"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

Baby Spitfire

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Old 02-24-2014, 09:05 PM
  #1
MJD
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Default Baby Spitfire

I pulled this out of the festering 1/2A drawer last week and looked it over. It came from a friend's estate sale years ago and I ain't run it yet. So I limbered it up which went very easily, it feels like it is in good shape. I then pulled the head - well rather the whole cylinder because the head was really tight - and looked inside, looked like a not-broken engine. I also wanted to checkout the glow on my panel and find a good setting. Looked good all round. So I primed it and pulled it through a number of times, took some time to work the goo out of it but got many encouraging pops. I was holding it in my hand at the time (tsk tsk, that's irresponsible, but I've felt more power from a few strands of 1/4" rubber). After a while I pulled the old 5" wood prop and bolted on a 6-3 MA, figuring the flywheel action wouldn't hurt. Lots of intake prime, a shot in the exhaust, blow it through... and a mighty flick.. brrrrrrrrrrrrrrrrrrrrrrrp! Finally, it generated enough power to increase in rpm from my hand start..

A few more times and it loosened up nicely and generally started to feel like a willing participant. So I hacked out a ply mounting plate and will fire it up shortly, using some nice castory fuel with a medium dose of nitromethane, probably 15%. I noticed that a Cox .049 plug wrench (C type) filed down a hair thinner will fit the head nicely .I might have 2 or 3 old short Fireball plugs somewhere or whatever they are called. What heat range would you suggest for this thing?

Now I need a Sniffer kit.. the two are made for each other. It would be fun to see and hear this gently brrrrrrrrrrrrping a little RC free flight around.

64 years apart.. and a few rpm.
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Old 02-24-2014, 09:49 PM
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I'm always amazed by stories like this. Consider how corrosive nitro is. I had a G-Mark .061 that sat in a drawer for 10 years fail shortly after I tried running it. The crank rusted completely through. Either there wasn't enough protective varnish build up or the crank wasn't surface treated to delay decay.
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Old 02-25-2014, 04:19 AM
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OMG I've never seen a crank go through like that, oh man!

I found a Sniffer kit on eBay last night.. the marriage will be complete.
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Old 02-25-2014, 07:53 AM
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An old nylon 6x2 prop too...while you're at it.
I could see gradually working up to long engine runs under semi free flight control using elevator and rudder servos for trim control. If the plane was a solid enough flyer, then I might put some Trexlar balloon tires on it [with a removable under carriage].
I had a 48 inch span, .061 G-Mark powered model with balloon tires and it was fun to see it land and take off from fairly rough grass.
IIRC, where the G-Mark crank rusted through the material was only 1/16" to 3/32" thick....but putting the engine away with raw nitro left in it probably explains how an engine in dry storage can go to pot like that. Engines with the thin wire wrist pin circlips, [basically plain steel music wire] is a 5 cent item that can destroy an engine after they rust and lose their spring tension.
That cowled model shown above turned out looking real nice.
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Old 02-25-2014, 09:02 AM
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That's just the form so far. I moved the build thread to the Extreme Speed forum (and the 1/2A was forum was pretty much asleep anyhow), that is a more appropriate category despite the engine size. I am nearly done shaping the form, need to clean up the surface really smooth-like, then hit with release compound then get to work on the mold.
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Old 02-27-2014, 10:55 AM
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It dawned on me last night that the shiny aluminum sleeve under the exhaust ports was a bit more important than I realized - it completes the porting.. so when you try starting the engine with it installed upside down it barely runs off a prime and has just enough power to spin the prop faster than you flicked it. But, smarten up and turn it the right way around, and the engine behaves like an engine again. Eureka!

Now to get it to draw fuel. Spraybar is clear, I can choke fuel from the tank, NV open until it is almost falling out.. nope.

The other thing I realized is that there is a small
press in venturi insert missing. But.. it is upstream of the spraybar and doesn't seem to define the venturi diameter right at the inlet so I am puzzled why it doesn't suck. However I suspect the NV is leaking air big time. I got tired late last night and stopped at that point (and wasn't sure if the noise was making it up two floors to the bedroom.. I know the hard way she can hear an .010 up there.). Time for the small silicone tubing over the NV and I'll use an auxiliary tank for the moment just to weed out some possibilities. You can see the insert here on this shined up example:

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Old 02-27-2014, 12:26 PM
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I've got one of these and it doesn't have the carb venturi either. So I wonder if it was a supplied part that was installed optionally depending on the use of the engine.

I haven't tried to run mine yet.


Hey, CP. I heard about the nitro being corrosive too. But not in engines that were run. It suggests that you used raw fuel on it then packed it away to let it fester. Perhaps you were trying to loosen the engine up? Anyway, I'm sorry to hear that it rusted like that.

The only engines I've had an issue with rust is my well used OS 40FS. As you know they use exhaust blow by to lubricate the lower and cam areas. Well that "lube" is loaded with moisture and combustion byproducts that are all very corrosive. Flushing the case with after run options does only a little to help and over a couple of years of regular use the bearings and insides all corroded. I ran it anyway despite the "sandy" sounds until it had finally had enough. It was ugly inside when I opened it up.
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Old 02-27-2014, 03:30 PM
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Ha ha!

It's the simple things.

A while ago I bought a few feet of the two smaller sizes of silicone tubing from Texas Timers. Glad I did, they are so handy in all kinds of situations. In this case the needle valve is not much over 1/16" diameter, so I sleeved the threads up with a short piece of the smallest stuff, then the next size up goes over the spraybar and NV for an airtight seal. I blew through the fuel line and opened the needle until I got a "that sounds about right" hiss, and clamped it up to the flight box. Fueled it up, finger over the vent, filled the fuel line and a drop in the intake, light prime.. and no word of a lie, first flip it took off backwards, so I stopped it by hand (ahem), then flipped forward - bingo. Took right off, 4 cycling but steady, so I brought it up to a fast 4c, pulled the glow clip, and it ran off a tank without a hitch.

So the Sniffer has a powerplant.
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Old 02-28-2014, 06:35 AM
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At the end of each flying session if you pull the fuel line, connect the booster and start the engine to run off any residual fuel left in the crankcase it will lessen the chances of leaving raw fuel inside. Remember that alcohol absorbs moisture and nitro forms nitric acid.

I do not have a Baby Spitfire but I have its brother the Spitzy .045 (the one with the tank on the bottom). Runs nice.

George
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Old 02-28-2014, 07:29 AM
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Quote:
Originally Posted by gcb View Post

I do not have a Baby Spitfire but I have its brother the Spitzy .045 (the one with the tank on the bottom). Runs nice.

George
George -

I believe in all the years I've been reading this forum this is the first time you didn't have an example (or more) of an uncommon engine that was being discussed.

andrew
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Old 02-28-2014, 07:49 AM
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George - usually that is what I do, and I fire some after-run into the intake and cylinder and flip them through a few times. "Usually" that is - I don't exactly have a perfect track record.. but my engines seem to last fine.

Judging by the power output on a 6-3 this will be a nice combo with the Sniffer. It won't haul a ukie around at 70mph but it will be perfect for this.
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Old 02-28-2014, 08:35 AM
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A good UC for that engine might be the VECO Scout or for FF, the Dakota.

George
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Old 02-28-2014, 08:47 AM
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Quote:
Originally Posted by Andrew View Post
George -

I believe in all the years I've been reading this forum this is the first time you didn't have an example (or more) of an uncommon engine that was being discussed.

andrew
Here's my Spitzy...I don't really fly it using that reverse-pitch prop, that was just for pic.

George

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Old 02-28-2014, 08:51 AM
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Well I have a Midwest Sniffer on the way - I believe it came out in 1952 so makes it somewhat contemporary to the engine. An .045 is on the large side but prop choice or even an intake restrictor can take care of any issues. The kit box makes reference to .020 up to .060. Last time I checked that was a bit of a power spread.

If it looks outlandish I think I have a beat up K&B .020 somewhere. Could always go Pee Wee but I'd prefer more vintage. I flew one FF maybe 30 years ago on a Testors .049 (or Wen Mac..?) and it was stupid overpowered of course, IIRC I finally lost it.

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Old 03-02-2014, 09:54 PM
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It's not the nitro that is corrosive, its the methanol. Nitro does ceate nitric acid when burned, but unburned it is relatively non corrosive with a PH close to neutral. Methanol however is corrosive to pure aluminum, not so much to aluminum alloys, and also corrosive to brass. Add a little moisture which the methanol soaks up and it is even more corrosive. I have worked with nitro burning race cars and some think it is corrosive because it was a safety item to clean out the aluminum nitro tanks. But that is because the patina that builds up on aluminum can react with the nitro and cause it to explode on impact. Steel tanks are supposedly no problem, but still a good idea to clean them just the same. Course drag racers mix methanol with the nitro as well.

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Old 03-02-2014, 11:22 PM
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Default baby spitfire

was my favorite engine when a kid. Flew one on a fire baby and a civy boy.It has plenty of power if u put it in an airplane that flys.probably one of the best quality 1/2 as from that time period.the mini zilch is another good airplane for this engine.It came with an aluminum firewall mount.and glow plug clip.I have a new one in the box stashed.also have both of the spitzys and a jim walker royal spitfire with throttle control.I store my engines with ATF.some with Marvels air tool oil.
Tom
If you want a fun sport ff track down a set of fat albert plans.It goes up and down no danger of loosing it in a thermal
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Old 03-03-2014, 04:38 PM
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Quote:
Originally Posted by MJD View Post
Well I have a Midwest Sniffer on the way - I believe it came out in 1952 so makes it somewhat contemporary to the engine. .......
Here's a closer look at what's in the box.
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Old 03-03-2014, 05:05 PM
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It came today.. ahhhhhhhh. I feel reassured reading in the instructions how it was designed with the Baby Spitfire or OK engines in mind.Talk about a quick build too.

Oh yeah - Andrew - thanks for saving me the trouble of getting the plans scanned!

I think I will translate these into CAD. Too cute not to.
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Old 03-03-2014, 05:42 PM
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Interesting airfoil that could be utilized in a few other airplanes?
A friend had one (Sniffer) powered by a Pee Wee that came down in a Olde Folks trailer park and was never seen again..

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Old 03-04-2014, 07:38 AM
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Quote:
Originally Posted by skaliwag View Post
Interesting airfoil that could be utilized in a few other airplanes?
Actually, that looks like a true Clark Y.

This foil has been around for years and is really a well designed foil, especially for slower aircraft. What has happened over time is modelers, sometimes being a lazy bunch, have dropped the slight bottom curvature from the spar forward in favor of cutting a completely flat bottomed foil and adding only a slight rounding to the leading edge.

Realistically, this "modification" probably has had little effect, considering the speeds and weights of our models. You might see a slight improvement in performance if you added the curvature back in, but except for staying true to the design or searching for the last bit of lift, it does add some time to scratch building. If your ribs are lasered, then by all means stick with the original foil.

andrew

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Old 03-04-2014, 09:47 AM
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That's not even close to a Clark Y. A clark Y is flat from about 15% (guessing) of the chord back.
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Old 03-04-2014, 11:13 AM
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Quote:
Originally Posted by Sport_Pilot View Post
That's not even close to a Clark Y. A clark Y is flat from about 15% (guessing) of the chord back.
I agree; and I added an edited retraction thinking it might be undercambered, but when the foil is rendered at 100% and 150%, it remains flat, at least on my monitor. I've rotated the plan thru 360 degrees to see if there is distortion.

It looks undercambered, but difference is less that a line width and the PDF may have an anomaly when scanned, especially since it is on the edge of the plan. There is a slight hump at about 30%, but I think it is drawing and/or scanning related.

So, unless you've got a better print, I think it's flat from the spar back. Admittedly, foils of that generation were undercambered, but this shows a slight and short hump, not the usual camber running from the LE to the TE.
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Old 03-04-2014, 11:31 AM
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I think you are looking at the center rib which is flat because it is over the fuse. The typical ribs (shown on the other end of the wing) are undercambered.
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Old 03-04-2014, 11:49 AM
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You are absolutely correct. The wing ribs are undercambered.
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Old 03-04-2014, 07:22 PM
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Dang this thing is cute. I've been fondling all the bits this evening and poring over the plans. My wife is looking at me oddly.

I'll get a copy of the plans printed before building anything. I'm jealous of my buddy's Lightnin' Bug kit, I was over Sunday and got to play with it a bit. I remember losing the last one quite clearly now. Too much fuel looping/corkscrewing madly away on a Testors .049 as I recall.

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