Having a hard time hovering and flat spinning...running a 11x4 prop. I was told for hovering I need a 12x3.25 ish? Suggestions?

what is the plane doing when you try to flap spin?
what is it doing when you try to hover?
what engine do you have on the plane?

I was out practicing hovering yesterday with my knife and with an 11/5 and a 10/5 it hovers.
I ran out of elevens so I used the next thing in the box which was an 10 inch prop.

in a flat spin it just kinda "funnels" for lack of better description (nose down aileron type roll)...it never wants to get flat and in a hover it wants to tip nose over in any direction...I think it might be a balance problem, too nose heavy...suggestions? Oh yea, 46fx...I tried Morris' tuned pipe...DO NOT WASTE YOUR MONEY IT IS CRAP. Unfortunately bringing this up to him he gets insulted and says he doesn't deal in cash so I'll have to take store credit...funny how he deals in cash when I have it in my hand...

What exactly is the crap part about it ?
I have heard different things ! Would like to know, because I just ordered one. Have high hopes from this pipe.

Sounds like its too nose heavy. I'd try to move the engine further back on the fuse and maybe the battery. With a further aft CG the tail should come alive.

I've been beating my 6lb TT(thunder tank)Fun Tiger with a 46fx and MAC muffler. It revs faster and seems to turn more R's with the 11x5 zinger, but it does climb better with a 12.25x3.75 APC.

...mine flat spins good with CG @ 5 1/2 back - that's probably a little too tail heavy, though - 5 to 5 1/4 is probably about right - i was using an OS 46 w/APC 12.25 x 3.75, stock muffler - hovered pretty good...

Okay, you have your idle...and you have full throttle...nothing in between no happy medium no nothing and it's loud as all get out. You spin something like 15600 full and 3k idle. See, the Knife from what I've been told likes mid range stuff, you rarely fly it at full because of the throws you have with the surfaces that and you don't need full for 3d flying. So you're left with a pipe that'll haul butt but won't do what you need it to do for that plane. If you want it, and wanna save money I'll give it to you CHEAP like 15, 20 bucks...box it up and ship it your way. But for 50 bucks it is sooo not worth it. I'm running stock muffler now and it's quieter, there's a highly noticable improvement in midrange and I honestly can't say I noticed a huge difference at full throttle. The minute he hears you have a 46fx he pops out, oh you need this header and pipe...horse crap. Just my 2c.

Setting your CG right is the most important thing in regards to being able to hover and flat spin correctly with a Knife. Mine is set at almost 3/4" rear of the recommended CG. Hovering is a cinch and flat spins are absolutely flat. Plane climbs when put inverted if I don't touch the elevator. BTW, this is using a mere MVVS 40 (w/ tuned pipe) and an APC 11x4 prop (balanced).

In regards to the Rossi pipe for your OS 46? How far away is your tank from your engine? I've got one of these setups and it runs silky smooth through transition. Even more linear than with the stock pipe. Yes it is louder, but I like the sound of a tuned pipe... What I have found is that when using this pipe, tank location is a bit more finicky. You'll want to keep the fuel tank as close to the engine as absolutely possible. I tried my Knife with a TT Pro-46 with the Morris/Rossi pipe and the fuel tank still in the wing and found that it did not produce enough tank pressure when the plane was vertical... I had to set it VERY rich on the ground to do any hovering, and transition (when the plane was not vertical) suffered. Moved the tank closer and the engine ran as well as when I bench tested the engine/pipe combo... BTW, I'm getting 16k rpm on my TT using this pipe (using an APC 11x4 prop). That's 2000 rpm more than a with the baffled stock muffler. It makes a HUGE difference when pulling out of a hover vertically!

My fuel tank is on the opposite side of the engine, no problems getting pressure that I can see. It's not the transition that's the problem, it's the non existant mid...I have idle and I could go mid on my stick and it wouldn't be any different (maybe a few hundred rpms) than full. Maybe I'm doing something else wrong...

Check the fuel lines. Sounds like the fuel isn't being drawn until the carb is WOT... Not exactly a good thing. Most 2Cs do have a flat spot in the midrange, but nothing as bad as what you're seeing. You may want to play around a bit with your low end needle valve just to make sure you're not too lean down low. Also try a colder plug. I used to think that hot plugs were the thing for these ABC engines, but I've been experimenting with different plugs and have found that colder plugs actually work better with the higher nitro (I use either 15 or 20%) content. Power with my setup is extremely linear.

Maybe his low end needle needs to be adjusted to run with the new pipe.

If I were to hypothetically keep this pipe...what would you do, given the symptoms...

It depends on if you are an engine guy or not. Some are and some aren't. I am just now getting to where I feel like I can tune an engine. Have one of the guys at the field take a look at it. I bet you just need to richen up that low end a little.

There are a couple of things to consider about the knife. Once done, this plane will do anything you want it to. The posts about the cg are well taken. It hovers and flats better with a rearward cg. Weight at some point affects the overall performance of the plane too. After a couple of repairs, mine is 4lbs 8ozs and hovers all day long. It will back down or climb at my discretion, and easily does tail landings. I run an old MVVS .40 on a mousse can muffler and it's plenty. I never saw the need to get 15k and up on a hoverbatic plane? These are slow hoverbatic flyers. I just use an 11x4 wooden prop cut down a little to give me the spool up and performance I need. Most 3D stuff is done at half throttle or less depending on the maneuver.
My tank is in the wing and I use a Cline with excellent results. If you really want to snap, flip and hover, try the vortex strips on the wing. Doesn't really affect hovering or 3D stuff, but makes a world of difference in snapping, tumbling and spinning maneuvers. The instructions for the Fun Design and Top Cap have some really good tips on flying and hovering Morris planes. I have most of the Morris videos starting from 1995 and watch them frequently. Tony Ayer and Tom Stryker were definitely ahead of their time. I would correspond with Tony via email back then and talked to Walter Morris frequently when I had questions on their set ups etc. Can't go wrong with the Knife as an all around hoverbatic go kart

What is a vortex strip? It it triangular balsa? Stall strips?

If I'm not mistaken, the Top Cap booklet outlines the different lengths and placements. Have you tried them on any of your profiles Billy?

If you can't get that pipe to work buy a Tower Hobbies 46 ABC muffler. Thy cost $13. and will give you the midrange throttle response you want. They fit a O.S. 46, a Thunder tiger46 and an Irvine 53 and other Irvine engines in that size range.

I don't know anything about it. I'll go back and look at my books.

It might be worthwhile reading up on pipe tuning. Macs website has a good article on it.

I don't have a lot of experience with pipes yet, but I used the can from the MVVS 49 conected to a macs header pipe with great results on a GMS 47 recently. The header pipe comes a little longer than you will need. You tune it by cutting the header 1/4 inch at a time and measure peek RPM. the first couple times i cut it i got 300 RPM more, then 200, then only 100 more, so i figured i was close and left it alone. the throtle responce is outstanding and the needle settings are not sensitive. The length between the ehaust port and the expansion chamber is pretty critical, so if the guy insists you need a different pipe he might not just be trying to get into your wallet. The header pipe you have might be too short.

A lot of folks are playing with Mousecan pipes now. You start with a macs header (20$) and add an empty mouse can, spend a few minutes tuning it, and viola! you have a screaming beast ready to leap off the ground and rip up some sky! they almost always provide great midrange too. It is a little work but worth the effort.


Bob is right about CG. very important for flat spins. tiny bit too forward and you never get the tail down, tiny bit too far back and you have trouble getting out of the spin. the little tweeks can change a boring plane into a beast

hang in there