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What happened to the Baby Great Lakes, tiny Stearman?!?

SFCHiatt

There’s no such thing as too much horsepower.
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Well, simply put, I failed to properly shrink the top wing fabric to 350 degrees. The Stewart Systems did NOT fail.

Prior to departing for AirVenture, I flew the heck out of the tiny Stearman for 48 hours with no signs of fabric failure. Then on the way to OSH, I stopped for fuel in Duncan, Oklahoma. I do not have a charging system, so I took the opportunity to recharge my battery with a charger plugged into the local FBO while the plane sat on a very hot tarmac. The actual temperature was 106 degrees. Heat is not a problem for properly covered airplanes, but it is a problem if the fabric was not properly shrunk/heated to 350 with 3 cool down periods in between.

So, I departed Duncan and as I leveled off at 3500 agl I was very surprised to see a small amount of “ballooning” between a few ribs. The advantage of the Baby Great Lakes is I can see the top wing while in flight. Caution prevailed and I landed in Parsons, Kansas where I began to diagnose the situation. Some sagging was obvious however, the root cause was not obvious. I heated the sagging fabric with some parchment paper and an iron. That did bring it back tight however a quick trip around the pattern returned the ballooning. At that point, I decided to park the plane and take the support van to AirVenture.

The plane was disassembled and trailered back to San Antonio. I was still not totally sure what happened, so I carefully removed the 50-hour fabric from both top wings. I found nothing, the stitching looked good, ribs looked good and still nothing was obvious on what could be the cause.

All along I was seeking guidance from a lot of very experienced builders. One of the very wise old timers suggested I iron the back of the fabric at 350 and see if it shrinks. Well, it did, as mad as I was that I failed so horribly, it was a relief knowing I found the root cause.

I’m 100% sure that a very good iron, (what Stewarts sells) was run across the fabric at 350 degrees. The failure happened because a proper 350 degrees across every inch, 3 times with a cooling off period between did not happen. Therefore, it’s likely a lot of the fabric was not properly shrunk.

So, while flying after the paint and fabric was VERY hot, it stretched to a point it could never return too and hold properly.

I want to take a moment and say a few things about Andy Humphrey and the Stewart Systems process. As I mentioned previously, this failure was totally my fault. Stewart Systems did NOT fail. Having said that, after I discussed the issue with Andy, he sent me everything I needed to recover and paint the top wing FOR FREE. He even paid for shipping. If you haven’t priced stuff lately, that was $800 even for my tiny biplane.

If I wasn’t a happy Stewarts System representative, I sure am now.

The wings are recovered and painted, and they look amazing. I’ll put it all back together and be flying early next week.

I’ll be at AirVenture 2023 although, I’ll be trailering the Tiny Stearman to Brodhead where I’ll assemble it and fly to OSH where the plane will sit in the Stewart Systems display area all week.
 

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