Installing antenna in Vertical Stabalizer

[Bruce Fenstermacher]

I'm installing a V Dipole antenna in the top of my vertical stabalizer There was no antenna there before so the top or cap of the vertical stabalizer was riveted on. I've looked at several 170s with this antenna installation and I think they all have the rivets in the top replaced with 6/32 machine screws.

Here are my questions. Must I use a machine thread screw to reattach this cap or can I use a sheet metal type screw through tinnerman nuts to secure it? If I must use a machine threaded screw like a 6/32 can I use a tinnerman type speed nut which clips on or must I use a riveted lug like a NAS687?

I know of course it will be up to what my A&P likes (and is acceptable practice) but since he doesn't do a lot of this type of thing I'm looking the opinion of those that know this airplane.

Also the entire inside of my stabalizer is zinc chromated. Did it come this way from the factory.? If not, does any one know if L-19s came all zinc chromated inside. I have several other parts from a L-19 on this aircraft, maybe the vertical stab is also.

Thanks

[GAHorn]

Some 170's were corrosion proofed at the factory. This includes those designated as "float planes" and "agricultural" planes. (In the 1950's it was very expensive to import personal aircraft into Central/South America. If the airplane were equipped with "agricultural" or "photo" kits, then they were exempt from the high tariffs. Therefore, many aircraft were so equipped in anticipation of international sales. A convincing argument for agricultural use would be that it was corrosion proofed against chemical attack, and had spray-bar attachment capabilities. My own '53 model had both ag and photo kits installed, subsequently removed during restoration, but the anti corrosion treatment was restored as a nice feature.)
Whatever fasteners your mechanic chooses should meet FAR 43.13. Keep in mind that if anything comes loose at the top of the vert. stab. it will likely jam your rudder. Do it right.
Re: using L-19 parts on a 170: Be careful. Just because they fit doesn't mean they are correct. Example: The elevator tips (counterweight horns) are identical to the 170B EXCEPT that the right one has the incorrect amount of lead weight inside it. Simply installing an L-19 elevator tip/counterweight may lead to flutter because it will be too heavy for a 170B. (The L-19 has a larger/heavier trim tab that needs to be offset.)

[Bruce Fenstermacher]

George

What hardware would you choose to replace the rivets at the top of the stabalizer. I looked at 43.13 for some guidelines and found nothing definative and as you know different mechanics have different opinions. Sounds like you would favor the riveted on lugs over the clip on tinnerman type.

I didn't realize the L-19 has a larger heaver trim tab, I'll have to check one out closer. I wouldn't be surprised if I have the entire horizontal stabalizer and both elevators and trim tab from an L-19. I'm sure you wouldn't remember but my '50 A model has L-19 wings with hardpoints installed. Some day I may hang static rocket pods from the hardpoints just to draw a crowd.

[GAHorn]

Since it's unlikely to ever have a need to re-enter the area after the antenna is installed, I think I'd favor self-locking rivets.
Have you considered installing an overhauled Narco VOR antenna, such as that used originally and mounted on top of the cabin? That's what I intend if ever I install a VOR in my airplane. gh

[Bruce Fenstermacher]

You are right about not having to go back in but if you ever should what a pain to remove those self locking rivets. The local brain trust would accept tinnermans and 6/32 machine screws but thought that the rivet on self centering lugs like the NAS687 would be the best choice. So after 3 hours of work I have now installed all 19 of the NAS687s and will use 6/32 screws.

Actually George after a lot of thought I'm removing the Narco antenna and installing a com antenna in its place. I plan to install a second com antenna in the future and will then install both of the com antennas in the top corners of the back cabin area as Cessna seems to be doing now. After discussing antenna location with the local avionics and antenna brain trust they said it would be better not to have the Narco nav antenna so close to the com antenna. And that now might be the time to locate the Nav antenna in the vertical stabilizer. Then a friend gave me the antenna for free to install so what the heck.

As I said earliar my airplane isn't even close to original so I'm not concerned about that.

Besides I'm getting rid of all that drag of the Narco antenna so that my hybrid A model modified with the B model wings will go even faster than either your straight B model or Joe's straight A model

[N1478D]

[quote=

Besides I'm getting rid of all that drag of the Narco antenna so that my hybrid A model modified with the B model wings will go even faster than either your straight B model or Joe's straight A model [/quote]

I am probably being pedantic but you cannot legally call George's plane a straight B, only the A models can be called straight. And, it's the drag of those non-straight wings that you and Eric like that contribute to the slowness. Yours might have to be called a D model, a converted 56 straight tail 172 is using the C designator

[zero.one.victor]

Bruce, I'm interested in the installation of B-model (or Birddog?) wings on your A model. I recently posted a new topic on "the hangar" forum asking about what would be required to install B wings on my ragwing--no responses yet. I believe that the flap linkage is the same on the A as on the ragwing.
Did you do (or hire done) the wing installation,or was the airplane already so equipped when you bought it? What all was required for the wing switch? I imagine that a 337 was done detailing the changes made.
Thanks.

Eric

[Bruce Fenstermacher]

OK Joe you caught me with the dihedral which mine has. Since my paper work doesn't specifically mention changing the struts to the longer B model (it probably should) which gives the added dihedral I've often thought about getting a set of A model struts and going with the "flat look" which I prefer. As for the D model designator I've very seriously considered a military paint scheme and calling my plane a L-19F (that's F for fake ) and sneaking into the military flight line at fly-ins and airshows.

[DaveF]

Reviving this old thread because I'm planning to install a VOR antenna in my vertical stabilizer.

Bruce, what did you do about the fasteners in the upper fin rib? My mechanic would be happy with pulled rivets, but I don't like them if there's any chance of having to remove them. And it's not just one or two; there's 21. I'm leaning toward nutplates.

How did you route the coax from the fuselage into the vertical fin? If you run it below the horizontal stabilizer then it has be routed up through the stabilizer center skins, which have no holes. Did you send it from the fuselage into the dorsal fin and then into the vertical?

[Bruce Fenstermacher]

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Rib #16 was the only thing removed and all rivets where replaced with 6/32 machine screws and rivet on nut plates. As for the routing of the coax I don't actually recall how I routed the coax but it was not difficult other than crawling down the tail boom to insure the coax was secured and not interfere with any cables.

[DaveF]

Ok, thanks. I was afraid that routing the coax would be a problem.