How many wing ribs?

supercub

MEMBER

Let me check my GPS, gee how'd we ever navigate w

• Aug 27, 2020

• #1

It's my understanding that wood spar J-3's had 12 ribs and Piper went to 13 ribs on the metal spar J-3's and PA-11's. I believe the PA-18-95 also had 13 ribs. Did the number of ribs change over the years on the PA-18 models? Thanks.

 

mike mcs repair

Registered User

chugiak AK

• Aug 27, 2020

• #2

16 ribs


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K

KevinJ

Registered User

Canyon, tx

• Aug 27, 2020

• #3

Any idea of the weight difference between a 13 rib wing vs the later model wing?

 

Crash Jr.

Registered User

Anchorage, AK

• Aug 27, 2020

• #4

Like mike said they went from 13 to 16 ribs on the 150 horse models. The earlier -95, -105, and -135 models had 13 ribs. I think even the Ag models had 13 ribs with flaps. My understanding is it had to do with the gross weight increase from 1500lbs to 1750lbs.

Here's a couple old threads on the subject:
https://www.supercub.org/forum/archive/index.php/t-27483.html
https://www.supercub.org/forum/archive/index.php/t-26546.html

 

supercub

MEMBER

Let me check my GPS, gee how'd we ever navigate w

• Aug 27, 2020

• #5

Crash Jr. thanks for those links, If I read them right, even the 150hp Cubs had 13 ribs. I've looked in the parts manual, and that's what the drawing shows too. So when and why did they go to 16 ribs?

 

Steve Pierce

BENEFACTOR

Graham, TX

• Aug 28, 2020

• #6

Without looking in my parts manual it is my understanding that the 16 ribs came on the early PA18-135s and PA18-150. I don't believe Piper ever delivered any 150 hp Super Cubs without 16 rib wings. The number of ribs had nothing to do with gross weight only with the Vne. I don't think you could reach the PA18-150 Vne in a dive with the wings removed but I am not willing to try either. All this can be varified in the parts manual and is from memory which tends to fail me on a regular basis.

 

1

1934A

SPONSOR

SE Montana

• Aug 28, 2020

• #7

I was told that they went to the 16 rib on the 150hp models. All the 95, 125, and 135hp models came from the factory with 13 rib wings. I was told that it had nothing to do with gross weight, but Vne. The closer spacing between the ribs was supposedly to keep the fabric from fluttering.

 

Steve Pierce

BENEFACTOR

Graham, TX

• Aug 28, 2020

• #8

 

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AkPA/18

MEMBER

Big Lake Ak

• Aug 28, 2020

• #9

Steve Pierce said:

I don't think you could reach the PA18-150 Vne in a dive with the wings removed but I am not willing to try either.

Click to expand...

Lol you would be surprised how quick it happens

 

mike mcs repair

Registered User

chugiak AK

• Aug 28, 2020

• #10

AkPA/18 said:

Lol you would be surprised how quick it happens

Click to expand...

I remember when fermin was doing tests to try to get STC.


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