WITCHDR

I was thinking about putting a 100cc engine in a 50cc plane 29% Sbach.
Has anyone attempted this?I realize the balance of the plane will be an issue but can't I offset the weight by
mounting the batterys and other stuff towards the rear to compensate. I want to use the plane for 3D but my thought was
the horsepower would over take whatever center of gravity issues i would have.

Tired Old Man

My Feedback: (1)

It can be done, has been done with other models, can create many issues, and does not in any way offset center of gravity issues. An uncontrollable plane remains uncontrollable regardless of the amount of power it has.

aussiesteve

I say do it but make sure someone videos the flight from start to finish and post the video here please.

If you want the plane to last more than one flight here is my advice
CofG is very important. If you don't understand the importance of it - do not attempt to do what you are proposing and go find an experienced instructor to explain it. Nose heavy is really not very useful for 3D - no matter what power you may think you have.

Wing loading is very important. If you don't understand the importance of it - do not attempt to do what you are proposing and go find an experienced instructor to explain it. (Notice a pattern forming here?). High wing loadings are not very useful for 3D.

IF however you have a 50cc Brick in the plane and it already flies reasonably well, then placing a similar weight 100cc with more power would be a blast. You would be better to consider a stronger engine in a similar weight range.

STUKA BARRY

Small plane BIG engine is called a GeeBee. Your concept is about 80 years too late. The Granville Brothers did just that in the 1930's.

AirWizard

My Feedback: (3)

You are going to have prop clearance issues.

daveopam

My Feedback: (9)

If you are just after power, put a DA-85 on it. I don't think you will have a great 3D plane by just adding power. Great 3D is about wing loading as much as power to weight. Adding weight ups the wing loading no matter the CG.

David

Tired Old Man

My Feedback: (1)

More than anything else, great 3d, or any other type of flying, is about practice. More practice, and then more practice.

The plane is generally the easy part. A well designed plane with appropriate surface areas and percentages, correct surface travels with accurate servos and a good set up, better than average wing area with a thick wing planform and round leading edge, adequate battery capacity, a capable transmitter for mixes, a receiver that will handle all the servos and power leads, a reasonably aft CG, and a power to weight ration of 1.5 to 2 to 1 does the job.

More power does not help, and certainly more weight is counter productive. What you add on the nose has to be offset at the tail, so you end up adding more weight. That weight increases wing loading which generates the need for more speed to generate the lift for manuevers that need to be performed at slooowww speeds. Yes, a wing is still generating lift at high alpha, just mostly at the upper leading edge instead of the entire upper airfoil. So more weight cuts heavily into an already reduced lift condition.

It does not require a lot of power for 3d, just enough of it. Beyond that and all you get is weight. If the plane is designed around a 50cc engine, weighs less than 18.5 lbs, you already have enough power if you did everything else right. You can install a 454 in a VW Bug, but did that act make the car better? Only if all you wanted to do was go fast. For everything else it would be without value.

If people really wanted to learn how this model aviation stuff worked they would pick up and read a copy of the FAA's Student Pilot handbook. Once you learn a litle bit about aerodynamics you stop doing a lot of dumb stuff and start doing smart stuff that improves your flying ability tremendously. You then undestand the various relationships involved with flight, and how to recognize them.

WITCHDR

THANKS FOR EVERYONE'S INPUT-IT HELPED ME UNDERSTAND A LITTLE MORE ABOUT WING LOAD AND DYNAMICS OF A PLANE.
I WILL DO MORE RESEARCH AND HOPEFULLY PUT TOGETHER A PERFECT PLANE.
HAPPY FLYING.

DadsToysBG

My Feedback: (35)

We all want the "perfect plane". If you find it let us know. That will stop us from buying any other plane. What most of us settle for is a plane that we enjoy flying and is more compilable then our fingers. Dennis

clivemc

as per everyone else posts above - DONt do it - its not all about power, you can never have too much power, but you can always have too much weight......

the Wasp

My Feedback: (1)

today, most light 86" span 3D planes will hover with a good 50cc engine, and yes I agree a 100 would be way to much,,,,, so how about a 70cc

TOM, here in my home town we have a MG Midget with a Ford 302 in it

Jim

Tired Old Man

My Feedback: (1)

I know where there's a Vega with a blown big block, but it doesn't get used much. Go straight and go real fast is it's only purpose. Still pretty neat though

the Wasp

My Feedback: (1)

ummmmm,,, RC Plane drag racing LOL

aussiesteve

We actually do that sometimes - but we do it vertically.
Fly along level together then when someone says "go" - pull up and see who accelerates upward the fastest.

Kinda fun but look out for mid-airs

Tired Old Man

My Feedback: (1)

Like a mass launch foamie death match but on a larger financial scale?

apalsson

My Feedback: (1)

You won't need a long film!

The Sbach is an extremely sleek plane and goes well on the rated engine
Besides, heavy planes make bigger holes in the ground

apalsson

My Feedback: (1)

A nice side effect from that is your plane will vibrate apart in 10 minutes.
DA-85 = vibrator = ladies engine

If you're after that effect, why not an MT80? .. a lot more power, not all that more vibration

jester_s1

It's an unpopular fact among the DIY crowd, but I'll point out that this work has been done for you already. Several companies put out plane and engine combos that are good enough for world level 3D competitors right out of the box. There was a time when serious aerobatic pilots, especially 3D pilots, had to adapt bigger power systems to their models to get the best performance, but now the experts have done the experimenting for us to determine the best combos. Every year newer models come out that are a little better than the one before, but it's doubtful an inexperienced modeler will do a better job.

Tired Old Man

My Feedback: (1)

Doubtful? How about assuredly doing worse?

DadsToysBG

My Feedback: (35)

Now TOM you of all people know how many experts are here. They spend a lot of time on the computer telling us this LOL. All witchdr has to do is listen to them. Or he can go to IMACC competition or a Huckfust and ask a million questions. Maybe not every answer will be the best, but getting information from guys that fly alot is better then non at all.
Remember the guy that asked about 120 and pipes? Dennis

Tired Old Man

My Feedback: (1)

I don't want to think about the number of IMAC planes I've been asked to fix because the set ups were deplorable. Of course they were set up by some people that had won a few contests or were nationally acclaimed for their flying ability. Seems nobody ever researches their building ability and knowledge of correct installation practices, or even if they were the ones that had built the plane they flew and then sold. But hey, so and so flew that plane to a win in the super duper IMAC/3d extravaganza....... Their personaly flying ability is so great they would have won flying a winged brick.

You are absolutely correct in your observation. People have the option of following directives from people presenting a solution that best aligns with what the user wants to hear. Unfortunately they frequently do.

DadsToysBG

My Feedback: (35)

I never said he would get the best information, but at least he would get something useful to sift thru. With my experience with pattern flying. I believe this group spends more time with their equipment and planes getting the best out of them.
I do believe that the OP has not started flying much and has only done some reading and not in great detail. He also had no reference to to go by. Has I have said in the past why buy power if you can't use it.
My new plane a H-9 Suk has a 150 3-w. I can fly it a 1/4 quarter. !/2 does most of what I need. With OP question in mind, why do I need a 170 or 200? The plane weighs 36 1/2lbs. The engine is around 75lbs of thrust I believe.
Also thanks TOM for your help on my thread. I rebuilt the carb. It was 10 years old. Upgraded the carb plate. Completely checked my fuel system and changed the plugs. they were also 10 years old. When I checked the gap on them they were not even close to .020. Maybe like .010. Plan on testing it Sunday.
The hard part is resetting the needles. The engine was so right, now I have to start all over. Dennis

Tired Old Man

My Feedback: (1)

Wow! Normally the gap becomes wider with use and age. It must have been pretty tight to begin with. Your Tillotson is very sensitive to very small changes. A Walbro is intolerant of large needle changes but the Tillotson is more so. But it is a very good carb for those with a little patience and understanding. I went throuh one on another 3w 150 this past weekend. As you noted, the 3w 150 is a VERY strong engine. The need for a 170 would require a much heavier plane or the desire to initiate a moon walk.

As always you're welcome and I'm looking forward to reading the success story describing what you did and the final results.

DadsToysBG

My Feedback: (35)

My carb is a Walbro on this engine. Using AI information I set the needles at 2 1/2 out on both as a starting point. I'm using a Vess 32B. Dennis

nonstoprc

My Feedback: (90)

From my interaction with local iMAC or pattern pilots, I had the conclusion that these pilots have long passed the point to make an engine run well. Their pursue is the ability to fly perfect maneuvers under any conditions. Not many people can do it!