Power

Now we have to decide how to power this beast. Glow is easy, an OS 120AX would be ideal for the 2 stroke fans and any of the .120 to .140 size 4 strokes would also work well.

Epower has turned out to be a bit more difficult, at first I had decided to go with an F3A equivalent system on 10S, this would be super broverpower but after checking out the total weight of such a system I am not quite sure if that is the right thing to do. The F3A outrunner is a whopping 27.6 oz, we will need a 100 Amp controller at 4.5 oz. And at least 2 5S 3300Mah batteries at 31.6 oz. This comes to a total of 63.7 oz. (almost 4 lbs!) and we still need the mounting hardware. Hanging that much weight on the nose of the plane is probably not going to work very well either.

A smaller system on 8S should still be more than enough power and quite a bit lighter. The OS 120AX weighs 31 oz + 3 oz for tank and lines + 10 oz for fuel + 3 oz for servo and linkage = 47 oz.
8S size outrunner is 17.5 oz + 4.5 oz for controller + 26 oz for 2 4S 3300 = 48 oz.

A 1512 series Neumotor would work and be a bit lighter as well.

Anyways I think I will wait until I get it framed up and see how much weight it is going to take to get it to balance before I make a decision.

 

Construction

I am going to stick with the wing joiner block system, despite the earlier problems with the Sb45. Now that we have everything worked out I am sure this way is better than the wing tube method. Transferring the fuse load to the wing directly at the wing spars has to be better than transferring it through a tube and 2 or 3 plywood ribs.

I have decided to go with a fuse width of 5/8". A 5/8" tube is almost the same strength as 2 1/2" tubes and lighter as well, and a 3/4" tube would be way more than is needed for a 65 size plane.

I am constantly surprised at how few scratch builders there are here especially since our planes have such a high mortality rate. One would think that with the high cost of kits and arfs in the larger sizes that many would do it for the cost savings alone. I ordered more than enough wood from Clay at The Balsa Store to build two Sb65's and the cost was only about $80.00.

The only difference between a scratch built and a kit is a few parts to cut out, on all the Sbachs I have tried to keep the amount of cut parts to a minimum,

To cut out a kit all you really need is two power tools, a scroll saw and a small 8" drill press. They do not have to be anything special, you can probably get both of them on sale from Harbor Freight for about $120. With 65 size kits costing over $150 one could almost save enough on one scratch build to pay for the tools.

 

Plans for the SBACH profile
pete@therundels.com

 

Full size printed plans on D size paper with patterns for all the parts are available, pm me for details.

 

Build

Cut the wing, aileron, fuse, rudder and stab layout drawings from the plans sheet. Allow enough room as needed around the layouts for taping to the build table. Cover them with wax paper or your favorite 'keep the parts from sticking to the plans' material.

Cut out the rib patterns from the parts sheet leaving about 1/8" all around for final cutting. Glue them to the 1/8 X 3 X 36" balsa sheet. If you lay them out carefully they will just fit on 3 sheets. Note that you will need to stack two sheets together for cutting to get two sets of ribs. I usually stack up 4 sheets for an extra set, it is no more effort to cut and it is always good to have an extra set. While cutting keep a piece of scrap wing spar material handy to check the fit in the rib cut out for the spar.

 

Cut out the nose doubler, servo trays, root rib doubler from the plans sheet allowing about 1/8" all around for final cutting. Glue the patterns to the 1/8" plywood and cut out the parts.

Do the same for the wing spar shear webs and hatch from 3/32" plywood.

Cut the 5/16 X 3 X 24" balsa sheet in half and glue one on top of the other to make a 5/8" thick lamination. Glue the wing attach block and the top nose block patterns to it and cut them out.

Lay and cut out the tail parts from the 3/8" thick balsa sheet.

Remove the fuzzies from the edges and sand all the parts smooth.

Now we have ourselves a kit.

 

Looking good, Ron

 

Your a sick man Ron! :wink:

Keep up the good work!

 

Wings

The wing should be built first. The wing attach block and the root ribs are fitted together as an assembly and the wing built around it. This way when the wing attach block is glued in the fuse we will be sure the wing will fit to it properly.

The wing is built in two panels and both panels are built together, upside down over the wing plan layout which is drawn upside down, that is the right wing is on the left side on the plans.

Start by selecting the two root ribs, the 5/8" balsa wing attach block and the two 1/8" plywood rib doublers marked for the attach bolt and the wing locating dowel hole. As accurately as possible drill out a 3/32" pilot hole in each of the hole locations.

Lay one of the root ribs on the build table and using a couple of scrap pieces from the wing spars and the 1/16" plywood wing shear web or a scrap piece of 1/16" ply as a gauge, glue the 1/8" plywood rib doublers in place. Use a 3/32" drill bit in the pilot holes to line everything up. Do the same for the opposite rib. Be sure to make a right and left side.

 

Brutus do you have mine built yet?

 

Brutus do you have mine built yet?

Still waiting for Ron to post plans... :wink:

 

So I am curious why you went with the 45 verson tabs rather than the tube verson that is on the 55?

 

opcorn: 8) opcorn:

 

So I am curious why you went with the 45 verson tabs rather than the tube verson that is on the 55?

The thing about the 55 is that the second rib takes all the transferred load from the fuse to the wings. This plywood rib transfers the load from the tube to the wing spars. With more Bros wanting to put the batteries in the wings it would mean cutting this critical rib. One could make the tube longer and make the third or fourth rib plywood but this adds a lot of weight without any gain in strength.

The wing joiner block system transfers the load directly from the fuse to the wing spars, which I think is the way it should be. It is lighter and easier to build than the tube system, and if you cut out the leading edge ribs to make room for the bats it will not affect the wing structure.

I know some are leary about the joiner block system after Rookies failure, but I think it was a blessing in disquise, it showed a possible weakness in the build which has been rectified. There was a reason I sent one of the prototypes to Rookie, I knew if anyone could break it he could, and he did. Thanks Rookie, sorry about the receiver tho.

All of the Sbachs are prototypes, they are new designs and an experiment in new ideas, one cannot try something new without having some risk.

Maybe it is a bad idea and it will not work, I dunno, but I want to try it. I have not been able to break mine and I have tried to.

I am seriously considering building another 55 with the joiner block system, a lighter build for electric power only and room in the wings for the batteries.

 

I've at least got the wings for the .45 on the board,... Progress is slow,... I"m a bit burnt lately, but it'll live again as an R-wing,... I'll be doing everything I can to make sure this wing doesn't fail,...

EXCEPT for the way I'm gonna fly it! :twisted: I'm gonna tear it off again if it is possible.

Don't worry about the RX,... it was bound to happen sooner or later that I'd have a plane tear a RX in half on impact. :shrug2: With the way I fly I'm really surprised that was my first! :twisted:

 

Gotcha. I think the tab method can work well. I was just wondering the reasoning and that makes purfect sense. Thanks!

 

Clamp the ribs to the wing attach block using the 3/32" drill bit in the holes to line everything up. When you are satisfied that all is straight and lined up, drill through the ribs and block with a 7/64" drill bit for the 8-32 wing bolt, then drill through 3/8" at the back of the rib for the 3/8" wing locating dowel. Take the right side rib (the one opposite the wing hatch and drill it out for the 8-32 T nut. Fit the whole assembly together with the bolt and 3/8" dowel. Put some wax paper between the wing attach block and the root ribs to keep from accidentally gluing the wing to it.

 

I think I might need one of these. Subscribed,

 

Will I get to fly one in South Kansas City? Please!!!!!!!!

 

Very nice!! opcorn:

 

I think I might need one of these. Subscribed,

And it's gonna last you . . . ? :lol:

 

Cut the two lower 5/16" X 3/8" hardwood wing spars to length and place them over the wing plan.

Take the root rib assembly and place it over the wing spars lining it up square with the spars. Be sure the ribs are tight to the attach block. Glue the ribs to the spars taking care not to get any glue on the wing attach block.

If one is using CA glue for part of the build be very careful that the glue does not run down and accidentally glue the wing locating dowel in.

Place each of the 1/8" balsa ribs in its proper location on the wing spars, square them up and glue them to the spars. Check that the trailing and leading edges of the ribs line up, trim as required.

Cut the 2 5/16" X 1/2" trailing edge spars to the proper length and angle. Glue the trailing edge spars to the ribs in the notch provided.

Cut the lower wing spars (upper during the build) slightly longer than needed. Mount them flush with the root rib and glue them in the spar cutouts in each of the ribs. Let the excess hang past the tip rib. The extra will be cut off later with a razor saw. Do the same with the 3/8" square leading edge gluing it in the notch provided in the nose of the ribs.

 

Will I get to fly one in South Kansas City? Please!!!!!!!!

Sure.

If it lives that long. :wink: :roll:

 

Trial fit the aft 3/32" plywood spar shear web between the root and second rib, trim as required for a good fit.

Glue the 3/32" plywood hatch and 1/8" servo trays in place. The hatch can be located in either the top or bottom of the wing. Note that the servo trays are glued under the wing spar and angled slightly to match the angle of the ribs. If the plane is to be glow powered and it is desired to have the throttle servo in the wing rather than in the nose an additional servo tray can be glued in at the root rib.

Cut 4 pieces of 1/16" X 4" balsa 32 1/4" long then cut each one at an angle 4" on one end and 2 3/4" on the other for the leading edge sheeting. The remainder of each sheet is used for the spar webs.

Glue the 3/32" plywood aft spar webs in place to the spars, between the first and second rib and to the doubler at the root rib. Try not to get any glue inside the pocket formed by the wing spars and the ply spar webs where the wing joiner block slides in. Use epoxy or carpenters wood glue for all the wing joiner parts.

Cut each 1/16" X 4" wide balsa spar webs to length and angle with the grain vertical between the spars and glue in place between the ribs as shown on the plans.

 

LOOKING good RON

 

OK, if you are burning to have the batteries in the wings now is the time put everything in place to do it. Decide what size batts you want to use and make up the trays to hold them. Attached is a pic of a couple of batts placed between the ribs on the plans. The short 3000Mah fits nicely between the ribs, the long 3300Mah extends past the third rib, if you want to use a battery of this length or longer this nose rib will have to be moved outward.

Make a new nose rib and glue it in place. Extend the plywood fwd spar web out to the new nose rib. Use this spar web to attach the battery trays. If you are going to use a heavy battery you may want to make a new spar web out of 1/8" ply instead of the 3/32". This is just a suggestion right now as I do not know yet how the balance is going to work out. After I get it built I will try a few batteries and repositioning the tail servos to see what it is going to take to get it to balance.

The distance between the first and third rib is 5 1/8"