Neil Guildford

I've just bought a second hand Cermark F16, wow what a huge plane. The previous owner had an OS 91 and said it wasn't fast enough.

Someone's help with the best engine for this plane would be appreciated. The only problem is I need to keep it under 80dbs for my clubs sound limit.

Thanks
Neil

Razor-RCU

My Feedback: (50)

80 DB's ....hmmmm

I have no idea what sound limits these produce ( our limit is 96DB @ 10 feet) but---

Flyboy Dave had (I believe) an OS-1.08 big block on his and it flew well I think.... Sorta a bulky airframe- The Jett-90 would be the most powerful other than using a DF engine like an OS-91VRDF, the Jett has a pleasant sound but is pretty loud---[X(]

Another gent. was *****g out his ST G-90 and reported good results in this plane, again nnnnno idea of the DB's

Sure is pretty! I have the Cermark F-20 and the Tower Hobbies-75 flies it purty well-

Cheers!
James

Neil Guildford

Thanks for your input. The noise issue is sure going to be a problem.
Neil

Cyclic Hardover

My Feedback: (3)

Jett.90 and the 91fx are not even on the same sheet of music. You need sustaining RPM, Torque and the whole thing and the Jett .90 will give you this. 1.08 will not do anything for you. Get that Jett with a 12/7 prop top start and it will be impressive.

THEGRINCMAN

My Feedback: (41)

I think that any engine you use is going to be too loud. I would be willing to take this problem plane off your hands.




The Grincman

Neil Guildford

Is there a quiet pipe that would go on the Jeti 90 to keep it within 80dbs? Maybe I could over prop it?
Neil

bob27s

My Feedback: (19)

Hi Neil,

Nice F-16 ya came into there..... those are good birds!

Achieving anything close to 80db with these big block engines is near impossible.

My older pattern 60 engines never made it much below 90 db. The best I had was my Hanno .61, hanno clone carbon pipe, soft mount everything, 13.5x10 prop just over 9000 rpm... and I recall that just about got to 86db.

The only thing I have run in the "60" block engine that came close to the 80db mark is my BSE-100.

That BSE-100 engine, installed in the Aeroworks Edge..... 15x8 APC prop turning just below 10,000 rpm (somewhere around 9,700 rpm ground), and with the turbo-jett installed, check on grass at 3 meters at between 82 and 84 db. If I had the engine soft-mounted, the installation may have hit closer to 80db.

A turbo-jett muffler installation on that plane is not practicle. So lets rule that out for a moment. Also, it is probably not practicle to convert the front end to a soft-mount engine installation (hyde mount or similar). On that F-16, prop clearance is a factor.. anything over 12" dia is going to be tough. With that in mind....

The best I could see you could hope for....... Jett 90L engine (side or rear exhaust), combined with a Mac's quiet pipe, set long for somewhere around 12K rpm, and a 12x12 or 11x13 prop. I can not make any claims to the actual sound reading you would receive from this, but from a technical standpoint, this set up is fairly quiet on the ground, and will still allow the engine to unload a bit in the air.

Although I have not personally used them, I understand the [link=http://www.justengines.unseen.org/pipesjen.htm]"purple" 4 chamber pipes [/link] and Genisis pipes available in the UK from Just Engines are VERY quiet with minimal power loss. The 4 chamber Hatori pipe I have tried was pretty versitile... ran both for RPM and torque... very broad tuned band once set up properly. I understand the purple pipe is a hatori clone of sorts. YOu may want to consider these as well (For either a Jett 90 or OS 91).
For header reference, the Jett 90 bolt pattern is the same as a ST-75 (47 mm)

I hope this is helpful. Let us all know how things work out

Bob

Neil Guildford

The Noise limit will be tested at around 6 meters, so therefor a Jett 90 may be achievable with the correct muffler/pipe.
Neil

Neil Guildford

I'm told by piping an OS/ASP/MVVS etc 91 I will achieve good performance, albeit not as high reving as the Jett but quieter.
I am wondering if by putting a secondary pipe on a Jett 91 and the over proping necessary I may be loosing the extra performance I started out with, leaving me with a final output similar to something far more simpler.

Hmmn-
[&:]
Neil

bob27s

My Feedback: (19)

Any of the engines you noted will work well. They all respond well to higher RPM pipe tuning and resond fairly well to lower rpm torque applications. Some better than others. The ASP 91 is a phyiscally larger engine (unless they have a 91Fx clone now).

The advantage of the Jett engine, is that Dub will built it specifically for the rpm you ask for. Any power loss would be no different than any other engine. There are notions that all Jett engines 'have to' scream at high rpm to function and produce power. Not true. The standard Jett SJ-90T is a slightly altered 90L engine, supplied with a longer muffler timed for 10-12K rpm instead of 14-15K rpm. With a pipe, you have more flexible tuning ability and can pull the engine down to the 10-11K range. The pipe shift the torque curve.

Consider this.... power output is directly proportional to the amount of fuel burned in a given time. HP=lb/ft per second. Energy over a given time. At higher rpm, around 14K rpm, you convert 14K "units" of fuel to mechanical energy every minute. At lower rpm, say 10K rpm, you convert 10K "units" of fuel to mechanical energy. To create the same energy at lower rpm, you either burn more fuel, or create more force over that time. Creating more force each stroke requires increaing displacement. Stuffing in more "fuel" and burning it... that is what superchargers and turbocharges do (and tuned pipes for practicle purposes). For the most part, we live in the world of the "naturally asperated" model engine. YS 4-stroke engines are the exceptions.

If you want to turn down at much lower RPM to keep the noise down, you may wish to compensate for the loss of combustion engery by going up in displacement, maybe consider the BSE-100L or BSE-120L. That is exactly what these engines, and the .60L, 65L & .76L are specifically designed and built to do... low rpm, heavy torque. They perform in a similar manner to larger 4-cylce engines... however there is never the concern of over-reving the engine, as exists with most 4 cycle engines. Both are exactly the same physical size as the 90L. APC makes a 13x13N and 13x13.5N prop intended for 120 size warbird racing. I know that on the "big" cast case SJ-120 they work great, and the BSE-120 should turn them just as well. Cutting them down a bit to 12: diameter if needed for ground clearance and/or to get the rpm up a little is ok. The 100L will want to turn between 9500 and 12,500 rpm. On the 120L, you have to load it to turn between 9000 and 11,500 rpm (typically turns a 16x8 above 9200 for reference). The idea here is to prop the engines to keep them in the power band.

Combine the 10K rpm, small diameter heavy pitch prop (low tip speed), and perhaps substitued a full size 4 chamber pipe for the stock muffler.... and its going to be as quiet as you might get.

Anyway... I hope this information is helpful. I will ask around a bit and see if anyone has some rpm or sound data on the 120L with some of the warbird props.

Bob

Neil Guildford

I have chosen to go for an ASP 91. It is in a similar crank case to the OS 61 and therefor slips into the airframe with ease. At £79 I couldn't resist. I intend on testing the ASP 91 with a quiet muffler and seeing how this stands up to power and noise.

I will, with any luck, be flying the plane at the weekend and will report back after.

Neil

Neil Guildford

Here's the plane ready for its test flight. The ASP 91 slipped in nicely. The only thing I had to change was the rear mounted needle, back to standard to save carving the front the the plane.

Test flight this weekend.

HELP................Anyone know where the CG is????

Neil

Neil Guildford

Flew the maiden today.

6 inches behind the leading edge of the wing (from the flat bit) felt a bit nose light, so further flights will have the CG further forward.

I see what people mean when they say its not a particularly fast plane, especially when compared to something like a magnum, but it flys beautifully straight and looks superb with the wheels retracted on a low pass over the strip whilst rolling.

It is very easy to fly and landings and take-off are almost a non-event.

The ASP 91 is certainly powerful enough to get airborne, even from a muddy winter field, but lacks the verticle performance. I was running a 14x6 apc prop and this wouldn't have helped with speed (Very quiet though). I will now start experimenting with props

Neil

bob27s

My Feedback: (19)

14x6 ! eeek....... but I bet its not too noisy.

Were you able to check db levels ?? I know that was an initial concern.

Put a 12x9 on there. The 14x6 is working like an air brake

Dave03B

Neil Guildford

12x9, you sure?

Neil

bob27s

My Feedback: (19)

The engine is very similar to a OS91FX.

Cut down the front disk area (smaller prop diameter). It will increase the take-off roll a bit, but you will get higher top-end speed. A large diameter prop works like a speed brake. That is why the aerobatic guys use them... for consistant speed and to slow the plane on down-lines.

Try a 12x8 and 12x9. Will load the engine about the same as what you had, keeps the noise down a bit...yet will unload the engine a bit in the air and allow it to accelerate.

Neil Guildford

I was unable to find an APC 12x9 but have bought a 12x8 and 13x7 to try

Hope this makes a difference

Neil

Flyboy Dave

My Feedback: (21)

I would have said a 12-10. What was the ASP turning ? I bought one on a whim
but haven't run it yet....the price was right....[sm=surprised.gif]

FBD.

Razor-RCU

My Feedback: (50)

I actually have a 10x10 APC on my 60 sized F-20 (Tower-75) and it flies better overall than the 11x9 I was using---

You would think that the vertical would suffer but I guess the additional speed helps the initial vertical lines---

Keep us posted

LUDS96

My Feedback: (23)

I just Love my Cermark F-16. I run a Super tiger 90 in mine with a tuned pipe. Turns a 11x9 prop static 12,900 which converts to about 14,000 in the air. A quiet tuned pipe may get your sound level down. You have the ASP power plant already let me know how you end up with props. My 14,000 Rpm works out to 100 plus in air speed over the prop! Not to shabby! It does fly great, take off roll is steady and climb out is slow as it builds speed. But power dives and rolling passes are Sweet. I took the Fiberglass scoop off of mine and fabricated a new bottom to the wing with a small sccop for looks and lost all that frontal area. I ripped the retracts out on my grass field ,along with the whole nose, and replaced them with fixed gear. I have a New one in the Box When I build it I'm going to move the nose retract back where it is on a real F-16 with a big front tire for my grass field.
Revers Brother 52

vicman

My Feedback: (10)

WOW! You still have that thing in one piece???! [X(]

Neil Guildford

Well after a good first flight, the next the rudder push rod (snake) bent causing a loose rudder flapping around in the wind.
I was forced into an emergency landing which meant a wheels up belly job. I thought it went well but in turn the scoop shattered. I've remade one from blue foam and glassed it with Poly C. Just needs painting and then I can start experimenting with props on this ASP.
Neil