Jay Burkart's blog View Details
Posted by Jay Burkart | Aug 08, 2015 @ 02:50 PM | 4,278 Views
I took the Racer to the SAM contest at the Toledo Weak Signals SAM contest and got to fly it about 3 flights.
Tuesday night before the contest got a long check out flight without a bunch of contestants around and it flew well, Had to put in a lot of down trim so there seems to be still too much wing angle of incidence so added 1/8 shim at the wing TE.
Flew it the next day at the contest in the Texaco event and it did fine.
Actually won the event with a 23 minute flight. This model does fly a lot different than the large Airborn and I need a lot more flying with it and do more trimming to get best thermal performance. Seems to fly a lot slower and doesn't track as well compared to the Airborn.....
So best to fly it a lot and become more familiar with it and trim it.
Posted by Jay Burkart | Aug 01, 2015 @ 02:11 PM | 4,738 Views
Assembled the entire Racer this morning and checked the CG.
Came out to 55% which is right in the ballpark. Probably will move it back as I test fly it.
Racer is complete except for some wing decals and other "pretties"
Wish the Polyspan looked whiter. Probably needed to bleach the edges of the exposed balsa to make it look whiter.
Had hoped to try Florist Spray but can't find it in white.
I want a translucent white finish on the main wing panels.
I find that when flying in blue skies it back lights and virtually glows
at higher altitude so I can see it when thermaling.

Anyone have any ideas for making it a whiter translucent?
It has to be a Polyspan type covering.
Posted by Jay Burkart | Jul 31, 2015 @ 05:10 PM | 4,437 Views
I've got the Racer finished to where I am ready to test fly it......
I also made wing storage/transport bags and also for the H. stab and rudder.
Right now waiting for delivery of a new 5 cell 2550mah Eneloop receiver/servo battery pack.
I plan on taking the Racer to it's first SAM contest next week at The Weak Signals annual SAM contest up north of Toledo.
Hope I can test fly it before then, otherwise that's when it gets test flown, but it's about the nicest wide open field around to do it.
I'll try to get some assembled pictures soon.
Still waiting on the rest of the decal set too.
Posted by Jay Burkart | Jul 15, 2015 @ 05:21 PM | 3,884 Views
Here are a few pics of my covering of the Racer.
I used Ultracote on the tail feathers and wing tips. The center section
of the wing I am using Polyspan for the extra rigidity.
I had discovered on the Airborns that the wings were susceptible to wing flutter if dived and since the Racer wings are essentially the same design I am making every effort to make the wing as torsional stiff as possible.
Posted by Jay Burkart | Jul 15, 2015 @ 05:14 PM | 3,678 Views
I have gone onto to installing control rods and the servos.
I had hoped to be able to mount the servos right back by the Horizontal stab in the Racer just as I had done in the Airborns but the nose moment is so short that it proved to be a problem. So I've put in some Sullivan Semi flexible Gold n rods.
At 48" these allowed me to mount the servos in front of the 50% wing chord
right in front of the CG where I will start flying the model.
With the very large lifting stab it may prove out that the flying CG I end up with may be back as far as 70% of the chord but I'll see.
I also am using the Sullivan Ball links at the control horns to make for easy disassembly same as used on the Airborns.
Posted by Jay Burkart | Jun 14, 2015 @ 02:02 PM | 4,196 Views
These are some pictures of how I go about joining the whole wing tip section to the main center section. This is a removable joint using 1/4' CF rods and a 3/32 wire locator pin.
I use my wing jig to hold everything in alignment. The joiner sockets holes are predrilled in the ribs, Since the wing sections were cut on the correct angle on the radial arm saw, this gives me the main spars, TE and LE to align the very end ribs on to both the center sections and tip sections so I can glue it in place then run the joiner tube with a dummy kerf rib sandwiched between, through at the right angle for the joint. The main tube within the main spars are tacked into place with CA glue, then the rear locator pin tube is put through the ribs and supported on each side by some balsa pieces.
When all this is in place and well tacked in, I take a razor saw and cut right through the 1/16 kerf allowance rib and on through the joiner tubes.
This then gives me the two wing sections with the tubes installed. I then box in the spars with 1/16 ply and fill in with some end grain balsa with gaps and back filled with epoxy and microballons. Then the end ribs are capped over with 1/16 ply end cap ribs....Continue Reading
Posted by Jay Burkart | May 30, 2015 @ 01:24 PM | 4,938 Views
I've rough framed up the Center Sections of the three wings. I added shear webs all the way the length of the main spruce spars. The center bays shear webs are 1/16 ply as that forms the box for the joiner tubes. I then filled the gap between the vertical grain balsa filler pieces with long set epoxy filled with microballons to
still give it structure but no so much weight. I immediately capped all those spaces between the ribs where the wing joiner box with 1/16 ply to make the other side of the joiner box.
After the joiner box was done then I added two more sets of shear webs at the front sub spars and the rearmost sub spars to try alleviate a flutter problem seen in these wings. Then the center section bottom was sheeted with 3/32 balsa.
At the TE there was some additional pieces added just in front of the TE made out
of trailing edge stock, this is to reinforce where the rear wing mounting bolts are passed through. Then the top of the center section is sheeted also with 3/32.
Posted by Jay Burkart | May 20, 2015 @ 05:26 PM | 5,102 Views
I've come a way on the build of the center section for the three wings.
The Center section on the Racer is about 5.5 ft span. It is built in one piece and then bisected after it is framed and the center section planked. I cut right down the center where I place a dummy rib for kerf allowance right thru the brass receiver tubes for the joiner CF rod.
Note that the ribs are all provided with a little extra platform piece where they join onto the TE to allow for the TE to follow the curve of the under camber wing section. I will build the tip joiners after framing the tip sections when I have the center section halves mounted on my wing jig.
Posted by Jay Burkart | May 11, 2015 @ 09:08 PM | 6,180 Views
I've been quite a while getting all the parts ready for the Wing build.
I've bonded .014 Carbon Fiber strip to the 1/2" Spruce main spars, both center section and tip sections. Also the 3/8 ID brass tube for the center section build.
This involves roughing up the exterior of the tube for a good epoxy bond and end caps in both ends of the tube so the carbon fiber rod has an end stop.
Also the TE pieces needed to be laid out and the rib notches milled.
Also the TE needs to be spliced to make them long enough with scarf joints and a butt joint at the center where the wing will be cut in two panels.
Posted by Jay Burkart | Apr 23, 2015 @ 04:50 PM | 5,889 Views
I have finally started mounting the gear in the fuselage and landing gear mounts.
Main landing gear will consist of a 5/32 front gear and 5/32 rear angle brace.
I mounted the maple hardwood slotted mounts in the fuselage and will be actually bending the wire later. I also came up with a way to easily change the motor battery without having to remove the wing each time and also keep the battery as far forward as possible. I made a battery tray that slides into the fuselage from the front under the motor and the tray allows adjusting the battery fore and aft to best adjust the CG....Continue Reading
Posted by Jay Burkart | Apr 08, 2015 @ 09:58 PM | 5,686 Views
I started building the fuselages for the Racers and have built 5 of the six sides so far. I found that this is slow going as I have to soak the 5/16 longerons in hot water with a little ammonia for about 6 hours or so to make the front 1/3 pliable enough to make the bends in the front section of the fuselage. There is a fairly severe curve from the top and up from the bottom and using hard balsa required a long soak. Anyhow there are No cracks and no buckling. After gluing in all the verticals and diagonal braces plus gussets I let the longerons dry thoroughly overnight to take the form. Nice thing about CA is that it glues wet balsa nicely.
the fuselage longerons are almost 5 ft. long so I had to join on extra pieces to all the longerons, so not the extended scarf joints in the pictures, I am using about a 4" long joint, I also learned to prime each piece in the joint with a little thin CA first let that cure and then do the actual joint with medium CA. I also do all joints for all the other structure with Medium CA, then I will re-glue every joint after the fuselage sides are joined.
I am fighting having an issue with this model being tail heavy so you see that I even cut the firewall to where the Lipo is even as far forward as possible....Continue Reading
Posted by Jay Burkart | Mar 31, 2015 @ 08:00 PM | 10,267 Views
Next on the board is the building of the Horizontal Stab and Elevator and mounting the V.Stab onto the Horizontal to make it removable.
This H. Stab is very much different from the Airborn since this H. Stab is a lifting stab. So that makes it much thicker plus having an airfoil to it.
This stab is about 1.125 thick at it highest point. I wanted to make the slot mounting of the Vertical stab about the same as I used for the Airborns.
I digressed from the plans on part of the ways of fastening the V. Stab to the
Horizontal, the plans called for two nylon screws going up through the Horizontal and up into the bottom of the vertical. But I worked out a way to use a carbon fiber pin in the Vertical so that it just pins it at the leading edge and only one screw goes up through the Horizontal and into the base of the Vertical at the Rudder hinge line. Also I had some problems with the 5/16 thick balsa at the hinge joint.
This piece had to be 11/8 thick and the length of the H. Stab 48 inches. I had several pieces of 5/16 X 3 stock and when I ripped it to size down its length the pieces of stock would immediately warp badly. This is probably because the wood was cut too green when it was made into 3" planks. So I had to steam the pieces and warp them back straight.
One issue that comes up with the Racer is that it has a short nose moment and the
size and weight of the tail feathers may be a problem to be able to get it too balance. With it being electric...Continue Reading
Posted by Jay Burkart | Mar 24, 2015 @ 10:08 PM | 6,048 Views
This evening after finally sanding and fitting all the parts from the short kit, I started to build the Vertical Stab and Rudder.
Pretty conventional build except for my way of mounting the V. Stab. to the H. Stab.
Notice the bottom of the V.Stab that there is a sandwich of balsa and 1/16 ply base with a modified blind nut where a 8-32 nylon screw passes up through the H. Stab. The front LE of the V. Stab will have a carbon fiber pin sticking out.
More on that as I get through the build.
Been doing it this way for about the last 15 years on many Airborns.