I have seen my first combat event and i feel I must get involved!! I have done a few searches in this forum for some powerful .15 engine but I seem to have come up short.

So then I guess the question is what is a good and powerful .15 sized motor to run in combat?

OHH BTW we are flying the Spad gnat.

Do you have any rules about the engine to follow, or are you flying straight Open A rules?

There are several very high power, but high dollar .15 size engines, like the Cyclone and a bunch of others. They typcially run close to $200 each though.

Around here, the OS CV-A is used a lot, it's a bit expensive, but it's got good power, and is easy to run. It's not legal for SSC class though.

Norvel makes a couple of powerful .15 engines as well.

The Megatech .15 is on par with the CV-A, but a lot less expenseive. Quality control appears to be a bit hit-or-miss with it though.

Magnum makes a .15 that has good power, but the carb needs attention. If you look at the Magnum notes on my website, you can see how to fix up the carb to make it work right.

The OS LA is very popular in SSC, though it's not perfect either. The backplate can crack or loosen and leak air, and you have to remove the muffler baffle to get any power out of it.

There are other options as well, lots of .15 size engines out there.

The FORA.15 is a great A class engine.

I can agree with montague on this one..
For a deciently cheap class A motor go with the .15 CVA, This has lots of power for a half way decient price. The price is a little on the expenive side, but the quality is A+. I have this motor in my Lanier Ripper and it really makes it move. Remove the baffle, and it really screams.
Though only if i could keep the plane in the air. Now thats a differant story!

Well thanks for the response. I am not sure of any rules just that no bigger than .15. They are flying the SPAD Gnat and for the most part it seems to fly OK but it seems like somewhat of a dog in the air.

The Fora is a powerful .15, it's in the same class as the Cyclon I mentioned earlier. It will also set you back close to $200 by the time you get it set up, it aint' cheap, that's for sure.

The Gnat was designed for SSC (though it's not competitive against the current SSC planes), and is great in Gnat vs Gnat combat, where everyone has to deal with the same limitations. I'd guess that if guys are flying Gnat combat in your area, they probibly also have engine rules that are simular to SSC, or even more stringent. That would outlaw a Fora or a CV-A for that matter.

And, just as a thought, a Fora on a Gnat.... boggles the mind.

I have the OS LA .15 and its a super little engine for less then 60 bucks with tax.
Like they said... drill out the baffle at least twice as large of hole.
I cut the needle valve assembly off the back plate and just let if be supported
by the fuel tubing and it works fine.
15% cool power fuel.

I took mine apart and lapped the piston in and then ran one tank of fuel on the ground.
Ran it rich and then would peak the needle till it stopped two cycling and then right away
turned it back rich. Do this through the first tank. Run just slightly rich for first 3-4 flights
and after that it was a screamer. Cuts down the break in time to an absolute mininum.

Wayne G.

Wayne, I hate to say it, but that kind of break in, espeically the lapping of the piston to the liner is really bad for ABC engines like the OS LA.

On an ABC engine, you want as tight of a fit as possible between the piston and liner at TDC, you want a pinch, interference fit, not a slip fit. When the engine heats up, the liner expands faster than the piston, creating the proper fit. If the fit is already loose, when the liner expands, you loose power.

Interesting that the Russian/Ukrainian Control Line F2D engines (Fora, Cyclon, etc.) are making their way into the RC Combat field. Must be Lee Liddle's influence. These are nicely made engines, very lightweight (about 4 ounces), but they have their drawbacks. They run best at ungodly RPMs (30,000 or so), requiring the use of a hand made fiberglass prop. F2D rules limit the venturi size to 4mm, the engines can probably withstand some opening up of the venturi, but too much and they'll likely blow up. With the suggested prop (see below), a good one will drag a 400 sq. in. F2D model around at 90 mph (that's on 52 foot lines - probably go faster in RC without the line drag). The Fora is around $200, but the latest Cyclon can be had for considerably less (I think $100). (There are a bunch of others, btw. - Redko, AKM, Viper, Kodjol, etc.)

I think there is a Cyclon version with a RC carb, but I think the Fora comes set up for CL - no throttle. I'd be interested to see how various people solve that particular problem.

Incidentally, there's a Fora .29, too, specifically for Class B RC Combat (from George Cleveland's web site). Most likely a destroked .36 (for CL Fast Combat use).







RC Cyclon:

Iskandar,
You are right about the CL engines now being tried in RC Combat. Several years ago we first tried Cyclon PC4's with Kalmykov's own design carb. That was before we were using bladders. The learning curve with the hipo FAI engines was too steep for us then. Now that we understand more about the metalurgy, the longer break in cycles, and the use of more head shims, plus the bladder pressure systems we are able to run them quite well.

George Cleveland lent me a Fora .15 for test on one of his Falcon 72 ARF RC Combat wings. I propped it with a MA 8X3 instead of the "meanie greenie" that George provided. The choice was to have low pitch, high thrust rather than high rpms. The engine is probably not its happiest at 19K to 20K but pulled the Falcon with authority. As a point of reference the OS LA with a mousse can, running on bladder will turn a MA 8X3 over 18K and close to 19.

I talked it over one long evening with Lee Liddle and his conclusion is that we are not yet seeing the performance advantages of the FAI CL Combat engines because our planes are not optimized to their power bands. He thinks lighter, smaller planes with thinner wings will be needed to effectively gain the performance that the engines offer.

For the balance of this year I will run a Cyclon in Open A as well as OS LAs on mousse cans. The RC combat Open A class has a bright future but if we start with pricey FAI engines requiring bladders we may be putting to high of a technical learning curve in front of fliers and possibly be impeding its development. The rules allow us to run anything we want in "Open" A but I think we have to be careful not to kill it in its infancy.

Just to continue what Lou was hinting at, A class has been most popular here, on the east coast. But it hasn't been Open A with Fora's and such. Those of use who have known about the FAI engines have left them alone. Instead, we've flown Magnums, OS CV-As, Megatechs, Norvels and such. These engines run fine on standard setups, are cheap, and pull a small 2lb plane around very well. Not as fast as B class, but faster than SSC. Wingspans are usually in the 40-55inch range.

Carnage out here has been low, less than SSC actually, since the impact damage as been about the same, but the mid-airs less common, so the planes last longer in the A class here than then do in SSC, at least for me. Now, if everyone started running Fora's, that would change in a hurry. The damage per mid-air would go way up, even if the mid-air rate remained about the same.

Btw, I'm not surprised the Fora wants a smaller plane, I actually was guessing that would be the case a while back, though I was impressed with how well a Fora will pull a regular Falcon around. I'm pretty sure that if Fora's (and other such engines) become common, it would totally kill combat in this area, guys just don't want to deal with that level of cash and complexity. But if the pilots in this area continue to use some self-restraint and compete with the engines available, then I think things will go along as they are.

Anyway, what engine to buy for A class depends on where you're flying it. If you were here on the east coast, I'd suggest you think about it before spending $200 on an engine, and maybe see just how much fun these little planes are with out those engines. And realize that trying to talk someone in to getting in to combat is a lot easier if they don't have to spend that much money on an engine (and remember, you need multiple engines to be competitive).

However, if you are flying in an area where everyone is already using Fora's (if there is such a place), then I suspect you're going to have to shell out the big bucks to get started.

I still think a $200 Fora on a Spad Gnat is kinda silly. The Gnat was designed for SSC, so I'm guessing the origional poster is either flying Gnat combat, or SSC rules. If that's not the case and they are flying A rules, then ditch the Gnat and get a better handling airframe. (Nothing against the Gnat, Gnat vs Gnat looks like a TON of fun. But it won't stad up against current SSC or A designs)

Yeah, I'm all for keeping costs down and preventing the upward spiral of technology. F2D is a classic example of an expensive class to fly - $200 engines, $4 propellers, and you get the chance to destroy two planes per match! Fun to watch, though. So I like the SSC idea - it's very much akin to CL Speed Limit Combat, where you can fly any engine you want, you just have to keep the speed under 75 mph. But, as you know, there are people out there who will use whatever will give them an advantage within the rules, hence even if one is against the idea, it's a good thing to know about all the options and therefore be prepared. The class I thought would be natural for the F2D engines was the original 1/12 scale combat class - here's where an ultra lightweight, fuel sipping, very powerful .15 would really help, given the wing area and size constraints of the class. One drawback would be the incredible amount of 30K RPM noise, but perhaps a mousse can would help fix that (not allowed in F2D). The exhaust layout is perfect for a rearward pointing mousse can.

Then again - I remember what someone told me at the 2000 Nats, when I and a few other CL Combat pilots wandered over to the RC Combat site - he said if you go much faster than they were going already, your streamer would shred and you'd lose points!

That said - I'm curious if you'd tried the RC Combat plane with the supplied prop. The molded carbon/glass props used in F2D are in the range of 7x3.5, probably a little small for a 72 inch plane, but they do let the engines rev at where they are making peak power (about 30K). I figure if someone could get Kalmykov or Chornny to mold a 7.5x3 or 8x2.7 with thin blades, it'd be better than the APC 8x3. 18K RPM is way below the power band.

One engine I think should be tried is the SC .15 (or its identical twin, the ASP .15). These weigh about 4 ounces, and are twin ball bearing. Most 2BB .15s weigh 6 oz. This one looks like a bored out .12. Strangely enough, they don't seem available in the U.S. - I got mine from Just Engines, in the U.K., for use in the New Zealand/South African/to be decided elsewhere version of Speed Limit - .15 engines, speed limit 3 sec/lap. About US$60 each, shipped. Haven't run them yet but I've built planes for them.

If I were to take up RC Combat, I'd use bladder tanks from the outset, since I'm very familiar with them. I'm just wondering how they work with RC carbs. Do you really need an RC carb, or will a shutoff do? Or a two speed throttle (full speed and idle)? I understand Lee makes some sort of carb for his Magnums. To get the most out of a bladder tank, you want a huge intake. Dang - almost makes me want to give it a shot..

In SSC, you have to have a fucntional carb, and the carb has to be the stock one that came with the engine. In the other classes, you can use just a shutoff if you want, no need for any other speed. A fair number of guys do use bladders with standard carbs, some handle it better than others. (a common trick is to hook up the remote needle backwards, it seems to make it work better under pressure, at least that's what I hear, since I haven't done it myself).

So far, though, I haven't seen a need to go to using bladders in any class. I get engine runs that are fine on normal suction tanks, and I don't 0 rounds due to broken bladders. Given how close many of these contests are, I'm not in a hurry to try something that may cost me a contest at this point.

Oddly enough, bladders are most common in SSC, where there is no power increase, since you can't enlarge the carb throat to take real advantage of the fuel being under pressure. I have no idea if many guys open up their other carbs to get more power on a bladder. If Lee is making his own carbs, I didn't know it, but it doesn't surprise me. It's not allowed in SSC, so he must be doing it in the other classes. He might also just be moding the existing carb. I know he has some Magnum engines, and the Mag carbs need work to begin with.

About the 1/12 scale combat (2610 class), you're right, a really light but powerful .15 would be useful, espeically in the twins. The competitive single engine planes are actually fairly large and to be durable enough, they are actually rather heavy. I'm not sure one of those .15's would really do well. Keep in mind that it pays to be bigger in RC Combat. I'll take my 55" Firebrand over a smaller, faster plane anyday. (The firebrand isn't exactly slow, however)

Yes, there is such a thing as too fast. The streamer is part of it as you said. Also, since the action is farther away and in 3 dimentions, if your closing speed is too high on your target, it becomes very hard to line up on a target. If you're chasing a slower plane, it's often best to throttle down. I was flying some practice this weekend, I had one of my planes running at near-idle in order to catch one guy who was kind of fluttering around.

(a tip I need to remember to try this weekend, if I'm one of the last with a streamer, and the guys chasing me are running bladders (I don't), I need to throttle down. Since they can't slow down, the closeing speed will make it harder for them to get me. Should be fun.)

Out of curiosity, do you have a link to that SC or ASP .15? I just looked at JustEngines, the ASP .15 looks an awful lot like the Magnum .15, espeically the carb. I'd swear it was the same carb, and now that I think about it, I think I heard someone say they do use the same carb. However, the bore/stroke numbers are different on JustEngines for the ASP compared to the Magnum's numbers on Gloabal's website.

Iskandar,
I use a bladder on my OS LA .15 engines. Initially I used a pinch type shutoff but have since gone to just closing the throttle barrell to shut off the engine. I do not use a restrictor in the line or a second needle valve. It works very well. You can throttle down about 25% but any more causes the engine to load up rich and you cannot clear it.

The hardest part of the bladder system was sourcing the right materials and then setting up the syringes to fill the engine properly.
A bladder will improve the performance of any engine because it force feeds the engine all the fuel it can take, the limiting factor then becomes how much air you can get into it. Also the running characteristics of a bladder are much better than that of a tank. A bladder is consistent from start to finish of the run whereas a tank will tend to lean out (on a inexpensive .15) once airborn.

The bladder is also far simpler and cheaper than a tank and if it goes bad (burst) you simply throw it away and slip in a new one. I carry about a dozen in my flight box to replace as needed.

The original Scale Combat class aloowed the use of a .15 if the full scale airplane used an inline engine, and you were allowed a .19 if it was a radial engined plane. The big gripe back then was that the planes were far too small - a 1/12 Mustang had little over 200 sq. in. Phil Cartier was telling me that some locals were thinking about using the Ta-52 which had a decent wingspan. I guess someone wised up to the fact that Fleet Air Arm fighters like the Fulmar were significantly larger than land-based fighters, so I started seeing pictures of these in magazines, and Mr. Clean on the CL Stunt forum mentioned that torpedo planes were also allowed (hence 500 sq. in. Avengers). I guess the lightweight .15 won't be of as much use these days, since the modified rules allow bigger engines for use, and airplanes are larger, too.

I must admit, I've never seen a Magnum .15, but comparing weights on the Just Engines web site for the ASP and on the Hobby Shack (Hobby People these days?) web site makes me think they're different engines. The ASP is small - looks like a .12 in size. Put it next to my old Super Tigre X.15s, they're tiny. The place to get info is the Just Engines web site. Nice thing about Just Engines - they'll let you order the engine with different mufflers, without the carb, etc. etc. and adjust the price accordingly.

I've used bladders for a long time (since the mid 70s) so I'd naturally want to use them. Yeah, they can burst, but if you use the right stuff, it doesn't happen very often, and not at all if you replace them periodically. The materials aren't hard to get - CL Combat suppliers have everything needed, including the syringes and fittings. To avoid blown bladders, use the "Fast Combat" sized tubing - 1/4" i.d., 1/16" wall, preferrably Phil Cartier's Yellowjacket tubing or similar. Avoid the thin walled stuff people use for 1/2-A Combat. If you don't want to worry about the inside of your bladder compartment getting soaked with fuel, enclose the bladder in a balloon - if the bladder bursts, the balloon contains the fuel. A remote needle works great - the usual advice is to find the RC needle valve assemblies for the OS Max .10FSR, since these have very fine threads. In my case, I drill and tap the intake stack on the engine for a DuBro fuel nipple and the fuel goes from the remote needle to that. It is also possible to put the fuel intake elsewhere on the crankcase (some people put the nipple on the backplate), but it makes the engine a lot more prone to flooding. I think the CL Combat column one of the recent Model Aviations was about bladder tanks.

Incidentally, bladders do tend to run rich the last 15 seconds or so of the engine run. Usually not much of a problem. One thing to avoid is "false pressure" - if your bladder compartment is too small, forcing too much fuel in the bladder results in higher than normal pressure, which leads to a lean run after some fuel is used.

The SPAD Gnat is the club combat plane of choice at our field. We have some powered with OS LA, Thunder Tiger, Magnum, Norvel, and mine with an OS .15 CVA. The most powerful engine of the bunch by far is the OS .15 CVA. Our only engine rule at our club is that it must be a .15 size engine. Just remember, you are either chasing or being chased in RC combat, which do you want to be? Go with the speed baby!!!!