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J-3 on 29" ABWs

stearmann4

stearmann4

FRIEND
Tenino, WA
Guys,

After of convincing myself I don't need them, I think I really need 29" Airstreaks on my J-3. Most notably because I came across an almost new set that a friend had on a 65hp Champ and didn't;t like em'. I currently have (legally) mounted 8.50 AirTracs on Cleveland wheels/brakes with DA safety cables installed. My only concern is will the extra weight place an additional stress on my stock J-3 gear? I have a C-85 Stroker with a 74" Sensenich metal climb prop, so power shouldn't be an issue.

I'm getting the STC paperwork and will obviously have to make an updated W & B, anyone have ay lessons learned, or what the weight increases will be between the 8.50s and the 29s? I tried to search the archives, but after almost 2 hours I figured it would just be faster to ask again.

Mike-
 
I've been running 29s for a few years now and I'd hate to go back. I put SC gear legs on with a doubler inside the axle. Overkill....maybe. One thing I have learned. Resist the temptation to take the covering off the gear legs on a J3. It is a bigger performance hit than the tires themselves. I'm going to cover them this winter.

Good luck ......Mike
 

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tophand said:
Resist the temptation to take the covering off the gear legs on a J3. It is a bigger performance hit than the tires themselves. I'm going to cover them this winter.
Click to expand...

Good to know, cuz' that was the first thing I was going to do.

Mike-
 
I actually like the looks of the open gear legs a bit more. I've been flying with them open for about a year now and maybe it just feels slower. I've been trying to figure out a removable cover.

I guess that I should really qualify that to say that it's only really noticeable on long cross country flights. I'm about a 100 miles from anywhere out here so I spend quite a bit of time looking out the window. Flying around close you don't notice it so much.

.....Mike
 
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if you would go on a diet, you wouldn't notice the weight of the tires as much there chubby!
 
Jeez with friends like you who need enemies. Was it you that left the door open when you came down???

.....Mike

Finally got released Sat. (from the tanker base smart %$#)
 
MTV, Does it require heavy duty gear or is it heavy duty brakes? I am currently flying an experimental on 29" bushwheels but I seem to recall the STC stating heavy duty brakes when I had the 26" bushwheels installed on the Champ I sold. You have my curiosity up as I don't recall the requiement for heavy duty gear, but that may have been airplane specific also.
As a side discussion, I sold the 26'' tires to upgrade to 29's and after doing so I wish I would have just kept the 26's. They were all I needed for the spots I was landing. Granted, the 29's look better but they are not needed for the majority of these small light planes. Opinion of course.
 
MTV.. I remember seeing that somewhere but I just read through the STC and the installation instructions and it didn't say anything about HD gear. It was just a quick once over so I may have missed something in the instructions. The STC however has no mention of the gear or brakes at all. There are limitation notes called out on the STC but I don't have those right now.

.......Mike
 
From page 10 of 10 of the FAA approved model list for installation of Alaskan Bushwheel, inc Tundra Tires:

1. Must have heavy duty brakes

2. Must have PA-18 type gear or other Heavy Duty Type gear installed under separate approval.

3. Seaplane models are eligible when converted to wheel gear under separate approval.

Notes under the J-3/PA-11 approval state that Notes 1, 2, and 3 apply to these aircraft.

MTV
 
I am seeing J-3s come in at 850 lbs empty with standard gear and not much else in the way of heavy stuff. What do they weigh when you hang heavy brakes, gear, the obligatory safety cables, and really big tires on?

Yes, I know a J-3 can perform at 1400 lbs, but insurance doesn't work at those weights.
 
Bob,

My 11 weighs 832 with Clevelands and 26 inch Streaks. That's a recent weight on certified scales.

MTV
 
Late J3 gear is the same part number as Super Cub gear. 90 hp J3 on 29" Airstreaks would be illegal if the FAA knew how much fun it is.
 
751# with 29" Airstreaks and Clevelands and the obligatory cables. "No springs honest weight"

......Mike
 
tophand said:
Resist the temptation to take the covering off the gear legs on a J3. It is a bigger performance hit than the tires themselves. I'm going to cover them this winter.

Good luck ......Mike
Click to expand...

How much of a performance hit is it, really? I left the gear legs of my -12 uncovered and like it that way. Do you really mean there would be a noticeable difference in cruise performance if the gear legs were covered??
 
Of course leaving the gear legs uncovered won't effect your cruise speed, you'll just need more power to hit that same cruise speed.
 
courierguy said:
Of course leaving the gear legs uncovered won't effect your cruise speed, you'll just need more power to hit that same cruise speed.
Click to expand...
This hits the nail square on the head.

I too have a stroker, so I have a bit of extra power. Enough to still cruise at 90 if I keep it at full throttle. But that's not very efficient. My plane has a "notch" where it like to run. That's around 2350. Before putting on the uncovered gear legs it would cruise at 90 indicated at that rpm. Now it's between 80-85mph at the same rpm. I just thought it might be useful to let Stearmann4 know before he cut the fabric off. As I said before I like the uncovered gear too, that's why I left it off. The performance hit is enough my J3 to make me seriously consider recovering the gear.
Hoonahcub tells me I should just go SC and quit fooling around. He is probably right I just can't let him know that he is. :smile:

......Mike
 
I got 29's six months ago. Glad I did. 811lbs w abw, clevelands, wag aero wing tanks, Scott 3200 tw, microair xpondr and a 406 elt.

Prolly now more than 10lbs diff than 8.5s which are pretty heavy - and illegal too. You are only supposed to go up to 8.0s w clevelands
 
Have been using 24x11x4 and like them, need to beef up my brakes, any suggestions? Have a spare set for sale if anyone interested. Also am in process of rebuilding my 85 as a stroker, any recommendations? Only one I have priced so far is Don's dream machines.
 
duckhunter10 said:
Have been using 24x11x4 and like them, need to beef up my brakes, any suggestions? Have a spare set for sale if anyone interested. Also am in process of rebuilding my 85 as a stroker, any recommendations? Only one I have priced so far is Don's dream machines.
Click to expand...

He's what I do, I wrote this for j3.com, It works if you do it right.

Re: Goodyear brakes, hints and tips to use them till they don't work and then some
Bruce, jack the plane up so that the tire is free to turn, loosen the bleeder and pump like hell till the tire won't turn and close the bleeder with the tire locked, now open the bleeder a little till the tire will just move and then close the bleeder. What your trying to do is remove the air gap between the pads and the drum. It helps if you do this with help but I do it all the time alone. Caution, you need to hold and support the tube coming out of the expander tube with one hand while you push the nipple of the squirt can against it or you might damage the expander tube, you need to pump as fast as you can to keep up with whats leaking out, it helps to use a t-shirt rag as a gasket between the nipple and the bleeder and pump the 5606 thru the rag. You should have great brakes after this so either screw your tires on or run them at 20psi. I like them at 10psi and screwed.

I've got over 1500hrs on expander tube brakes and 25" Goodyears. I can do a run up to 2400rpm before they start to roll, on wet grass they will slide.


Click on the photo and it will start a video of a j3 with stock brakes and 25 Goodyears. Had a cruise prop and only staticed at 2350




I haven't added fluid to the master cylinder in years. I don't even look I fill from the bottom.

Glenn
 
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cubdriver2 said:
He's what I do, I wrote this for j3.com, It works if you do it right.

Re: Goodyear brakes, hints and tips to use them till they don't work and then some
Glenn
Click to expand...

Good info, Glenn, but what do you do with GoodRICH brakes? :lol::wink:

MTV
 
New member, just purchased a 1946 J-3 project. I would like to put big tires on eventually. Were do I find the STC and what combination of brakes would be sugested? It looks like there is disagrement on the gear legs required. Joe B
 
No disagreement... What MTV posted in #8 and #11 is correct. Also read Steve Pierce's posts #14 and # 25. You may be lucky and already have the heavier gear.

......Mike
 
I think most go with the Cleveland kits. You can get those from Airframes Alaska along with the tires. Grove Brakes is an option too.

.....Mike
 
Aren't all the "legal" Grove brakes for the J-3 four inch wheels? That'll definitely limit the choices of tires....

MTV
 
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