Author Topic: Plane Size for OS 46LA (Read 7193 times)

Tim Wescott · « **on:** April 10, 2013, 11:35:57 AM »

I've managed to get my hands on a couple of OS 46LA engines. Looking through the posts here there seems to be an astonishing range of planes that work well with this engine, but I'm wondering if there's an accepted and recognized range of sizes/weights of plane that work well with this engine.

Specifically, I've been drooling over Paul Walker's 1991 Impact article (60 inch span, around 660 squares), but that plane was originally built for a piped 40. Is it too big for a 46LA with a muffler? If not, what weight would you have to hold it to for it to work well (I'm finding that building light is as much of a challenge for me as flying).

In the absence of any guidance I think I'd either build to the outlines of that Impact at that size, or maybe scale it down by 5% or so for an area of 600 squares. I'd leave out the take-apart features (I'm not going to the World's any time soon!) and possibly shorten the nose to balance with a muffled engine instead of piped. I'd certainly hate to go big, then find out that I have a nice airframe without enough power.

Thoughts? At the rate I build I should probably start on my 2014 ride soon!

Mark Scarborough · « **Reply #1 on:** April 10, 2013, 11:47:08 AM »

Tim,
I have flown the LA 46 in airframes from the Oriental,, up to about 620 squares.
I personally would say something in the 600 inch range is about perfect.
as to shortening the nose,, I say NO,, one of the biggest problems I have had is building the tail light enough,, its far easier to add a half ounce to the tail, than an ounce to the nose... finish weight has more effect on making a plane tail heavy ,,,

there are lots of good planforms for the LA out there,, pretty much anything that flew with a supertigre 46 is a candidate,,
make sure you have ground clearance for the 12.25 x 3.75 prop since this seems to really be a key in this engines happiness,,
( in my experience)

dirty dan · « **Reply #2 on:** April 10, 2013, 01:16:37 PM »

Tim,

Do not automatically shorten the nose on an Impact, scaled down or not. Do you have any idea of the weight of a 40VF?! I don't know either, never having owned one, but they are a load. I can remember during a flying session a couple years ago hearing Paul tell Howard the RO/Jett .61s and .65s are lighter than a 40VF.

In any case the only serious mistake I made--and it wasn't a deal-killer--with the Wimpact series was to slightly shorten the nose on the first one.

While it makes a difference as to how one calculates the wing area of an Impact you might want to check your conclusion. This design is commonly cited as being of 700 square inches or so.

In any case 600 inches sounds about right. I have seen lots of success with the 46LA, just not that much success!

Or maybe not. The most recent in the Wimpact series is the W500. Yes, a full 500 inches of wing area. Piped 25FP for power.

Another suggestion: Whether scaled or not my view is the Impact, even after all these years, ought be built as shown on the FM plans. That means a foam wing among other things. And don't go changing stuff willy-nilly. Example: There are folk who will use a clear canopy on this design. Wrong. The wood canopy is there for a reason and while this might "just" be a detail, our best PA models have all the details covered.

Dan

Tim Wescott · « **Reply #3 on:** April 10, 2013, 01:39:11 PM »

I was going off of measurements of the minuscule plans in FM -- so I could have easily mis-measured the wing chord. I was surprised at the figure I came up with since I've heard the 700 figure quoted often.

Matt Colan · « **Reply #4 on:** April 10, 2013, 02:26:26 PM »

Hi Tim,

In my experience with the OS LA 46, putting it in an airplane the size of the Impact would be a huge mistake! I currently have one in a Vector ARF here at college and it's happy as can be with that airplane. At home, we have LA 46's in a P-47 and F-14. The P-47 and F-14 have wing areas around 630 if my memory is correct. If I were to build another smaller airplane for an LA 46, it would be a plane with wing area ~600-630 square inches.

The problem with putting a motor like the LA 46 in an Impact is you may be able to get by with it in stunt heaven conditions, but when the wind comes up and you're dealing with turbulence, the motor won't have enough guts to punch through the rough air. My Oriental Plus has a PA 40UL in it and the plane flies great in calm air, but when the wind comes up, the plane is really struggling to get through the pattern and I really have to nurse it through the pattern. On the flip side, my Trivial Pursuit with a big RO-Jett 76 in it punches through that rough air like it's nobody's business.

Tim Wescott · « **Reply #5 on:** April 10, 2013, 02:41:54 PM »

Thanks Matt -- I like the way you phrase that, because that's indeed just what I wanted to avoid: having a fair-weather plane that wouldn't cut it when the wind comes up. I don't know about the rest of the country, but most of the contest venues in the Pacific Northwest (not least of which is my home flying field) feature trees and/or buildings that generate lots of turbulence any time the wind gets high, and when it gets windy here its gusty, not steady.

RandySmith · « **Reply #6 on:** April 10, 2013, 03:47:30 PM »

Either VECTOR full sized or a randy Smith Vector 40, many are flying now with that engine
There is also the DreadNought 40 , SV-40, and Tempest 40 . Shrike, Staris, Satona, Apex

Randy

Geoff Goodworth · « **Reply #7 on:** April 10, 2013, 06:50:32 PM »

Dan, you make a very good point. According to the list published in Stunt News Sept-Oct 1998 which I was looking just last night, the 40VF weighs 11.90 oz. The LA 46 weighs 8.8 oz, with a factory NVA and venturi and no muffler.

Tim, the Ku-ring-gai club field in Sydney's north is fairly bumpy and the LA 46 does a very good job with an ARF Vector 40 and with the Shoestring 40 that Bob Reeves and I developed around the Brodak P-40 wing which is 565 sq in.

If you want a kit build rather than an ARC/ARF, you could always change the tips of all the flying surfaces of a Vector 40 kit and turn it into Randy's SV 40 to look a bit different.

Steve Fitton · « **Reply #8 on:** April 10, 2013, 07:12:28 PM »

Don't overlook some of the classic designs for an LA-46. The Sig CL-3 Chipmunk and the Nakke would be well suited to the LA and a tongue muffler. If West Coast contests run the same way as East Coast ones, a good classic plane can work for you on both days, by entering Classic stunt Saturday and then the Pampa skill classes the next day.

When you are not tearing up much equipment you can build that Impact and piped VF-40.

A modern era design well suited to the LA-46 is the Time Machine 40. I used to use a FP-40 in mine and the LA in the slightly larger Time Machine 50, but Jim Svitko put the LA 46 in the 40 size Time Machine and got some really good flying planes.

My personal 2 cents is that the modern designs (Vector, Time Machine, Legacy 40, etc etc) will tolerate an LA-46 and a heavy APC prop better than a classic design will.

Tim Wescott · « **Reply #9 on:** April 10, 2013, 08:09:41 PM »

Quote from: Geoff Goodworth on April 10, 2013, 06:50:32 PM

If you want a kit build rather than an ARC/ARF, you could always change the tips of all the flying surfaces of a Vector 40 kit and turn it into Randy's SV 40 to look a bit different.

I will almost certainly scratch build it, whatever 'it' turns out to be.

Randy Cuberly · « **Reply #10 on:** April 10, 2013, 09:59:41 PM »

Tim,
The standard Impact, though a terriffic flier is too big for just about any of the standard 46's. Certainly a VF46 would fly one but that's an enormously powerful engine that weighs about 12+ ounces without a muffler. An LA 46 would fly one but not competitively.
I flew for many years a Scarinzi Blue Angel at 625 Sq inches and 54 oz with an LA46 that I built in 1997 (The first one at a VSC) and the same airplane is still being competitively flown today by Burt Brokaw with an LA46 (not the same one

).
I would consider that about the upper limit for comfortable use of an LA46, and in places like Tucson in the summer time it needs a lot of nitro "help".

I do think an Impact scaled down to about 600 to 610 sq inches would be a great project and would require no design changes beyond just shrinking it.

I would make 53 to 54 oz the target weight...very light balsa and finish.

Good luck with it and I hope you do it!

Randy Cuberly

Brett Buck · « **Reply #11 on:** April 10, 2013, 10:02:57 PM »

Quote from: Tim Wescott on April 10, 2013, 08:09:41 PM

I will almost certainly scratch build it, whatever 'it' turns out to be.

Look at the later ST46 designs, those in the 600-630 square inch range. If it flew with an ST46, it will fly better with an 46LA.

Brett

Randy Cuberly · « **Reply #12 on:** April 10, 2013, 10:10:47 PM »

Quote from: Brett Buck on April 10, 2013, 10:02:57 PM

Look at the later ST46 designs, those in the 600-630 square inch range. If it flew with an ST46, it will fly better with an 46LA.

Brett

I don't know...I remember having to whip like crazy to get through the wingover with a couple of those things

.
I do agree with your premise however!
I flew a 60 oz Magnum with a really good ST46 and it was NO fun in the wind!!!

Randy Cuberly

Brett Buck · « **Reply #13 on:** April 10, 2013, 10:24:24 PM »

Quote from: Randy Cuberly on April 10, 2013, 10:10:47 PM

I don't know...I remember having to whip like crazy to get through the wingover with a couple of those things .
I do agree with your premise however!
I flew a 60 oz Magnum with a really good ST46 and it was NO fun in the wind!!!

That's way too big for an ST46, that's almost back to the 70's style "scaling rule" monsters. Think 625 squares, mid 50's at most - like all the later Ted ST46 designs.

Brett

Dennis Moritz · « **Reply #14 on:** April 10, 2013, 11:59:02 PM »

Vector 40s are excellently matched to the LA46. I have seen many of this combination work well. The larger 40 sized planes seem very comfortable with LA46 power. Orientals, Cardinals, Noblers. Engines are often run at a loafing 4-stroke, the power coming on when required at different points in the pattern. In windy condition leaning the needle still makes for controllable power. I have seen a few good running ST46s that appear to have more grunt than an LA46. Typically they use a higher pitched prop. Perhaps this indicates an ability to make more torque. For the money, it's hard to beat LA46s for repeatable/usable (even docile?) stunt power. These engines are tunable as well. Responding to different venturi sizes, and the addition of a head shim or two, when useful.

Brett Buck · « **Reply #15 on:** April 11, 2013, 12:09:07 AM »

Quote from: Dennis Moritz on April 10, 2013, 11:59:02 PM

I have seen a few good running ST46s that appear to have more grunt than an LA46. Typically they use a higher pitched prop. Perhaps this indicates an ability to make more torque.

It indicates that the ST46 torque drops off much more quickly with RPM. I don't have the data to prove it, but I expect that you would find the 46LA torque at ST46 in-flight revs (maybe 8700) at least as high, and much higher torque at 11,000. You run an ST46 on 6" of pitch because it doesn't have the poop to spin 4" of pitch at any useful diameter and have any breathing room in the maneuvers. I tried that.

Brett

Perry Rose · « **Reply #16 on:** April 11, 2013, 05:06:57 AM »

I have several planes powered with the .46LA. They range from 500 to 664 sq. in. and all right around 50 ounces, both profile and full body, trike and conventional gear. Airfoil seems not to matter either. I have Vector .40, Cardinal, Pathfinder and Strega airfoils and all fly great in all conditions with the .46 LA. Home brew fuel with 2% nitro 22 to 24% oil and around 300 feet MSL. 11.5 x 4 and 12.25 x 3.75 APC props work very well.

Brad Smith · « **Reply #17 on:** April 11, 2013, 06:04:17 AM »

You said you have 2 LA .46s how about the LA HEAT kit rsm has its twin engine 834 sq inches 65 inch wing span.

Joseph Lijoi · « **Reply #18 on:** April 11, 2013, 07:23:14 AM »

Quote from: Brett Buck on April 10, 2013, 10:24:24 PM

That's way too big for an ST46, that's almost back to the 70's style "scaling rule" monsters. Think 625 squares, mid 50's at most - like all the later Ted ST46 designs.

Brett

Werwage Juno, Bob McDonald Aquilla if you like I beams.

Doug Moon · « **Reply #19 on:** April 11, 2013, 10:01:14 AM »

The Buccaneer 740 with an LA 46 in it is a killer combo. I know because I used to fly a 740 for quite while. I started out with an FP40 in mine. Cruised through intermediate with it. Then used the Buccaneer 746 with a piped motor in Advanced.

Years later I borrower 740 built by Don Hutchinson and put in an LA46 and it killed! Even without appearance points I was able to be competitive in Exp.

The Buccaneer 740 is really great model for what you are talking about. Simple construction, very standard and up front type stuff. It builds very fast. Mid 50s is easy to achieve as well. Balances just right with the LA and tongue or Lightweight tube muffler.

Joseph Lijoi · « **Reply #20 on:** April 11, 2013, 10:17:21 AM »

Quote from: Doug Moon on April 11, 2013, 10:01:14 AM

The Buccaneer 740 with an LA 46 in it is a killer combo. I know because I used to fly a 740 for quite while. I started out with an FP40 in mine. Cruised through intermediate with it. Then used the Buccaneer 746 with a piped motor in Advanced.

Years later I borrower 740 built by Don Hutchinson and put in an LA46 and it killed! Even without appearance points I was able to be competitive in Exp.

The Buccaneer 740 is really great model for what you are talking about. Simple construction, very standard and up front type stuff. It builds very fast. Mid 50s is easy to achieve as well. Balances just right with the LA and tongue or Lightweight tube muffler.

Here are the specs:

http://www.ultrahobbyproducts.com/Plans_List.html

575 squares

Jerry Higgins · « **Reply #21 on:** April 11, 2013, 10:20:48 AM »

I have an LA 46 in an Oriental and a Brodak Cardinal 40, both in the 43 to 46 oz range. We fly at between 5,000 and 6,000 feet here in Colorado, so power is always a good thing. On 64 ft lines and with an 11X4.5 prop the combination is great, even on a hot, windy day in July. The engine growls around in a somewhat fast 4 cycle and only speeds up slightly when the nose is up. When I fly at lower elevations I either add a foot to the lines or drop the pitch to 11X4. At this elevation in hot weather I have noted that the LA sags in maneuvers on 600 + sq in 50+ oz airplanes. I doubt if you fly at high elevations, but my point is that on the smaller planes (< 600 sq in) the power this engine puts out is great for handling the wind. My only negative on this engine is that it wears out quickly.

Jerry

Jerry Higgins · « **Reply #22 on:** April 11, 2013, 10:24:43 AM »

I would agree with Dough Moon's assessment. A Buc 740 is about perfect, or anything with about 575 sq in like the Cardinal 40 or a variant.

Jerry

Tim Wescott · « **Reply #23 on:** April 11, 2013, 10:32:53 AM »

Quote from: Brad Smith on April 11, 2013, 06:04:17 AM

You said you have 2 LA .46s how about the LA HEAT kit rsm has its twin engine 834 sq inches 65 inch wing span.

One engine to fly with. One engine to replace the first engine after I do something stupid in an overhead maneuver and whack into pavement at 60 miles per hour.

Joseph Lijoi · « **Reply #24 on:** April 12, 2013, 06:36:45 AM »

Quote from: Tim Wescott on April 11, 2013, 10:32:53 AM

One engine to fly with. One engine to replace the first engine after I do something stupid in an overhead maneuver and whack into pavement at 60 miles per hour.

Tim if you are still at the point of this being a good possibility then I would suggest building threeTed Fancher Doctors.

Steve Helmick · « **Reply #25 on:** April 12, 2013, 07:28:52 PM »

Don't f'get, Tim, it's gotta fit in that little Fjord (sic) of yours. But I was going to mention that a nice match for the .46LA is an Oriental PLUS. Rod Claus is flying the one he got from Mike Haverly (Mike is apparently a major source of OPP's in the NW). I flew it once, when it had the RO-Jett .40/pipe setup in it. I don't remember a lot about it, but I'm sure it was ok. I know that it had a bunch of nose-weight in it. The Profile Cardinal is a good flier, despite having too much flap area...it would be an educational experience because of that. Other good choices are the Pathfinder/Starfinder and the Forerunner (UHP kit/ribs/plans), and Dave Trible's profile Sukhoi 26 (2 time winner of the Aussie NATS in F2B!). Crist Rigotti has designed some good profiles for the .46LA, and might even have plans available. Don't be shy about taking a full fuselage design and making a profile out of it, or scaling up/down. I'd agree entirely that 550/620 sq. in. is good for the .46. Choose any of the above, build it straight and fairly light, and trim, trim, trim. Don't forget to use the tachometer...

Steve

Tim Wescott · « **Reply #26 on:** April 12, 2013, 08:10:40 PM »

Quote from: Steve Helmick on April 12, 2013, 07:28:52 PM

Don't f'get, Tim, it's gotta fit in that little Fjord (sic) of yours.

So maybe I should make it take-apart?

Dang -- I just said that to be a smart-ass; now I'm wondering if maybe it's the way to go.

At any rate every time I build a bigger airplane I look at that little Ford and say "nah". Then I find that it fits after all. Who knows where it'll end?

Mark Scarborough · « **Reply #27 on:** April 12, 2013, 08:43:40 PM »

well as long as you can get it to the field,, usually the trip home it fits easier,,
Oh wait, I outgrew that phase,,

Steve Helmick · « **Reply #28 on:** April 12, 2013, 11:47:49 PM »

Quote from: Tim Wescott on April 12, 2013, 08:10:40 PM

So maybe I should make it take-apart?

Dang -- I just said that to be a smart-ass; now I'm wondering if maybe it's the way to go.

At any rate every time I build a bigger airplane I look at that little Ford and say "nah". Then I find that it fits after all. Who knows where it'll end?

Maybe you could try test-fitting some OP's bigger planes into the Fjord after a flying session or contest? See if Tom B's Score will fit?

Steve