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Midwest AT-6 Overhaul

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Old 07-26-2011, 12:54 PM
  #1  
smkrcflyer
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Default Midwest AT-6 Overhaul

I purchased a used Midwest AT-6 airframe with Robart retracts a few years ago and Im finely getting around to working on it. This will be my first warbird, first gas engine and first retract plane. Its also the largest plane I have ever had, so a lot of first in this one. I will not be doing the maiden flight on this one.

I will be installing a G-26 magneto engine the previous owner used a G-23. The radio equipment will be all new 2.4 GHz with 6v battery. I€™m also installing a new fuel system. My plan is to get the plane in the air this year and see how it flys. If it flys well and I like it Im going to strip it and redo it with some kind of covering and latex paint. Ill also use a new canopy and cowl.

The previous owner installed a single flap on the outside of the center section of the wing. Im not going to use this because other people are not having a problem flying this plane without flaps as long as the CG is correct. I fly at a very nice grass field with a long runway (www.farviewflyers.net) so landing should not be a problem. The plane as it sets now without radio equipment or fuel system weighs 14lbs so I€™m thinking flying weigh should be around 17lbs.

My first question is related to servos. I did not see a recommendation in the manual for servo torque for each control surface. I will be using two servos for the elevator one for each side. I normal use Hitec or Spektrum servos. So what size servos should I use for each Rudder, elevator and ailerons?

I€™m going to replace the old golden rod linkage with new solid metal. Should I use 2-56 or 4-40?

Any suggestions or advice with this overhaul will be appreciated.
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Old 07-26-2011, 01:14 PM
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Default RE: Midwest AT-6 Overhaul

That really looks nice in the bare aluminum! I think if it were mine, I just enjoy it like it is!

As for pushrods, go with 4-40.  I have used carbon fiber pushrods with no problems if your servos will be in the front, as I assume they are.   As for the flaps, I would recommend you stay with them.  Just a little flap has the same effect of increasing the washout in the wings thus reducing the tip stall speeds, so it's a little insurance against that.  Also if you go to another warbird ( you probably will) that uses flaps a lot, you will be more comfortable with them.

Just my two cents!

Dash
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Old 07-26-2011, 04:29 PM
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Default RE: Midwest AT-6 Overhaul

With or without flap just keep the speed up and you'll be fine,, I flew mine without,, if you try and flare too much it will bounce,, do a nice wheel landing and it will stick. you'll see.

Servos? anything in the 80-100oz range will be more than enough IMO, seams to me they advertised that as taking standard BB servos back in the day

I flew mine with a quadra 40, hs605 servos mounted in the tail,, and it balanced out with no extra nose weight.,, I'm sure it was in that 16-17lbs range,, to long ago to remember exactly

Agree 4-40 would be better


good luck

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Old 07-26-2011, 04:41 PM
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Default RE: Midwest AT-6 Overhaul

Thanks everyone for your comments I will think about keeping the flap and I will go with the 4-40 hardware.

I got the engine mounted. I removed the block of wood that the previous owner used to mount the G-23. It made the G-26 stick out too far from the end of the cowl. It was 1 3/4 of an inch thick and I only needed 1 1/8. I think I'm going to use the Great Planes Large Engine Isolation Mount for it.
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Old 07-26-2011, 07:43 PM
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Default RE: Midwest AT-6 Overhaul

Yeah watch out for the bunny hop on landings and just don`t try to crawl in on landings it will bite you. If you going to paint don`t get heavy handed keep it under 25 pounds and you will be fine. That means watch the weight you putting in the tail. You don`t and you will cry with the weight you will have to put in the nose.
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Old 07-27-2011, 01:12 AM
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Default RE: Midwest AT-6 Overhaul

Yeap,, These were notorious for needing over 2lbs of nose weight when using a glow 2c engine [:@]

Going with the 40cc gasser made it easy to turn a bigger prop, fly most of the time at 1/2 throttle and balance out easy,,

With that 26cc you'll probably CG out good as is,, you might even have to move the radio gear aft a bit.

Also,, nothing wrong with the OEM HD Nyrod configuration when it's done right

Good luck
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Old 07-27-2011, 06:01 AM
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Default RE: Midwest AT-6 Overhaul

Flew mine with a Webra 1.20 and had to add 2 lbs. I liked the flaps as they definitely affect tip stalling. Did hop it occasionally on landing, not a particular problem. I used regular S-148 Fut. servos and flew 3 yrs. with no problems. Used the nyrods and had no problem. A fast plane with an O.S. carb and an APC prop. Raced it in pylon. Fun...........Doug
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Old 07-29-2011, 05:47 PM
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Default RE: Midwest AT-6 Overhaul

I fly mine with a Moki 135, it flys just fine but set it down too hard and it is like a pogo stick. Actual shock absorbing oleos would be a blessing on this bird but I don't know where to find any. A little touch of down elevator( just a touch!!) at the instant of touch down nails it on the ground. Be prepared to go a go around on landing if it bounces very high as it can stall if it slows in the bounce.
Don't worry about having to put weight in the nose. It has to be balanced properly to fly right and weight is weight whether it is engine or lead.
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Old 07-29-2011, 10:26 PM
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Default RE: Midwest AT-6 Overhaul

ORIGINAL: JL1
Actual shock absorbing oleos would be a blessing on this bird but I don't know where to find any.
Not sure what gear you are using but Robart make retracts and functional struts specifically for this airplane.

ORIGINAL: JL1
Don't worry about having to put weight in the nose. It has to be balanced properly to fly right and weight is weight whether it is engine or lead.
Very true but don't rely on the recommendations given by Midwest regarding CG. They show it much further forward than necessary and it actually makes the airplane much more prone to tip stalls as well as harder to land properly. I have my Midwest T-6 balanced as shown below and it flies fantastic. Not to mention how much lighter it is (about 16 pounds) because I was able to remove a bunch of nose weight. That measurement is 5.5" in case it is not easily read in the diagram.

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Old 07-30-2011, 02:14 AM
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Default RE: Midwest AT-6 Overhaul

I am using the Robarts specified for this plane.
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Old 07-30-2011, 02:58 AM
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Default RE: Midwest AT-6 Overhaul


ORIGINAL: Chad Veich

ORIGINAL: JL1
Actual shock absorbing oleos would be a blessing on this bird but I don't know where to find any.
Not sure what gear you are using but Robart make retracts and functional struts specifically for this airplane.

ORIGINAL: JL1
Don't worry about having to put weight in the nose. It has to be balanced properly to fly right and weight is weight whether it is engine or lead.
Very true but don't rely on the recommendations given by Midwest regarding CG. They show it much further forward than necessary and it actually makes the airplane much more prone to tip stalls as well as harder to land properly. I have my Midwest T-6 balanced as shown below and it flies fantastic. Not to mention how much lighter it is (about 16 pounds) because I was able to remove a bunch of nose weight. That measurement is 5.5'' in case it is not easily read in the diagram.

Chad,
I read your posts about the CG and how moving it helped so I will do the same.

I have the engine mounting block sanded down to the firewall. I found this cool drill attachment from Gator (see attached) that made the job easy.

I ordered the parts I need to finish this build so it will be a week or so till I can get back on this.
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Old 07-30-2011, 09:40 AM
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Default RE: Midwest AT-6 Overhaul

ORIGINAL: JL1
I am using the Robarts specified for this plane.
These?

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXES34

These are the gear I am using and the oleos function well for me. I have on several occassions found it necessary to replace the springs with lighter ones in order to soften up the oleos in Robart struts as they normally are very stiff from the factory. Is this the issue you are having or are you using some other type of strut with no oleo whatsoever?
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Old 07-30-2011, 12:51 PM
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Default RE: Midwest AT-6 Overhaul

I'm not having a problem. As I stated, a little touch of down elevator nails it. they are stock, robart,spring loaded gear. I was simply trying to give the fellow with the questions a heads up.
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Old 07-30-2011, 03:03 PM
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Default RE: Midwest AT-6 Overhaul


ORIGINAL: JL1
Don't worry about having to put weight in the nose. It has to be balanced properly to fly right and weight is weight whether it is engine or lead.
I'm going to say just partly true,,
Mine was over powered with the 40cc, but having that extra power vs. dead lead weight was a bonus.
IMO, a DLE 30 would be perfct for this bird
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Old 07-30-2011, 06:26 PM
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Default RE: Midwest AT-6 Overhaul

ORIGINAL: JL1
I'm not having a problem. As I stated, a little touch of down elevator nails it. they are stock, robart,spring loaded gear. I was simply trying to give the fellow with the questions a heads up.
Roger that, I misunderstood your statement regarding the oleos.
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Old 07-31-2011, 03:35 AM
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Default RE: Midwest AT-6 Overhaul

This being my first gas plane how do I setup the gas tank? Is it the same as a 3 line glow plane, carb, fill & vent?
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Old 07-31-2011, 06:43 AM
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Default RE: Midwest AT-6 Overhaul

O you'll get many opinions on that one,,
I prefer a 3 line system, just for the fact I have seen too many times air trapped in the fill "T" section of the 2 line systems cause sputtering.
If you do go with a 2 line, I recommend you have the fill line come out of the fuse below the tank level so air doesn't get trapped in the fill line.

good luck
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Old 08-06-2011, 03:20 AM
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Default RE: Midwest AT-6 Overhaul

Looks like I cant use the 40-4 wire push rods for the elevator hafts. I didnt realize that the outer tubes are not crossed and the 4-40 rods bind up. So it looks like Im going to have to use 2-56 rods. Im not sure if 2-56 solid rods will work or if will have to go with semi-flex. The plane was flown with the yellow semi-flex so I guess they will work for me.

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Old 08-06-2011, 04:27 AM
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Default RE: Midwest AT-6 Overhaul

A trick a few Kits have used with solid 2/56 rod in the outer tubing is,,

Take and cut 1/4-3/8" pieces of the inner tubing, and slide then over the 2-56 wire spaced every 3-4",, this makes the fit snug in the outer tubing and stiffens the wire to tube conection,, you know what I mean,, the wire isn't rattling around in there,,

Good luck
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Old 08-06-2011, 09:17 AM
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Default RE: Midwest AT-6 Overhaul

ORIGINAL: smkrcflyer
Looks like I can’t use the 40-4 wire push rods for the elevator hafts. I didn’t realize that the outer tubes are not crossed and the 4-40 rods bind up. So it looks like I’m going to have to use 2-56 rods. I’m not sure if 2-56 solid rods will work or if will have to go with semi-flex. The plane was flown with the yellow semi-flex so I guess they will work for me.
I had the same issue when I rebuilt my Midwest Texan. I could not get solid 2-56 rods to work and even just the yellow nyrod itself was binding more than I was comfortable with. My Dad came up with the fix which, I'll be honest, I was a bit leery of at first. What we did was used flexible cable, ala throttle cable, with short sections of the yellow nyrod glued on to it every 3-4 inches like scale only 4 me mentions above in regards to the solid rod. A short length of solid rod is soldered to the cable using brass tubing as a coupler just before the push rod exits the fuselage and that is what is connected to the control surface. When we got it all done and hooked up I was amazed at how smooth and free it operates while still being almost completely slop free. It has worked perfectly in my airplane for a couple dozen flights now and I have no more worries about it not being up to the task. Necessity is the mother of invention.
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Old 10-18-2011, 04:18 PM
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Default RE: Midwest AT-6 Overhaul

I finally got some time to work on this again. I put it on the balanced with it set to 5.5" back and its nose heavy. It needs 0.66lbs on the tail to balance it so I'm going to move the batteries back. I have two 6v packs under the tank. The total weight of the plane is 15lbs.
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Old 10-18-2011, 04:52 PM
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Default RE: Midwest AT-6 Overhaul

With the batteries moved back as far as I can I still need 0.33lbs in the tail to balance it out.
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Old 10-19-2011, 09:08 AM
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Default RE: Midwest AT-6 Overhaul


ORIGINAL: Chad Veich

ORIGINAL: smkrcflyer
Looks like I can’t use the 40-4 wire push rods for the elevator hafts. I didn’t realize that the outer tubes are not crossed and the 4-40 rods bind up. So it looks like I’m going to have to use 2-56 rods. I’m not sure if 2-56 solid rods will work or if will have to go with semi-flex. The plane was flown with the yellow semi-flex so I guess they will work for me.
I had the same issue when I rebuilt my Midwest Texan. I could not get solid 2-56 rods to work and even just the yellow nyrod itself was binding more than I was comfortable with. My Dad came up with the fix which, I'll be honest, I was a bit leery of at first. What we did was used flexible cable, ala throttle cable, with short sections of the yellow nyrod glued on to it every 3-4 inches like scale only 4 me mentions above in regards to the solid rod. A short length of solid rod is soldered to the cable using brass tubing as a coupler just before the push rod exits the fuselage and that is what is connected to the control surface. When we got it all done and hooked up I was amazed at how smooth and free it operates while still being almost completely slop free. It has worked perfectly in my airplane for a couple dozen flights now and I have no more worries about it not being up to the task. Necessity is the mother of invention.
believe it or not, BVM used cables in his older F-86 and T-33 kits. He told you to tin the portions that were outside of the sheath. They worked at nearly 200 mph! His outer tube was a tight fit around the cable like a throttle cable. Chad's setup effectively duplicates the small outer portion buy positioning the innner nyrod every few inches. Brilliant idea, I will file this away!!
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Old 06-24-2012, 03:49 PM
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Default RE: Midwest AT-6 Overhaul

Im back working on the AT-6. Im trying to get the plane to balance on the CG at the 5.5 inch mark but to do that I have to add 1 lb in the area right behind the wing. The way it is now Im at 4.75 inch back from the front of the wing this is near the back of the CG area on the plans. Do you think it will be ok to fly this way or should I add the weight and get it closer to the 5.5 inch mark? Im going to have an experience warbird pilot fly the plane for the first time.

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Old 06-24-2012, 08:32 PM
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Default RE: Midwest AT-6 Overhaul


ORIGINAL: smkrcflyer

I’m back working on the AT-6. I’m trying to get the plane to balance on the CG at the 5.5” mark but to do that I have to add 1 lb in the area right behind the wing. The way it is now I’m at 4.75” back from the front of the wing this is near the back of the CG area on the plans. Do you think it will be ok to fly this way or should I add the weight and get it closer to the 5.5” mark? I’m going to have an experience warbird pilot fly the plane for the first time.
Should be just fine for test flying smkrcflyer. Get it trimmed up and then adjust the CG back more to suit your flying style if necessary.
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