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Servo Question TF F4U Corsair by TF.

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Servo Question TF F4U Corsair by TF.

Old 07-01-2016, 04:45 AM
  #1  
gregoryshock
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Default Servo Question TF F4U Corsair by TF.

Airplane: http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHU80

Due to many issues that I'm not going into on this thread, I think I'm going to just scrap my build. But if you can convince me that it's worth continuing I might....

Before I throw up my hands and quit. I want to explore something here:

One of the problems is the servo set up on the ailerons. TF wanted me to use just one standard servo to power both ailerons. They did this by running nylon push rods out to bell cranks and then to each aileron. I hate nylon push rods because in my experience on my hog biplane by sig they change a lot. Expand and then you loose your trim settings. And not just by a click or two, but sometimes 4 or 5. On the biplane I was riding my trim all the way to the end, and then I had to re adjust it on the airplane, only to change it again in the air. Eventually I was right back where I started (repeat) Finally I replaced the nylon with a metal push rod and the whole problem went away. For that reason when I was building my Corsair I decide to put servos at each aileron.

As I was building the Corsair, there was a lot of online researching, and trial and error going on. My Dad noticed that the weight of the airplane kept going up and and up. This caused my Dad and I many arguments and frustrations. We looked over things online and thought that we could save a little weight by using one of these http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXN676 at each aileron.

Last summer it was finally time to put the finishing touches on the set up. That's when the real problems began. I realized that I didn't know what propeller would fly the plane with the engine I installed. I did lots and lots and lots of research. For about a month I talked with the experts, as well as people in the forums, and got lots of conflicting information. By the end I had to just make a guess and the guess was wrong. The airplane made it up a few feet and wouldn't clime any higher. I had to crash land it into some tall grass.

The Damage wasn't bad.... And yet it was bad enough.... While everything is fixable (meaning I can get it back to the condition it was in before the crash) There are some things in the build of the model that I don't think is worth changing to make right. That's why I'm thinking about throwing the model away.

Right after the crash all of the servos are fine but the micro servo gears stripped out. Did I make a mistake by using those servos at each Aileron? *If it was a mistake, then I think I'm ready to throw the model away. The problem is it doesn't look like I'll be able to fit in standard servos at each aileron. There is also a big question on the weight they might add to the model. (My Dad has argued with me about that)

Total Model Weight before the crash:
About 9 to 10 pounds.

Engine before crash
OS 75.

Current Engine:
OS 91.

Current Weight:
Unknown.

Current Condition of Model.



























Last edited by gregoryshock; 07-01-2016 at 05:29 AM.
Old 07-01-2016, 06:20 AM
  #2  
Hemikiller
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HS-81s are good servos, but due to their "mini" size, cannot withstand abuse or shock like a standard size servo. They should be fine on the ailerons, but I would install the metal gear kits in them if you decide to rebuild. The ARF version of this plane has individual aileron servos. Mine has HS-5485HBs all around.

http://www3.towerhobbies.com/cgi-bin...?&I=LXUW28&P=Z

or for $2 more, upgrade to the HS-82MG.

http://www3.towerhobbies.com/cgi-bin...&I=LXTRE2&P=ML

Looking at your posts, it seems you were running a 14x7 3 blade?

http://www.rcuniverse.com/forum/ques...l#post12080807

From experience, I have never had good luck with 3-blades on 2 stroke engines and the one you chose, IMO, was far too large for the AX75. I tried them a couple times and never went back due to poor thrust and speed.

For your current 91, I would recommend you use a 2-blade prop called out in the manual. Once you learn the airplane and are comfortable with it, you can always test different propellors to see what they'll do for you. Don't overthink it, just use what OS recommends and get 'er back in the air!
Old 07-01-2016, 09:13 AM
  #3  
gregoryshock
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Originally Posted by Hemikiller
HS-81s are good servos, but due to their "mini" size, cannot withstand abuse or shock like a standard size servo. They should be fine on the ailerons, but I would install the metal gear kits in them if you decide to rebuild. The ARF version of this plane has individual aileron servos. Mine has HS-5485HBs all around.

http://www3.towerhobbies.com/cgi-bin...?&I=LXUW28&P=Z

or for $2 more, upgrade to the HS-82MG.

http://www3.towerhobbies.com/cgi-bin...&I=LXTRE2&P=ML
Thank you for the suggestion. I was thinking the same thing. Metal gear if I decide to put the plane back together. I am aware that the ARF uses two standard servos for the Ailerons. That is part of what bothers me. I don't know of any model airplane fitted with micro servos for each aileron like I did.


Originally Posted by Hemikiller
Looking at your posts, it seems you were running a 14x7 3 blade?
Thank you for reading my old posts. But they are old posts. I'm not going to run any 3 bladed propeller this time. And probably never ever again.

Originally Posted by Hemikiller


http://www.rcuniverse.com/forum/ques...l#post12080807

From experience, I have never had good luck with 3-blades on 2 stroke engines and the one you chose, IMO, was far too large for the AX75. I tried them a couple times and never went back due to poor thrust and speed.

For your current 91, I would recommend you use a 2-blade prop called out in the manual. Once you learn the airplane and are comfortable with it, you can always test different propellors to see what they'll do for you. Don't overthink it, just use what OS recommends and get 'er back in the air!
just use what OS recommends and get 'er back in the air!

In the past I had good luck with OS recommendations. But this time I found out that even if I put the maximum size 2 bladed propeller on the OS engine, it won't run at the RPM that Bax (OS support guy) says it needs to run at. *That is one of the contradictions that caused me to take a blind leap of faith. I currently believe that Bax is right and the OS manual is wrong.

For the record lets drop all mentions of 3 or 4 bladed propellers. I just did what seemed right for me at the time... What pulled the plane the best on the ground. 3 bladed moved the plane and the 2 bladed ones I had didn't appear to do the job for me. It was an honest mistake. I will never try to use a 3 or 4 bladed propeller again. Something strange was going on... And I'm not sure that I want to continue talking about it anymore. I upgraded to a bigger engine, hopefully with it's power and a decent 2 bladed propeller it should pull.

Current Issues that still need corrected on the airplane:

Aileron Servos

Landing Gear

Hinge Repair

Monokote

Cowling

Last edited by gregoryshock; 07-01-2016 at 09:25 AM.
Old 07-02-2016, 11:30 AM
  #4  
DavidAgar
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The Top Flite Gold Edition kits tend to build heavy. I am thinking that yours weighting at 9 t0 10 pounds is just about correct, maybe even a little on the lite side. As far as servo's, I used Futaba Standard servo's on mine. Anything less than standard servo's, in my opinion would not be enough. The nylon tubes for the aileron's might be able to be replaced with Sullivan cable. As far as engine and prop, I would think that Bax would be an excellent source for information and I would run with what he says. The Corsair is a great flying plane. For landing's, it must be flown to the runway with quarter power and have the power cut over the runway threshold so to eliminate the chance of a stall. For take off, the plane needs speed to fly. Keep it on the ground as long as possible prior to lift off. You will be happy when you get her rebuilt and in the air. Good Luck Dave
Old 07-03-2016, 07:16 AM
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https://www.servocity.com/html/hs-22...l#.V3krhxw7uCY https://www.servocity.com/html/hs-12...l#.V3ksAxw7uCY Would be picks I bet you could get a standard one in there if you wanted. The ones you put in are a little small. I have done it for mid size WW1 planes. They are too delicate even though they have power. I would never scrap a plane because of servos.
Old 07-06-2016, 03:12 PM
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ronwc
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I have built and flown most of the TF warbirds over the years. Here's a few ideas that might help you. Although these were originally designed for 61 size engines, most guys used 75 to 91. As you found out, three bladed props are not very efficient on two stroke engines, use a two blade 13x6 on a 75 and a 14x6 on a 90/91. Although they build heavy, work to keep them light. All standard servos work best, with two on aileron. Forget the whole flap thing. Keep it all simple, mount engine on side instead of inverted if possible. Fly nose heavy at first and adjust that by moving battery back later if needed. Keep speed up on take off and landing, learn to use rudder.

Last edited by ronwc; 07-06-2016 at 09:19 PM.
Old 07-06-2016, 09:17 PM
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Chad Veich
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From the looks of it I would say you have a good airplane on your hands but just need a few minor "tweaks" to get it going. I have flown half a dozen Top Flite .60 size Corsairs with everything from a .61 two stroke to a 1.20 four stroke and anywhere from 9 1/2 to over 13 pounds. They all flew just fine. If yours is somewhere between 9 and 10 pounds then, as noted by Dave above, yours is on the light side of the spectrum! At that weight they are real sweethearts assuming that you've built it straight and true. And the .91 ought to pull it around like a Rocket. I flew my 65 inch wing span, 11 3/4 pound Hellcat with the OS .91FX and it was radar gunned at over 100mph. It it's running right, and you've got a suitable prop on it, there will be absolutely no problem with it pulling around a 10 pound Corsair. My first TF Corsair was just over 10 pounds and flew beautifully on a Super Tiger .75 two stroke. Put some good aileron servos in it and get that engine dialed in and I think you will be very surprised at how nice the Corsair flies.

Good luck!
Old 07-07-2016, 09:24 AM
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gregoryshock
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@ronwc All good suggestions and I agree with you. But I got a question for you. How do you change the mounting position of an engine? The engine is mounted at a bottom angle like TF suggested in the Manual. Thank you for the prop size suggestions if I ever get it running again I will try those sizes for sure!

@Chad Veich I think mine might be a little over 10lbs maybe 10.5. I'm not sure. The total weight of the model depended on what battery pack I put in and how much weight I had to add to the nose. Some on this sight suggested that I mount the battery pack on the firewall or hang it from the engine mount or something like that. I looked and looked, and measured several times. I don't think it's possible to do that on this model. Not enough room under the Cowl. The people who made this suggestion didn't own a TF Corsair.

6v 2000 mah batter pack the model was around 10 lbs. With the 6v 4200 mah battery pack it was closer to 11 lbs. These larger packs was chosen to run the radio system and electric retracts.

http://www3.towerhobbies.com/cgi-bin...&I=LXNHS4&P=ML

http://www3.towerhobbies.com/cgi-bin...&I=LXMTX4&P=ML

I like it when people who worked on TF version of the Corsair responds. Often times those responses are the most helpful.


Last edited by gregoryshock; 07-07-2016 at 09:46 AM.

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