Model for a K&b 3.5 Engine

[Phillip Kenney]

I have a K&B 3.5 engine with the rear exhaust that I would like to find a plane for. Preferably a kit, or a short kit or plans. With the rear exhaust the nose movement would probably have to be slightly longer and if I remember correctly the engine is substantially stronger than the average .19 so a model with an engine recommendation of .15 to .19 would not be the choice.  Use would probably be sport flying and a profile would be preferable.. Any suggestions other than buy a different engine?

[Dan Berry]

Thyis is not a docile engine.
On a 7.8 x 4 prop you can expect 21-22,000 rpm.
I would look for another engine.

[Dane Martin]

Sell that to a free flight guy, or trade him for some good control line engines. Like Dan said, it's a monster.

[Jim Carter]

Howdy Phillip!  Assuming you already know how to build, why not mount it in a Perky or on a 15 sized Sig Shoestring?  Actually, there's any number of .15 sized racers you could replicate and have a ball flying!  Don't worry ... just build and have some fun!!  There's a fellow, Larry Marx, who designed a model called the POD RACER that is a neat little scratch built plane, I built two of them.  It's easy to build and should be a ball with that engine.  I contacted him back in 2015 through the Brotherhood of the Ring site but maybe some of the guys on this site could be kind enough to hook you up with his contact information and you can get a set of plans for your own building and racing enjoyment.

Jim

[GERALD WIMMER]

Hello
I used a number of K&B 3.5's on my own design combat models back in the 1980's and they went well but the 3.5 was not a user friendly engine like a ST X21. I then designed a small stunter based on the Dazzler with upright engine and muffler in the fuselage behind the engine. The initial design had flaps and trike under carriage and Fox 19 then a Fox BB19 but with the K&B 3.5 I removed the undercarriage and just went for high speed stunt. It was a lot of fun but the engine was a worn out ex R/C car sample and I never did the upgrade to a better 3.5 and proper pipe. I still have it tucked away in the modelling home, perhaps I should dig it out and upgrade it...

Regards Gerald
PS Also did a K&B 6.5 powered profile stunter but it had too many conflicts in the design concept and I should have shot for a high speed fun stunt model not a draggy large profile model.

[Phillip Kenney]

All , thanks for the suggestions. Jim you are close to the desired idea. I am a 73 year old guy who has been in modeling for over 50 years. The years have not been all that kind to me and I now have diabetes, low vision and  stage 4 kidney failure, In spite of that I still truly enjoy spending time in my workshop building. Assuming I either track down plans for the Pod design or maybe go with a old kit designed for a .35 the true mission is to build something to keep me from sitting around watching television. Most likely if and when I build it, somebody else in the club will fly it and I will enjoy the hell out watching it fly.
With that said , this is a fairly new engine so the power should be excellent. Do you think it would fly a smaller sized .35 plane? Maybe a Top Flite Tutor, one  of the Midwest larger P\profile warbirds or one of the many new versions of the venerable Ringmasters?

[Dan Berry]

It will fly those planes. It won’t be real happy propped down to do so.

[Dan McEntee]

   I'm not trying to discourage you from control line, but you should consider trying some rubber power models, either sport or scale models. If you really like to build, the world is your oyster with free flight models
  Type at you later, 
  Dan McEntee

[Phillip Kenney]

Thanks  Dan. With my vision the way it is I find it very difficult to build anything that\t has a lot of small parts, be it small plastic pieces for scale modals or small pieces of wood for rubber type models. Be it 1/2a, which I am building the Wizards for which you provd scans or something in a bigger scale C/l seems to be the most enjoyable.

[GERALD WIMMER]

Hello Phillip It may best best to swap the K&B 3.5 for a OS LA25 (or even an old 35) which would be much happier flying a 35 sized model , even with an RC carb, they are a easy handling pleasant sport engine very different to the high rpm 3.5.
Sorry to hear of your health problems , a bigger slow flying model would more fun flying on longer lines where your rotation is easier otherwise semi scale looks great from the sidelines .
Regards Gerald

[C.T. Schaefer]

Here are a couple of thoughts. A Sig Buster would hold that motor well. Years ago I built one to hold a K&B series 61 .29. Beefed 'er up some. It flew well and eventually saw several hot .40's.  A Flite Streak would work well also and could be re-engined easily. As you know, the 3.5 comes with a 'pressure' venturi so you would have to run it like a combat motor or make a smaller suction venturi.   Have fun!   TS

[Jim Carter]

   Hey Mr. Kenney!  Guess what!!  As you know, everybody's got their opinions and that's okay but rather than "reinventing the wheel", why not just build yourself a plain ol' Ringmaster!  Yep, a plain ol' replica, Matt Kania style, profile .35 Ringmaster with a separate detachable, plywood motor mount fitted for the K&B and fly to your hearts content!!  Yes, it's a bigger airplane but the engine is a powerful engine and I am quite sure it's more than enough power to get you around the circle and probably faster than you'd expect!  Heck, if an old well worn McCoy 19 will fly one, I'm willing to bet your more powerful K&B will do it as well.  The pictures are to give you an idea of the type motor mount I'm speaking of and the type plane.  Whatever you decide, just do it with the intention of having some fun!!

[Dane Martin]

I'll have to dig up my video, but we actually put a K&B 3.5 on a ringmaster during one of the fly-a-thon's. Now of course, mine had a bladder set up and I think it was a taipan 7x6 prop. We were running 2.5 - 2.9 second laps on 52ft lines. Now we were purposefully trying to go fast. I'm not saying you can't show that down, but that's the kind of thing this engine is capable of, even on a lowly ol ringmaster.

[GERALD WIMMER]

I'll have to dig up my video, but we actually put a K&B 3.5 on a ringmaster during one of the fly-a-thon's. Now of course, mine had a bladder set up and I think it was a taipan 7x6 prop. We were running 2.5 - 2.9 second laps on 52ft lines. Now we were purposefully trying to go fast. I'm not saying you can't show that down, but that's the kind of thing this engine is capable of, even on a lowly ol ringmaster.

Hello
Well done Dane!,  90mph on a Ringmaster with the old K&B 3.5 is faster then a lot of combat models.
Wonder what a pipe would add?
Regards Gerald

[Tim Wescott]

I'll have to dig up my video, but we actually put a K&B 3.5 on a ringmaster during one of the fly-a-thon's. Now of course, mine had a bladder set up and I think it was a taipan 7x6 prop. We were running 2.5 - 2.9 second laps on 52ft lines. Now we were purposefully trying to go fast. I'm not saying you can't show that down, but that's the kind of thing this engine is capable of, even on a lowly ol ringmaster.

Was it faster or slower after the wings came off?

[Dane Martin]

Was it faster or slower after the wings came off?

Slightly faster. We also quickly learned straight and level was the only way it was going to get more than 1 flight. The wing was clapping on any turn. I have no idea how we managed to keep it together for as long as we did. I still have the engine, at least

[Steve Helmick]

A rear exhaust engine, side mounted on a typical profile is a bit of a problem. Fitting a muffler usually interferes with the fuel tank. I'm not sure if there is actually a muffler for a K&B 3.5, but I'd want one. If it is in the way of the tank, remember that the fuel tank can be mounted on the inboard side of the nose. Easiest with a rectangular clunk tank...pretty simple to do then.

It WILL fly an S-1 Ringmaster (the original .19-.35 size). I'd look for a 9-3-ish APC prop to try, and restrict the venturi in some way or make a small one.  I have flown an S-1 with a K&B .18 for the Ringmaster Fly-a-Thon (first week in October), and it did the job in level flight.  Steve

[Mike Hazel]

There is a muffler for this engine. The chamber goes sideways instead of back, and has an angled outlet on each end. 

[Reptoid]

     First of all the 3.5 K & B is a .21 size engine, not a .15 or .19 as some have implied. It is a powerful competition engine and is still used frequently in Competition free flight. It will not run well on a suction tank with the stock needle and venturi.
     Sounds like you want something easy to build and easy to fly. You'd be better off to sell the 3.5 to a free flighter and use the money to get a nice sport engine designed more for what you want like an OS FP 25 or LA 25. There are enough guys looking for them for competition it shouldn't be difficult, and you should get enough for it to pay for the sport engine. There are enough issues coming back and relearning without knowingly making it more difficult.
      Maximize the fun, minimize the problems