Hangar 9 Sbach 342 60 Electric Conversion

[wilmracer]

So, while the Pitts is under construction I have found I have a beefy power system and full setup without a home. Since returning from Flite Fest I've been looking around to see if I could find a home for this setup. Something I can have fun flying this summer/fall.

I came across a reasonable price on a new in box Hangar 9 Sbach 342 60 ARF that I think will be an ideal candidate for the power system transplant. Previous owner had unpacked and checked stuff out but hadn't gotten around to starting it yet.

Website with details can be found here: http://www.horizonhobby.com/airplanes/almost-ready-to-fly/sbach-342-60-arf-han4215

I'll be grabbing some shots as I go. The conversion shouldn't be hard at all as electric was an option for this model, although they did design it with a different power system in mind. I think my setup will keep me on the lower end of the weight range and should give some impressive performance. The Pitts IS being rebuilt (after repairs to the P40) but in the meantime the Sbach should prove fun!

 

[Spitfire222]

Sweet! As you know, I love Sbachs, so I'll be keeping an eye out on this! I'm interested in converting some large ex-glow planes to electric, so I want to see how you set this one up. Can't wait to see it fly!

 

[wilmracer]

Sweet! As you know, I love Sbachs, so I'll be keeping an eye out on this! I'm interested in converting some large ex-glow planes to electric, so I want to see how you set this one up. Can't wait to see it fly!

I was actually thinking about yours as well when I looked at this one. The Sbach is really a slick looking design.

 

[Joker 53150]

Looking forward to it, as I learn a lot during your builds!

 

[wilmracer]

Looking forward to it, as I learn a lot during your builds!

This will be a lot less of a build than anything I've done in a while. I picked the plane up earlier today and have been nocking out the basic stuff between chores. There have been a fair number of spots where the covering needed to be cleaned up, but I guess that isn't uncommon on ARFs. TBH I've only had one balsa ARF before... and eflite extra 360. I seem to remember it having a bit less to clean up, but that was years ago.

I'll get some pictures up before too long. It is definitely a pretty bird.

 

[wilmracer]

Pictures from today. Got the tail put together and did a dry fit minus the electronics and power system. I did spend some time cleaning up the covering too.

Got a spinner on order as well.

 

[Bricks]

Curious what is the size electric. kv. and batteries are you are going to put in this bird? It weighs according to specs 6 1/2 to 7 1/2 lbs and being 3D?

 

[wilmracer]

Curious what is the size electric. kv. and batteries are you are going to put in this bird? It weighs according to specs 6 1/2 to 7 1/2 lbs and being 3D?

So this is a case of having a power system and looking for a good transplant candidate. While I rebuild the Pitts the power system from that will be living in this one. I'll have to see how I like the performance.

Motor: Scorpion 4020-630kV
Max. Cont. Current 95Amps
Max. Cont. Power 1500W

ESC: Scorpion 100Amp ESC
Castle Creations 10Amp BEC

Prop: Xoar 15 x 7 x3

Battery Turnigy 5s 5000mAh 50C

On this setup I should see a top speed of around 55-60 and thrust north of 12lbs. I can play around with other prop options as well but I have a supply of these beautiful xoar props that I already paid for and I'd like to be able to use them :black_eyed:

Reading through other builds online it looks like I'll be replacing the tail wheel and most of the pushrod hardware that came with the kit. I'll also be doing a full inspection of every glue joint I can reach, and will be beefing up the LG plate. There are threads of this thing weighing in as much as 10+lbs which might explain why the gear plate proved too weak, but my goal is to be right at 7lbs AUW. The 3D guys don't seem to think this is a true 3D plane, which I am perfectly fine with. I'm just looking for a plane to work on my aerobatics with and I think this will do nicely.

 

[Bricks]

I picked up a Great Planes Reactor 3D 58 inch CHEAP that the guy ripped out the landing gear. I am rebuilding it and converting it over to electric using a Turnigy SK 5045 600kv with a 15X8 prop on 6S 5000mah 45C it puts out 1350 watts with a 63 amp draw. I am hoping this Reactor only weighing in at a little less then 6 1/2 lbs this motor will be a good fit. For me it is always a struggle when converting from gas to electric finding the right size with out spending a few hundred $ on a motor.

 

[willsonman]

I always love an electric conversion, while this one is technically not a conversion. This power setup should be more than ample as you are producing thrust at a 2:1 ratio and 200W+/pound. As a bunch of guys from my club fly 3D and IMAC, these airplanes have the minimal reinforcement in the name of weight savings. Guys at my club have gone so far as to put in aluminum angle stock to reinforce the landing gear plate. Something to consider. It may also be prudent to purchase a spare set of landing gear. I really look forward to this as I think that these high-performance planes are marvels and I love to see them fly. Not my style, but cool no less.

 

[wilmracer]

The angle stock sounds like a good idea. It does sound like the gear has been an issue for some folks, but like you said they cut as much weight as possible on these things. I know the tail wheel has to go. No way it will hold up to our grass field.

 

[wilmracer]

Almost done with my mods to this one. As willsonman pointed out... this wasn't really a conversion as there was an electric option available. This project turned into more of a ARF improvement rather than a full conversion. The model as shipped is solid but has several issues with hardware that needed to be addressed.

Landing Gear - Largest area of complaint was the landing gear being very susceptible to damage. To address that:

• Latteral and torsional basswood supports were added to the attachment plate for the mains. The gear is made of two aluminum sections and a common issue was the plate splitting in the middle. The latteral supports should address this, and the torsional supports should make the gear less likely to pull out. I will grab some shots of this tonight as I forgot to take pictures.
• Axels on mains were terrible. Hangar 9 used a threaded bolt as an axel with nothing to protect the wheel from the threads. Multiple people have had the wheel hubs chewed up by the threads after normal usage (see picture). I replaced the axels with REAL 5/32 axels cut to fit the wheel pants.
• As I fly from a grass field I wanted a bit larger wheel. I swapped in some light weight 3 1/4" wheels to replace the 2 3/4" that Hangar 9 used. This required cutting a bit from the wheel pants for clearance. The before and after pictures show the difference. It is subtle but the weight change was minor and the new wheels should play nicer with our field.
• Tailwheel had to go. This tailwheel setup had a tab into the aft fuse and was directly connected to the rudder. Many others reported replacing this tailwheel after only a handful of flights, and some had damage to their rudders. I installed a light ply plate that will fit the CF tailwheel support from the wreckage of the Pitts. I just need to pick up a 1/8" arm and hook up the springs to the new bracket burried in the rudder. Changes the stance on the ground a bit but will hold up a lot better to the grass field.

Power System - I'm going with the system that I pulled from the Pitts, which is just a bit different than the recommended Power 60.

• I was pleased to find the included mount would fit the motor mount for my Scorpion motor. I just needed to add 1/4" standoffs to each end to clear the cowl. I was expecting to have to build a new motor box but got lucky.
• The design for the electric version of this model calls for instaling the ESC on the underside of the battery tray, inside the fuse. This area gets efectively NO airflow and this seemed like a really bad idea to me... Strap the hot ESC to the bottom of a Lipo and give it 0 airflow. I used a sharpie to "paint" the bare wood underside of the motor mount/firewall black and then mounted the ESC on the outside of the firewall. In this location it is exposed to tons of airflow and is right above the exhaust port in the cowl. Should work perfectly.
• Cut a few CF spinner and balanced the Xoar prop. This setup took a fair amount of ballancing but is ready to go now. I know 2 blade is more efficient, but I really like the looks of the 3 blade and I already had them

Hardware - Another common complaint was that the pushrods and linkages were poor for the cost of this kit. I replaced all the included hardware with ball links and more solid wire. There is 0 slop in any of the linkages and they should hold up to anything. The kit also included an Aluminum wing tube. Some have seen this deform over time, and it is a bit heavy. I have a CF replacement tube that I'm going to test out. I'll know tonight how that works out.


Still need to get her on CG scale once the new wing tube and tailwheel arm are installed, but ATM the weight looks like it will be right at 8lbs. I would have liked to be around 7 3/4 but I'm happy with the modifications. With 12 lbs of thrust she'll still have 1.5:1 thrust to weight. Hope to get her in the air next weekend!

 

[wilmracer]

Done and ready for maiden. AUW for maiden will be 7lbs 15 5/8oz. That is right in the middle of the advertised weight range and less than most of the completed models on the RC groups thread. If I hadn't made the mods I did, particularly to the mains, I might have hit the 7.5lb mark, but I feel good about flying her from our grass field.

Included is a shot of the new completed tailwheel mechanism. As part of our club's regular contests we do "Taxi races" and I wanted a setup that would provide lots of authority and be very solid. On the grass field I expect she will be able to turn on the spot.

Without adding any weight she balanced in the middle of the CG range. When I add the pilot figure (should arrive in a few days) I'll have to readjust, but for now I feel good about it

Thunderstorms in the forecast the rest of the week but Sunday looks like it might be good for a maiden! Fingers crossed.

 

[willsonman]

Looks awesome! I love your tail gear mod but I'm concerned about the stress it will put on your servo. One low divot in the field may strip it but I'm not sure what servo you have for the rudder. A Good MG one may be all that's needed to address this.

This is your third maiden this year? Well, after the first two less than enjoyable ones... third time is the charm right?

 

[wilmracer]

Looks awesome! I love your tail gear mod but I'm concerned about the stress it will put on your servo. One low divot in the field may strip it but I'm not sure what servo you have for the rudder. A Good MG one may be all that's needed to address this.

This is your third maiden this year? Well, after the first two less than enjoyable ones... third time is the charm right?

Yeah, third maiden on one of mine... fourth if you count a maiden I did for a guy at our club. Fortunately his went off beautifully. Hopefully this one goes smoothly too.

Rudder servo is a Turnigy 620DMG High Torque (https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=71285). 10.6kg/cm (190oz/in). I originally had the spring wires included with the tailwheel installed but I found that it wasn't really giving the tailwheel any authority. My hope is that the links on the tailwheel arm will slip before any really significant force is imparted to the rudder or servo. Not sure if that is how it will work out, but we'll see. Another option might be to add a loop to the linkage arm to act like a spring and give a bit. I'll see how it works on taxi testing and maiden.

 

[Joker 53150]

The springs I've used for the tail wheels on the 1/4 scale Cubs appear to work very well so far. If the plane is sitting stationary the wheel doesn't move much, but when it's rolling it moves nicely with the rudder without any major stress on the servo. It's worked well enough that I'm using that same type of setup on the 1/4 scale Pietenpol. Both grass and paved runways have been tested and I'm happy with results either way.

 

[wilmracer]

The springs I've used for the tail wheels on the 1/4 scale Cubs appear to work very well so far. If the plane is sitting stationary the wheel doesn't move much, but when it's rolling it moves nicely with the rudder without any major stress on the servo. It's worked well enough that I'm using that same type of setup on the 1/4 scale Pietenpol. Both grass and paved runways have been tested and I'm happy with results either way.

Cool. I may just have to bring the springs along and do a taxi test with each.

 

[Spitfire222]

Let us know when you plan on heading out for the maiden, I will try to be there! Good job on the quick assembly.

 

[wilmracer]

Let us know when you plan on heading out for the maiden, I will try to be there! Good job on the quick assembly.

Vince: I'll let you know! At the moment I'm hoping I can get out there on Sunday but I'm watching the weather and trying to coordinate with my lovely camera girl

I did a few tests with a set of springs and found that there really wasn't much steering authority at all. It was a bit better on grass than asphalt but neither really wanted to turn well. I tried it with the springs stressed and un-stressed. I think it is because of the short distance and vertical difference between the control horn and steering arm.

I'm going to see about adding a spring loop to the original pushrod design to guard against some of the feedback force, but I don't think the springs themselves will work. Another option would be to use some low test fishing line (8 lb or so). That would likely snap before transferring too much force to the rudder.

 

[wilmracer]

Vince - really sorry I didn't reach out this morning. I wasn't sure until we woke up this morning if the wife was going to be willing to come out (or if I'd be up for it either) so it was a last minute decision. That being said...

Got 2 flights in on the Sbach this morning. My CG was in the dead center of the range but I think I'd like it just a hair more nose heavy, but she flew really nice. WAY more capable than I am, so it will be a good one to work on aerobatics with. I'll need to look at opening up some cooling for the battery as it came down a touch hotter than I would like, but the motor and ESC weren't bad at all, especially considering it was about 85+ at 9 AM today.

Really fun to fly... Now I've got to get that pilot painted up and rebalance her. Hopefully the weather breaks before too long and I can get out and get some more stick time with her.