Hello,

I am considering putting a 90 size engine into a 40 size plane. I understand that I will have to counter balance the tail to ensure the weight and balance stays where it should but I am hoping for some advise. Has anyone done this before? Any thought and suggestions would greatly be appreciated. Thank you!!

I'm sure someone has done it before, but why? Even a 60 sized engine is way over powering the model. And you had better reinforce the firewal to take the loads. Prop clearance may also rear its head.

Good luck,

Chip

Hi

Sounds like its worth an experiment.....get the correct C of G and lateral balance and see how she goes.

PS.. please don't blame me if you pull the wings off first flight, half throttle?????????? Mind you power is sooo adictive.

Cymaz

Didn't I see this on Myth Busters? Oh, no...that was the car with the rockets strapped on the roof.

I used to fly a great Planes 40 size Extra with an OS .91 FS. Flew fantastic.

I replaced a 2-stroke 40 size engine with a 4-stroke 91 size engine.

MR G

I have been doing just that many times for a long time, it is no problem and very fun. It is addicting you know and it can get boring to fly with anything less afterwards. I have had different 40 sizers powered by both 91 four and 91 two strokes. My latest "overpower project" is a 20 size dogfighter with a very much tuned ASP XLS 52. Vertical flight is about as fast as level. I usually just move my reciever battery back to avoid dead weight like lead in the tail. On one plane I had the battery just under the rudder. Go ahead and have fun, nothing wrong about "thinking outside of the box" and having more than enough power. If it is fun then it is right, afterall it is a hobby

Its definetly doable. It works better on some airframes than others. What plane are you looking at?

I had a 91 4 stroke on a 40 sized 3D plane and it had a great power to weight ratio.

I converted my old Pizzaz to a ST 90. First I cut out the old motor mount system and mounted a round nylon mount to the firewall. This way I could slide the engine way back. Then I mounted two mini servos in the tail and the CG came out just right.

David

Goldburg's Cub 40 will support up to a .91 4 stroke. I have one for mine and it flies great.

Thank you all for your help. I'm was thinking about putting a 90 size 2 stroke on a somethin' extra or on the tiger 2....something that will move...want to easily break that 100 mph mark...I'll reinforce everything before flight. Thanks again!

If all you want is to break 100mph, put a TT 46Pro in a Q500 airframe and run an APC 9x7 prop. Easy 120mph with an easy landing, aerobatic airframe to enjoy.

Just my $0.02.


Mark

If you want speed stay away from the somethin extra. Its a fun acrobat but has a thick airfoil, not good for speed.

A plane like the sundowner, venus, or tracer are sporty planes that are a bit speedy.

I would also say no tp the Sig SE. The wing is just to thick. The Goldberg would not be my first choice but it will do what you want. Also remember RPM=speed. I good strong 60 will do what you want unless you allready have the 90.

David

.90/4S in a CG Tiger 2? To heavy mate.
Even with a standard.46 2 stroke, that plane needs/deserves tail weight to bring it out and show just what a lovely flying plane it is.
Having said that and flown a T2 for many many years albeit, years ago, it would benefit from a little extra power, todays modern light weight .50 plus somethings for example... but a .90 4 banger is counter productive IMO. Ground clearance, extra right thrust, tail weight, tank size ... yuk.
Still, who give a F'? Just go for it and have fun.

I have a YS 1.10 in a generic .40 size trainer with two bays lopped off each wing. This aircraft was assembled to compete in our local trainer pylon race series. It's good for about 115 mph in level flight and hardly slows down when put into a vertical upline.

As well as moving everything (battery, receiver etc) as far aft as possible, I put the tank on the CoG. The CoG is a constant 10mm further forward than the recommended location.

It flies so sweetly at part throttle that I can still use it to train beginners with the buddy box.

I have a Saito 180 in a Diabolic 60 sized 3D plan and the power is insane and very much "Diabolic" Plane is not much bigger or heavier than a UCD-60 and still it lands like a large trainer, veeery sloooow
So I would say too much power is just fine as long as the plane has enough wingarea and is strongly built. And do not run full throttle in a dive as it may destroy the plane.

A tuned pipe will bump up the speed without the added weight.

I have mounted several 90/91 engines in 40 size planes and really liked the results. Some of these were retrofited in after flying them with 46/50 engines. The added power is great and worth considering. You must choose your plane carefully because some planes will be nose heavy. When I build from a kit (Ultra Sport 40+) I add about 3 inches to the rear of the fuse. This counteracts the extra torque and weight. I have had a 90 on a Sig Something Extra with longer landing gear without lead. None of the 40 planes I mounted 90s on needed hardly any lead to think of it, because of the extra planning I did. If you need more advice give me a PM and I will give you some suggestions.

I power mine with a Saito 90TS twin. The extra weight helps balance out the floats and it works great.

many people do it,,
here is a World Models .46 size (57" span) P-40 with the ASP 91 4St,, your 2St should be a little lighter,

here is another World Models P-40 flying on the prop with a MLD 23cc gasser engine

Jim

Hello I have an old Skyline MX-2 its a 57" glow 3D plane. It has an glow 2 stroke OS. 46fx in it, flies nice but is one of my old beater planes. I'm thinking of adding a brand new 2 stroke OS .91fx with Pitts muffler that I got from another plane which I converted to gas. I have the motor mounts as well, would you think the plane could hold up adding this motor? I do mild sport flying nothing crazy just looking to see if I could have a speed project to have fun with. Any advise I would be appreciative.

the OS FX61 and FX91 are lugs, heaver than other brands of the same size. I would rather see you sell the 91 and buy an OS 55AX, it should be a bolt in fit and have 3x the power of your 46. or even the OS 50sx, it's a lot more powerful than the 46

Jim