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OS RG-M .21 or OPS .21 Side Exhust

Old 06-21-2005, 03:39 PM
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donzi18
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Default OS RG-M .21 or OPS .21 Side Exhust

I will be putting one of these engines in a 31 inch Aeromarine Challenger deep Vee hull.

Which engine is the all around best engine?

I looking for reliability / available parts / speed.

Wich engine would be faster?

Any feedback would help.

Thanks
Old 06-21-2005, 11:50 PM
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Ron Olson
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

Tough choice between those two. Compare the numbers of each. Both engines you should be able to get parts for with no trouble.
Old 06-22-2005, 06:28 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

ORIGINAL: Ron Olson

Tough choice between those two. Compare the numbers of each...
Any idea where one can get the numbers for the side exhaust OPS? Aeromarine doesn't show them. In fact, even the pic appears to be wrong (it looks like a rear exhaust).
Old 06-22-2005, 09:35 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust


ORIGINAL: piper_chuck

ORIGINAL: Ron Olson

Tough choice between those two. Compare the numbers of each...
Any idea where one can get the numbers for the side exhaust OPS? Aeromarine doesn't show them. In fact, even the pic appears to be wrong (it looks like a rear exhaust).
OPS87700US
Old 06-22-2005, 09:59 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

ORIGINAL: donzi18


ORIGINAL: piper_chuck

ORIGINAL: Ron Olson

Tough choice between those two. Compare the numbers of each...
Any idea where one can get the numbers for the side exhaust OPS? Aeromarine doesn't show them. In fact, even the pic appears to be wrong (it looks like a rear exhaust).
OPS87700US
Sorry, when I said numbers I meant things like horsepower, weight, etc.
Old 06-23-2005, 12:50 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

I just found my Aeromarine catalog. I can never seem to find it when I need it but here's the numbers that they give. The OPS .21 Supermarine (rear exhaust engine), 2.55 HP at up to 42,000 RPM. The side exhaust is 2.4 HP and up to 39,000 RPM. Note the "up to", that's what the catalog says. Those are some pretty tall numbers. If they were true, I'd see a lot more of them at the races kicking Nova Rossi, Rossi, CMB and MAC booty.
I'm not saying that they aren't good engines but I have doubts about those numbers. O.S. seems to be closer in real world numbers so take the comparison from there.
Old 06-23-2005, 07:22 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

42K!!!!!!!!!!!!! I'd like to see that engine now. Probably ran for a few seconds with absolutely no load while they got the readings and exploded immediatly there after. My MAC at near 30K sounds like it wants to come apart. I can't imagine what 42 sounds like. I'm not from Missouri but they would have to prove those figures to me in a real world situation.
Old 06-23-2005, 08:15 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

They must come with better rods than my OPS .45, that one would never survive such RPMs. Ron, thanks for the numbers. I too wonder how accurate they are. I'm also looking at .21 engines. I like the fact that the OPS comes with a pipe, but since I've already got a couple spare 3.5 size tuned pipes, for "experimental" planes such as the one shown here, I can save some money by going with the OS.
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Old 06-23-2005, 09:42 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

This practice of putting some unreal numbers in ads got the attention of at least one magazine. RCCA got to the point of not having unproven RPM and HP numbers mentioned as they too knew that some motors were in capable of revving as high as was claimed. One was saying that they got 50,000 RPM out of a .15 engine. I won't mention the name of it here but you and I know that somebody was trying to pull the wool over a lot of eyes. I think that it is RC Driver magazine that had an interesting article from a person that built his own Dyno and was testing various engines to see how close the claims were. Most of them were only putting out about 1/2 of the advertised HP and the RPM wasn't even close to what they were claiming. He went as far as breaking in the engines and finely adjusting the tuned pipes to get the maximum numbers.
I totally agree with you John and Chuck. If an advertiser wants to say that their engine cranks out so many RPM and HP, show us how you got those numbers! What fuel, pipe and whatever other info plus the Dyno used to get your readings.
Old 06-23-2005, 11:02 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

It's amazing what 110% nitro will do for an engine. Chuck, off the subject and regarding your delta (Sig Wonder with swept wings?). I was discussing pipe length with a guy that has a balky ST G34H with an APC 8-8 engine on a Diamond Dust. The pipe length looked very long to me. All relative to my experience with high revving boat engines. What engine do you have and what is the pipe length (Plug to pipe weld bead)?
Old 06-23-2005, 12:24 PM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

This might bring back memories, it's a K&B 3.5 with a Macs 3.5cc unmuffled pipe. It's actually a Lanier Shrike 10. Fortunately, the field is isolated, so the noise isn't a problem. I'm running a 7x8 APC prop right now. The RPMs are low, somewhere between 16.5 and 17k. I don't have the formula for accounting for drag and prop slippage, but I think that puts it somewhere in the 110-120 MPH range.

I'm in the office, so I'm relying on my memory, I think the pipe length is 163 mm (edit: not sure what I was smoking, the pipe length as flying is 254 mm). I broke the engine in for a while on the bench and then added the pipe. I kept shortening it until the needle became extremely fussy. I then backed the pipe out a bit and used that measurement for setting it up on the plane. In theory, the engine is supposed to be able to turn 25k. At some point I may go with a slightly smaller prop so I can get the RPMs up into the low 20s (and hopefully more speed), but for now, it's plenty fast. When I do this I know I'll have to shorten the pipe some more. I've only got 3 flights on it so far, I wanted to keep it reliable to start off. If the ST is balky, it's possible the pipe is too short. The easiest way to find out is to lenghten it a bit and see what happens. The plane pipes are probably set a bit longer than you would be used to for boats, the RPMs are generally lower unless you are looking at racing engines.
Old 06-25-2005, 08:43 PM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

Nice looking plane. Is it a kit or an ARF? Looks to have a 40" wing span based on the balusters on your railing. I'm assuming 4" spacing on 2" X 2" balusters. The pipe length has to be near 225 to 250 MM. My A Hydro runs a K&B 3.5 MAC pipe at 9". 163MM is only 6.4". I built a Sickle (SPAD flying wing). It has TT GP42 in it. Have no idea how fast it is but it's a ball to fly.

Better stop this airplane talk. Ron will chastise me.
Old 06-25-2005, 09:33 PM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

Thanks John. It's a kit. Not sure why I wrote 163 down, perhaps too many nitro fumes. I just checked and it's set at 254 mm. The wing span is 36". Ron, forgive me for starting this. Back to boats. Oops, forgot to mention, the plane became a boat yesterday. Deadstick over the lake with not enough altitude to make it back to the runway. A friendly kayaker got it for me, it was floating just as happy as could be. No damage, and since I've got boat experience I knew to open up the radio compartment to let it dry out, it was dry as a bone.

And now really back to boats. I'm bummed because the local club is firmly entrenched in gas. It seems they've weaned nearly all members to get rid of their nitro engines. There are a couple holdouts with 20 riggers and one also has a .90 mono. They discourage anyone new from even considering nitro. I finally got my started in 1987 Dumas Hot Shot IV running today. After some of the usual tweaking, it started running pretty well, but I felt it was almost a waste of time. There's nobody to run it against. I really want to build something in the 20 range, with one of the engines in this thread, but I'm beginning to feel it's hopeless. I may have a heart to heart with the club prez to see if he'd be willing to support steering newbies to sport 20 tunnel or perhaps 20 mono as a lower cost entry option. Right now his idea of keeping costs down is to steer newbies to someone else's second hand boat. Is there a national migration to gas, as a few people told me today, or is it just select areas (such as here in the middle of nascarville)?
Old 06-26-2005, 01:24 PM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

Chuck, I share your frustration. Our club seems to be trending towards gas also. I enjoy the smaller engines (.21 and .45). I also have a Rossi 65 powered Scale Hydro that hasn't been in the water for several years because the District doesn't support Scale Hydro. All you see at our District races are gas mono's, cats and hydros. So many gas classes I can't keep track. I used to travel the East Coast, Washington DC to Connecticut, for District races when we were in District 1. We split off and formed District 11. Since then gas has been king and the guy that started the move to the New England District no longer races power boats. He's entirely Rag Boats. Thank GOD for airplanes.
Old 06-26-2005, 02:10 PM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

What I can't figure out, (actually, I have a theory) is why NAMBA and IMPBA can't manage to attract the people buying all these smaller nitro boats. It seems that thousands of them are being sold, but they must be getting run as fun boats.

My theory is that the people in the sport who are willing to spend $300-400 on a .21 engine actually chase away the entry level people. It's the same with the gas people, they chase away, or convert, people who are interested in nitro. A sport 20 class in mono, tunnel, and hydro with realistic $ limits on engines would be great for people starting out. Unfortunately, many clubs don't understand this, so the hydro people move to 20 riggers with $350 engines and the monos are all gas engines. They forget the beginner and abandon the classes that might attract them. Heck, they even mess up tunnel hulls by allowing all sorts of exotic mods to the engines. Sure, there's sport tunnel, but how many clubs work to maintain an active sport class so new people have somewhere to race?

I've posted comments about this on IW and got a few supporting responses, but for the most part, the hard core racers just don't understand the nature of the problem. As you said, thank god for airplanes, a person can invest $300-500 for their entire setup and have a great time. If one wants to do any kind of organized boat racing, that amount won't cut it if one wants to compete.
Old 06-26-2005, 06:31 PM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

I've had several bites from new boaters and have invited them to our club activities. I get promises, send them a club schedule and they never respond. I suppose we intimidate them with the level of the equipment we run and the complexity of it all. The trend seems to be, buy it ready to run, no complications, and go out to the local puddle and have fun. BUT RACING WITH SEVERAL OTHER BOATS THAT ARE EQUALLY MATCHED IS FUN DAMN IT!!!!!!!!! They just gotta give it a try.
Old 06-26-2005, 07:43 PM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

Very true. That's why I think it would be so beneficial if some of the experienced club members kept a few low cost, and slower, stock classes running. First, it would be fun, and second, it would be something the club could use to help train new racers. The problem is they just can't leave well enough alone so they start modifying the engines to get more speed, and before you know it, the low cost, beginner class is gone.
Old 06-27-2005, 12:10 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

hopefully Bill Zuber and Jon Equi are still working on this. I talked to Bill about tihs back after he got into office and was then working on re-doing the ABS class rules for most of the mass-produced boats. They still want to keep them under .165 cu.in. but I tried to convince him to take it up to .18 as they aren't really any faster. I don't know about the mufflered only engine rule as a lot of the boats now have tuned pipes. I suppose that the pull-start only rule may stay in place also. They are also trying to get race and membership fees lowered also for new boaters or those with the low-dollar boats. don't hold your breath waiting for the IMPBA as you might know how slopw they are at this stuff.
Any club can hold a class for any boat and have their own rules for a class like this, there just has to be enough interest shown for them to justify having it. I'm just hoping not to see 6 Miss Bud's racing all at once! That would be a mess.
Old 06-27-2005, 09:53 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

42000 is more like the number of pieces left after it exploded........

Old 06-29-2005, 09:55 AM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

ORIGINAL: Ron Olson

hopefully Bill Zuber and Jon Equi are still working on this. I talked to Bill about tihs back after he got into office and was then working on re-doing the ABS class rules for most of the mass-produced boats. They still want to keep them under .165 cu.in. but I tried to convince him to take it up to .18 as they aren't really any faster. I don't know about the mufflered only engine rule as a lot of the boats now have tuned pipes. I suppose that the pull-start only rule may stay in place also. They are also trying to get race and membership fees lowered also for new boaters or those with the low-dollar boats. don't hold your breath waiting for the IMPBA as you might know how slopw they are at this stuff.
Yes, intertia is hard to change.
Any club can hold a class for any boat and have their own rules for a class like this, there just has to be enough interest shown for them to justify having it. I'm just hoping not to see 6 Miss Bud's racing all at once! That would be a mess.
The clubs can help promote the hobby by maintaining some interest in the starter classes. Running the big, fast, and loud boats sure is fun, but if this is the only stuff running, what's the newcomer do? It does no good to have a beginner class in the rule books if the club doesn't keep it active. Unless the club has a steady stream of beginners, some of them need to keep running the entry classes. Otherwise, the occasional newcomers are always told "we don't run that stuff", so he's forced to go to the more challenging (and expen$ive) stuff, or find another hobby. I bet if I totaled the price of my 6 flyable planes it would be less than what many spend on their modified gas boats. Anyway, this problem ain't gonna be solved in this thread.

If you do witness one of those 6 Miss Bud boat races, please film it.
Old 07-02-2005, 09:24 PM
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Default RE: OS RG-M .21 or OPS .21 Side Exhust

Hey I have one of the Miss Buds , but it has been repainted blue and white. I have also done many upgrades to it. I also gave a 21 rigger, a3.5 tunnel hull and a 54 inch deep vee that is gas, but like the nitro's better



Larry

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