When is the larger dorsal a must ?

drjeff · Post by **drjeff** » Fri Mar 30, 2007 00:26

I have a buddy who is rebuilding a 7AC and has decided to put a 90 cont on the front vs. the 65hp. He has already covered and painted the plane, so adding the larger dorsal will not be that easy.

When talking to him, I mentioned that he might have to ad the larger dorsal to be legal but I was not for sure. I ran this by Nathan tonight and he gave me some good advice about looking at the STC list on Aeronca.com. My problem at this site was all the engine conversions did not mention whether or not you had to have the tail mods.

If anyone would like to chime in, please do. Since joining this group a few months ago, I have been a big sponge trying to soak up as much info as I can in order to avoid costly mistakes.

Thanks to all who have tollerated my ignorance!

mike newall · Post by **mike newall** » Fri Mar 30, 2007 05:59

From what I researched, up to and including 85hp is OK with original tail. 90 and above, you need the dorsal.

Now, here is something to consider.

Above 85hp, the top speed won't improve, the short field performance is already excellent with the 85hp, the weight will increase so you may have a single place Champ and the C-85 is a lovely, easy engine to operate.

So why go above 85 ?

Post by **joea** » Fri Mar 30, 2007 06:35

Adding to what Mike said, above 85 hp you have the recurrent wing spar inspections as well.

Regarding the dorsal, you might look at the various STC's out there for Aeronca's. Believe that one of them allows you to put larger engines on the airframe without the larger dorsal fin.

Joe

jerrymjr · Post by **jerrymjr** » Fri Mar 30, 2007 09:36

The new 7EC has an O-200 with the smaller 7ACA fin. Its even certified for spins.

I am not sure why Aeronca decided it was really needed. Certainly a little extra directional stability is nice, but nothing you would worry about.

Dennis · Post by **Dennis** » Fri Mar 30, 2007 10:46

The Buzz Wagner STC for the 0-200 engine does not require the large tail.

Dennis

Nathan K. Hammond · Post by **Nathan K. Hammond** » Fri Mar 30, 2007 15:46

Hey Jeff, good talking with you last night. Give me a hollar next time you swing through the area.

Wagner STC...............O-200/O-235...... No big Tail
Lasher STC.................C85-8/-12............No Big Tail
Service Letter 13........C85-8..................No Big Tail
Service Letter 14........C85-8..................Yes Big Tail
Service Letter 15........C90-8..................Yes Big Tail
Service Letter 56........C90-8/-12............Yes Big Tail

nkh

Orlan H Franks · Post by **Orlan H Franks** » Fri Mar 30, 2007 16:42

My research for refurbishing 7AC N2618E is as follows:
C85-8 limited to gross weight of 1200# with small vertical stab OK.
If you just add the 7CCM larger v-stab you get another 80# gross from 1220# to 1300#, with probably 7-8 pounds of that 80# consumed with the V-stab leading edge hoop weight, more fabric and more paint, or another 72-73 pounds available load carrying to revised certificated gross of 1300#. The original small v-stab leading edge tube remains in place as the larger 7CCM sized hoop attaches to it.

Bill Pancake's 7AC NC1890E has a C-85-8 with McDowell Air Starter and the small size original 7AC vertical stabilizer. HP? Don't ask! His 7AC flys very well as we all know.

If you raise HP to 100.0 (or more) then you have to do the spar inspection annually, regardless of engine designation. The out for this is to replace the spruce spar with alloy spar, same as American Champion will do for you at their factory, using your delivered wings for ribs and your other re-used refurbishment required wing parts. Orlan N2618E

drjeff · Post by **drjeff** » Fri Mar 30, 2007 22:44

As always with this bunch of guys, ya'll always come through! Thank you very much. I just sent this information along to Bill. I am positive it will help.

David Johnson · Post by **David Johnson** » Sat Mar 31, 2007 09:45

SL #56 Does require the dorsal fin kit #178 to be installed on the Master Parts List. I don't know of a service letter based conversion that will let you go over 85hp with the small tail. But I haven't looked thru them real good. I tend to go to sleep looking at stuff like that...I flew a 7BCM for many years, had a strong C85-8. No add on's and real light. Small Tail. Most fun I ever had. When you loaded it heavy, it tended to hunt a little from side to side. On a long trip your legs would get tired from working the rudders. Small tails spin real nice, large tails don't seem to spin right to me. Feels sorta funny, I didn't like it at all. I fly a 7HC some. 135hp Lycoming, small vertical tail, with dorsal fin. Heavy plane with a good bit of power, it needs a larger tail also(Nate-don't tell anyone I fly a nosewheel some). Citabria's have a taller and deeper vertical tail, real good directional stability. Top brace wires are longer than a Champ, I think. Jerry, does the tail on the new bird match a Champ or Citabria? Or in the middle somewhere? Which brace wires does it use? Nate, I am still trying to get up a trip to see you during the week. I will call first. Everyone in Georgia is enjoying the nice weather now! David Johnson

mike newall · Post by **mike newall** » Sat Mar 31, 2007 18:43

jerrymjr wrote:The new 7EC has an O-200 with the smaller 7ACA fin. Its even certified for spins.

I am not sure why Aeronca decided it was really needed. Certainly a little extra directional stability is nice, but nothing you would worry about.

Jerry,

I am so glad you went with the small fin !

I flew an O-200 7AC in Florida once, no electrics, very light, brilliant fun - flew just great with a small tail.

Personally, I just don't like the look of the dorsal, it isn't really needed IMHO.

There are some of us Brits coming to Sun n Fun - I hope you will be there, I will look you up on the ACA stand.

Mike

Nathan K. Hammond · Post by **Nathan K. Hammond** » Sat Mar 31, 2007 22:16

David, your secret about flying a Champ with training wheels, is safe with me. And I'll keep that rumor about you and lady's clothes quiet too.

Yeah you need to swing on down, better yet fly down. About got the shop behind the house finished and hoping to fly the New Standard this week, maybe. Give me a hollar.

*Thanks for the CD's, Dereks got some for you.

nkh

David Johnson · Post by **David Johnson** » Sun Apr 01, 2007 08:38

ooooooooouch! Hope none of our wives read this! Seriously, we once had a real masculine fellow come by our airport. Wearing flops. Evidence remained of toe nail polish. Very interesting. David J

jerrymjr · Post by **jerrymjr** » Mon Apr 02, 2007 09:38

Orlan H Franks wrote:If you raise HP to 100.0 (or more) then you have to do the spar inspection annually, regardless of engine designation. The out for this is to replace the spruce spar with alloy spar, same as American Champion will do for you at their factory, using your delivered wings for ribs and your other re-used refurbishment required wing parts. Orlan N2618E

1) 90 HP is the cut off for the spar AD.
2) Wood spar ribs are not compatable with ACA metal spar ribs. Milman STC uses them, but we won't get into that.

Not trying to be a pain; just want the facts straight.

shorty · Post by **shorty** » Tue Apr 24, 2007 22:19

David Johnson wrote:ooooooooouch! Hope none of our wives read this! Seriously, we once had a real masculine fellow come by our airport. Wearing flops. Evidence remained of toe nail polish. Very interesting. David J

Don't worry she won't have to read this. as I've read it and will relay th' message!

Naw I wouldn't do that to you. jus' jokin'.

can I use yer hanger?

David Johnson · Post by **David Johnson** » Wed Apr 25, 2007 07:00

Shorty, you don't remember how full of junk my hangar is do you? I am afraid I am going to get hurt in there, and I know where everything is!!! David

National Aeronca Association Bulletin Board

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