Optional flush screws for plate covers?

[bertschb]

I'm working on Section 10 of my empennage kit (rear fuselage). On page 10-7 it refers to optional #27 dimples for a couple holes. I spent half an hour scouring the plans to figure out what this option is.

I think I found it on page 10-32. You apparently just replace the kit provided round head AN526-632R8 screws with optional AN507-632R8 flush screws as shown below.

My question-
Why are these screws optional??? Why would I not want flush screws? I thought Vans would always opt for a flush screw (and flush rivets) if possible.

-Stumped new builder

 

[Bgill]

I agree..

I feel the same. For a few more minutes, the covers are consistent with all the rest. This is probably a very low pressure area but why be different. I opted to change all my cover plate screws to SS Torx (6 lobe). They are off and on very quick at inspection. I don't paint them either. If any get galled, swap out for new - keep a stash on hand.

 

[lipper03]

Don't know why flush wasn't the std design, but watch for the fact you also have to countersink the longeron, so just watch the plans, and mark correctly what to dimple and countersink. And also be sure you test fit and mark the panels, so you don't get them mixed up and end up with two right sides or two left sides. Almost happened to me, caught as I was like I should check this one more time before dimpling.

 

[Doug Rohrer]

SS Galls

I had several SS screws gall on me while removing inspection covers. Major PITA to resolve. Now I use standard AN screws exclusively.

 

[georgemohr]

We did the flush option. There are many flush screws all over the airframe, so like you I'm not clear why this is even an option.

 

[mturnerb]

If I were doing again - I did flush screws - I would NOT do flush screws. There is no measurable performance advantage and the screws are in a relatively hidden place (you only see them if you crouch down under the HS). Just not worth the extra effort for a minimal cosmetic gain. But this is a classic "Mikey likes it" situation.

 

[Jetmart]

I was perplexed by the option as well.
I like flush screws, nicer for cleaning. Nothing sticking up to catch micro fibre cloths.

 

[1949MGTC]

I flushed all but the top two. I didn’t want to countersink the channel.

Bill