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Jul 13, 2017, 09:43 PM
Airfield Hermit

Ever have an engine you didn't know what to do with?

I've got an OS .40 4-stroke that i had inverted. Anyone that knows the FS-40 knows that this is an air-bleed carb. It didn't like inverted as it ran rich at idle. I tried drilling the hole, yada-yada....

Figured that these are good engines, they're just not Australians at heart. (you know, inverted, upside down, toilet flushes backwards, etc.)

So, anyways, I've got this recently retired engine, and I'm trying to find something to put it in that ISN'T inverted. Sideways or straight up should be fine. Not in a hurry, as I'll be doing bearings and such before it goes into the airframe. But WHAT airframe?!!!!

I know, asking what should I do" in a forum full of enthusiasts is like bringing a pizza to a Jenny Craig meeting. But here's what I've been thinking. It's a smaller engine swinging an 11x6 prop. I don't want a 3D plane and I already have a Stick, a Kadet Sr, a couple of Pitts and the Sig Rascal 40.

I was thinking of a vintage-looking plane, but not necessarily a vintage design. By that I mean, I want 4 channel, I like the Stinson SR9-styled wing but not necessarily one with massive dihedral or kinked wings with high-dihedral ends.

I really like the Great Planes Old Timer, and thought of putting ailerons on that. But, ALAS, it is discontinued. If I could find a kit, I might try it. So, what does anyone else think might make for a good candidate, now that you know kind of where my head is at?

I know, undecided kid comes in here and asks what HE should do like he has no direction or ambition. But hey, it makes for (hopefully) an interesting thread! Any suggestions are greatly appreciated!
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Jul 14, 2017, 12:11 AM
Registered User
Scarf up an Ace 4-40 kit or scratch build one. It is one of the most fun airplanes I've ever owned and that is exactly the engine I used in it. Stupidly I sold it but kept the engine. Found another kit, can't wait to build it. They fly like an A-10, not really fast but extremely maneuverable.
Jul 14, 2017, 06:48 AM
Registered User
Build a Sig LT-25 for the engine. It is a great kit and with that engine you will get 30 minute flights from a 6 oz tank. I was flying my LT-25 yesterday with the FS-40 (pre Surpass). The FS-40 is not the strongest engine but it just sips fuel. For my set up I found the best prop is a 11X5. I have many gallons of fuel through the FS-40 on the LT-25. If I get the time I will build another LT-25 as a back up.
Jul 14, 2017, 09:45 AM
Airfield Hermit
I had thought about a Senorita! Which is a smaller version of the Kadet. I was also thinking of kit-bashing this to make it more like I want (tail dragger, ailerons, scalloped wing with little or no dihedral.) Thinking of rounding out the tail feathers too (think Cub). Might make a cool kit-bash project! That 40 should pull it around great.

I did a Senior a few years ago and loved the way that one flew. Here's a link to that build. Sorely tempted to do this with a Senorita unless an Old Timer comes along.
Jul 14, 2017, 11:11 AM
Registered User
How about a slow flying old timer?

Jul 14, 2017, 01:22 PM
Registered User
AA5BY's Avatar
I've seen interesting sporty bashings of the LT-25.
Jul 14, 2017, 04:10 PM
Send lawyers, guns and money
ahrma_581's Avatar
I have a Surpass FS 40 in a Taibi B Pacer built from a Klarich short kit.

It takes off at a 30 degree climb with 1/4 throttle, cruises around at idle, and I have to kill it with t.cut on aproach to get it on the ground.

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Jul 14, 2017, 04:56 PM
Registered User
earlwb's Avatar
You could also go big with a Sig Kadet Senior Kit build. These kits build up very light as the model used a open box structure, more in tune with free flight planes in the past. So the huge plane flies more like a glider. A .60 four stroke overpowers it by quite a bit. So a FS40 ought to be just about right.
Jul 14, 2017, 09:22 PM
Airfield Hermit
Thanks everyone for your suggestions. I've looked at some of the vintage airframes and some do look pretty cool. I've been gravitating to the Old Timer as that looks more sport/scale, and thinking the Senorita since that one allows for kit bashing so well. I currently have a Senior with a '91 4-stroke on it and had a great time flying it yesterday. That got me thinking about the smaller Senorita a little more for the 40 sized engine.

I also have a scratch-built Howard Pete that my dad built a few years ago. It had a 40LA in it but has been sitting on the shelf in my living room for years now. Wondering if it isn't time to bring that plane out of mothballs. I'll be talking to day about it tomorrow. While it's not a relaxing, slow-flier like the Senorita would be, it would definitely be cool and something different!

The great thing about this hobby is the vast spectrum of options. The bad thing about this hobby is the vast spectrum of options!
Jul 14, 2017, 09:28 PM
Registered User
I can't believe I'm suggesting an ARF, but this one would seem to fill the bill...

One of Dave Robelen's last designs was a Perky Grande, or something like that. AMA plans would have it. High winger with ailerons designed for exactly your engine. Scratch build. Now I feel better.


My engine I don't know what to do with is an old HB 40 PDP Blitz. It starts and throttles so nicely on the test stand I don't want to part with it, but it is as heavy as my old 60s and newer 46s while not making as much power. So what to do with a great running, heavy, pretty powerful but not that powerful motor?
Jul 14, 2017, 09:43 PM
Registered User
AA5BY's Avatar
Yep, that Aviator Pro looks like a great choice to fit the OP's requirements.
Jul 14, 2017, 11:06 PM
Club Saito | Genesis 8:11
Bunnyshooter223's Avatar
I like the Taibi B Pacer, Quaker, and Sig LT25
Last edited by Bunnyshooter223; Jul 14, 2017 at 11:14 PM.
Jul 15, 2017, 03:03 AM
Airfield Hermit
Originally Posted by AA5BY
Yep, that Aviator Pro looks like a great choice to fit the OP's requirements.
LOL! Now THAT's funny. Here's why...

That little engine that just doesn' t like to run inverted (hint: OS 40 4-stroke), is IN a Sig Rascal 40 right now! And you're right, it flies it great, but it doesn't like upside-downness.

Figured that a swap out for an engine with a low-speed needle would help the reliability of the plane. Then, I'll install the engine in whatever airframe I decide upon with the valve cover pointed to the sky, like nature intended.
Jul 15, 2017, 04:57 AM
Registered User
AA5BY's Avatar
Yep... I'm laughing now.
Jul 15, 2017, 08:19 AM
Registered User
I've heard that complaint about the OS 40 FS before. I usually try to side mount my four strokes, but with the OS 40 I think that puts the needle valve sticking out the bottom.

Robelen's Perky Grande was published in Model Aviation April 2007. Span is 63 inches, so about the same size as the LT-25, but airfoil is semi-symmetric. OS 40 FS mounted upright, "like nature intended".


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