[Jack Beck]

We are ready to install the lower empenage gap cover(F-994A) that has the optional rubber channel which fits between the lower surface of the HS and the gap cover. What is the advantage of adding this rubber channel? If we do elect to use it, how have you secured it in place?

 

[kevinh]

We are ready to install the lower empenage gap cover(F-994A) that has the optional rubber channel which fits between the lower surface of the HS and the gap cover. What is the advantage of adding this rubber channel? If we do elect to use it, how have you secured it in place?

I did not use it. I just trimmed the F-994A (not really - buy the RV-7 equivalent ) to have a uniform 1/32" gap. It looks prettier in my opinion - not that anyone ever sees it once the plane is actually sitting on the ramp.

Every annual I peek inside - clean and dry. Any rain goes out through the drain hole.

 

[Kevin Horton]

What is the advantage of adding this rubber channel? If we do elect to use it, how have you secured it in place?

If you interested in squeezing the last knot out of the plane, you will want to fill the gap with something, to avoid the drag of air moving through the gap between the fairing and the HS.

 

[Jack Beck]

Thanks Scott,
No we tried but were not satisfied with the fit. Can you tell us how you tweaked the fiberglass... We definitely need to edit the shape of the empennage fairing to get a good clean connection to the aluminum surfaces. We hear that you can use heat but this is a new frontier for us.

 

[Paul Eastham]

If you interested in squeezing the last knot out of the plane, you will want to fill the gap with something, to avoid the drag of air moving through the gap between the fairing and the HS.

Anyone care to hazard a guess as to how many knots we're talking about here?

 

[Kevin Horton]

Anyone care to hazard a guess as to how many knots we're talking about here?

Probably less than a knot. All by itself it wouldn't be worth worrying about. But if you are the type of guy who works every detail to minimize drag, the total difference from working on all the details might be 5 kt. This is simply one of those many little details that might add up.

If you attend air race events, you may have seen aircraft with gaps covered with vinyl tape. The air race guys don't spend all that time putting tape over the edges of fairings, etc for the fun of it. They do it because they know that air moving through gaps creates drag.

 

[JonJay]

Fairings Etc... top fairing, .025 bottom

I used the Fairings Etc.. fiberglas fairing on the top. It fit very well. I threw out the lower fiberglas fairing and used a simple strip of .025 to match the bottom of the HS. The top fairing wraps around the leading edge and when laid on top of the .025 aluminum bottom fairing, it makes a nice transition. It is not as clean and neat as a full wrap fiberglas fairing, but it finished very nicely all the same. The gap is less than 1/32".
I refused to spend "several hundred hours" on fiberglas work on my airplane and used aluminum every where I could, including wind screen fairings.