Build Thread: Selextra 500
 

Hi everyone, I received a beta kit from Steve (skaliwag) at selecthobbies.com for his new Selextra500. This a a sorta scale Extra for .049 to .061 engines. He also has a larger one for a .10 size engine. These kits can also be adapted to e-power.
I have the "international" version with the wing spars cut down to fit an economical box for shipping. The box contains laser cut sheets and plywood, stick stock and sheet stock. Also there is a hardware package as shown in the photo below. The 32" X 23" plan sheet is rolled with some of the stick stock inside. There are three additional letter size sheets with a kit inventory, a wing center section detail drawing and a sheet wood cutting guide. The completed plane will have a 30.5" span and 215 square inches of area. Flying weight is stated as 14 ounces. The kit is designated RC-30 and is called the Selextra 500.
I plan to power it with a BigMig .061 R/C version.

RE: Build Thread: Selextra 500
 

I'm building the wing first. The first order of business is to "liberate" the ribs and other parts from the two 1/16" balsa laser cut sheets. I have them segregated as to R-1 and R-2.

RE: Build Thread: Selextra 500
 

will be following as I just contacted him about getting the 900 version.

RE: Build Thread: Selextra 500
 

Here I've pinned the spars in place and laid out the six R-1's in position.

RE: Build Thread: Selextra 500
 

Next I glued in the six R-1's, making sure they are square to the spar and vertical.

RE: Build Thread: Selextra 500
 

Next glue in the six R-2's taking care they are square and vertical. Here I've laid out the 1/16" X 5/8" balsa material for the shear webs, ready to cut to length. Shear webs, in larger planes, are usually installed with vertical grain. These will be laid in with the grain horizontal, which will be fine on a model this size and weight. As drawn, there would be some ply center joiners with web between, but I am going to put in a full depth 1/16" ply web in the center bay for simplicity.

RE: Build Thread: Selextra 500
 

Nice job Hollis. On the proto, for kicks, on one side I put a rib down then a shear block then the next rib and so on to the outside. Don't think it makes a difference.
I agree the ply "strap" is not needed. Ply web won't be needed either as the grain is longways.

RE: Build Thread: Selextra 500
 

Thanks for the tip Steve!

RE: Build Thread: Selextra 500
 

Now that the webbing is in place, the top spar plus the 1/4" square balsa leading edge pieces can be glued in place. That's all for today, tune in tomorrow as we continue the build.

RE: Build Thread: Selextra 500
 

Looks interesting ..do you have a pic of the plane..box art


guamflyer P-40 Bro # 5 & #6

RE: Build Thread: Selextra 500
 

Mine is a beta kit, no box art.

RE: Build Thread: Selextra 500
 

Next I glued on the trailing edge 1/16" X 1/2" balsa strips. The straight edge was laid along the wing to be sure the ribs stayed down with the tabs on the building board.

RE: Build Thread: Selextra 500
 

Now install the top center section rear sheeting and the front turbulator spar.

RE: Build Thread: Selextra 500
 

It's time to turn the wing over and carefully trim off the rib tabs. Prepare the R-T and R-L parts from the 1/8" balsa laser cut sheet. Glue these in place on the front of the ribs. These parts are the mounts for the landing gear blocks and front wing hold down tongue.

RE: Build Thread: Selextra 500
 

Glue on the bottom rear trailing edge sheet and the bottom rear center section sheeting. Next, cut the landing gear blocks to length, glue them in and then glue in the bottom front turbulator spar.

RE: Build Thread: Selextra 500
 

Next sheet the bottom forward center section.

RE: Build Thread: Selextra 500
 

Now before the top forward center can be sheeted, we need to get the plywood wing hold down tongue in there. In the first photo you can see the groove that the R-T pieces make to capture the tongue. Part of the upper center leading edge will be removed, then the tongue will be slid in place from behind. Also round the leading edge to the profile on the plan (or as I did, round the center part-I will round the rest when I do my finish sanding and shaping).

(You can also see the ply center web I glued in. I really don't think ply is needed since the wing has no dihedral and all the center section sheeting spans the whole section with no breaks at the center line.)

RE: Build Thread: Selextra 500
 

See? It will fit. I am going to epoxy the tongue in, it has a very important job! Before doing that, I will round the leading edge in this area. At this point I will finish the top forward center section sheeting, cap strip the R-1's at the wing tips, trim off the excess stock and cap the trailing edge with the 3/16" X 1/4" balsa pieces.

RE: Build Thread: Selextra 500
 

looking good so far..

RE: Build Thread: Selextra 500
 

Thanks!

RE: Build Thread: Selextra 500
 

Before I finish the rear wing hold down and aileron linkage, I want the fuselage in hand. I've learned two things about fuselages over the years. First, you must make a right and left side (starboard and port will work as well). Secondly, it must be put together straight, or you may as well cover it in yellow and continue the theme. I have the habit of laying out the sides in mirror image so as not to goof up. You will see that some 1/8" square balsa longerons and other bracing must be installed before fitting the formers and joining the sides. Note that there are some burn marks to aid in former location. The ones on the inside will be covered by the longerons, but note in the last picture that the marks are on the edge also where they can still be seen.

RE: Build Thread: Selextra 500
 

"" The ones on the inside will be covered by the longerons,"" Good point Hollis.. I am going to move those marks inboard. Lines could be drawn by builder joining the dots too. Which also helps in making a matched opposite pair.

RE: Build Thread: Selextra 500
 

Prepare the fuselage sides (right and left) by gluing in the 1/16" laser cut wing saddles, front botton fill and 1/8" square balsa longerons. Note that the longerons do not go all the way to the tail end because there are some laser cut fill pieces for that spot, top and bottom. Also glue in the 3/8" X 1/16" spruce (maybe basswood?) stiffener in the nose section. The laser cut tick marks are perfect for aligning this piece. Then glue in the 1/8" square balsa and 1/4" X 1/6" balsa uprights. There are some nose doublers that go in ahead of the firewall, and I prefer to glue these in after the sides are joined.

RE: Build Thread: Selextra 500
 

Next prepare the firewall and formers F-1 and F-2. I drill my engine mount holes, fuel line holes and throttle cable hole in the firewall. Then I flip it over and glue in the blind nuts for the engine mount. Glue the top and bottom cross grain pieces to each of F-1 and F-2. This will prevent them from splitting along the grain (you're making a balsa plywood in effect). Cut the top notches from the cross grain pieces.

RE: Build Thread: Selextra 500
 

Time to join the fuselage sides. If you made a right and left, it should be a happy marriage. Use the plan view to keep the sides aligned. Remember, we want no bananas here! Since the fuselage is flat along its top side, I lay it upside down and tack glue the firewall and two formers in place. When I am satisfied that all is straight and square I will glue it up solid with thin CA. Next add the the top and bottom tail fill pieces.