Kyosho 40 Spitfire II Conversion

[FAA]

Kelvin its fine.

Just keep the fin and horizontal square like Ed said above.

The difference I see in relation to the wings is so insignificant that it won't have any effect on the flying qualities of the model.

[DavidN]

A spit is on my list. I have the B50 10L with the 6.7 GB. How do you think that would that work?
DavidN

[kelvin]

I ran the numbers in Motocalc and with the 6.7 and 14x10 static amps is 26. If Motocalc is wrong like in my intial prediction then the static amps may be a little higher, maybe 30-34.

The 14x12 prop shows 30.1 amps so if Motocalc is over 5-8amps again then it would be about 35-38amps. It might work.

Motocalc show 107oz of static thrust for the 5.2 and 14x10 and 79 oz for the 6.7 and 14x12. I those numbers would be higher if the amps are up but it shows the relationship.

I think any prop over 14" is getting too big. I think you might have prop clearance issues. The plane's tail come up on the take off roll and I think a 15 would come close to striking the run way.

Are you going to hack the gear if you get it? It just takes a little patience to cut the new ribs so they fit the contour of the outter sheeting.

I wish I could upload a video of this thing flying.

Kelvin

[jrb]

Kelvin, reading between the lines; are you considering re-gearing?

If yes & with the same motor, then tweaking MotoCalc’s parameters to match what you saw with the 5.2 & 14x10 will help you get a closer prediction of the performance with the 6.7.

By re-gearing you might also want to consider a 3 blader; I have done the calcs but MAS a 14x9, 16x8, & 16x10 that might be from which to start? My 4 blader was made from an APC 15x11 trimmed to 12.5.

[kelvin]

Originally posted by jrb
Kelvin, reading between the lines; are you considering re-gearing?

If yes & with the same motor, then tweaking MotoCalc’s parameters to match what you saw with the 5.2 & 14x10 will help you get a closer prediction of the performance with the 6.7.

By re-gearing you might also want to consider a 3 blader; I have done the calcs but MAS a 14x9, 16x8, & 16x10 that might be from which to start? My 4 blader was made from an APC 15x11 trimmed to 12.5.

I'm always in favor of tweaking.

I'm not sure what to change in Motocalc to get the amps up to the real world.

I would eventually like to try a 3 bladed prop as long as I can use a 3 blade spinner on it. I have one but have no idea if a 13 or 14" 3 blader will fit. The 3 bladed spinner is one of those that Hobby-Lobby used to sell.

After I get some flying experience on Spit II I want to try these modifications

Add landing gear doors
Add a balsa radiator to the wing and oil cooler to the fuselage. (gotta make sure I've got all the bugs out of the retracts so no more belly landings)

I haven't seen an electric plane fly with a 3 or 4 bladed prop yet.
That's quite a reduction from a 15" prop to 12". I guess you chose the 15" because of the wider blades. Did you just cut the blades down a little at a time then measured the current draw?

Kelvin

[jrb]

Kelvin, that’s a good approach; though I didn’t get there that way.

Kind of new that I wanted to be @ about 12.5; so I drew a lines @ 12.25, 12.5 and 12.75, and thought the 12.5 profile looked square enough – most of the scimitar was gone.

A black permanent marker to color the gray and yellow Monokote (front side only) did the tips.

It pulled the amps I wanted on the 1st run-up. Loaded the motor up similar to a APC”E” 16x10 (12.5x11x4), but ran smoother, quieter, generated more velocity, and thrust!

If I can get my capture card working I’ll be like you trying to get the video uploaded someplace. Maybe I ought to just get the audio going 1st – its an awesome sound.

[kelvin]

I glued the tail surfaces yesterday and fitted the wing to the fuse to accept the nylon bolts. I forgot that I had to buy new blind nuts for the nylon bolts and luckily I still had Spit 1's blind nuts. You have to drill out the mounting plate holes a little for the large blind nuts to fit.

Heres the tail and the tail wheel glued and tail surfaces hinged and CA.

[kelvin]

Next I cut out the slots for the control rods on each side of the fuselage. This has to be the most tedious frustrating part about this ARF. I used Spit 1's measurements and cut them out. You have to make the slots a little bigger than necessary to get a drill bit or other tools to carve out the thick balsa behind the fuselage skin for the control rods to clear. I'm going to use Spit 1's control rods since they werent damaged in the crash. I guess thats why they put flight recorders in the tails of aircraft.

I painted the inside of the cutouts with the brown acrylic paint shown the Spit 1's thread. Here is the elevator control rod slot.

[kelvin]

Here is the rudder control rod slot. I don't know why they can't have these slots already cut. There is so much thick balsa in the tail. I know, to keep costs down.

[kelvin]

Elevator control linkages were installed. After the elevator and rudder control horns were installed I then glue the servo mounts down. The control horn keepers that sandwich the horn to the surface had a defect. One of the hole was too big so the screw wasn't able to tighten down. So I used Spit 1's.

I'll go back later to apply some loctite to those set screws.

[kelvin]

Here the RR Merlin engine is mounted. The motor mount screws were kind of long so I cut them down with the motor tool cutting disk. A little loctite was applied to all the screws.

[kelvin]

I also soldered the UBEC and connectors onto the new HM 70 3p Opto. I used some small tie wraps as strain relief for the UBEC wires. Bullet connectors are used to connect to the motor.

[kelvin]

Here is how I'm going to mount the ESC. Cooled directly from the outside from the air intake that I will cut out of the cowl. One tie wrap is used to hang the ESC.

[kelvin]

Here is the front view. I decided to keep the ESC to one side to allow air to get to the motor also. Air exits (I hope) through the hole in the mounting plate and the oval hole below the mount.

[kelvin]

One of the new things I want to try is an aileron rotary driver system (RDS). With this system there is no external linkages showing.

You can make most of the parts but for my first time I purchased the parts from

http://www.irfmachineworks.com/rds/

I purchase two control rods already bent with a flat ground at one end, two aluminum couplers, 2 sets of Kimbrough RDS plastic couplers and two pockets. Total cost with shipping was about $38. You can use Paypal and Walt emails you when he is going to ship and when the expected delivery is known.

I'm using the old wing of Spit 1 to test out the system. tomorrow I'll hook the servo up to a radio to test it out. It seems to work OK by hand. There is no slop at all in the aileron.

I cut a tray out of balsa to use as a template for 1/8 light ply.