Rear spar finish tape

[aviator79]

Out of curiosity, what is the function of the finish tape along the rear spar? I understand reinforcement along the rear of the fuel tank. Is it cosmetic further outboard than that?

[Esser]

It doesn’t make sense to me. The radius is very large and it doesn’t touch.

[Floog]

Mine touched the spar in several places. Probably because of the way I shunk the fabric. I think my fabric is more concave over the rear spar than most I've seen. However, I've seen no wear or adverse performance...

[Floog]

If I recall, the build manual suggests putting anti-chaff tape along the top of the rear spar which I did not do.

[jrevens]

It seems to be very close to the surface of the spar, and on some examples evidently touches a little. Under flight conditions, I suppose it's possible for the fabric to touch the spar when the wing flexes, etc. Anyway, I think it's pretty standard practice to add finish tape sometimes when the clearances between fabric and structure are real small, and the possibility of contact under certain conditions exists. In this instance I kind of like the tape there because of the relatively large unsupported areas and the fact that the wings do flex. That's just my opinion.

[David47]

I ran tape along the length of the spar, definitely required in the tank area, more for cosmetics outboard of that. Didn’t add anti chafe tape.

[HighWing]

That tape has been in the manual since the Dan Denney days. Then, the fabric was the light weight uncertified fabric and maybe there was more movement of the fabric in the prop wash and slightly beyond. I did it on both planes and no regrets.

[aviator79]

That tape has been in the manual since the Dan Denney days. Then, the fabric was the light weight uncertified fabric and maybe there was more movement of the fabric in the prop wash and slightly beyond. I did it on both planes and no regrets.

I wasn't planning on skipping it, just curious.

[Jfquebec]

I did it to...👍👍

[Jfquebec]

The wing on bench ,the fabric touch the Spar maybe one inch.. so i think in flight it will be more..

[WISDAN]

Tape on rear spars was also recommended by a local fabric aircraft refurbishing business friend. He's an A&P and has done beautiful work for years.

[aviator79]

I just finished heat tightening, and there is very little clearance between the fabric and the spar. Definitely makes sense now.

[Floog]

The top of the wing is low pressure in flight (it sucks). With just the finish tape over the fabric at the spar (it touches at every bay) I've had no sign of wear in 1,300 hours.

[jrevens]

If I recall, the build manual suggests putting anti-chaff tape along the top of the rear spar which I did not do.

I think I misread this the first time, Floog. I didn’t use anti-chaff there either. Just finish tape. I mistakenly thought that was what you were talking about. Thinking about it, the spar surface is (or should be) smooth, and the anti-chaff tape has a rougher, softer surface. Little particles of dirt or whatever would probably become embedded & stuck to the surface of the tape over time, potentially causing more wear than the bare metal. I think it’s all pretty academic, in this instance anyway (I’m sure everyone else does too). I didn’t receive any anti-chaff tape in my kit at all. I had to buy a full roll from Debra, and I believe that she said they hardly used any on their builds.