Razor Back Option

[dginok]

I'm trying to decide whether I should install this on my Super Sport. Does anyone have an opinion regarding this feature, whether it is useful/desirable?

[Dick B in KY]

From pure asethics it looks good, is not hard to install. Don't know if it helps increase anything or not (haven't flown my SS yet).

Dick B

[dginok]

Thanks Dick!

[MotReklaw]

I like it too, but no experience with how it performs.

[jtpitkin06]

The razorback option applies to the model 7 SS. It is a 3 inch high dorsal fin extension to the vertical stab reaching forward and tapering to zero height at the rear of the baggage compartment.

According to the supplement in the builder's manual it "does add to the yaw stability of the aircraft."

The option is made from a 5 foot long piece of aluminum tube and a plywood rib. The parts weigh about 7 ounces. The increase in fabric is negligible.

This photo shows the razorback tubing and the plywood support. It is bonded in place with Hysol at the rear. The front end of the tube slips over a weldment and is bonded to a fuselage cross member.

John Pitkin
Greenville, TX

[Geowitz]

Ahh yes, I just always called it a dorsal fin. Thanks.

[HighWing]

I know of guys that are incorporating this idea on the earlier models as well. I have been told that it simplifies the fabric covering in that area. One thing on the IV, there is usually antenna mounting plates on the top surface of the fusalage, and extending the dorsal fin to the turtle deck will eliminate the use of these mounting plates. If going all the way forward, I would suggest cutting them out for weight savings. I terminated mine just aft of the forward plate as I still wanted the com antenna to be mounted there. For weight savings I also eliminated the wood rib most guys are using as I sort of thought that it was a bit of overkill as the linear length of the shrinkable fabric on each side of the tube is less than a foot and shrink pressure on the aluminum stringer would be minimal. I glued a couple of aluminum stand-offs under the rib similar to the stand offs on the side stringer - no wood there and longer runs between standoffs.

Keep in mind that for the IV, it is not a kit option, but a builder design option and I am trying to work toward simple and light.

Lowell

[cainbird]

I added one to my model 4 when I rebuilt it. I used a piece of 3/8" 4130 molly tubing and bent it and welded it in place. I dont know if it added any yaw stability or other benefits. I did it for aesthetics. There are photos in my profile.
Good Luck~Cain B

[dholly]

I did something similar on my Avid Mk-IV. A word of caution to any Avid builders considering this... the Avid flaperon counter balance weights are positioned on the flaperons so as to fit into this area with the wings folded... ie., watch your clearances... don't ask me how I know this. :o

[szicree]

The dorsal came standard on my Super Sport. It might be a good idea to install one so that your plane looks as up to date as possible (helps with resale).

[dginok]

I'm convinced! It shall be installed.

Thanks all,

[kitfoxrk]

I am looking for the instructions for installing the razorback option. It came with the kit I have, but I can't find any reference to it in my build manual. If anyone would be able to share the instructions, I would really appreciate it. It looks like it's pretty simple, but I just want to make sure I don't miss anything.

Thanks in advance for any help.

Bob

[jmodguy]

I would like to get one of these! I didn't see it in the Kitfox catalog. ANyone have any pricing info??

[jiott]

Look at Tom Waid's build website. I believe he made his own razorback. It looked simple and easy. Maybe he will chime in and post a link to the right pages.

[jmodguy]

jiott
Found it. Thanks for the heads up. You're right, looks easy enough...

[Tom Waid]

Go Here!
(http://tropicaltuba.com/Kitfox%20Project/Kitfox9.htm#Razorback)

My SS may be one of the last with this type of razorback.

[jmodguy]

Is the razorback an aluminum tube or steel?? Looks to be aluminum...

[Tom Waid]

On my SS it's aluminum.

[jmodguy]

Anyone have the size of the tubing (dia, wall thickness, and temper)? Maybe some height measurements at some cross tubes?? I want to add this to my KF5
Regards
Jeff

[RV6flyer]

The razorback option applies to the model 7 SS. It is a 3 inch high dorsal fin extension to the vertical stab reaching forward and tapering to zero height at the rear of the baggage compartment.

According to the supplement in the builder's manual it "does add to the yaw stability of the aircraft."

The option is made from a 5 foot long piece of aluminum tube and a plywood rib. The parts weigh about 7 ounces. The increase in fabric is negligible.

This photo shows the razorback tubing and the plywood support. It is bonded in place with Hysol at the rear. The front end of the tube slips over a weldment and is bonded to a fuselage cross member.

John Pitkin
Greenville, TX


Were you able to bend the tube by hand?

[bbs428]

I made mine from an old, straight, knot free, 1" pine board and used the router to round off one side.
Worked out great. Attached the fore and aft ends, then pulled it down until it looked right.
Made some brackets from aluminum, pine, aero-poxy and some pop rivets.
Turned out strong and light. Covering proved to be no problem.

[RV6flyer]

This is what I just did to my 5 project. Bonded with epoxy and flox. The tube is bonded at the forward edge of the antenna mount plate and at that a small rib about midway. Sorry about the rotation. It is OK in m file. Do not know how to fix this.

27541

[bumsteer]

I didn't see it answered here and could find nothing on a search. From someone who made the razorback from aluminum, what size and temper did you use? From the photos I found looks like some used 5/8 inch and others look like 1/2. Thanks for any help.

Rick

[RV6flyer]

I used 5/8 0.035 5052 0. Very soft and very easy to bend. Filled it with sand and bent it over the top of my 6:50 X 6 tire. I got an length of heavy copper house wire and bent and fitted first to see what I wanted. Used that as a guide for bending the 5/8 tubing.

Allan

[SilverFox5]

Rick
I used 6061-T6 aluminum 5/8" OD x 0.509 ID x 0.058 wall.
I think I bought 6 feet
Than I bought 1 foot of 6061-T6 aluminum 1/2" OD x .0.043 ID x 0.035 wall.
With this I could slip the 1/2" tube inside the the 5/8" tube and epoxy it to the exact length.
I took about 4inches of the 1/2" tube, cut it in half length wise and welded it to about a 6" pc of 1/2" tube to make a (T) shape that slipped inside the 5/8" tube. The 4" half moon pc was epoxied to the fuselage frame.
I had a co-worker do the aluminum weld. I do not have a welder for that.
To bend the tube I made a template from 3/4" thick plywood and screwed it to a wood work bench. Worked great.
I made the wood supports from aircraft grade 1/8" thick plywood.
See pictures.276572765827659

[bumsteer]

Thank you gentlemen. I bought a section of 5/8 inch .035 wall 6061-T6 but after looking online wasn't sure if it would bend without cracking. Obviously it can be done. I also like your T attachment. Then thought about 5052-0 but closest dealer is backordered and shipping costs for tube are insane. So I'll give the 6061 a try. My fuselage has the second antenna plate and even though I don't plan on using now I'd like to keep it useable so the razorback itself is less than 3 feet. Again, I thank you.

Rick

[SilverFox5]

Rick
l forget what length I bought.
But I did end at the back of the antenna mount.
A layer picture attached.

Joe
Kitfox5

[bumsteer]

Was able to bend my razorback successfully today. Thanks again Joe and Allan. Now if it will just warm up I can get it installed and finish covering.

Rick