vmsguy

Hello all,

I decided to start work on my Ultra Sport 60. I know it's not a "crash" and rebuild.. But it is a rebuild...

Last winter, February I think, I went to a RC auction and came home with 3 airplanes. A unfinished Sig Ryan STA, a Long EZ ARF, and a completed US 60.

I was sure that MinnFlyer was going to bid on it, but didn't...

Anyway, I got it for a good price..

I've kept it, untouched, for several months now...

I decided to start work on it.

Some of my goals are:

1. Converting it to Electric power.

2. Converting it from a trike to a tail-dragger

3. Convert the stock aileron setup to aileron and flap configuration.

From the pictures, you can see it was a trike setup, and had the glow motor mounted vertically. There are those on this forum that believe a vertically mounted engine on an US should be illegal....

This will be a challenge. I am fortunate, I have a US 60 kit, new in the box, I can use for templates for parts. I hope people here will find it interesting, and as I come up with questions, I hope I'll be able to get answers...

vmsguy

When converting an glow powered aircraft to electric, I see three major issues to contend with.

1. Access. Unlike glow, where you can merely pump fuel into an otherwise nearly inaccessible fuel tank, electric demands quick and easy access to the batteries.

2. Cooling. The ESC needs cooling, the battery and motor needs cooling as well, but the ESC is the most important.

3. Weight. Normally a motor and battery are lighter than the glow motor they replace. Rebalancing the plane is critical.

I started my work by removing the front wheel and motor mount. Then I tested the intended electric motor to see if it'd actually fit in the motor bay.

I got the next idea from looking at ARF designed for electric motors. I decided I'd make the entire cockpit area forward removable. The bottom of the cockpit would come away with the canopy. I started out by pushing pins through the fuselage, and seeing where they come out inside, to determine where to make the cuts. Once I finished that, it was careful cutting, and eventually the cockpit came off. I cleaned up the cut away areas a little. I know I will have to reinforce the top of the fuselage, the cockpit bottom gave the fuse some strength. I removed the small are atop the firewall and shaved down the top of the firewall to match.

vmsguy

Second evening. I added a piece of balsa to reinforce the front of the turtle deck. I spent some time removing some of the coating. It's coming off very hard. A thin clear plastic film comes off, but the white color stays behind. I think I will end up having to literally scrape every inch of the old coating off. Second picture, you can see the new modified nose so far. My plan is to have two hatches. The first hatch will cover the motor bay area, and the second hatch will be the cockpit. Both hatches will attach a little like the wing. They will have pins in the front, and screw downs or latches on the back.

FallDownGoBoom

My Feedback: (1)

Vmsguy:

I hadn't realized you were electrifying the US from Minn's US build thread. Your ideas about hatches are good. My Minishowtime uses the pin approach, with magnets holding down the rear of the front hatch.

How will you approach the cooling problem? With the tight cowl/spinner interface on the US, there cant't be much airflow through the firewall. Maybe some sort of louvre/scoop system on the sides/bottom of the cowling, with an exhaust hole cut in the bottom of the rear fuselage, or maybe in front of the wing?

vmsguy

I have a couple cooling concerns.

1. Cooling the ESC.

2. Cooling the motor.

To cool the ESC, I finally figured it out. I'm going to build a air scoop/tunnel on the bottom of the cowl. Much like a P-40's cowl. It'll have a false bottom (if the plane's upside down) that the ESC attaches to. Air will flow in the front, and out the back. The scoop look is strictly for appearance. I will be able to remove the ESC, from inside the motor bay, once the motor is removed, of course. I'm probably not explaining it well.... But I got it figured out in my head.....

To cool the motor... I'm thinking of cutting two 1/2" by 2" slots in the cowl, one each side, to allow the motor to breathe.... I hope I can find some kind of mesh to cover the hole...

I HAVE to have a spinner on it. If I don't I think RCU will have me banned....! Some would say I'm committing sacrilege by electrifying a US... Going without a spinner may be the proverbial straw.


But I have a couple questions, one pretty quick, another a little longer.

1. How much gap should there be betweek the back of the spinner and the front of the cowl?

2. What's a "typical" propeller diameter used on a glow powered bird?

The reason I ask, is prop clearance...

I'm currently planning on spinning a 16x8 prop. But I don't know if I'll have the prop clearance.....

I really do NOT want to stretch the landing gear, or use oversized tires...

ser00

Hi VMS,

What an awesome idea! The distance between the spinner and cowl is 1/32 inch according to the us60 manual. Also, if you have the stock main gear wires on it, a 16-8 prop is too big. I have an APC 16-12 on my Ultrasport 1000 and I have about a half inch of clearance. I think the biggest you could go is 14 inch (more likely a 13 inch prop should give you enough clearance). As far as in cooling, go ahead and add air scoops to the cowl. I am currently building a US 60 and I am going to use a pitts muffler and build a functional air scoop under the cowl. I saw a picture of such a thing in the gallery on XTOL's build of his US60. Keep up the good work!

Happy flyng!

FallDownGoBoom

My Feedback: (1)

An electric US? Sounds pretty good to me. Put it on the ground, plug in the arming switch, and go fly!

The cowl air scoop idea for the ESC sounds good. And your idea about the slots in the cowling as well. What might look neat would be some fake exhaust headers in the slot, sort of like one might put on a P-51. Or you could do angled slots, like the cowl on a Beech Bonanza.

As Ser00 says, the plans call for a 1/32 gap between the cowl and the spinner. The way GP has you build the cowl that's probably achievable, but my gap ended up closer to 1/8-3/16's. You don't notice when it's 100 feet up!

I built mine as a tail dragger, the struts on my retracts are about 6 inches long, and I've got about 2" of ground clearance with a 13" prop when the fuselage is parallel to the ground. That's enough for a 14 inch prop (if I land and take off carefully!), but I think you'll have problems with a 16 inch prop unless you make the struts longer. One thought: don't the bigger electrics typically spin slower than glow engines? If that's the case, you mght consider a 3 blade prop that smaller in diameter to give you enough thrust.

vmsguy

More work over the weekend. The motor bay/cowl hatch.

I start by putting a blind-nut in a small scrap of plywood. Then added some balsa that covered the motor bay. I ended up making a piece of plywood out of balsa, botton and top grain runing lengthwise, and center piece running sideways. Once it was all dry, the razor plane and sanding block made quick work of shaping it down. I drilled a hole through the front and glued a length of toothpick into the front... just in case....

It doesn't look too bad.

I've only to make the cockpit hatching...

I've still to mount the motor and batteries and ESC.. But I've got to wait. I have to order the ESC.. I'll have to go with a high voltage ESC to spin a smaller prop faster.

I really, really don't want to have to lengthen the landing gear. So smaller, faster prop it is...

But while I wait for those parts to arrive, I can start working on the wing....

LeeHop

vmsguy - I'm enjoying this thread but you lost me on the last post.

What was the purpose of that scrap of ply with the blind nut in it? It looks like it disappeared. ?

What happened to that notch in the aft edge of the hatch? Looks like that disappeared too!

Sorry to be so dense[sm=spinnyeyes.gif]

vmsguy

Not a problem... I'll elaborate..

Picture 1. Has the plywood/blind nut held in position. This is to hold the hatch in place.

Picture 2. Has the bottom layer of the hatch in place.

Then I added a second layer of balsa to the hatch. I glued it to bottom of the hatch AND the plywood piece, cut the excess plywood off, then added a third layer. That's why the plywood/blind nut disappeared.

Picture 3 & 4. The completed hatch assembly before shaping.

Picture 5 & 6. The hatch sanded down to shape.

vmsguy

A little more work done tonight, I started on the wing mods.

First, I opened my US60 kit and found the wingribs 3, 4, and 5. I traced them onto 1/8" balsa and cut the front parts. I also cut the a piece to fill the lightening hole in rib 5. I cut all these pieces.. just in case.

Next I went to work on the wing itself. The covering is a pretty good job.. It's almost a shame I have to remove it all. But I got to it. I noticed the original builder used CA. CA has a an interesting property, it's kind of brittle. So, it you do a little prying, it can pull apart.

After I pulled off a bunch of the covering... I got to work on the sheeting. It came apart relatively easily. Because the builder used CA, the leading edge, and the trailing edge of the sheeting was glued, but the middle areas weren't. I cut the sheeting upto the edge of the #2 rib. Looks like I'll have to cut a doubler for that rib as well. Just so the new sheeting will have something to glue onto.

It looks like this plane saw a little damage. There looks to be a doublers on the #5 and #6 rib where repairs were made.

Picture 1: the front-of-rib copies.. just in case.. Looks like I'll need to copy rib #2 as well.
Picture 2: A pretty decent covering job.. Bummer to remove it.
Picture 3: The sheeting removed between ribs 2 and 6.
Picture 4: Looks lie some repairs were already done to rib 6.

vmsguy

I've been continuing work on the wing, but progress has been slow. I only have been getting a couple hours per evening to work. I stripped the sheeting from the #2 to #6 ribs in front of the spares, and cut back some sheeting from #2 to #4 ribs behind the spars. I removed the original landing gear stock because I need access to those ribs area. I will need to route servo wires in this area. The landing gear stock would only be in the way.

(Pictures 1 & 2)

Next I started work on moving the landing gear mount to the front location, making this plane into a taildragger. I also moved the landing gear out one bay. To do this, I cut the proper slots in rib 3 & 4, and then transfered that line to rib #5. Once I was satisified with this, I needed to "double" the front of the ribs. Since I had cut duplicates of the first few ribs earlier, I used them to make 1/16" plywood doublers for the front of the ribs. I also used part of the #2 rib duplicates glue to the sides of the current #2 rib. This will provide more area for the sheeting to glue to.

(Picture 3)

Once the glue was dry, I finally put in the landing gear stock. I mixed some epoxy and glued in the landing gear mounts.

(Pictures 4, 5 & 6)

Now for the fun.. Before I glued the landing gear mounts, I had cut and test fitted the sheeting pieces. With the landing gear in place, I would press the sheeting into the landing gear and dent the back of the balsa. I used that to determine where to cut. I glued the leading edge in place, and waited for the glue to dry.

(Picture 7)

Next for bending/gluing the sheeting in place. I found the most effective method for bending the sheeting was to shoot it with the heat gun. Then I used rubber bands to hold it in place. If there was a spot that needed a little extra down pressure, I'd add a little piece between the rubber band and the balsa

(Picture 8)

I got the heat gun a little to long in one spot, but both sides turned out pretty well.

(Pictures 9 & 10)

hrrcflyer

Hey Vmsguy,

There are those on this forum that believe converting a US60 to electric should be illegal too..[>:].

Sorry I couldn't resist. Good luck with your conversion.

FallDownGoBoom

My Feedback: (1)

What a great way to use the old stretched out rubber bands from my trainer!

vmsguy

I'm going for the sound...

My trainer is electric, and when it does a flyby you can hear the air moving over the surfaces.. It's really cool...

I'm really anxious to hear what the US60 sounds like during a fullspeed pass...

Problem is.. I'm not qualified to fly it... I'm wondering if I could find a volunteer to pilot it on it's maiden, while I film it....


Did you notice the piece of aluminum angle "under" the wing???? It makes it really easy to glue down a curved surface.. Or a surface a clamp can't reach.

And.. You can always add more rubber bands if you need more pressure....

I did a build on a Telemaster (build thread forthcoming in the scratch build forum) And used LOTS of rubber bands...

FallDownGoBoom

My Feedback: (1)

I noticed the aluminum under the wing: it's more elegant than the paint stir-sticks I usually use. When I sheeted my wing, I used a bunch of 3M blue masking tape to hold the sheeting down. While it works well in dry situations, if you have to use water/alchohol/windex to get the sheeting to bend, it doesn't stick very well.

Your rebuild is looking good.

vmsguy

Thanks,

I'm mostly done with the aileron mods... Gonna try a hidden servo setup.. Hard to explain..

Should be finishing up wing mods by the end of the week...

FallDownGoBoom

My Feedback: (1)

Hidden servos? or hidden activators? I've looked at a couple of the direct drive systems, but have never tried to implement one. Keep us informed, this will be interesting.

vmsguy

Work continues on the aileron modifications.

First I decided to put the ailerons between #6 and #7 rib. I swagged a size for the mounting plate, and cut away the cap strips for the mount plate to mount. Then I glued in the mount blocks.

(Picture 1 & 2)

Next I started work on the tubing for the servo wire feed. I measured the center of each rib, #2 through #6, and about 1 inch away from the sheer webbing. I used a 1/2" forstner bit in my drill, and drilled each rib. I then cut a piece of poster paper, 2" wide, and long enough to go through all the ribs, about 14". I carefully folded/rolled it into a tube. Then I fed it through the holes. This process puts many kinks and dents in the paper.. That's OK. The next step fixes that.

Once the paper was in place, I carved a piece of balsa about 1/2" in diameter.. A little less, and gave it a rounded nose. It's about 1" long, maybe longer. I tried to get the tube as straight in the wing as possible, then started the bullet shaped balsa in one end. It forces the paper round, and tight against the rib. With the bullet in place, I glued the tube to itself, and the rib.

(Picture 3 & 4)

Once one glue was dry, I used more pieces of balsa to push the bullet further into the tube. Each piece is about 1-1/2" long. short enough to fit between the ribs. The 2nd and 3rd pieces were also quite round, but don't need to be as large in diameter as the first. I'd push the bullet through to the next rib. Then glue. I also glued the tube between the ribs to itself, applying some scotch tape to pull it together and hold it there. The 3rd through end chunks of balsa are quite a bit narrower. They serve only as pushers, they don't hold the paper in place. It took a few nights, but eventually I had the tube glued all the way to the #2 rib. I pushed the thick pieces of balsa all the way through, then used a flexible pushrod tube to press the rest through clearing the tube.

A couple things to note... 1. The drill holes don't have to be perfectly cut, don't have to be perfectly placed. 2. The straighter you can make the path for the tube, the easier it is to push the balsa through. But it doesn't have to be.

(Picture 5)

Then it was onto resheating.

(Picture 6 & 7)

vmsguy

I've completed one side of the hidden servo setup I'm thinking of using.

First, I installed the servo onto it's mount plate, and installed the plate onto the wing.

(Picture 1)

Notice there is no hole, and the servo arm isn't visible. A look from the top of the wing.

(Pictures 2 and 3)

Next, I went to work and installed a control horn. The balsa scrap is used to hold the bottom of the aileron and the bottom of the wing flat.

(Picture 4)

Next, I attached the control rod to the servo arm (the servo is centered) and marked where I wanted to make the z-bend.

(Picture 5)

Next I flipped the control rod around, and connected both end. I had to notch the sheeting a little for it to clear. The servo is still centered.

(Pictures 6 & 7)

I continued to notch the trailing sheeting until the action would clear. Then I removed the sheeting between the ribs, and part of the cap strips. I then cut a sheet for the entire area between the ribs, replacing the cap strips and trailing sheeting I had removed. I cut a new notch in the sheeting. And extended the notch for both directions of travel to clear.

(Pictures 8 & 9)

I do not know if I'll continue to use this setup. While I'm sure it will work, the exit notch turned out longer than I had expected. The exit notch is about 1-3/4" long. Had I cut a notch in the mounting bracket, for the servo arm to extend through, the notch there would be about half as long. Then again, with this method, there is less control rod showing.....

Hmmm.. decisions, decisions....

vmsguy

Wing modifications are done...

Now back to the fuselage.

1st, attaching a tail-wheel.

I started by completely removing all covering. The heat gun really helped. Once that was removed I found a small patch of wood on the bottom of the tail. I decided I'd remove a part of the bottom sheeting and replace it with a piece of plywood. Before I put the plywood on, I'll insert some blind nuts in it, and also add some reinforcements to the balsa sides.

I started removing the sheeting and found lead buried under the small patch.

Picture 1.

I needed to cut a larger area away, and eventually got the entrie patch of lead, and sheeting removed.

Picture 2.

Next I cut a couple scraps, and glued them into the fuselage. While the glue was drying, I cut a piece of plywood to rough shape, marked for the Sullivan tailwheel, drilled holes, and glued in blind-nuts. Once the glue was dry, I placed the plywood in place, and marked where the drill holes came out. A little off center, but not too bad.

Picture 3.

I then used a forstner bit to drill down a little so the thickness of the blind nuts would sit in them. Then another bit to drill clearance for the machines screws to clear.

Picture 4.

Then it was on to gluing the plywood in place. Again I used the rubber bands.

Picture 5.

Next.. Onto mounting the motor and ESC...

FallDownGoBoom

My Feedback: (1)

VMS:

Your servo installation looks good. [sm=thumbs_up.gif]

What motor/esc/battery configuration have you decided to use? My first guess at power would be something like 1100-1200 watts to fly an UltraSport???

vmsguy

Mounting the motor poses a challenge.

To mount the motor in an existing fuselage so that it is centered in the hole.. As well as the right depth (front-to-back) so the spinner is about 1/16" from the front of the fuselage.

I started by finally deciding on a motor. The motor is a Rimfire 50-55-650. It should spin an 11x8 prop at just under 12,000 RPM.

First I made a spacer, the size of spinner back-plate, out of 1/16" balsa. I placed the motor in the fuselage, and bolted the spacer, the spinner back-plate, and a piece of broken prop onto the motor. I centered it onto the front of the fuselage, and clamped it place so I could get some measurements. The back of the motor mount is 3-3/16" away from the front of the firewall.

Picture 1 & 2

I decided to stage the engine mounting. I would mount a false firewall onto the real firewall, standing off a bit, and then mount the motor to it. It solves a couple challenges. One, the tight spaces of the nose would make one long bolt difficult to access. Two, it would allow me to swap out motors without possibly drilling and re-drilling the firewall. I could simply replace the false firewall with a new one, appropriately drilled for the new motor.

The biggest challenge was getting the motor mounted in the correct place. All I had to go on was the original glow motor mount.

Picture 3

The top of the motor mounts are flat, and presumably the "center" of the motor axle. First I cut a scrap of plywood into a "T" shape. This will let me mark the mounting surface.

Picture 4

Next I fired up a CAD program and drew out the bolt pattern for the motor mount, with a vertical centerline. Sorry the picture is blurry.. The camera must have moved...

Picture 5

Next I set the mount onto the paper, and pushed the screws threw. I clamped the "T" shaped plywood in place, drew a line, and came up with the center point on the mounting template.

Picture 6,7,8

Back to the cad program. I drew up a mounting block with 12 different hole locations in it. The first four hole locations are for the old motor mount. I will use these mount screws to hold a drilling template in place. The next four holes are for the drill locations in the firewall, and in the subfirewall. The final set of four holes are drilled in the subfirewall only, and are for the motor mount itself. That may sound confusing. Hopefully I can explain so it will be clear. In the drawing, you will notice different sized circles around the drill locations. These are representative of the stand-offs and the blind nuts. The difficulty lies in positioning everything so there is no interference between things.

Picture 9

vmsguy

Planning complete, It was time to drill holes.

I made two copies of the drill plan. I glued one onto a piece if 1/8" scrap ply. I drilled the the four holes for the original motor mount. And the four holes for the subfirewall mounts. I cut away excess and screwed the template onto the firewall.

Picture 1.

With the template in place, I drilled the holes for the subfirewall mount. These are the four holes on the sides and top.

Picture 2.

Now for the subfirewall. I cut a piece of 1/4" plywood. And drilled 8 holes. Four on the sides and top, and the four in the corners. This piece doesn't need the old firewall mount holes. Then I went ahead and put blind nuts in the subfirewall; the side/top holes in the front, and the corner holes in the back.

Picture 3 & 4.

Now for the moment of truth. First, using 1" standoffs, I bolted the motor to the sub firewall. Then using 1-7/8" stand-offs I bolted the whole unit to the firewall. The screws are easy to access from what was the fuel tank area.

Did it work? Yes and no. The motor is mounted well, and came out very close to centered. I believe I can adjust the mounts enough to center it.

Picture 5, 6, 7

But I did run into an issue I was afraid of. To get the clearance between the front of the fuse, and the back of the spinner, the tollerances have to be very, very close. The front of the motor itself, is very close to the fuselage nose. It leaves little room for working with the spacers. So close in fact, I couldn't get an extra 1/8" spacer into the setup, because the motor was actually hitting the fuselage. This concerns me. Even if I did get the spacer in, if there was any vibration of the motor, the motor could actually hit the fuselage. As it sits in the pictures, the front of the motor is just inside the fuselage. The motor is about 1/8" too far back.

I believe I have a solution that will help a lot. I will get another prop adapter for this motor. I will then cut the threaded shaft off one, and stack the two of them onto the motor. This will make the motor another 1/4" or so longer. I'll then be able to take a spacer out of the back, shifting the motor back a little. This will give me more slack and space to work with when mounting the motor, and give me the protrudence out the front of the fuselage so the spinner will clear the fuselage as well.

FallDownGoBoom

My Feedback: (1)

Looks good. Would increasing the diameter of the hole in the spinner ring help help with the motor/fuselage contact problem?