Pee Tee by Nor-Cal Aero – A “Fun Scale” PT-19 Kit - Build and Electric Conversion
Now that flying season is behind me, I think it’s time to build something again.
How I ended up with this kit is a bit of a story…. I bought a Lanier Stinger 10 kit early last year from someone at my club, but I later decided that I didn’t need another mid-sized plane. I thought that it maybe a little too small for the club field, so I put it up for sale here on WattFlyer. Around mid-November of last year SlowJohn and I started having some regular conversations via Email and PMs on WattFlyer. I had always been a fan of his “Sleek Twin” (http://www.wattflyer.com/forums/showthread.php?t=46722) and we have had intermittent communications here ever since I joined WattFlyer. SlowJohn saw that that I had a Lanier Stinger 10 Kit for sale here on WattFlyer and he was looking to build something a little smaller than most of his planes. So, I ended up trading the Stinger 10 Kit (along with the needed electronics) to SlowJohn for the Nor-Cal Pee-Tee kit. When we traded packages, SlowJohn also included plans for his Sleek Twin in the Pee Tee box. I was happy as a clam, but soon after we traded I noticed that he was no longer logging into Wattflyer. There were a couple of messages from others that he was not doing well (again) and then in March of this year I heard that he had passed away.
Since this kit is from SJ and he helped inspire me to build more, and hopefully to get into the design side, I thought that I should dedicate this build to him. Even though I never actually met him in person, I think SJ’s approach to modeling was spot on. He was always encouraging and supportive to others, and always experimenting, building and learning more about RC. So this build is for SlowJohn.
This is my first glow to electric conversion. So I’m looking for suggestions on getting this to be a nice flying plane.
Here’s some of the details from the plans of the Pee-Tee
63 in wing span, wing area 633 sq. in, 45 in length, 6 lbs weight.
The manual says to install a 50-60 4 stroke
I was thinking of these components: (Because I already have them)
Hyperion ZS 3025-10 Motor – 775 KV, 1150 Watts, 65 Amp Max
SkyPower 80 Amp ESC (From HeadsUpHobby)
iFlight 25g iS250PB Mini Servos (From HeadsUpHobby)
4S 4000 mAh batteries
12-13 in prop.
Since I want to go with a 4S battery and the motor has a 65 amp limit, it means I have about 900 watts as my max. I will need to keep the weight down for my selected power system. I hope I can end up around 5 lbs. It should be possible, as the kit seems over engineered for electric power. At a minimum I’ll do the following:
Replace the heavy 3/32 balsa sheeting with light weight 1/16
Replace the heavy solid tail wood with a custom built up one
Cut out some of the material for the fuselage sides.
Use a lighter weight covering, SolarFilm or something similar.
I am not sure if the iFlight servos I have are up to the task for the elevator and rudder. I’ll need to experiment with them some. The specs for them on HeadsUp’s site states that they should be able to crank out enough torque, but they seem small for the size of this plane. The kit seems to be in good shape (except for some mold in the box which has been cleaned out) and contains a nice hardware set as well. I only need to add pushrods and wheels.
Am I out of my mind trying this setup? I can’t find much out about this kit online and Nor-Cal Aero is no longer in business. Everything I’ve read in general says I’m in the ball park. I think 5 lbs will be light for a plane of this size, but hopefully what is stated as the expected weight on the plans is correct and achievable.
Lastly, this probably will start like a real SlowJohn build… My workbench is a mess and I bet I won’t even have time to clean it up for a week…
In true SlowJohn form, my progress so far is cutting one stick and cutting holes in 4 ribs! Not bad for a weeks worth! I've cleaned off my work bench as well, so now some work can finally begin. I've cut and pinned down the bottom spar which is 5/16 x 1/4 balsa. I am planning on a two servo setup for the ailerons, so I also cut a hole in the end ribs for a servo wire guide. It's a sheet of paper rolled into a tube to snake the servo wires in. It was suggested to do this in the plans and my Daddy-O has a similar setup. It works well in my Daddy-O. so I thought I'd go ahead with it. The plans show the servo sitting face down, but I'm going to mount it sideways so they are hidden. I'm also moving the servo over one bay because of this.
Maybe tomorrow I'll actually get to use some glue!
Slowly plugging along. Nothing surprising, this is a old school traditional type build. I'm using Titebond as much as possible, so it's a slow go. Each picture represents about a day of very part time building.
Main spars and trailing edge wood are 1/4x5/16 balsa and leading edge is a huge chunk o balsa. It will need plaining and sanding for a long time to get the correct shape. Just the inner three bays get shear webbing per the plans. I've made two small modifications to save some weight. The wing tip wood was reduced to 3/32 from 3/8 and the sheeting is 1/16 instead of 3/32. Just the cap strips are needed on the top, then it will be time to flip it over and glue in the landing gear plates and sheeting. A nice, no fuss, build so far.
Added the maple landing gear block and then added the bottom sheeting. Next it was time to make a mess... I started with a small hobby planer and hacked away at the leading edge. Switched to 80 grit sandpaper and attacked everything for a while and here's what's left.
It's just rough sanded, but it's finally looking like a wing. With the aileron/trailing edge stock, this weighs 6.5 oz. Not light weight, but not too piggy. I think the entire wing with landing gear and wheels will be just over a pound. I just weighed all of the electronics and battery and that's just under 2 pounds (31.5 oz). That leaves about two pounds for the fuselage and tail. I think it maybe possible to hit around my 5 pound target weight.
The 900 watt limit is the absolute max according to specs of the components I have. I'd feel better around the 750 mark, and I'm looking for a spirited sport flyer.... More power is always wanted.
One thing I discovered is that the included aileron stock (1/2 x 1 1/2) is now too thick with the thinner sheeting I used. I bought some 3/8 x 1 1/2 and that looks about right. I've also noticed that I built up the tip a little too much, more sanding and thinking in that area is needed.
Started on the right wing. Everything that can be done with the wing still pinned down is complete.
Finished off the right wing half today. This thing is big! The wing span is large enough that I will not be able to glue the wings together on my workbench... Not enough room. I'll probably just move my ceiling tile to the floor somewhere is the basement. I have a large level to help me find a flat area, we shall see.
Yep, the 80 grit stuff makes a lot of dust fast!. I actually used the planer a lot more for the right leading edge. A lot less dust that time. I was a little too aggressive and sanded right thru the sheeting at the wing tip. I had to add some wood back and gently sand again....
The wings are now joined and drying. This is just the butt joint using Titebond. I used Blue Tape underneath to hold the wing together and to keep the glue in the joint. It will get glass and epoxy later, after the trailing edge is glued in. This is all per the instructions.
Me, epoxy and fiberglass is not a good combination. It was one of those times where the initial apply was OK, but things just got worse as I tried to work the epoxy more into the glass. Then some threads worked loose, then I made more of a mess, then I accidently got epoxy on the my gloves, which ended up on the leading edge, then it was getting too thick to work with........ I was using a 30 minute epoxy that seem to thicken in about 10 minutes. Not sure if I got the mix wrong or what, Maybe I'll get some finishing resin for next time.
After letting it dry for 24 hours or so, I sanded it down some and then covered it with light weight spackle. It's not too horrible, so I think it will just have to do.
I created some covers/hold downs for the aileron servos out of 1/16 ply and 1/4 in balsa. I plan on using both small screws and some silicone caulk/adhesive when actually installing the servos. I think it should hold OK and I can still add another top "plate" over the servo if absolutely necessary.
I cut and sanded the ailerons from the 1 1/2 x 3/8 aileron stock I'm using. I do have a question for everyone, what type of hinges do you like for the ailerons? It would be hinging between the solid aileron stock to two pieces of 1/4 balsa glued together (1/2 in balsa). My normal course of action would be to use CA hinge with a covering hinge over the top. Other guys at the club really like using the pivot point hinges.
The kit comes with solid balsa tail feathers made from 1/4 in balsa. Big and heavy. I thought I'd try some built up ones and I kind of like how they turned out.
Here's what I did. I made templates from some FFF I still have laying around. I just traced around the solid pieces from the kit. I then reduced the size of the FFF template by 1/4 in by using my balsa stripper set at 1/4 in. Not perfect, but close enough. I laminated 1/4 x 1/16 strips to build up the curved sections. I first soaked the strips in water for a couple of hours so they could bend. Smeared them with Titebond and wrapped them around the templates. Most worked well, except the top of the rudder. That ended up folding and ended up pushed in too far as I tried to wrap it around the top.
I then traced out the solid pieces again on a piece of paper on my building board. I started on the outside with some scrap solid 1/4 balsa that I cut into 1/4 x1/4 sticks. This wood was lighter than wood from the kit. (National Balsa Aerolight Bargan grade left over from a build from last year) Trimmed the laminated sections to fit, but discovered that the top of the rudder was not the correct shape. So I cut a solid piece for the top of the rudder. Also for the bottom of the Vertical Stab, and places in the elevators and rudders where the joiner and control horns will be mounted. These were for additional strength. I was afraid that the vertical stab and elevators would not be stiff enough, so I used some 1/4 x 1/8 spruce sticks that were left over as well.
Everything ended up OK and I believe it is strong enough. The best part is that I saved a significant amount of weight. Total weight of the solid pieces from the kit was 3.8 oz or 109 gm. The new pieces weigh 1.6 oz or 46 gm. Less than 1/2 the weight.
I'm planning on a few modifications for the fuselage. Like the wings, the sheeting will be1/16 instead of 3/32. I'm adding some holes in the rear sides of the fuselage to try and make it a little lighter. The entire cockpit will be made into a removable hatch and a battery tray will be added.
One thing I noticed is that the plans don't quite match the precut parts and I just thought about the rounded top of fuselage parts that may not fit..... I need to look at those. So far I've just tried to build to the precut fuselage sides. Since the instructions say to build with everything to a zero incidence to the top of the fuselage sides, I thought this would be the best way to go.
Top of the fuselage is on the reference line on the plans. The rear lines up, but the wing saddle and front ends up about 1/8 in too short. The wing saddle has me a little worried.
Here's what's been done.... Marked the fuselage sides where the formers will go. Created the base formers from 1/8 x 1/2 balsa stock. Added the cross grained sheeting to the front of the fuselage sides. Mounted the first two formers. Mounted the front former. This is about 4 days of part time work...
This is the part that always makes me slow down to a crawl, but now done! Mounting the wing and tail feathers is always a challenge for me. With this build the top of the fuselage is the zero mark and both the tail and wing should end up with the same 0 deg incidence. And square to each other and the rudder should end up straight..... This is not one of the nice Stevens Aero or Mountain Models kits that does most of the work for you. It was lots of minor sanding, looking measuring.... I even found an App for my phone to help measure the angle. I don't have a true incidence measuring tool (Hanger 9 makes one that looks good) so I did it by hook and crook.
After adding the rest of the formers and adding 1/4 in square stock to the fuselage, I added the hardwood wing hold-down blocks. Mounted the wing and slowly sanded and fit the wing to where it seemed to be at 0 incidence with the top of the fuselage. This was hard to measure with out a good tool to clamp on the wing... I'd mount the wing to the fuselage, set the model on the floor (where it was flat) and shim up the wings until the leading and trailing edges were at the same height. Measure the height of the top of the front and rear fuselage to see if they were the same.... Disassemble, sand a little and do over... I also found an app the measures the angle the phone is sitting. I'd check the floor and the top of the fuselage as well to be the same. It probably would have been easier to buy or build an incidence meter. Once that was done, I glued the vertical and horizontal stabs together at right angles.... Then finally mounted that with some epoxy to the fuselage. Not sure if it's really exactly correct, but I think it's close enough for me.
Closed off the rear of the fuselage with 3/32 cross grained pieces. The plans called for 1/8, but I deviated to save a little weight.
A quick bit of sanding and it looks OK. Large hole for air flow!
I think I know how I'll mount the motor. I built the ring from 2 1/8 pieces of birch ply laminated together. Should be plenty strong. The metal cage is from Hyperion. One of the ultra cheap closeouts a while back.
Mounted the firewall and bottom front fuselage balsa pieces.
Added a dowel and some side guides to the hatch. Magnets will also be added later.
Front view. Still need to buy two more 8x32 blind nuts.
Now I need to start throwing all of the components in for a balance test to see where to add a battery tray in this cavern.
Some good news, with the motor, prop, cowl and ESC up front and the tail wheel, tail bracket, tail feathers, pushrods and servos placed where they should be in the fuselage it balances almost right on the CG. I don't think it will be hard to get the plane to balance. Battery slightly in front of the CG should be fine.
Here's a close-up of the motor mount.
And now a couple of pictures with the fuselage resting on the wing. I couldn't resist. This is on one large plane!
This much weighs 47 oz. I think I may just meet my target weight of 5 lbs.
Thanks Paul... I can partially blame you for my addiction to building RC planes. I still fly the Pocket Rocket at the park down the road...
The wing filets start with a piece of 1/32 ply. I used some saran wrap over the wing to make sure it does not get attached to it... I just used some titebond and then attached the wing and tightened it down so it would be the correct shape.
I then added a couple of shaped spacers that looked about right... Slightly larger than what was on the plans because the filets on the real plane are very large...
I cut a template for the outside of the filet from some paper and then cut some 1/32 balsa. Soaked it in water for a couple of hours then slowly worked the curve in. Once it seemed about right, I used a little thick CA to attach it. I split the filet into two pieces per side, front and back. I have added some light weight spackling to clean up some bumps and boo-boos.... I think it will be OK.
Getting close to the end of the balsa work! Just the roll over bar to make, and some more sanding, filling and fitting....