Tail surface rib stitching

[jmodguy]

I am getting ready to start covering my tail feathers over the holiday and have a question about rib stitching the tail feathers. How is everyone finishing their tail feathers? Is stitching required/needed? I plan to stitch the wings just wasn't sure about the tail feathers.
Any guidance/thoughts are appreciated!

Regards
Jeff

[Av8r3400]

I put a couple stitches on mine over each of the forming ribs. Just because the mood struck me to do so. No other reason. Modified model IV, with short ribs only on the fixed horizontal and vertical surfaces.

I don't believe stitching the tail is a mandatory thing.

IMO.

[Dave S]

Jeff,

I did not rib stitch for the Vertical stabilizer, rudder or horizontal stabilizer; however I did put stitches in the elevator.......personal preference based on the "flat" surfaces of the elevator.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp Drive

St Paul, MN

[Dorsal]

I did not stitch any tail surfaces but did do the wings.

[jmodguy]

Thanks for the inputs!

One other question - What are you-uns using for a heater core??
I plan on using two 12v PC power supply fans hooked to a dimmer with an off switch to move the air around.

I decided to go with Stewart Systems for my "skin". Painting isn't a bad thing to know how to do! Besides, the project came with a roll of Poly Fiber.

Regards
Jeff

[Dave S]

Jeff,

I purchased the standard heater core with my kit.....I believe Kitfox still carries these - they have all the hardware & muffin fans that goes with it. The earlier S7 Kitfoxes ran barb fittings straight through the firewall to connect to the core. I believe Kitfox now has a kit which runs hoses through the firewall and AN 180 degree connectors under the panel.

I have to say I like your idea of controlling the muffin fans for the heater....wish I had done that as mine is either on or off and unless it is darn cold outside, I have to keep switching it off and on to keep from frying.

This is a "some day" project for me.....somehow I will eventually retrofit fan controllers to moderate the heat when it isn't really bad cold outside.

Sincerely,

Dave S

Kitfox 7 Trigear
912ULS Warp drive

St Paul, MN

[jiott]

I also used the Kitfox optional heater kit with two 12v PC fans. I wired them up (as shown in the kit) so a SPDT switch either runs one fan or both fans. Very simple and after using it thru two winters I find that this "two speed" control is very satisfactory; no need for variable control. I also do not have any shut-off valve in the heater coolant line and find that even on a hot summer day (98 F) with both fans OFF there is no appreciable unwanted heat coming into the cockpit. I like the KISS principle.

[jmodguy]

Does anyone have a picture or specs/dimensions of the heater core? I am guessing it is a repurposed oil or transmission cooler. I have the fans already. Figure I can find a similar part for a whole lot less than the factory part.
The $$ I save will be going to an aluminum header tank!

Thanks
Jeff

[HighWing]

Does anyone have a picture or specs/dimensions...

Jeff, I think you are correct on the heater core. Mine is an oil cooler core - Earls I believe. These are available everywhere in multiple brands. The early models used to use the Earls oil coolers - not sure what is used on the 7s. My muffin fan has three wires that provide for a high and low speed. I found that I had to connect the high speed circuit to the first contact on my rotary switch because connecting the low speed wire to the first contact provided insufficient voltage to start the fan from rest. If I want low air flow, I turn two clicks right. The first click triggers the fan movement, then the second click maintains the rotation at low speed.

Regarding rib stitching the tail feathers, I did, but it was because I an idea I had been thinking of for years. I installed flexible ribs on the rudder to create a hidden method for rudder trim. A cam bends the ribs to modify the rudder airfoil shape. I needed to keep the fabric attached to the ribs which were made of Carbon Fiber arrow blanks. There was insufficient surface to glue the fabric to the ribs. And it is possible to take the surface to undercambered shape on either side. For consistency sake, I did all the rest as well. I doubt it is really necessary on conventional tail surfaces.

[N213RV]

I rib stitched everything..... All surfaces of the elevator, rudder, horizontal and vertical stab. And of course wings..... Overkill I know, but educational and I like the looks and added safety.

[jiott]

Lowell, I am really curious how you change the shape of your flexible rudder ribs? Do you have any pics of the mechanism? Did it work well? This is the height of experimental aircraft!

[Floog]

Jim, what is SPDT switch? Did that come with your kit?

[Dorsal]

I also wired mine to be adjustable though did by switching between both fans in series or parallel. I definitely like having the two speed control.

[Dave S]

Dorsal...that sounds like an elegantly simple solution.....happen to have some identity on the specific switch(s) you used?

Thanks,

Dave S

[jmodguy]

Floog
SPDT is a single pole double throw switch. Basically it has a center contact that is common and two contacts that are closed or open. One set of contacts will be open while the other is closed. It is also called an ON-NONE-ON switch.
A DPDT is similar but has two sets of contacts - Double pole double throw. DPDT switches are typically used in flap or trim motor switch circuits.
Regards
Jeff

[jmodguy]

OK for all that stitched the tail feathers...
The ribs are 1/8 thick and I am wondering how you compensated for the lack of cap strip. The narrowest reinforcing tape from AC Spruce is 1/4" wide and from what I understand should be the same width as the cap strip.
Sooooo.... How'd you do it???
I'm going to do it for the practice and as always - better safe than sorry!

Regards
Jeff

[jiott]

Stitching the tail feathers is totally unnecessary, but if you do it you would need to add capstrips to the ribs. Its extra weight and a lot of extra work. If you need practice, use a scrap piece of fabric over some kind of wood frame. After you have done one or two stitches you won't need any more practice. My 2 cents.

[N213RV]

I used the 1/4" reinforcement tapes on the 1/8" ribs, stitched them, then covered with 1" trim tapes. Turned out nice. I can send a picture later.

[HighWing]

Jim mentioned the weight added when we do our modifying. With that in mind and that I was building a Model IV, I converted all ribs to quarter inch urethane foam covered with a single layer of medium weight fiberglass. The weight issue was foremost on my mind as I was adding a lot of stuff to the tail - gap seals vertical and horizontal and fairing everything to reduce drag. Everything was done with weight in mind.

Gap Seal in Neutral

10178

Gap Seal fully deflected

10179

Elevator strut fairings and Horizontal / Vertical Fairings

10180

[Clark in AZ]

Nice job! What do you figure all of that did for the performance? Any numbers?

[jmodguy]

I used the 1/4" reinforcement tapes on the 1/8" ribs, stitched them, then covered with 1" trim tapes. Turned out nice. I can send a picture later.

Looking forward to seeing pics!

[Av8r3400]

So, Lowell, does that thing cruise at about 190 knots, or what? :cool:

[HighWing]

Nice job! What do you figure all of that did for the performance? Any numbers?

No real comparisons as both my IVs had the fairings from the get go. I pretty much did the same fairings on my first Model IV And most local flights were less than max cruise. On our group flights we always flew to the speed of the slowest airplane to keep the loose formation together. For me, at least, the fairings helped mostly with fuel burn. On one of the early flights to the Idaho Back Country, our fuel stop at Winnemucca, NV is still talked about. Six airplanes fueled and the fuel burn on the first leg was very interesting. The Rans S-6 Took 13 gallons. The rest were Kitfox Model IVs and fuel loads ranged from about 9-1/2 to 12 gallons. I topped up with 7.2 gallons. It was a three hour flight. The S-6 ran a 912ULS where four of the Kitfoxes had the 912 UL and the fifth ran behind a 582. My typical RPMs with the group ran in the discouraged under 5000 RPM range. My current IV, will cruise at just below 110 mph behind a 912UL. I think I could get a few more miles if I faired the spring struts and cabane on the landing gear. Then I just might pick up a Zipper from friend Hal.

I guess I should mention that I have never felt elevator authority was less than adequate, and three pointing has never been a problem with the gap seals.

Three pictures of the 1998 (earlier) Model IV.
The Horizontal stabilizer showing the tip.

10181

The Horizontal Stabilizer.

10182

A drawing of the method used to make the 1998 gap seals. The later model was made of fiberglass shapes without foam except for the ribs.

10183