skater_719

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i am purchasing a mini funtana and plan to put a small glow engine in it. I am having a hard time chosing what engine to use, size, 2 or 4 stroke, weight, fuel efficiency are all factors in the decision. its a fairly light plane at about 30 ounces, so i was thinking a .15 2 stroke would do but am worried about flight times. since it will only fit a 4 ounce tank in it , i was thinking 4 stroke but dont know about the extra weight. any help would be greatly appriciated.

flyinrog

My Feedback: (1)

There have been a few threads on this..the .15 2 stroke is all it will take, just live with the flight times..fuel it up and go again!....Rog

KidEpoxy

Electrics take either a long cool/recharge cycle or Big$$ on sets of batts
Fuelies just squirt more gas & go back at it... maybe even without somuch as opening a hatch

rainedave

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Has anyone tried one of those K&B .18s in that plane? Hardly heavier than a .15, but a lot more power. $90 and in stock:

http://www.mecoa.com/kb/aero/aircraft.htm

skater_719

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that k&b .18 just might be what i need, seems to be light enough, about 8 ounces with muffler. That would be pretty close to what a brushless system would weigh and put out even more power. hmm, any other oppinions on what motor would be a good choice?

combatpigg

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I've been waiting about 2 years to hear about someone, ANYONE who has used the K&B .18. We were told it was a actually a MOKI .18, [whatever that means]. The specs on the K&B .18 look good, otherwise the OS CVA .15 will haul that plane in style.

piper_chuck

My Feedback: (12)

A 4 ounce tank is plenty of fuel for a .15.

mtntopgeo

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There is a report in RCU user review on this engine. That member was quite happy to get 15,200 RPMs with a 8x4 prop . One of my $15 Ebay Enya .15-IV engines gets 15,100 RPMs with a 8x4 MAS prop, on 10% nitro. I have been trying to get one of these engines (K&B .18) to perform for the last couple of months. I started a thread in the RCU ENGINES (glow) forum. (I normally only look at the 1/2a forum, but didn't know if my inquiry, on the larger engine, would be welcome here). Don't be taken in by MECOA's specs about the big props, & big RPM numbers. With an 8x4 MAS, you ain't gonna get more that 15,500 RPMs with the factory muffler, on 10% nitro. In addition to what is listed on the thread, I also experimented with a tuned pipe borrowed from another .15 engine. Same resulte as with the mousse can; lost about 300 RPMs from what I got with the open header. I agree with the MECOA forum moderator, in that the answer to this engines performance limitations lies in the exhaust system, but i just don't know where to go from here. Right now, the K&B is back in it's box, in the closet. It'll probably stay there until someone can come up with some specifics, as to how to make it run. Gonna put one of my Cox Conquests on the Combat Mustang. Installation ain't gonna be pretty, but should perform nicely, without breaking an eardrum. ....... George K

combatpigg

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Well, you could put a 10x6 on a .40 size pylon racing engine and it will fall flat on its' face. From what I remember reading about the K&B .18, its' HP numbers were based on more like 18-19,000 rpm? If so, you got to prop it with less diameter and more pitch so it can get into its' sweet spot. I would see how it does with a 7x6 APC, then take a 7x6 and cut down to 6.5", just to see how the engine responds. If it can turn a 6.5x6 in the low 20s, then you've got a nice engine for a speed plane project. It will probably run strongest with a 3 or 4 inch long open header.

piper_chuck

My Feedback: (12)

The key to running an engine with a tuned pipe is experimenting with the pipe length. Start by measuring RPMs with just the header (wear ear protection). Then put on the pipe. If the RPMs went down I'd probably lengthen the pipe a bit to see what happens. If it goes up when you lengthen it, you know the pipe was too short. If it goes down more, too long. Typically you start with a pipe that you know is too long and keep shortening it until the RPMs drop a bit. The previous length is then the one you go with. I did this with my K&B 3.5 until I got somewhere around 19K with a 7x8 APC. Eventually I'll probably go with a tweaked 7x9, but for now, the plane (Shrike 10) is plenty fast.

A few more things to note. If you change prop sizes, you need to adjust the pipe length. Also, when you start getting too short, the needle becomes VERY fussy. One click can make the difference between on and off the pipe. It was when I reached this point with the 3.5 that I stopped shortening it. IIRC, the pipe gave me a boost of about 2K RPMs over what I got with the bare header.

Edit: I've got a second 3.5 that I'm still trying to figure out what to do with. Maybe an HOB Cheapass.

mtntopgeo

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cp, I thought that I was already using a small prop (8x4 MAS). MECOA says to use a 9x5, or 8x6 !!!!!!!!!!!!!!!!!!!!!!!! I'll give the 7x6 a try, next time I'm up to playing with this engine. Getting back to the subject of this thread, I sure wouldn't advise skater to try this engine on his new Mini Funtana....... piper chuck. thanks for the tuning tips. ......... I've also got a couple of K&B 3.5s. Thought that mine ran pretty dang strong, but nowhere near your #s. I have only run them with the factory supplied muffler using 10% nitro. .................George K.

combatpigg

My Feedback: (3)

A 2,000 jump is good, your .21 is probably designed for a pipe........the trouble with most sport engines is that the exhaust doesn't open soon enough and the intake doesn't stay open long enough for a pipe to do much good. Before shelling out $60 for an after market exhaust system for a $90 engine, I would want find out what kind of results to expect. Maybe K&B has a technical correspondent with some answers? We were told earlier [here] that it is a repackaged MOKI .18, and not to expect much from it.

The OS .32 on pipe gave an explosive jump in rpm, it has 180 degrees of exhaust duration, whereas most sport engines only have about 150. The .061 G&Z has close to a 10,000 jump, I've seen MCPs give 1500 rpm to an OS LA .40.......it really is a magical thing when it is working right!

combatpigg

My Feedback: (3)

MTGEO, I've never dealt with MECOA, they seem like a hands on kind of company, aren't they the ones who take trade in engines? 8x3 or 8x4 is probably what I would run on a .15 sized 3D plane, maybe even 9x3. I think an OS .15 LA will turn a MAS 8x3 about 17,000, and hover a 25-27 oz plane pretty well. I would try the .18 on the Funtana out of curiosity, either that or sell it and go another route. You should see the Morris Hobbies PenKnife perform with the MVVS .21! Maybe that would be an engine to consider. Ever seen a .15 sized plane do a "LOLLYPOP", or knife edged spin?

MyWay

Combat Pigg, The OS 32 does not have 180 degrees of exhaust timing. If it did it would be one sick puppy with a muffler on it. Thought you would like to know a little about the K&B 18, bore 16.3 mm and stroke 13.45 mm. OS 18 bore 16 mm and stroke 15 mm. Never could get th k&b to run hard. The OS 18 in comparison rips.

combatpigg

My Feedback: (3)

I measured the .32 2 years ago for a member here, posted photos and 180 is the figure I remember. It is a lot closer to 180 than 150 if my memory isn't 100% correct. If it doesn't have 180, then please inform what the actual figure is. I've got a Webra .50 that I brought up to 180 degrees [middle third of the port] and it runs at WOT very well through the stock muffler, but much better through a pipe.

piper_chuck

My Feedback: (12)

Welcome. I was pretty pleased with the results. The pipe made a big difference. So far I think I've only run ith with 15%. Someday I think I'll throw in some of the 50% I use for boat racing!

piper_chuck

My Feedback: (12)

Yup, I think the FIRE .21 K&Bs were designed for pipes. I tried to get some info from MECOA on the .18. I was going to get one for a Shrike. Unfortunately, they weren't particularly helpful. In the end I found the K&B 3.5s on eBay and since I've been running that same basic engine in outboard form for years, decided to go with it.

MyWay

Combat Pigg. The exhaust timing on a OS 32 sx is the same as the OS 25 fx, tower 46, tower 75, GMS 47. None of these engines are close to 180 degrees.

combatpigg

My Feedback: (3)

MYWAY, I just rechecked the .32, and it appears that I can't add numbers right. Actually, the numbers added up to 180, exactly, but I wasn't using my head. Here's what I got, exhaust opens at 102 ATDC, closes at 78 ABDC, number looks like 180, but it is actually 156 degrees of duration. I accounted for 10 degrees of piston dwell at TDC with the pointer before getting started. I realize the photos don't show much except that I took time out from my afternoon nap to get my hands dirty again. I hope the guy I gave the wrong numbers to awhile back [JAPANMAN] didn't go ahead and hog out a good running .32?

MyWay

Combat Pigg . Thanks for clearing that up. Put a LA .15 at 156 degrees and see what happens.

combatpigg

My Feedback: (3)

That is pretty much what Phil Cartier suggests doing to the Magnum .15 in this months' combat column, plus work the closing side of the intake port. Getting back to the Mini Funtana, the original poster didn't say what his expectations were, does he want a full blown mini 3D monster or just something to fly like an advanced trainer?

Sneasle

interesting.. so what all does that end up doing to the magnum? where can i find that article?

combatpigg

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The article is in Flying Models. The idea is to take a cheap .15 and turn it into more of a screamer for small props, high rpm, for a .15 C/L combat engine. With more exhaust timing, you lose the ability to turn larger diameter props, you lose the combustion force out the exhaust port sooner, less time to push the piston. more exhaust timing is part of the recipe for higher rpm type use. For a aerobatic, 3D type plane, you want a torquey engine that can handle a large diameter prop. some engines can give you a little taste of both worlds, that's why I like the LA .15 so much, versatile engine.

Sneasle

could it also be used as a speed engine for my next stang? or would doing this cause me to loose my throttle?

combatpigg

My Feedback: (3)

The Stang will be plenty fast if you just remove the baffle from the muffler, and run 7x5 or 7x6 props. If you get curious about speed, then try the plane with a 7x6 APC cut down to 6.5" and with the blades recontoured to look like prison knives.