mustang Fever

My Feedback: (2)

Strykaas:

The lake is frozen over, so there won't be any ROW attempts anytime soon. However, there's a big soccer field near here that gets pretty deep in snow. If we get a couple of sunny days in a row with temps above freezing, the snow will hard pack enough to support airplanes, then I might have a shot at an ROS test flight. The only thing that bothers me about that is that on a sunny day, it's really difficult to judge how high the bird is above the snow on approach to landing. (I fly hand-launched electrics there all winter, and that's the only real problem I have. I try to just set up a glide for the center of the field and then start holding it off as soon as I see snow. Usually works.)

Mine came out about 7 pounds with the Tower 46 and a 1600 mAh NiMh battery, including the landing gear. I mounted all four servos up front in the recommended location, and even with the heavy engine, I ended up putting the battery only about 2" forward of the CG to get proper balance. The bird has nice moments and balances easily.

I think I'm going to dispense with the landing gear altogether and keep this strictly a seabird. That humungous wing is just too easily blown over in a crosswind when it's above ground level.

I'll keep you posted. I really think she'll do great now that the bad servo is out of there and everything is working correctly.

Mustang Fever

My Feedback: (2)

Changed my mind again. Just can't let this bird sit all winter without flying it.

You can see in the pic that I shortened the landing gear considerably, put back in some positive incidence, and got rid of the scale, dual wheel setup in front. Being so much closer to the ground should help with the tipping over.

She's going to San Jose, California with us for Christmas, along with my GP Mustang, and will get test flown somewhere around the 20th of December.

Strykaas

Good I wish you the best of luck [sm=cool.gif]. Can you imagine how you'll get bored if everything goes fine and you end up stuck for a long winter without being able to fly it in Cadillac !!

gl2657

I have been reading this thread for a while, I just had to build an Arrow, I stole the colour scheme from another Arrow I saw on this forum (because I liked it). My Arrow hasnt flown yet (Been to windy) but I have had it on the water,
looking forward to getting it into the air. It has an Irvine .46 and an all up weight of 5.5lbs

Mustang Fever

My Feedback: (2)

Greg:

Pretty bird.

I only tried one water TO with mine before the weather got bad here, and a defective servo caused it to flip over. I thought the water handling was great, though. Very responsive to the rudder, with a small turning circle. Were those your impressions?

gl2657

Bob

That is what I found as well, Very nice and responsive on the water, in fact a had to tone down the rudder. Hopefully I'll get to fly it this comming weekend.

gl2657

Well I finally flew my arrow. Take off was smooth and uneventfull lifted off nicely. At full throttle it was almost uncontrolable in pitch. Half power was manageble. I am going to recheck the C of G as Im sure I have it wrong. The elevators are brutal...Otherwise it flew on rails and looks great in the air

PeterC

Sounds to me as though you have it a bit too tail heavy. Always err on the side of nose heavy to be safe and then you can take it out bit by bit. Are your elevator throws as per the instructions?
LOL and a Merry Christmas to all.
Peter

gl2657

I'll try more weight in the nose, luckily it doesn't need much to make a difference, The elevator throws are o/k. Should be able to have another go over Xmas..

Strykaas

Congrats for this maiden [sm=thumbup.gif], and good in flight shot [8D]
Moving the cg a bit forward will surely get it more manageable

Mustang Fever

My Feedback: (2)

Greg:

I found that locating the CG was easiest by measuring forward from the trailing edge of the elevons as indicated on the plans. The center of the allowable range is around 17.5". That's what I used when I balanced mine. I put some tape on top of the wing panels at that point, and balanced it upside down using a GP CG machine.

Lord willing and the creek don't rise, she flies tomorrow. The Santa Clara County model airport is the best field I've found to date. I'm joining the Tomcats Saturday so I can fly here whenever we are visiting my son and his family in San Jose.

Did you find that your bird pitched nose down at full throttle, or did the elevator function just get too touchy? Also, if the elevator was touchy, did the bird try to turn left on you? Every one I've crashed that was tail heavy wanted to turn left under any kind of power, but I don't know if that would apply to the Arrow, given the aft/high engine location.

Your bird sure looks good in the air.

gl2657

Bob

Thats exactly what I am going to do to get the correct c of g. Thanks
It did not seem to pitch much with power but the more power the worse she handled.in pitch. I am positive its a Cof G problem. Another couple of days and I should have it sorted.

I'll be interested in how yours goes, keep us posted.

I have spent a bit of time in San Jose, nice place. enjoy your holidays

Mustang Fever

My Feedback: (2)

Well, guys, I've had enough. After three attempts with this thing, I'm going to gut it and throw it in the dumpster so I don't have to take up space in my car hauling it back to Michigan.

It rolled straight as an arrow down the runway today, had plenty of speed, and lifted off by itself. As soon as the nose came up, it made a violent turn to the left and crashed into the fence. I haven't a clue as to why.

Gonna get me a Seamaster and put a Saito 56 on it.

gl2657

Bob...

Im sorry to hear that...Mine although a bit twitchy was fine laterally..I wonder what happened????

Mustang Fever

My Feedback: (2)

Greg:

I wish I knew, but every attempt I've made with it, it's acted squirrelly. I'm afraid of it now and I don't want to mess with it anymore. If it hadn't been for the safety fence at the field, the dang thing would have gone right into the club house.

Funny, the DIY channel ran a segment on RC seaplanes tonite, and one of the birds was a Sea Master. Very nice flier, but I'm getting put off by vague references on the show and in the forums about the pitch effects of a high mounted engine. It was funny watching the Sea Master and the Lanier 40 Mariner fly. The Mariner is such a pig by comparison. I mean, it takesoff and lands ok, but in the air it kind of mushes around, whereas the Sea Master is fast and nimble.

So......I ordered the plans for the RCM Sea Twin. The engines are mounted on the wing, so the only real problem will be the props throwing some water now and then, but I've had that a lot on my conventional high and low wing birds with floats, and it wasn't a real problem. Should fly real nice with a pair of Saito 72s.

I'm really desperate for a nice flying seaplane with a decent endurance so I can have some FUN! I really liked my little Heinkel 31 with the Magnum 15, but I couldn't fit anything bigger than a 2 oz tank in it, and it's no fun flying it when I'm constantly concerned about running out of gas. Then, last week, it fell off the hangar and busted the tail all to pieces, so I'm without a seaplane of any type, now.

A big part of this hobby involves luck, don't you think?

Merry Christmas

Strykaas

Hello Bob

I feel really sorry for what happened to you. And I see no real reason why it behaved that bad... maybe we will never know.
When you say 'when the nose came up' (without pilot input if I got it right), how much pitch did it get ? It looks like a stall to me...
Merry Christmas to you and yes luck is involved...

Mustang Fever

My Feedback: (2)

It was weird. It didn't come up very far at all, lifted off in almost a level attitude, and never got more than six inches off the ground.

Mustang Fever

My Feedback: (2)

Strykaas and Greg:

I've had a little time to think about the failure, now, and was able to talk with a very knowledgeable guy from Tomcats in Santa Clara County. I think I'll repair the very minor damage to the right wing (where the fence cords cut into the LE about 4") and try again.

I think I have a tiny bit of right thrust on the engine, which translates to left thrust with the aft-of-CG prop location. All three TO attempts have involved a left turn tendency, which was much more pronounced yesterday on the paved runway. (It wasn't obvious on grass or water, and I didn't pick up on it until I had a chance to remember.)

I think I'll put some thin washers under the right side of the engine mount. I'll keep adding them until I can measure, with the incidence meter, either 0-0 or a touch left.

Thanks to both of you for your encouragement. I really hate to give up on this one, as I KNOW they fly well.

Merry Christmas

Strykaas

Too bad I'm so busy now I can't work on my arrow... I'm with you Bob, keep the faith !

0-0 is mentioned on the plan, I think putting sidethrust is a bit risky... I would definitely go for a 0 sidethrust.

I hate to ask but, is your wing warp free ? when you say "left turn tendency", you mean left roll ?
Left yaw tendency shall be noticeable on the ground before leaving the ground... is any right rudder input required to hold constant track ?

I would also set the cg a bit more forward, this would help if your latest attempt was a snap roll ...

Mustang Fever

My Feedback: (2)

Strykaas:

The wing is very true.

No left roll tendency, but a violent yaw about the CG to the left.

No rudder input at all on the TO roll, she went straight down the runway. (Remember it's a trike gear)

Any ideas based on that?

Strykaas

Yes, I know this is a trike, but in some cases, the front wheel loses efficiency when speed goes up (less weight on it)... So it's indeed weird that left yaw occured only after liftoff.
I assume wind was straight down the runway there.
I also assume rudder fin is properly aligned (something you must have checked again & again from the first TO).
I also assume rudder was properly trimmed to neutral.
I also assume left yaw was so violent that nothing could be done with the sticks to cope with it quickly enough.
I also assume rudder has no play (play can become horrible when engine is at full throttle) => do you use a powerful enough rudder servo ? What about a slopy servo-rudder connection ?

So for the fourth TO attempt, here are what would be my plans :
1- engine at 0-0
2- increase rudder throws with exponential
3- setup a bit of rudder trim to the right
4- mentally be prepared to counteract the "violent" yaw from take off.
5- when airborne, trim this bird to get done with all these strange habits !

Mustang Fever

My Feedback: (2)

Sounds like a plan to me.

The only item on your list that may have been a factor was a slight crosswind. I don't know if that caused it or not, but in any event it happened so fast I never had time to move the rudder stick.