Reflections of a Tail Group Builder.
Posted: Sun Feb 19, 2012 5:11 pm
I thought that I should take a few moments to update "The Group" as to our
progress.
My brother and I are quite near the end of building the tail group. (sans
any fiberglass work). I have the left elevator on the bench, and all that is
left to do with it is to cut the hole for the trim motor and activating rod.
Then a little corrosion protection, and rivet it up.
Speaking of corrosion protection, we are using a product called Cortec 371.
It is a water based material, and we are applying it by using a small foam
roller. It goes on well, and dries rather quickly. We apply this material to
the sheet parts, and we spray some light Zinc Chromate on the ribs and
spars. The Cortec product is recommended by Zenith for their products, and
with their shop in Mexico, MO, less that 80 nm from here, it is easy to get.
Actually, it looks like a quart might do the whole airplane. (We don't have
any plans to put this machine on floats, and it will be hangered, so we
don't think heroic efforts to protect the skin are worth the time.)
We followed a recommendation to install some doublers in the corners of the
elevator skins. Actually, we went a step farther in that we also put some
doublers on the rudder also. The total weight gain from doing this must be
in the neighborhood for 5 ounces. During assemble of the gussets we applied
a small amount of an epoxy adhesive to each of the gussets. We put in a few
rivets, also, but it seems to me that the glue will stiffen the corners more
than the rivets alone.
In reflection, I had a very difficult time with the rudder. (the first part
of the tail group I built) I can't tell you why it happened, but after
drilling it out and having it all clecoed on the bench, I discovered that I
had a pretty good twist in it. I was able to get the twist out because I
initially drilled everything at size 40, and when going up to size 30, I was
able to realign everything and make it straight.
I discussed this with my friend from Troy, MO, Charlie Eubanks, and his
advice, which I think is very true, is that if the part is not flat,
straight, square, and true when you drill it, it will not get that way when
you rivet it. Something I will have to keep in mind.
We kept a close eye on the length of the spars for the elevators and rudder,
and found that we were able to have enough room to install brass bushings on
the load end of the control surfaces. (both rudder and elevators) I have a
buddy down the street with a machine shop, and he turned out some small
bushings for us.
One other thing that we have done is that we have left the leading edge of
the vertical fin un-riveted. (is that a word?). The fin is complete except
for the installation of the leading edge, and the attach bracket at the
bottom. Given that there have been some reported issues with the tail group
coming together at the last bulkhead, I decided that if I left the leading
edge of the fin and the attach bracket off, I would have an expanded option
to make it all fit.
I know that some feel that the root of the problem lies with the last
bulkhead, and that may be true, but I wonder if the fin attach bracket is
bent at the proper angle. Anyway, it will only take me 10 minutes to install
the fin attach bracket and rivet on the leading edge when the time is right.
One tip I might pass along to other builders is that I had a 4 foot section
of angle iron, must be about 3 x 2 x 1/4, that I cut up into 6 inch long
pieces. These are great for clamping ribs to so as to keep them in location
and plumb.
Another thing I did that worked well, was to use some small pieces of wood,
cut to the proper angle, and then stuck to the spar with double faced carpet
tape to hold the small leading edge ribs in place when I was putting on the
leading edges of the horz. stabs.
I have also learned that whom ever make those building time estimates that
you see in the front of a section in the manual, is a whole lot faster
builder than I am.
We are going to tape up any access holes in the parts, (to keep the bugs
out) and hang them from the ceiling.
I think we will put off the fiberglass work until spring, when the doors in
the garage can be opened.
That is the story from here:
Tim Hickey
Montrose, Iowa,
Rebel 808
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progress.
My brother and I are quite near the end of building the tail group. (sans
any fiberglass work). I have the left elevator on the bench, and all that is
left to do with it is to cut the hole for the trim motor and activating rod.
Then a little corrosion protection, and rivet it up.
Speaking of corrosion protection, we are using a product called Cortec 371.
It is a water based material, and we are applying it by using a small foam
roller. It goes on well, and dries rather quickly. We apply this material to
the sheet parts, and we spray some light Zinc Chromate on the ribs and
spars. The Cortec product is recommended by Zenith for their products, and
with their shop in Mexico, MO, less that 80 nm from here, it is easy to get.
Actually, it looks like a quart might do the whole airplane. (We don't have
any plans to put this machine on floats, and it will be hangered, so we
don't think heroic efforts to protect the skin are worth the time.)
We followed a recommendation to install some doublers in the corners of the
elevator skins. Actually, we went a step farther in that we also put some
doublers on the rudder also. The total weight gain from doing this must be
in the neighborhood for 5 ounces. During assemble of the gussets we applied
a small amount of an epoxy adhesive to each of the gussets. We put in a few
rivets, also, but it seems to me that the glue will stiffen the corners more
than the rivets alone.
In reflection, I had a very difficult time with the rudder. (the first part
of the tail group I built) I can't tell you why it happened, but after
drilling it out and having it all clecoed on the bench, I discovered that I
had a pretty good twist in it. I was able to get the twist out because I
initially drilled everything at size 40, and when going up to size 30, I was
able to realign everything and make it straight.
I discussed this with my friend from Troy, MO, Charlie Eubanks, and his
advice, which I think is very true, is that if the part is not flat,
straight, square, and true when you drill it, it will not get that way when
you rivet it. Something I will have to keep in mind.
We kept a close eye on the length of the spars for the elevators and rudder,
and found that we were able to have enough room to install brass bushings on
the load end of the control surfaces. (both rudder and elevators) I have a
buddy down the street with a machine shop, and he turned out some small
bushings for us.
One other thing that we have done is that we have left the leading edge of
the vertical fin un-riveted. (is that a word?). The fin is complete except
for the installation of the leading edge, and the attach bracket at the
bottom. Given that there have been some reported issues with the tail group
coming together at the last bulkhead, I decided that if I left the leading
edge of the fin and the attach bracket off, I would have an expanded option
to make it all fit.
I know that some feel that the root of the problem lies with the last
bulkhead, and that may be true, but I wonder if the fin attach bracket is
bent at the proper angle. Anyway, it will only take me 10 minutes to install
the fin attach bracket and rivet on the leading edge when the time is right.
One tip I might pass along to other builders is that I had a 4 foot section
of angle iron, must be about 3 x 2 x 1/4, that I cut up into 6 inch long
pieces. These are great for clamping ribs to so as to keep them in location
and plumb.
Another thing I did that worked well, was to use some small pieces of wood,
cut to the proper angle, and then stuck to the spar with double faced carpet
tape to hold the small leading edge ribs in place when I was putting on the
leading edges of the horz. stabs.
I have also learned that whom ever make those building time estimates that
you see in the front of a section in the manual, is a whole lot faster
builder than I am.
We are going to tape up any access holes in the parts, (to keep the bugs
out) and hang them from the ceiling.
I think we will put off the fiberglass work until spring, when the doors in
the garage can be opened.
That is the story from here:
Tim Hickey
Montrose, Iowa,
Rebel 808
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