Slingsby T-37 Skylark ~ 1/3-scale model by Peter Goldsmith (Build Thread by JimD)

[MarkRobbins]

Jim, in your color scheme do you remember how many rolls of white and red covering you used? Trying to get the right amount ordered...

[JimD]

Mark, the red was the better part of three rolls and the cream (white) was four rolls. The plywood sheeting was not covered, it was painted with Minwax Polycrylic Satin finish.

https://www.lowes.com/pd/Minwax-Polycrylic-32-fl-oz-Satin-Water-based-Polyurethane/999913687

[MarkRobbins]

Thanks, I think I would have been a little short. hope mine comes out half as nice as yours. on to the last big part today...

[DanR]

Both Ed and I have burned up the E-flite Power 32 motor on the Skylark. We both were using the recommended 60 amp ESC. The motors were used in short segments to get to altitude (we were not flying around under power).
I'm going to install another one but will leave the spinner off in hopes of getting more air to the motor.

Dan

[MarkY]

Dan, what prop were you using? Any problems with the ESC?

Mark

[DanR]

Both Ed and I are using a 14 x 8 prop but not the E-flite one . We have the 14 x 8 Aeronaut Cam. I'm not sure if there was a problem with the ESC. I was assuming the problem was in the ESC so I threw it away without testing it first and didn't notice the problem was really with the motor until installing the new ESC. The original ESC was probably fine.

Dan

[Ed DeRossi]

My ESC still works fine. All of the wires inside the motor are melted.

[Jim Gibson]

I've been concerned about the motor ever since I ran it thru Ecalc with the Talon 60 ESC and 14 x 8 prop. I was coming up with a motor current of 72.3 amps, 8235 rpm and 82W/lb. The Eflite specs say the motor is rated 60A for 15 sec. I have gone ahead and installed it based on the success that Peter and JimD have had with it, but I don't know how much they've flown theirs. The motor is well encased inside the balsa nose cone and getting rid of heat is obviously an issue. I'll be looking to see what ends up working for you guys. Eflite publishes little dimensional information on their motors so I don't know if a Power 46 can be fitted or not.

Jim

[MarkRobbins]

my cooling vent is rather small. i wanted to keep it discrete as I plan to fly it without the prop often. perhaps an exit needs to be cut for the air? Maiden on the slope this week, don't plan on using the spinny thing...

[Pgoldsmith]

I have a pretty small cooling vent, it’s about 3/4 x 1/4” directly below the propellor. Probably have had 30-40 charge cycles on the motor so far, No issues.
2 things, I’m not using a spinner, and I am using the E-flite prop. I haven’t done any testing with the Cams prop however im sure it’s similar. I think not using a spinner is more critical for cooling..
checked Amp draw last weekend, 63AMPs stalled on the ground. Not sure of the amp draw in the air however it’s typically less.

[Pgoldsmith]

Picture of my cooling hole.

[Jim Gibson]

I've been making slow, but steady progress on my Skylark and I've found the build thread by JimD very helpful(thank you! thank you!). I've finished the main wing panels and now have the fuselage pretty well completed. I've found the construction of the fuselage with the open framework and plywood skins, while not difficult, definitely not something you want to rush. I'm posting some photos of the fuselage and details that may be of help to some other builders. Of special note:

• The plans show the upper formers F15-F19 in line with the cross braces. In reality, I installed them just behind and attached to the cross brace.
• Peter supplies canopy former F7c, but it is not shown on the plans. I installed mine as a doubler on the front of F7b. I'm glad I did because when I glued the canopy frame to the canopy, the upper part of F7b moved rearward on me. I was able to sand it back into alignment for a good fit because of the addition of F7c.
• I decided to glue the canopy frame to F15 and leave F15 loose for better access inside the fuselage. I installed a super magnet on the underside of F15 to hold it in place in the front and the back of F15 slips under F7b. See photos for reference.
• I am installing my pilot on a sliding tray so I can easily remove the pilot for access to the rudder servo. Again, I installed a super magnet on the backside of the tray to hold it in position.
• I am routing the elevator servo cables inside paper tubes I picked up off the internet several years ago. See fuselage photos.
• I added some plywood pieces on the fuselage bottom at the rear of the plywood skin to tie it into the structure. I'm not sure what Peter had in mind, but I think what I came up with will help with the covering as well.
• For the launch dolly peg, I used some 0.210" OD carbon fiber tube I picked up at the local hobby shop. The peg slips into a 0.25" OD brass tube sleeve that is glued into a 2" long hardwood block that is glued inside the skid.

I've painted the area around the cockpit black which blurs some of the details. Let me know if you have any questions and I'll clarify what I can. Time to build the wing tip panels............

Jim

[Pgoldsmith]

Nice Job Jim, looks like it’s getting close. Just a heads up on the launch dolly, make sure you have plenty of clearance around the hole, mine is a 7mm hole with a 5mm pin. The aero loads will prevent the dolly from releasing if it’s not a loose fit. That is also why there is no hole doubler in the keel, the thicker the material also restricts the Dolly from releasing easy.
i also did a bunch more testing with the power system.
i flew the Skylark in a GPS race at Montigue where you had to climb to 400m (1350’) I checked the motor temps during the climb, highest temps achieved were just under 180f. We flew 8 rounds and motor run time each launch was 2:30 to 3mins. Capacity used was 1750 to 1850 mah. Both Speed controller and battery were cold to touch.
So in conclusion I’m thinking those that are using small spinners are deflecting air away from the cooling inlet, based on my testing I’d recommend “Not using a spinner”.
i was presently surprised with the temps and how well it climbed, it was also a successful event for the Skylark, although not a fast model it thermaled well and had decent LD. Most laps I achieved was 10 laps, or 28km in distance, which is around 15 miles, not bad for a built up woody..

[Jim Gibson]

Peter,
Thanks for the comments and confirmation that the original power setup can work. I have top and bottom cooling slots in the nose of my fuselage and plan to power up less the spinner, but may try a turbo spinner after I get some airtime.
Jim

[Jim Gibson]

Finally finished up my Skylark. Thought I would post some of the details & photos here as this thread has been very helpful during the building process. I have really enjoyed the build and Peter Goldsmith has really done a great job on the kit. Mine has come out with a 'sturdy' weight of 14 lbs. My CG is slightly forward at 100mm and I'm sure I'll be able to take some weight out of the nose by moving the CG back after I get some flying time in. I have almost 27 oz of lead in the nose to get it to balance at the 100mm. Covering is Oratex Fokker Red & Antique. It's still a very wet winter here in the Pacific NW which is going to delay the first flights for a while.

[JimD]

Very, very nice! Congratulations on the build and fabulous looking finish...hope your model brings you as much joy as mine has. It is a great flying sailplane that loves to sniff out lift.

BTW, Peter is absolutely correct about the launch dolly, keep it extra loose. Mine stayed with the plane on its maiden flight (and I thought it was a loose fit).