JohnMcGowan

My Feedback: (15)

good morning Kirk,
the cg range is from 2 1/4 to 2 3/4 so I just split the difference for a starting point.
Thanks, I will pick me up a 3 oz tank and give it a go.
Thanks again for all your help, I appreciate it very much.
On another note, the new magnum 15 XL has had 3 two oz tanks run thru it last weekend so I know it could stand a little more run time. I had a mas 8x4 prop on it and it was turning 14,500 rpms on 15% synthetic cool power. Im hoping that when the engine gets a little time on it , the rpms will come up more than that. I ran 1 tank of 30% heli fuel at the end and the rpms came up to 15,100. Is this anything to be concerned about (lower rpms than what I expected)?
John

Montague

The 8x4 prop is just too big for that engine. Overloading it isn't helping break the engine in, and may reduce the power you eventually get out of it. 14.5k on the overly large prop and 15% fuel is fine though.

The Magnums like a smaller prop. Break in with a 7x4 MAS, and fly with the 8x3. Throw that 8x4 away. And take a headgasket out if you haven't already, the Mags come with 2 installed. With the 8x3 and 15% fuel, depending on the weather, and after the engine breaks in more (they take a bit of time to reach full power), you should see around 17k, sometimes 17.5k or more, sometimes in the high 16s. Don't sweat it, if you are over 16.5, you'll be fine, the Mag XL unloads quite a bit in the air (well, if the airframe is clean enough anyway). The OS LA turns more RPM on the ground, but doesn't unload nearly as much in the air.

JohnMcGowan

My Feedback: (15)

thats what I needed to hear Kirk, I had no idea that 8x4 was too big. Im use to bigger glow 2 strokes and saitos 4 strokes, so these smaller engines will teach me something, lol. I will do as you say and remove one head shim. Do you see that the 30%heli fuel will be a problem?
I will go and buy me a 7x4 and re-tach after I remove one head shim and see what we get.
Our club combat meet will require the use of the 8x3 combat prop, as you stated.
You da MAN Kirk!!

Montague

I've never run 30% fuel in my .15s, so I can't say. I've actually never run anything other than 15% in my MagXLs. I did run some 5% in my XLS because that engine is too darn powerful.

JohnMcGowan

My Feedback: (15)

A guy at our club has a ripper with a ThunderTiger 15 on a car pipe that he uses 30% in it and it absolutely SCREAMS!!

glowplugboy

My Feedback: (17)

Outstanding! 2 oz. won't be enough, and if you can find the 3 oz. Hayes tank, this is the one for competition. I use a 4 oz. tank for sport combat. The CG instructions on the Ripper are not real specific, but the CG is pretty important on this model. Put your forefingers about at the spar and see how the model balances. It should be nose heavy. Keep moving your fingers forward to about 1/2" forward of the spar. That's the true CG point, at least for my Rippers. If you can have a nice level airframe somewhere between these two reference points, you will be fine, just don't fly it tail heavy![:-]
Regards,
Mike

JohnMcGowan

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Hi Mike!!
yes, my balancer was placed at 2 and a half inches which is right at the spar, and it was just a tad nose heavy, Ill say it was hanging nose down maybe 5 degrees or so, so this from what your describing should be just about right. We'll see this weekend
You doing ok?
John

glowplugboy

My Feedback: (17)

Hi John,
That will be a great starting point as the Rippers are CG sensitive. I am up and walking again, getting my "gate" back and less pain in the ankle which is good news. I had to layout of combat this past weekend because I got the flu! Ouch![:-][X(]
Mike

JohnMcGowan

My Feedback: (15)

update: Today I picked up a 7x4 mas prop and a 3 oz fuel tank but left the 2 oz tank on this evening just to try the prop before dark got me. Last nite I did what Kirk told me and pulled 1 head shim on the magnum 15. On 15% synthetic cool power and after I tweaked the low end just a tad to get rid of the slight rich low end hesitation I got an amazing 18,500 with still a couple clicks on the rich side to go. I didnt want to max it out just to see what it would do because I am only on my 4th 2 oz tank of fuel. Id say I got a winner so far , what about it Kirk and Mike? Im curious to see waht 30% heli fuel will do now! Alll I can say is I'm very impressed with this engine now!!! That little 7x4 made it scream. You were absolutely right Kirk, it needed that prop to help the break in and to turn up. Im excited!!
Thanks both of you for your advice!! All I gots to do now is fly it on the maiden this weekend. Will keep yall posted.
John

glowplugboy

My Feedback: (17)

Outstanding! I believe that Kirk meant the small prop as a break in prop, right? It might be a little small for flying. With it broken in on the small prop, you should be able to get the minimum 17,500 quite easily on a combat prop. I happen to sell 8 X 3's by the dozen if you need some....

Regards,
Mike

Montague

Actually, when we flew OpenA out here, we used the 7x4 most of the time. The Mags love that smaller prop in the air on a small, clean airframe. The 8x3 pulls the larger SSC planes a little better in the vertical, but slower in level flight. Of course, the A class planes were a bit smaller in the wing, and closer to 2lbs rather than 2.5

glowplugboy

My Feedback: (17)

Kirk, that is interesting. I have never seen Open A flown. SSC and Open B still remain the favorites here in Texas. I bet a .15 does like that small prop. BTW, the new Magnum .15 is a vast improvement over the old one, huh? Easily the equal of the LA .15, and is not too far off the performance of the CVA .15. And on only 15% nitro, too.

Montague

Well, the funny thing is that OpenA, the way we were flying it out here is that it was a lot like SSC now. However, there were differences. The mid-airs did almost do damage, the planes were lighter, and only a hair faster than SSC, so they climbed better, but the furball spread out more than SSC does, so there were less mid-airs and we spent less time repairing and needed fewer planes to survive a contest. SSC is like bumpercars sometimes, with constant mid-airs, and contests decided among the top pilots mostly by how well you do at avoiding heat-ending early mid-airs. We didn't have that problem in A class here.

(We flew with a sportsman's understanding not to use the super expensive exotic .15s developed for various FAI events. We are able to be competitive and sporting at the same time out here, but that's apparently not possible in some parts of the country)


As for the new Magnum XLS, it is more powerful than the old Magnum and way more powerful than the LA if it was allowed to run as it was designed to. Since SSC has an RPM limit, you have to work to get the engine down under the limit and keep it running well at the lower RPM. Part of this comes from the larger carb and exhaust openings. Those larger openings allow more fuel and air in and out, but they also reduce fuel drawing ability. I run a standard clunk tank, so the engine's fuel draw ability is a small issue for me, I need to make sure I launch slightly on the rich side to avoid getting lean towards the end of the tank. It's not a big deal, and I'm thinking I might reduce the exhaust opening to improve the backpressure a little. The new XLS has a better carb than the old mags, but it still leaks around the needle valve o-ring after a little while. The first few runs will be fine, but I ran mine, then let the engine sit a couple of weeks and when I ran it again, it was leaking like crazy.

JohnMcGowan

My Feedback: (15)

so Kirk, you think I should do my maiden this weekend with the 7x4 thats still on it or should I go ahead and start using the 8x3 combat prop? The actual combat meet isnt for a month or so yet, but I want to fly it and get the bugs worked out.
I couldnt get over that .15 turning 18,500 with the 7x4 !! Thats honking man!!!
Thanks!
John

Montague

Fly the plane with the 8x3, since that's what you'll be using in combat. The airspeed and thrust changes can mess with how tightly you can turn, so you don't want to set your elevator rates based on one prop, then fly with another.

Yeah, those Magnums are actually more powerful than the LAs. But they are designed to turn smaller props at higher RPM than the LAs are. As a result, the 8x3 is actually a little too big for them on the ground, and the engine is "lugging" and not getting in to it's power band. So they tach low on the ground compared to the LAs. The LA is already about maxed out on the ground, the 8x3 is almost pefect for it. If you put a 7x4 on the LA, it doesn't rev up much at all.

But, when the plane is in the air, the prop doesn't load the engine as much. The LA is already topped out, but the Mag can unload and get in to it's power band and I think pulls harder in the air, espeically if you have an airframe that isn't too bad in the drag department. So while the LA might turn an 8x3 at higher RPM on the ground, in the air, I think the old Mag unloads more. However, this also means that you need to be sure not to launch lean, since the unloading will cause the engine to need more fuel. If you can't hear an RPM change when you pinch the fuel line on the ground, the Mag is too lean, and while it's peaked on the ground, it will sag in the air. I see a lot of guys get this wrong with the Mag. A couple hundred RPM off peak is probably not enough, you need 500 or more, though I do it by ear, not with a tach.

The new Mags are set up to turn the larger 8x3 prop on the gound better than the old ones. So they tach higher, but I don't think they unload as much.

I think my dream SSC engine would be an old mag design with a new Mag carb and the engine internals built to the old Mag sizes, but with the new Mag quality. That would blow the current engines away, I suspect.

(one of the biggest internal differences in the old and new Magnums is the way the liner is made. The old Mags have a really odd liner. The intake ports aren't normal "windows" in the liner, they are slots that go all the way down, so incoming fuel is actually touching the downward moving piston. I don't know why they did that, but I suspect it limits power compared to the more conventional designs. The new Mag has a normal looking liner. One of these days I'll pull both engines apart (again) and take some pictures of the internals).

JohnMcGowan

My Feedback: (15)

Thank you again Kirk, you are a wealth of info for me concerning combat since I dont know what Im doing, LOL- I'll be back with more questions for ya Im sure.
Thank you once again !!
John

Montague

No problem, and good luck. Lots of guys in the combat community are willing to help guys getting started.

Tbone4life

I been playing with my LA .15 a little bit (added a mouse can type chamber to exhaust) and can get over 18k with a 8x3 master air screw combat prop and 15% nitro. I richened it up to where I can easily see smoke and still get 17,500 out of it.

Montague

Keep in mind that if you want to fly at an SSC contest, a mousse can muffler isn't allowed, and richening the needle is good for the engine, but not a valid way to drop the RPM down to 17.5k.

Tbone4life

I'm not good enough to fly in any sanctioned events. I fly with local friends at the air field.

Montague

That's cool. Though if you can fly the plane around and not crash in to the ground every other flight, you're good enough to fly at a sanctioned event if you want. There are lots of guys of a wide spread of skill levels at most contests.

JohnMcGowan

My Feedback: (15)

ITS ALIVE!!!!!!!!!!!!!! I flew my ripper today for the maiden. The first flight had way,way too much up elevator programmed into the plane , altho I eyeballed it and it looked pretty level before take-off. A fellow club member hand launched it for me and the thing went almost straight up!! I had to hold quite a bit of down in it to fly , made one or two short laps, and brought her in pretty as you please. I dialed out about 5 or 6 full rounds on the elevator clevis and fueled her up again and away I went for try number two. This flight was dead on perfect!!!!!! The little magnum 15 was tacking 17,600 with the 8x3 combat prop and actually moved the plane out pretty well. I still have my 2 oz tank on the plane so about 4 and 1/2 minutes is about it. I noticed on the hayes 3 oz tank that the clunk does not sit to the bottom of the tank, even after I installed a more flexable piece of fuel line to the clunk. It stays pretty much level with the nipple that its attached to. Any suggestions on how to remedy that so the clunk will reach the bottom of the tank? That piece of fuel tubing is no more than an inch or so long, btw.
I plan on going back tomorrow and burning up the sky with the ripper, It was a blast to fly that thing today!!! Thank everyone (especially Kirk and Mike) for their support and help. I would shake you hands if I coud reach you, LOL
John

Montague

Well, on the 3oz hayes, I do a couple of things.

I do use the tubing the tank comes with. I streach it a bit as I'm putting the tank together, that seems to help the flexibilty a little.

The other thing I do is this. When I put the clunk line on to the stopper, I give it a little tug to the side, so that while it's on the stopper fully, it has a tendancy to sit not-quite-square to the stopper. Now aim that part down, and you're good.

Oh, and don't sweat that this means that the clunk won't quite read the top of the tank in level inverted flight. Chances are you aren't going to do much of that anyway when low on fuel, and any negative G pushing will make the clunk reach. For that matter, you can probably just not sweat it at all, and chance are, you'll be fine.

JohnMcGowan

My Feedback: (15)

Hey guys,
I installed the 3 oz hayes tank but didnt notice that it included an nice little pinhole from the factory( at no charge I might ad, lol )
I took a #2 sheetmetal screw and screwed it into the pinhole, hit some ca around the threads of the screw and presto, no more leak!
We had several people bring their rippers to the field Sunday and Monday so we practiced some combat(my first) with the streamers attached. I couldnt believe how much the streamers slowed the plane down and induced drag on it!! But I managed to stay out of somebody elses prop and land with a full streamer but I didnt get any cuts either, Oh well, next time!!
With my magnum 15 and the 3 oz tank I am able to get a full 9 minutes of flightime at full throttle- I had people running out of fuel with the same tank size after about 5 to 6 minutes. I dont know whats up with that, but I aint complaing, LOL
John