Spar Attachment Mods

I have a personal (maybe irrational) hang-up when it comes to drilling four 0.188" holes at close proximity in the horizontal legs of the spar angles for the attachment of the interplane strut fittings. I have decided to incorporate "mirror image" fittings to completely eliminate the need for holes in the spar caps. The CAD images illustrate how this would work for the main spar. The first three images are per plans. The last three images are of the modified approach.

I do not mean to imply that there is any problem with the original design. but is interesting to note that as designed, the interplane tension wire puts the spar flange in bending by pulling perpendicular to the spar cap.

The proposed modification will add about 5 oz. per wing or 20 oz. to the airplane. I will save more than this in paint weight by using silver for the wings. Since weight added out on the wing has a magnified effect on handling, it is important that the "saved weight" also be on the wings.

The Jabiru 3300 I plan to use is about 25 pounds lighter than the normal O-200 so I have a few pounds to play with. I am confident that the airplane will come in substantially below 600 #.

Control Stick components

Most of the control stick components have been completed and ready for welding. The stick gimbal components were done in the traditional way, paper pattern, saw and sand. The aileron horns were done by waterjet.

I was not comfortable with trying to get the 3/4" hole through the longitudinal tube so I took it to my friends machine shop and he cut it using his milling milling machine and an end mill. I could see some serious potential for hanging and ripping something if I tried it with a drill bit in the drill press. It came out nice with no problem.

The 1-1/8" control stick is a real handful. I plan to replace it with a 1" diameter tube before welding. Of course that means remaking the pretty little pieces!

Fuselage out for final welding.

On Monday the 2nd I took the fuselage to Dale Doane for final welding. The fuse rode well on the racks I built for the Tundra. The weather was great so there was no worry about the fuse getting wet. Dale started welding shortly after I got there and is moving right along. The photo shows the cluster at the bottom of the firewall where the forward landing gear attaches.

I tried to get some photos of his work but my camera was acting up. I will add some more photos after my next visit. I intend to leave the fuse with Dale until we get all of the attachments made and welded on.

Installing Motor Mount Bushings

The following photos show the use of a fixture made to hold the motor mount bushings and washers in the correct position for welding. The appropriate hole pattern was carefully laid out and drilled in a piece of 3/4" MDF. It serves three purposes, first as a fixture for the motor mount bushings, second as a mount for the "rotisserie" forward pivot shaft, and third it will be used later to align the motor mount weldment when it is fabricated. This will assure a good match of the hole patterns if the welding distortion is not too great.

The last two photos show a small mod we made to the motormount bushing attachmment. We used rectangular tubing with one side cut away to make 45 degree gussets to reinforce the attachment. Again, a few ounces of added weight but it is in the area where the Jab engine saves 25 plus pounds so a little give back here won't hurt.

Aligning Landing Gear & Wing Attach Parts

The alignment of the landing gear and especially the wing attach fittings is critical. The plans call for 1.9 degrees of incidence for the lower wing and this is set by the position of the attach fittings relative to the lower longeron. The magic of CAD reveals the correct dimension of each of the four side plates which make up the two attach box fittings on each side. The fittings in the photos were cut by waterjet complete with the attachment bolt holes correctly offset in each part to achive the 1.9 degree incidence.

One method of ensuring the proper alignment uses threaded rod, tubing and spacers of the correct length to make an "assembly" which can be positioned correctly before welding. The following photos show the fitting assemblies for both the landing gear attach and lower wing attach components. The fuselage is upside-down in these photos.

Note that the wing attach fittings establish a 1.9 degree angle of incidence.

EAA SportAir Fabric Workshop

Tom and I attended the SportAir fabric covering workshop in Lakeland over the past weekend. We were very pleased and impressed with the experience. Lynn Zaro, the workshop leader, was fantastic. Not only is she a world class fabric expert but also a great teacher. This was a very helpful workshop. We both came away with complete confidence that we can do a very good job covering the Skyote. Wish I could have left the TIG welding workshop with the same degree of confidence!

Wing & Gear Attach Fittings

Made the first run of fittings with the new waterjet source today. Due to limited time available today we only cut the 0.080" wing and landing gear attach fittings. We will cut the remainder of the order next week when I return from the SportAir Fabric covering workshop in Lakeland, FL.

Everything went well. The quality of the work is excellent.

More Parts in CAD

Today I managed to convert all of the more demanding fuselage attachments to CAD. This includes the wing attach boxes, the landing gear attach plates, motor mount plates, etc.. I also did the elevator and aileron bellcranks and horns. Hope to get them all cut by waterjet later this week.

New Waterjet Source

I met with a possible new source for waterjet services this week. The owner is very interested in learning to fly as his wife and her father and brothers are all pilots and airplane owners. He was very interested in the homebuilt market as a possible outlet for his services. Better yet, he is excited about the possibility of building a Skyote for himself! He is totally agreeable to helping set up standard "batch files" (my terminology) for fitting kits and might be willing to serve as the source for fittings. The prices quoted are much better than my initial supplier. This could work out to be a very good arrangement for Skyote builders as well as other homebuilders. I will be taking metal and DXF files to have fuselage attachments cut later this week.

RV rudder Pedals for the Skyote?

Some quick measurements reveal that Van's RV-8 rudder pedals will fit nicely in the Skyote. I don't plan to use the adjustable pedals although they would easily fit. The whole assembly works very well on our RV-8. Everything including brake cylinders is included in the package. Up to 1 1/2" can easily be removed from the width of the assembly. If this works out, it will be another time saver.

A half-set of pedals from the 7A would also work if you wanted to stay with the overhead pivot. However it looks like RV8 pedals would make a cleaner installation.

Or maybe best yet, RV4 rudder pedals!

The Fuselage is Tack Welded

The fuselage is out of the jig! Dale Doane tacked welded the main portion of the fuse yesterday. After I fab the finger plates and other fuselage attachments, I will take the fuse to Dale's shop in Newnan, GA to complete the welding. I continue to be impressed by the VR3 tubing kit. The tube which extends rearward from the bottom center of the firewall looks crooked because it is! This is where we ran out of Argon and that particular tube is still loose.

Just so happens that Glenn Bridges got his VR3 fuse tack welded and out of the jig the same day!

Prepping Fuselage for Welding

I disassembled the fuselage and polished all of the weld areas this week. Acetone was used to clean the weld areas inside and out to remove oil contamination. I am a little concerned that oil contamination may migrate from the interior of some of the tubes, especially the ones in vertical orientation.

I have arranged with Dale Doane, an A&P who works for Delta to weld my fuselage. Dale plans to fly his Cessena from Atlanta and tack weld the fuse here in my shop. I will then take the fuse in my truck to his shop in Atlanta for finish welding. We had hoped to get started this week but now it looks like the weather isn't going to cooperate.

Glenn Bridges has his VR3 fuse all jigged and polished and started tack welding today. looks like he will be ahead of me for a while!

Center Section Spacers

Made a couple of sets of spacers for the center section today. The .115" and .300" spacers were too short to easily make from the purchased spacers so I made them from scratch using bar stock. The .250" long spacers were purchased from www.aluminum-spacers.com.

Next will be the 1"x 1" x 1/8" "C" channel fittings for the ends of the compression struts.

Rib to Leading Edge Clips

Made 70 angle clips to attach the ribs to the
leading edge tubes today. I taped 7 or 8 clips together and
"gang" bent them as a group to save time. The bender is so accurate I was able to adjust for the added thickness of the tape so the bends would come out exactly right.






I had to push the holes outward toward the ends of the
angle legs a little. As drawn, there is not sufficient room for
a rivet puller to operate. The drawing
references " 4 number 3 rivets". The rivets which go in
the tube must of course be pulled rivets.

Compression Strut Bushings

Tom and I made two sets of bushings for the ends of the compression struts last week. We started with 3/4"x 3/4" x 5/16"ID spacers from http://www.aluminum-spacers.com/. We made a mandrel for the lathe so we could turn down the barrel of the spacer to 0.652" leaving a 0.060" flange at one end

The bushings fit nicely in the 3/4"x 0.058 wall x 6061 tubes. The "hammered" effect on the ends of the bushings is from tumbling the parts after the spacers were made.

Priming the Spars

We had some nice weather (70 degrees) earlier this week so Tom helped me prime the spars for one wing. First we pulled all of the spar caps and webs over a 3-M wheel to polish all the edges smooth Then we scuffed every thing good with Scotch-Brite and cleand with a degreasing cleaner.

We are using RM brand DE15 epoxy primer and it seems to work very well. I used PPG DP40LF on my RV7A but that paint store closed. (Edit: See updated post as I have reverted to DP40LF)

The three cans in the picture......$335.45 +tax Ouch!

P.S. The funky looking parts near Tom's left hand are wing root strakes for our RV-8. They are reported to lower the stall speed significantly and eliminate a strong tail buffet which occurs near stall speed.

Bending Rib-to-spar clips

Bent the rib-to-spar clips for one wing today.

The following pictures show a clip in the process of being bent.

The first in the sequence shows part in position.

The second shows the ram just touching the part which is "zero".

The third shows the part at 0.210" ram travel after zero. This will result in a part with 82.8 degrees included angle.

The fourth is the finished set for one wing.