Sig Sundancer 50 Biplane electric conversion?

[JUSS10]

So this is my second post in the last few days in the balsa forum. In the thread about the Corben super ace I am scratch building, I had mentioned I was going to a swap meet this morning. Well a buddy and I got there just at end and they were closing up shop when we walked in. Did a quick once over and saw a big Sig biplane that I just loved. Guy had $50 on it and say make an offer, I got it for $30, probably could have got it for less but oh well. Its a Sig Sundancer 50. I went to the swap meet looking for a biplane. Was hoping for something a bit smaller but it was just so cool and the price was right. The plane is in amazing condition except the cowl with is hacked up a bit from different engines that had been in it over the years. Other than that the covering is perfect and its a sound plane.

Would love to convert this thing to electric. It is specd out for a .40-.60 nitro motor. looking to put a G46 or similar motor in and hopefully be able to run it on 4S as I have a nice nanotech 4S 3300 lipo laying around.

Anyone have experience on converting larger nitro to brushless?

Here are some pics. I already pulled all the nitro gear out, if all out I'll hang it up on the barn cause its just a gorgeous plane.

Justin

 

[Joker 53150]

And THAT is a perfect example of why I love swap meets! Darn good find, I would have jumped on that one as well. Towards the end of a swap meet is when you can really find some great deals, as sellers have to face the reality of dragging the plane back to their car, back into the house, and then repeat the cycle over again for the next swap meet.

Regarding the use of the G46, I think you'll find the motor way underpowered if you run it on 4S. I'm using that motor on a Sig Astro-Hog, a Kadet Senior, and a 1/4 scale Pietenpol, but I'm using a 5S pack, which is the max voltage it's designed for. Using a 4 cell you won't get the full power of the motor.

 

[rockyboy]

That's a great deal on a beautiful airframe! :applause:

I'm considering using this motor on my Sig Kadet Senior as a glow 46 replacement (where Joker is running a G46 on his). http://www.headsuphobby.com/Power-Up-46-Sport-620kv-Outrunner-Brushless-Motor_p_723.html

Please double check me here, but I think it's got a little more grunt in addition to having a higher voltage ceiling for 6s fun It's tricky to directly compare though as I don't see wattage or thrust metrics for the G46.

 

[JUSS10]

Yeah I was pretty excited. Bummed I only caught the end. Guys were already half packed up and loading their cars by the time I got there. airframes were going for $10 but I saw this from across the room and ran to it. Probably a good thing I got there late or I would have spent way too much money or came home with 10 air frames... haha

I actually got a guy from a the local club I just joined who offered me a motor for a great deal. its a Tacon Bigfoot 46

http://www.hobbypartz.com/96m605-bigfoot46-4020-670kv.html

seems like people are running 4 and 5s through it. Like I said, I just had the nanotech 4s and was hoping I could use it. I know there is no replacement for more voltage and its better to have more than less. Regardless I'm going to grab this motor and maybe some other parts from the guy (hoping for an ESC and prop as well)

I think I have some matched full size solar servos for the wing and I should be able to scrape up two other full size servos for the rudder and elevator.

Also need to come up with a tail wheel. He tossed one in from and Extra 300 but I don't think it will work. I'll likely just use the wheel he gave me and come up with some sort of mount. I found the manual and can see how the original wheel worked.

I fly a taranis Q-X7 and usually use DSMX with a module but I'm thinking I'll spend the money on a frsky telemetry receiver for this guy so I can monitor battery voltage while flying. Though I didn't spend a lot on this plane, I still want to treat it like the $200 kit is if I were to out right buy it.

Will definitely lean in to some help on converting this but everything seems to be coming together pretty well.

Justin

 

[JUSS10]

Also plan to "blueprint" this one and make a foam version as well. I just love everything about this plane. Its a nice cross between the full blown aerobatic/3D bipes and the more traditional bibe airframes out there. I had never heard of the model till I saw it but its is easily one of my favorite biplanes that SIG made looking through their catalog.

 

[rockyboy]

I think that Tacon would work for you - it would be good to weigh the airframe though, and then do some maths to figure out how much it will all weigh with motor and battery to figure out the thrust needed and guide you to the right prop selection.

And yeah, I'd go with a FrSky receiver on this one too - DSMX/2 is for DTFB - that's why it starts with the D

 

[JUSS10]

Yeah I plan to bring the plane in to work now that its gutted and toss it on a shipping scale and get an accurate weight. I'll then start adding the weight of 4 servos, receiver, motor, battery, etc.

Also got a buddy I fly with who flies 550 helis and has a few 6s packs so I could borrow his to run it on 6s as well.

 

[Joker 53150]

Too bad that cowl is hacked up as bad as it is. It doesn't appear Sig has them anymore, but it would be worth a call to see. Fiberglass Specialties has a lot of Sig cowls and other parts, but doesn't list that particular model. Maybe somebody on the various RC forums on FaceBook has one from a destroyed plane.

 

[JUSS10]

I did shoot sig an email to see if they have plans or anything else on the plane. Its really a cool beast, kind of makes me scared to fly it once its all built. I'm a good pilot and my flights rarely end in a crash anymore (that was my fault at least) but I've still only been flying a few years. I will have someone far better than me do the maiden and give it a shake down.

I was thinking of modeling the cowl in cad any maybe trying to 3D print it on my FDM printer or SLA printer at work? Its pretty large though so I don't know. may try and fit some blue/pink foam in there and try and shape whats missing and glass over it then cut the foam out from the inside... I guess I should focus on getting it flying first.

Justin

 

[JUSS10]

so I was digging through my pile of "large" RC stuff and found two new Airtronics 94358 ERG-VB High Torque aluminum servos. Double ball bearing. Might be a bit overkill but think these would work for the wing servos?


Specs
Modulation: Analog
Torque: 4.8V:160.0 oz-in (11.52 kg-cm)
6.0V:200.0 oz-in (14.40 kg-cm)

Speed: 4.8V:0.13 sec/60°
6.0V:0.10 sec/60°

Weight: 2.06 oz (58.4 g)
Dimensions: Length:1.54 in (39.1 mm)

Width:0.79 in (20.1 mm)

Height:1.47 in (37.3 mm)
Motor Type: Coreless
Gear Type: Hybrid
Rotation/Support: Dual Bearings

 

[JUSS10]

Also heard back from SIG. They said the plane was made overseas so they have no plans or real documentation on it. Seems kind of odd that they wouldn't have plans. It was an ARF when it came out so you just had to glue it together, but I assumed these planes would have come with plans so you could fix them after a crash. Did they just figure if you crashed, it was junk and you would go spend another $200 on a new airframe? Seems crazy.

Anyway, they did have a few parts left in stock but no cowl.

 

[rockyboy]

so I was digging through my pile of "large" RC stuff and found two new Airtronics 94358 ERG-VB High Torque aluminum servos. Double ball bearing. Might be a bit overkill but think these would work for the wing servos?

I'd say "If they fit, they fly!"

 

[roversgonemad]

Build a foam plug and patch the cowl. There's a guy in our club that does it all the time. When he's done, you can't tell from the outside it was ever patched.

Funny comment on DSMX. I run it in everything. If it's expensive, I run a satellite. My only issues have been when I have cheaped out on Rx batteries and had brown outs....

 

[JUSS10]

Build a foam plug and patch the cowl. There's a guy in our club that does it all the time. When he's done, you can't tell from the outside it was ever patched.

Funny comment on DSMX. I run it in everything. If it's expensive, I run a satellite. My only issues have been when I have cheaped out on Rx batteries and had brown outs....

Glad to see I had the right idea with the foam plug. I'll definitely give it a shot.

Honestly, the only time I've had issues with DSMX is when I was using a cheap knock receiver. Once I ditched those, I haven't had an issue since. I've flown by schools and other large establishments that no doubt have strong wifi signals but still no issues with good receivers. That said, I have the taranis radio, I would like the telemetry down link, and bonus, frsky is known for great signal strength so I figure its time I actually try and frsky receiver.

 

[Joker 53150]

Also heard back from SIG. They said the plane was made overseas so they have no plans or real documentation on it. Seems kind of odd that they wouldn't have plans. It was an ARF when it came out so you just had to glue it together, but I assumed these planes would have come with plans so you could fix them after a crash. Did they just figure if you crashed, it was junk and you would go spend another $200 on a new airframe? Seems crazy.

Anyway, they did have a few parts left in stock but no cowl.

I guess that doesn't surprise me too much, but I'm glad that most of their stuff now is in their hands. Maybe they used to offer the cowl and other items as repair parts, but eventually that well dries up. I still recommend posting on a few of the FaceBook RC forums - there is a good chance somebody has some parts laying around.

Or the other idea of patching it. There are tutorials I've seen in the past that go step-by-step through the process. It's a lot of time to get it right, but if you have no other options it's worth the effort and a good opportunity to learn!

 

[JUSS10]

so I took the plane to work last night and threw it on a shipping scale. Dry weight with no electronics at all is 3lbs 8oz (1570g). Seems heavy but I don't really know much about balsa planes.

I'm going to go pick up that tacon bigfoot 46 today with a suppo 60A esc. The guy said it swings a 13x8 really well on 4s or an 11x5.5 or 12x6 on 6s.

Not a ton of documentation on the motor other than a lot of positive reviews both on hobbypartz and on RC groups. I'll do some digging and see if I can find some thrust data.

What is the general rule of thumb for motor thrust vs all up weight of a plane? I know it needs to be greater than or equal to for the plane to "hover" or have any sort of vertical. Just wanted to know if there was a formula of sorts.

Justin

 

[Geeto67]

... It was an ARF when it came out so you just had to glue it together, but I assumed these planes would have come with plans so you could fix them after a crash. Did they just figure if you crashed, it was junk and you would go spend another $200 on a new airframe? Seems crazy....

ARFs rarely if ever came with plans. Usually the mfg sells "replacement" parts for a couple of years and then discontinues the airplane. It's the same way now, except a little worse. I have an eflite ARF balsa cub that I shelf damaged a couple of weeks ago. the plane was discontinued this year, and already I can't get some replacement parts for it so now once the plane isn't selling the parts go too. I was lucky and found a fuselage on ebay from a hobby store in GA, but the next time I crash the plane it's probably going to be rebuilt and recovered without eflite replacement parts.

If you have basic balsa skratch building skills and tools repairing a crashed air frame isn't that hard once the parts are NLA, but lots of people in the hobby now don't have those skills so most of the time a crash is the end of the airplane.


here is how you fix your cowl: get some fiberglass mat and resin, apply the resin to the inside of the cowl and then lay down the mat over the hole. cut a foam plug the same shape as the hole and epoxy it to the glass mat you just laid down. then epoxy and glass mat all over the outside of the cowl. You can then sand back the epoxy till it looks flush and use some light body filler (like bondo) to smooth out any bumps. once you paint it should be undetectable.

Now, here is your opportunity to learn a new skill. It's not hard to make a home vacuum forming setup to make small parts out of plastic. MAke magazine had a good writeup of how to make one in your kitchen:
https://makezine.com/projects/make-11/kitchen-floor-vacuum-former/

you can then just tape over the original cowl's hole, and then vacuum form a new cowl out of plastic. If you crash and destroy the cowl, you can then make a replacement part. this is a good skill for modelers flying obsolete planes.

 

[rockyboy]

Yep - here's something I copied into a notepad from a post long ago:

50-70 watts per pound; Minimum level of power for decent performance, park flyer/slow flyer models
70-90 watts per pound; Trainers and slow flying scale models
90-110 watts per pound; Sport aerobatic and fast flying scale models
110-130 watts per pound; Advanced aerobatic and high-speed models
130-150 watts per pound; Lightly loaded 3D models and ducted fans
150-200+ watts per pound; Unlimited performance 3D and aerobatic models


Think of thrust (oz or grams) in the same kind of ratios - just replace 'watts per pound' w/ 'percent'

 

[Geeto67]

oh...something else I forgot.

If you are intent on flying this, and you will probably crash it, you may want to get yourself a profile or contour gauge.

https://en.wikipedia.org/wiki/Profile_gauge

A contour gauge takes the profile of a surface, if you can identify the fuselage and wing bulkheads and ribs you can take a profile of them with the gauge and make a "pattern" for replacement wood parts. This is an old trick, but a useful one for flying a plane you don't have plans for and didn't build. The only downside is that if the plane is wood sheeted, you may have to account for the thickness of the wood.

make yourself a bunch of repair patterns before you fly the plane so that should you screw the pooch you can just punch out some new wood pieces and have at it.

Harbor Freight charges $5 for their 6" contour gauges and that is cheap insurance.


I'm starting to think it might be a good Flite test video or article to cover some of these old hobby tips and tricks.....

 

[rockyboy]

That would be a great article to write up!