PDA

View Full Version : PA11 vs J3 Rear Gear/Strut Fitting



D.A.
03-21-2020, 07:53 PM
Hey you PA11 guys, is the PA11 rear gear fitting/strut fitting like the J3 or the PA18? I believe the J3 is 2 layers of .090 and the SC is 2 layers of .125. The reason I ask is because I see a lot of PA11's modified with an O-290 and HD gear and big tires and so on, but the J3 requires a few structural mods to take the extra HP. So I guess that's 2 questions - LOL, gear fitting configuration and why is it easier to put big-ish HP on a PA11 than a J3?

Thanks in advance.

bob turner
03-21-2020, 10:05 PM
My J3 has PA18 gear legs and PA11 struts, with no mods to the fitting. Don't know if that answers your question.

Yes, I have field approvals for the struts. Univair gear legs are sold as J3/PA18 legs - slight difference in brake orientation, but nothing else.

Steve Pierce
03-22-2020, 08:38 AM
Landing gear is the same on the later J3, PA11 and PA18. Early J3 had a lower gross weight and 5/16" gear bolts and lighter shock struts than the later J3/PA11 with 3/8" gear bolts and a heavy tubed shock strut. The rear gear/strut attach fitting is much beefier on the Super Cub. I believe it all has to do with the gross weight.

S2D
03-22-2020, 08:52 AM
D.A.
I know you are asking about a specific fitting, not the gear legs or other stuff. I think they are the same. but will check when I get to the airport. I've got both an original PA-11 and a J-3
When we redid the topdeck on a couple local 11's to be more like the 18, we replaced the gear/strut attach fitting with a supercub one.

D.A.
03-22-2020, 12:54 PM
Early J3 had a lower gross weight and 5/16" gear bolts I must have only dealt with early J3's because I remember the 5/16 bolts.

D.A.
03-22-2020, 12:59 PM
When we redid the topdeck on a couple local 11's to be more like the 18, we replaced the gear/strut attach fitting with a supercub one. Actually, there's an example of what I'm talking about, PA11's being modified to be more like a PA18. Did you also put a bigger engine on them? I know there have been a rare few J3's updated with more HP but I've seen SEVERAL PA11's modified. And of those modified PA11's they usually have an O-290. What I can't get my head wrapped around is the fact that I believe the strut attach fitting is very light compared to the SC, so how do they get any useful load if they aren't increasing the GW, and if they're increasing the GW, how do they do it with the light fitting?
Thanks

Steve Pierce
03-22-2020, 02:20 PM
I doubt they get a GW increase with the engine upgrade. Early Super Cub is 1500 lb GW. I haven't heard of any Cubs where the fittings failed. That stuff makes the engineers feel good, pilots can justify anything. ;)

bob turner
03-22-2020, 07:46 PM
I looked into a gross weight increase for the Helio. Feds sent me to a couple DERs. Answer: almost impossible, but lots and lots of cash could conceivably make it slightly less impossible. Want a Super Cub? Cheaper to sell the 11 and buy an 18. Way cheaper. Opinion.

tempdoug
03-22-2020, 08:41 PM
anyone ever see this drawing to modify a sport trainer to accept a 150hp.https://www.wagaero.com/observer-super-sport-supplemental-drawings.html

D.A.
03-22-2020, 11:02 PM
anyone ever see this drawing I know one of the things they do is add 2 more tubes, one left and one right, from the forward spar attach area to the top of the firewall area. You know how the J3 has the 2 tubes at an angle in the windshield area, the WagAero HP upgrade mod has 4.

tempdoug
03-22-2020, 11:38 PM
i will look in there drawings what they have for the thickness of the spar attach fitting, just curious if in this drawing for extra hp if anything was mentioned about it.

S2D
03-23-2020, 04:11 AM
You can pretty much convert the later j-3s to pa-11 configuration. Dont know specifically what bigger engine mods you refer to but one factor in allowing them might be fuel tank location.

Sent from my E6910 using Tapatalk

Steve Pierce
03-23-2020, 06:33 AM
Not so in the past but now you cn only get a field approval for up to a 10% horsepower increase.

skywagon8a
03-23-2020, 06:40 AM
anyone ever see this drawing to modify a sport trainer to accept a 150hp.https://www.wagaero.com/observer-super-sport-supplemental-drawings.html


I know one of the things they do is add 2 more tubes, one left and one right, from the forward spar attach area to the top of the firewall area. You know how the J3 has the 2 tubes at an angle in the windshield area, the WagAero HP upgrade mod has 4.
Use caution if using Wag-Aero drawings to modify a certified airplane. Anyone can produce drawings for experimental licensed airplanes. Only FAA approved ones should be applied to certified planes.

tempdoug
03-23-2020, 07:50 AM
Use caution if using Wag-Aero drawings to modify a certified airplane. Anyone can produce drawings for experimental licensed airplanes. Only FAA approved ones should be applied to certified planes.

only posted that for reference for what they do. its .090 thick from there drawing.

tempdoug
03-23-2020, 07:52 AM
whats the groove measure on the inside of the fork?