ampeater

My Feedback: (1)

I'm starting my Platt 190, going to do it as an electric - hey, somebody was bound to do it. I was going to do the 109 first, but the 190 is so nice I just couldn't wait. It'll be a slow start, I'm still finishing a P-38 that's about 90% done, and have to fix a little Kobra I biffed a couple weeks ago.

I got the stab mostly done, but moved on to kitting the fuse while I waited for my G-10 to get here for the hinges. I'm not doing too much to lighten it up, I'm shooting for 16 -17 lbs. I've had other electric conversions where you lighten them so much they turn into kites. I did away with one of the front formers, and made two others out of lite ply instead of AC. I did put in a bunch of lightening holes. I'll be using 1/2" motor beams rather than 3/4".

Here are a couple of pics of where I am.

I'm starting on some of the mass props to estimate how this is going to balance. My stab will come in about 1 1/2 oz. less than the reference Dave gives in his instructions. But my motor and batteries will be about 50 - 55 oz. Good thing there's a lot of room to shift batteries, because I'm a little nervous about being nose heavy - I know something you never hear of with this plane.

Baldeagle

My Feedback: (7)

Looks good. keep us posted. Rich

tubig

interesting fuselage jig you have. where did you come up with it?

ampeater

My Feedback: (1)

It's an Adjusto-Jig. I got it about 20 years ago, I don't think they make them any more. But it works great. I had to make some stilts for the formers since the fuse tapers up toward the rear. But the jig holds all the formers true so I can build the crutch to the formers rather than the other way around.

Redwulf__34

What is the wingspan on this bird? Gonna be big for an electric, eh?

ampeater

My Feedback: (1)

The plans are 79.5" span, but I'm going to sneak an extra 1/2" out of it to make it legit for IMAA events. It will be the biggest electric I've built, but the systems are coming down in price, and you're starting to see more big systems. I'll be able to break up the battery packs to use in smaller planes when they're not in this one. I already run 4S packs in a Somethin Extra and Kobra. I'll just series two of those packs I already have to run in this one. I'm shooting for using an 8S at about 60 amps for 1800 watts. That'll give great performance. If I wind up needing nose weight, I can either go to 10S for more power, or bigger packs for longer flights (we need no stinking lead ).

mobyal

Interesting thread. I'll follow along here to learn from you.
Al

ampeater

My Feedback: (1)

I got the spine sheeting, motor rails, and battery box done. The box shown on the plans is perfect to hold a bank of LiPos . I was going to make the motor rails out of maple, but rather than mill them from scratch, I already had some poplar milled to 1/2", so I used it. The way the box goes together, it will be plenty strong. I'll add some tri-gussets to give some more support to the nose wall.

On to the fin. Dave's shows a swingee on the plans to activate the rudder. Has anyone used these before, are they durable? If so, I have a few in my parts bin and will use one, but I may try something different. Has anyone else built this plane keeping the rudder linkage hidden?

jaka

Hi!
Stay away from the Swingees...they are no good!
Used them many years ago (both models) and they were good at first but after first flight excessive play developed . I used the bigger black swingees (and blue coloured too) on ailerons on an "Old Tiger" pylon racer powered by an OS 20 cc four stroke built from plans in MAN in 1985-1986.

Regards!
Jan K
Sweden

ampeater

My Feedback: (1)

The instructions suggest building the fin right on the fuse. But I thought it's be easier building it on the flat bench and installing it later. So I cut the ribs and shaped the LE and TE. I drew centerlines on the LE and TE and, since they're tapered, shimmed them over the plans so the centerlines were parallel, and glued the ribs in between. It worked out great, now I have a single assembly to glue to the fuse. I have to wait for my Shindins to get here so I can figure out how to mount the TW to the fin before I install it.

I think I'll forget about the swingee. I'm going to use a pull/pull to a vertical bellcrank in the fin, then a short pushrod to a horn hidden in the rudder. But it's going to have to wait till my TW gets here since it has to squeeze in there around the TW.

ampeater

My Feedback: (1)

I checked the motor fit, and I have 3/16" all the way around the rotating can. I'll gusset the firewall to bolster it a little more.

I cut a blank for the turtle deck on the bandsaw. I tacked it into place, then traced the cross-section at each former from the plans. I transferred the tracings to card-stock to make templates. I used a sanding stick and the template at each former to give me the reference cross sections. Then I used a plane and sandpaper to shape it the rest of the way between the formers. I popped off the turtledeck and hollowed it out. Before hollowing it was 2.4 oz. After, it is 1.3 oz. I'll final sand it after I install the fuse sides.

tubig

i have the swingees set aside for this plan but i've never used them before and so not sure about them. i would very much like to see your setup for this hidden rudder linkage. please post how you do this as you progress (so that i might be able to copy it if needed ) excellent work so far!

ampeater

My Feedback: (1)

Wow, it's been a long time! I've been working on other stuff while waiting for my retracts to come in. They're finally here and I'm back on it, I installed the stab and tailwheel cylinder. Some guys complain that a rudder might be 1/16 of an inch too tall, or retracts are a half degree off, then hang big honking control horns on the surfaces. I don't mind the little off-scale differences if they make the plane fly better (I need all the help I can get), but one thing I don't like is exposed control horns. So I always try to figure a way to hide them. This plane is a challenge for the rudder horn, there's a lot going on in this little area. I have a couple ideas on how to solve this. The first one I'm trying is a combination pull/pull and rotary drive system. I made a rotary shaft and a G-10 horn to attach to it. I'll make a bushing/pillow block setup to mount the shaft, and run a pull/pull from the front of the plane, over the top side of the fin, and down to the G-10 horn. I bent the rotary shaft to 35 degrees. 45 degrees of horn deflection will give me about 20 degrees of rudder. The spacing of the pull/pull holes is only about 9/16, that's as big as I could get away with. Next, I'll make the rudder with the rotary shaft pocket in it, make my pillow block, and give it a try.

ampeater

My Feedback: (1)

The rudder and bearing block are just about done. I made bushings out of some HDPE I had laying around. I'd have rather used a harder plastic, but it's what I had. The bushings are mortised into ply standoffs and the standoffs are epoxied in place. I made a pocket for the rudder shaft out of 2 formica pieces, and inserted it into a mortise I made in the rudder while I was building it. The bend in the shaft is lined up with the hinge line. It looks like it's going to work. I can easily get up to almost 30 degrees of rudder. Next, I'll make an idler bellcrank for the other end of the pull/pull, and place it toward the front of the plane, then I can run the wires. Once I make sure it works, I'll finish the rudder, then on to the retract. I think I'm going to try and run the rudder and tailwheel steering wires from the same idler up front and one servo. From what I hear though, the steering is pretty touchy, so I'll put the steering holes about half as far out as the rudder holes.

Does anyone have any suggestions of what the ratio of steering to rudder throw should be? Does half as much steering as rudder sound right to cut back the touchy steering??

ampeater

My Feedback: (1)

I made the idler crank and a plate for the rudder servo. The rudder servo is mounted ahead of the cg, which is good because I'm scared about being tail heavy. The rudder cables will go in the outer holes, and the tailwheel will go to the next ones in. Hopefully, I can also fit the retract and canopy air valves and servos in the same plate when the time comes. On to the cables....

v6goose

Excellent stuff Ampeater!

I too hate horns and flight surface 'junk' and I'm going to put the HD RDS system into my 1/5th P51.

I'm learning a lot from your thread, even at this early stage. Thanks for the brain food.

Goose

adam d

it lookin real good cant wate to see further pics
p.s. likein the calender in the background!

jack41

Ampeater, Great thread, I too am a big warbird leccy enthusiast. Right now I'm perfecting my skills and knowledge on .060 size birds,(P-47 TF, VQ Zero), you are real trailblazer at this point in time. 1/5 scale and larger will be common in the not to distant future I believe! What size motor and esc are you using? Again will be watching your thread with great interest.
Regards, Jack

ampeater

My Feedback: (1)

Adam, The calendar is G. Gordon Liddy's Stacked and Packed, I highly recommend it .

Jack, I have an AXI 5330/FAI, and I'm probably going to use 9S2P or 9S3P A123 cells, I'm not sure exactly yet, we'll have to see
how much power they put out and how much weight I need in the nose. But at half the cost of
lipos and 20 minute charge times, I think they'll be just the ticket for a bigger plane where
the extra weight over lipos will be OK.

I made the cable bearing blocks out of some poplar and nylon 8-32 screws I had laying around.
I have 3 of them, two on the fin and one under the stab. The good news is it works fine, I can get
up to about 30 degrees of rudder (2 inches). I'll probably only use about an inch and a half.
The bad news is that right now it has too much friction. On the stab block I put a piece of shrink
tubing over the screw thinking it would reduce the friction, but I think it increased it. I'll
remove it and maybe add a loose fitting piece of aluminum tube over the screws to act as a bearing.
I also need to decide whether I can live with those cables over the air cylinder. I think it'll
be fine, but I may put a dab of grease there.

Once I get the friction worked out, I'll try and get the tailwheel to fit in there somehow.

BobH

My Feedback: (2)

Many full scale WWII planes had their tail wheels restriced to about 5 degrees both ways for take off and landings. So just a bit of tail wheel movement is plenty.

Isn't there a more straight forward conection to the rudder? I fear you are asking for mechanical problems with the current system. I'm just wondering here.

ampeater

My Feedback: (1)

Bob, thanks for the info on the tail wheel. I thought I'd give this a try, if it doesn't work out, I'll remove it and just go with the external horns I was trying to avoid. That would be easy an easy fix, just run the cables straight out the back. But the plans show a swingee (that is a lot weaker than what I have) and a similar run of flex cable to the top of the fin to a crank with a rod going down to the swingee. The problem is the retracting tail wheel takes up most of the lower tail section, and the air cyilinder is almost the width of the fin almost all the way to the top. What I have is a pretty straightforward run of cable over some bearings, I think it'll be OK if I can work out the friction.

tubig

you might try this. PTFE is really slick stuff, used a lot where low-friction is required.

sorry, back link. go to mcmaster-carr (www.mcmaster.com) and search for "Mechanical Grade PTFE". it a white plastic-type material.

ampeater

My Feedback: (1)

I gave up on the hidden rudder drive, there was too much friction that I couldn't get rid of and the rudder
had a hard time centering. So I took it out and am going with the external control horn. Not as nice,
but reliable.

I started on the tailwheel. At this point, the rudder is only supported by a small joint at front and
the side stringers. Once you start carving away the side stringers to make room for the tailwheel, there'll
be almost nothing holding the fin on. So I put on a rear portion of the fuse sheeting to support the fin while
I work. I hope the tail section is strong enough, considering that the fin takes the tailwheel load, and most
of the side stringers will be carved away. Just in case, I layed up some carbon fiber on the inside of the rear
sheeting.

After the rear sheeting was put on, I carved the profile to the right shape. Now I'll build up the fuse sides
around where the tailwheel goes in, like on the full size FW. I hope I can get this huge tailwheel yoke
to fit in the fuse. Oh, the steering tiller is about 1/16" too wide on each side to fit between the sheeting.
I'll have to take that down a bit too.

carlbecker

My Feedback: (3)

Isn't the bottom of the rudder fairly thick. You may be able to make a pull pull horn wide enough for good leverage, about the same width using channels to the servo. Of course you would be able to see it but you might get almost hidden.

ampeater

My Feedback: (1)

I'm not the fastest builder around, but it's been a while since the last update.

The tail section is just about done, have some more minor filling to do. I got the sliding canopy set up, now I can finish the pull/pull rudder and sheet the port side. Ribs are cut out, but I want to get a little further on the fuse before I start the wing.

I bought a couple DeWalt A123 packs and made up 4 packs of 5S A123 cells. I'll start out with 10S2P and see what I get out of it. The A123 are the way to go, a lot less cost, faster charging, and I'm not afraid of the extra weight in the nose.