Skribnod

I have a question for the experienced modellers, I recently built a spacewalker II arf from seagull models. I equiped it with a magnum xl40 which barely got it off the ground. Wingspan is 60" fly wieght 6lbs ,i recently installed a saito 72 and on maiden flight it came off the runway at about 20 ft and torque rolled to the left. I was amazed at the short distance that it hopped off the ground at 1/3 throtttle. Could it have been that the new saito has too much torque? Or was it that the plane did not have enough forward movement to keep flying? I figure it was pilot error and did check all controlls before takeoff. I think maybe I may have fed in too much up elevator because of the fact of the magnum 40 that was installed prior. A friend of mine suggested that the new saito may have too much power but the airplane does call for a 52 two stroke engine. Thanks

hooleydog

My Feedback: (24)

No such thing as overpowered. I had a 52 inch span plane, and the recommended size was a 30, So it had trouble taking off on grass (had to be on full throttle, plus a long run), so I put in a 45 and wow it took off with less throttle, and in a lot shorter distance too (it flew great). My Lt-40 has got a 70 span, so I fitted a 61 (not the recommended 46). Since your plane fly's great with less throttle, just use less throttle on takeoff (since your engine is bigger), So don't worry (though if you want, you could fit a 61 size engine)

ballgunner

My Feedback: (1)

You can overpower an airplane and upset the design parameters even if you get the CG right. A lot depends on where you fly and what the runway conditions are. I like a .60 in the Senior Kadet but then I fly at 5000' ASL where density altitude and temperature begin to take over. I have always failed to understand why manufacturers list a 78" model like the Senior Kadet as requiring power from a .25 to a .40. At sea level, 2995 " of mercury and 65 deg. F it might work. That's a standard atmosphere and all full scale designers state the useful load, range and gross weight based on that figure. They also supply a graph in the pilot's handbook to compensate for current conditions at your site. With RC models you have to figure it out for yourself. Just remember, on a hot day at high altitude the largest size recommended by the manufacturer plus one size up will do the trick. Putting a 454 V8 in a cigar box will make it go real fast but it's not a good practice.

hooleydog

My Feedback: (24)

Well, I'll take back what I said bout something. You can overpower a plane if you go way oversize but my case I have not. (Maybe you should have gone up to a 51), and cos my plane is bigger, I went up 2 sizes, plus the airframe is strong too (I did some changes), it can take a 61. I found some websites showing fliers flying a LT-40 with an 61, and having no problems at all, even using the same engine mount and undercarridge (Which myself did change).

00000000000000

I was impressed with the Ultra Stick 40 I got recommending a .58 2-stroke or a .72 4-stroke right on the ouside of the box. Their manual even mentions the Saito .72 Nice to see a manufacturer recommending an engine you can have fun with. I'll probably try an Irvine .52 in mine. - Joe

Skribnod

Thanks for the info all. I am going to try the flight again this weekend but with little or no elevator at takeoff. I think i need to get more ground speed up. I fly from a grass field wich is kinda bumpy but is 400 feet long. I guess if i get enough speed up it will probably not roll over. I think my problem was pilot error and not the airplanes fault.

cappio777

My Feedback: (2)

After all has anyone seen the GE commercial where they put a turbofan engine on top of the Wright flyer?

It flew!

vinnie

My Feedback: (1)

Skribnod, I believe you have correctly diagnosed your own problem. Allow a bit more ground-speed before take-off. The .72 should be fine for your plane.

MinnFlyer

My Feedback: (4)

Ditto to everything Vinny said.

There's no way that thing is overpowered. You just got off the ground before you had flying speed.

rc-sport

My Feedback: (12)

What you witnessed is called the tip stall. It has caused the death of many planes. Give it throttle, let the tail rise as it builds up speed and then gently pull back on the elevator. I hate to a graceful plane like the Spacewalker leave the ground at a 45, it should be a gentle climb.

3DFanatic

My Feedback: (5)

"overpower" is a term that the people who fly in circles came up with. There is really no such thing as "overpowering"

rc-sport

My Feedback: (12)

You can't over power but you can Over weight a plane with to much engine.

cappio777

My Feedback: (2)

I saw a guy put an OS 46 VX DF on a goldberg skylark, for about a week or so it was a fiery little demon. But the day came when the wing folded and it became a really fast missile.

Hmm, nah, you cant overpower an airplane....

DBCherry

My Feedback: (4)

Gotta agree Cappio. I've seen it too.

skribnod,
Did you use rudder during that take off roll? It could have been part of your problem.
Dennis-

3DFanatic

My Feedback: (5)

Cap - it wasn't overpowered, it was understructured.

cappio777

My Feedback: (2)

I like that statement!......now, isnt that relativistic as how you want to look at it?

3DFanatic

My Feedback: (5)

I don't think so. If there's no such thing as overpowering, and the wings came off from going too fast. There must not have been enough structure. Simple logic [8D]

cappio777

My Feedback: (2)

If there is no such thing as overstructuring and the wings came off then it must have been overpowered!

Tired Old Man

My Feedback: (1)

The Saito 72 should be a perfect match for your plane. You will find that you may want to allow a longer takeoff run with the heavier engine to permit gaining flight speed. What you encountered was a departure stall caused by insufficient flight speed at the time of takeoff.

In the future, should your plane leave the ground prior to gaining what you believe to be adaquate flight speed, keep the plane low and level, within 1/2 wingspan of the ground, and gain more airspeed. This will keep you in what is known as "ground effect". This is a condition where there is a "cushion" of air under the wing caused by the compression of the air by the lifting wing.

Skribnod

Well guys I thought I had it all figured out but..... I took the spacewalker back up again today, now keep in mind the box it came in calls for a 40-52 2stroke or a 50-72 4stroke , the assembly manual calls for a 46 2 stroke or a 53 4 stroke, and the website calls for a 40-48 2 stroke. I checked all controll surfaces and also did a range check after I tuned the motor (was a little humid today). My buddy was running the camcorder as usuall and the girlfriend was at home......because we cant let them know about all the planes now can we? LOL. I proceeded to the far end of the grass runway (which is 400 feet long ) and did 3 taxi runs. After going approximately 20 feet the airplane wanted to lift the tail and it wanted to leave the ground. I then repositioned the airplane at the beginning of the runway and started to increase the throttle slowly to get it up on the main gear. It increased speed for about 100 feet running on the main gear . When it hit about the 150 foot of runway mark the airplane lifted off at a 25-30 degree climb out. At this time I was at 1/2 throttle and going straight out. When the airplane was about 15-20 feet off the ground it started torqueing to the left and i corrected with right aileron. It then straightend level but as soon as I left up on the right aileron imput it rolled hard to the left and at that point there was no saving it. It rolled almost completely upside down before hitting the dirt. The flying wieght of the airplane is 6-7lbs and has a 61inch wingspan. Could the Saito 72 have caused the torque effect swinging a 13x8 prop? the airplane flew slow with the Magnum 40xl 2stroke engine but was just underpowered and needed all the runway to take off. I later found out my buddy looked up from the camcorder and didnt get the full roll, just a little of the climb out and that was all. I wish i would have the video to show but i do have pictures of the airplane after the crash. My question is why will this plane jump off the runway at 25 feet but wont fly after getting enough groundspeed? Oh yeah I almost forgot to mention the broken motor mount we found right after the crash. I hope the engines ok because it didnt break the plastic nosecone or the prop all the way off.

Skribnod

I forgot to mention I balanced the airplane with a GP planes balancer and got it to balance at a 20 degree angle nose down since i like to keep it a little nose heavy for stability. This is a picture of the front of the airplane with the prop and nose cone still in one piece. I added some epoxy to all joints in the fuse to strengthen it up because of the hot glue they use just doesnt seems strong enough.

cappio777

My Feedback: (2)

Take off at 1/2 throttle?

[sm=surprised.gif]

3DFanatic

My Feedback: (5)

There's no such thing as overpowering OR overstructuring. There's just a point when the weight of the structure with the materials at hand becomes rediculously impractical!

cappio777

My Feedback: (2)

I would have used a 13x6 on that saito but the only difference would have been more rpms and better acceleration during take off. What I dont understand is why you kept the engine at 1/2 throttle on take off? Initial climb out needs all the power you could give it and normally as you accelerate down the runway you should be already at full throttle before you pull back on the stick. Seems to me that one wing dipped and the airplane was at the merge of a stall when you added aileron so it aggravated the situation and without enough power to fight the amount of drag it dropped a wing. Sorry for the crash, looked like a gorgeous bird. []

Skribnod

I ordered a new airplane tonight , at $119 its not a bad price . I'm not upset about the crash only the fact that I dont understand why it happend. I would have gone full throttle going down the runway but it was traveling at quite a good speed to begin with. It was moving faster than the 40 would move it but yet it winged over. I am going to install a super tigre 51 on the new one this week and see what that one does. Im just a little leary of putting the 72 back on the new one since it torqued over 2 times in a row with the second crash being the killer of the 2. I dont believe takeoff speed is a issue here but more of a torque issue once the airplane gains altitude. I have other planes in my hanger that have no issues and no flight problems running 4 strokes and 2 strokes alike. Everything from the rascal 110" to the Agwagon and Giant stuka. I even overpowered my T34 mentor and it never rolls like this one. Im trying to get some info because I have the 1/4 scale GP spacewalker and I dont want to make this mistake with the bigger more expensive one.