"China Walking" ????

[Joe_Knesek]

Terry, after reading John's comments I realized a few more differences in my boat compared to yours. I mounted my tank in front of the motor instead of the side and I used a mini rudder instead of the regular 20 mono Speedmaster rudder. It's much shorter and also thinner than yours. The turn fin is made from spring steel and is much thinner than an aluminum fin. John told me about the offset strut a long time ago but I planned on keeping that to myself. Since he's let that out of the bag, I offset mine 1/8.

Another thing I learned from John is to balance the boat on 3 axis. It's not always possible to do but the closer you get the better the boat will handle.

 

[oldlugs]

Hey guys; I just wanted to say THANKS!

Some of the best info I've seen so far is in this thread, and I've searched and bookmarked several. I'll soon be setting up a new Speedmaster 20 and re-doing a used Microburst, and much of what I learned here will go into both boats.

Duane

 

[Ron Jefferson]

Joe: The real fact of the matter is... I actually said "Engine 1 to 1.5 inches up in the boat" and was talking about Terry's boat and not yours. I haven't seen your boat, nor set-up and really don't have an opinion either way.

What I do know is...

Not keeping the center of gravity low in a boat will effect the handling more than likely in a negative way. 1/2 an inch here or there, 1/2 a lb in the side of a hull and not centered in the boat can make the difference between a perfect set-up and a piece of ****. And, not to challenge statements like "but how much fuel is in that small 20 tank anyway" or, "back in the late 1970s and early 1980s" will make you but a puppet.

I never got caught up in what someone else tried in the past. More what I could prove to myself. Stubborn? yes. Follower? no...

Rj

 

[F.Orlic]

I can't figure out what is the benefit of running geared? I'm new to monos but I can't see any advantage with boats we run in North America. My .21 mono will run 52-55 MPH with stock X440/3, for that to happen I have to turn 30-31000 RPM, now for geared engine with 1:1.5 ratio turning X452 you have to turn34-35000 RPM which is very unlikely from what I seen. FSRV boats are different as they carry a lot more fuel. I always try to run smallest blade possible with most pitch because in general heavier boats need bigger blade. Geared boats sure look neat but as far as benefits goes I'm not sure.

 

[Joe_Knesek]

I can't figure out what is the benefit of running geared? I'm new to monos but I can't see any advantage with boats we run in North America. My .21 mono will run 52-55 MPH with stock X440/3, for that to happen I have to turn 30-31000 RPM, now for geared engine with 1:1.5 ratio turning X452 you have to turn34-35000 RPM which is very unlikely from what I seen. FSRV boats are different as they carry a lot more fuel. I always try to run smallest blade possible with most pitch because in general heavier boats need bigger blade. Geared boats sure look neat but as far as benefits goes I'm not sure.

I guess time will tell. I'm going to find out just how many RPMs your motors will turn Franko!

 

[F.Orlic]

I can't figure out what is the benefit of running geared? I'm new to monos but I can't see any advantage with boats we run in North America. My .21 mono will run 52-55 MPH with stock X440/3, for that to happen I have to turn 30-31000 RPM, now for geared engine with 1:1.5 ratio turning X452 you have to turn34-35000 RPM which is very unlikely from what I seen. FSRV boats are different as they carry a lot more fuel. I always try to run smallest blade possible with most pitch because in general heavier boats need bigger blade. Geared boats sure look neat but as far as benefits goes I'm not sure.

I guess time will tell. I'm going to find out just how many RPMs your motors will turn Franko!

Enough to run 45-47MPH with geared setup

 

[Joe_Knesek]

I can't figure out what is the benefit of running geared? I'm new to monos but I can't see any advantage with boats we run in North America. My .21 mono will run 52-55 MPH with stock X440/3, for that to happen I have to turn 30-31000 RPM, now for geared engine with 1:1.5 ratio turning X452 you have to turn34-35000 RPM which is very unlikely from what I seen. FSRV boats are different as they carry a lot more fuel. I always try to run smallest blade possible with most pitch because in general heavier boats need bigger blade. Geared boats sure look neat but as far as benefits goes I'm not sure.

I guess time will tell. I'm going to find out just how many RPMs your motors will turn Franko!

Enough to run 45-47MPH with geared setup

Frank I'm not sure how you are figuring the speed but I'm sure it's well thought out. Here's my rational for building the geared 20 Speedmaster. A 40 mono runs an X450 and is much heavier, has more hydrodynamic drag & the motor turns less RPMs but is 5 to 10 MPH faster than a 20 mono. If the geared motor turns the same prop & RPM as the 40 mono it's going to be faster because it's lighter and has less hydrodynamic drag.

 

[Terry Keeley]

Terry. The best thing for the model is to not have counter act for forces. Having the tank on the left is something you don't Want to have to counter for at slow speed. Having the rudder full to the right is something you don't want to have to counter for at high speed. The ptoblem is this.............At different speeds different hardware either effects or does not effect the ride of the hull. So.................to make it simple, put all the hardware where the boat is comfortable at all speeds. Don't build a plane that you know will flutter. If you build a wing that bends under pressure a tail spin eventually becomes tighter and tighter as air speed increases making an uncontrollable spin to the earth unless you can slow down airspeed enough for the wing to straighten out. Then you can pull out of the dive. That's airplane terms for what is happening here. Just put the tank in front of the engine, move the rudder to the left until it is about 1/4 inch from the outside edge of the prop, Move the strut to the right a bit, and you are ready for top speed. If the boat is wild after that.....Raise the strut to settle the boat into the water for control. If that doesn't meet your satidfaction then there are trim tabs. As for mounting the rudder to the left of center for straightaway records...... NO. that would really make the boat lean to the right. The distance from the rudder to the transom also effects how much the rudder holds the bow down in the corners and the straightaway. As does the depth and width. Believe me.......a mono is an animal that can be balanced a number of ways. Making changes that work at 55 mph don't work at 60 mph etc. It takes a lot of experimenting or a lot of luck at high speed because the effects of the hardware change as speed changes.

Thanks for all this great info John, you've made me think about things I probably wouldn't have figured out on my own. I can see I need to move the tank and get the rudder closer to the C/L and I think for now I might try a turn fin on the left. Next season I'll move the strut to the right, then look out! h34r:

Terry, after reading John's comments I realized a few more differences in my boat compared to yours. I mounted my tank in front of the motor instead of the side and I used a mini rudder instead of the regular 20 mono Speedmaster rudder. It's much shorter and also thinner than yours. The turn fin is made from spring steel and is much thinner than an aluminum fin. John told me about the offset strut a long time ago but I planned on keeping that to myself. Since he's let that out of the bag, I offset mine 1/8.

Another thing I learned from John is to balance the boat on 3 axis. It's not always possible to do but the closer you get the better the boat will handle.

Got the mini rudder too, how do you balance in 3 axis?

 

[oldlugs]

Got the mini rudder too, how do you balance in 3 axis?

Front to back, side to side, top to bottom...?

 

[Tofastformellow]

Many thanks go to mr finch for bringing the stut thing to the light

Jason

 

[Joe_Knesek]

Got the mini rudder too, how do you balance in 3 axis?

Front to back, side to side, top to bottom...?

The third is not top to bottom. It the balance above & below the drive angle, both mechanical & static.

 

[oldlugs]

...the balance above & below the drive angle, both mechanical & static.

I'm afraid that I'm saturated with 2 buck chuck... :blink: please explain... It'll soak in by morning...

 

[DaveMarles]

Frank, I respect your ideas of course, but you should really try geared. The basic advantage as I see it is that for sure Frank Orlic can go 50 mph plus with the small 3.5cc Seaducer and his experience/engine tuning/ prop knowledge etc and there will be others too but I bet the majority are way off that. The difference with gears is it makes it easy for (almost) anyone to go fast. The motor is easier to operate, doesnt slow in the corners so much, throttles and picks up easier and runs with more power because you can use 34000 plus rpm and you can also use a bigger boat for similar speed hence better stability.

 

[F.Orlic]

I can't figure out what is the benefit of running geared? I'm new to monos but I can't see any advantage with boats we run in North America. My .21 mono will run 52-55 MPH with stock X440/3, for that to happen I have to turn 30-31000 RPM, now for geared engine with 1:1.5 ratio turning X452 you have to turn34-35000 RPM which is very unlikely from what I seen. FSRV boats are different as they carry a lot more fuel. I always try to run smallest blade possible with most pitch because in general heavier boats need bigger blade. Geared boats sure look neat but as far as benefits goes I'm not sure.

I guess time will tell. I'm going to find out just how many RPMs your motors will turn Franko!

Enough to run 45-47MPH with geared setup

Frank I'm not sure how you are figuring the speed but I'm sure it's well thought out. Here's my rational for building the geared 20 Speedmaster. A 40 mono runs an X450 and is much heavier, has more hydrodynamic drag & the motor turns less RPMs but is 5 to 10 MPH faster than a 20 mono. If the geared motor turns the same prop & RPM as the 40 mono it's going to be faster because it's lighter and has less hydrodynamic drag.

Joe, lets do some math, lets forget about any speed losses due to slipage.

If your engine turns 34000 RPM (most likely not) with 1:1.5 gear ratio spinning X450 = 59.2 MPH (theoretical speed)

Good .45 (in a mono) will run 25-27000 RPM spinning X450 = 68 MPH (theoretical speed)

Good .21 (in a mono) will run 30-31000 RPM shinning X440 = 63 MPH (theoretical speed)

As I said before this works very well for FSRV boats due to their design and weight. Engines for FSRV boats are also timed higher for higher rews, and run sub drive with much smaller props. They also run different course and they run slower.

.21 engines are low on torque and any extra drag or added rotational mass does not do them any good.

IF it works I will be the first to convert mine if it doesn't work do not feel bad Joe, I sepent countless hours and pile of money on thing that never worked out.

Dave, if I can run close to record with heat racing engine and high nitro and very limited knowledge of monos than anyone can do it. Yes , you are probably right about gear drive is more forgiving but I'm not looking for easy simple things, performance is what drives me.

 

[Tim_Duggan]

.21 engines are low on torque and any extra drag or added rotational mass does not do them any good.

I found gearing them actually has the effect of dramatically improving the torque at the prop because torque is multiplied when gear reduction is used. This therefore allows things that don't normally work on direct drive, such as considerably shorter pipes / lengths and higher engine timings to be used.

Years ago ( before seaducers) I converted a direct surface drive mono powered by a rossi to a gear driven surface drive with a cheapo thunder tiger engine. Transfomed that boat big time despite the inferior engine. The question I have in my mind is would I see a similar net gain when using a more modern boat and better engine?

Also - I don't see the additional drag in the driveline to be as much of a negative thing as the extra weight and motor height associated with a gear drive set-up, as well as the need for a deeper rudder blade (bigger props).

Just my experiences - shoot me down if you deem it needed.

 

[Joe_Knesek]

Frank you know I respect your opinion. If I didn't I would not be running one of your motors in the boat. In the long run you may be correct. If it doesn't work out I'll be the first to admit it on this site for the world to read. I'm going to the Flint record trials in 2 weeks so we will find out soon enough. I'm not expecting to set any records. I'm going because my son & I have never been to a record trial and it will be good preparation for the Internats.

One thing to consider it that Dave offers several spur gears that will allow me to adjust the ratio if needed. I am starting with 1.5:1 using a 20/30 set. You would be surprised how little drag the drive has. The shaft has hardly no bend and the motor does not have an axial load being applied by the prop.

 

[ids987]

I can't figure out what is the benefit of running geared? I'm new to monos but I can't see any advantage with boats we run in North America. My .21 mono will run 52-55 MPH with stock X440/3, for that to happen I have to turn 30-31000 RPM, now for geared engine with 1:1.5 ratio turning X452 you have to turn34-35000 RPM which is very unlikely from what I seen. FSRV boats are different as they carry a lot more fuel. I always try to run smallest blade possible with most pitch because in general heavier boats need bigger blade. Geared boats sure look neat but as far as benefits goes I'm not sure.

I guess time will tell. I'm going to find out just how many RPMs your motors will turn Franko!

Enough to run 45-47MPH with geared setup

Frank I'm not sure how you are figuring the speed but I'm sure it's well thought out. Here's my rational for building the geared 20 Speedmaster. A 40 mono runs an X450 and is much heavier, has more hydrodynamic drag & the motor turns less RPMs but is 5 to 10 MPH faster than a 20 mono. If the geared motor turns the same prop & RPM as the 40 mono it's going to be faster because it's lighter and has less hydrodynamic drag.

Joe, lets do some math, lets forget about any speed losses due to slipage.

If your engine turns 34000 RPM (most likely not) with 1:1.5 gear ratio spinning X450 = 59.2 MPH (theoretical speed)

Good .45 (in a mono) will run 25-27000 RPM spinning X450 = 68 MPH (theoretical speed)

Good .21 (in a mono) will run 30-31000 RPM shinning X440 = 63 MPH (theoretical speed)

As I said before this works very well for FSRV boats due to their design and weight. Engines for FSRV boats are also timed higher for higher rews, and run sub drive with much smaller props. They also run different course and they run slower.

.21 engines are low on torque and any extra drag or added rotational mass does not do them any good.

IF it works I will be the first to convert mine if it doesn't work do not feel bad Joe, I sepent countless hours and pile of money on thing that never worked out.

Dave, if I can run close to record with heat racing engine and high nitro and very limited knowledge of monos than anyone can do it. Yes , you are probably right about gear drive is more forgiving but I'm not looking for easy simple things, performance is what drives me.

Frank,

Just wondering if these prop sizes (X450, and I think you mentioned X452), are what others using 1.5:1 gearing are running, or based on theory ?

This is just idle curiosity by the way, I'm interested to know experiences of how well gearing works with surface drive. I have no doubt of its advantages with submerged drive, but the surface drive environment is obviously a little different.

Ian

 

[Ken Retallick]

Gear drives are working because a bigger diameter prop is more efficient than a smaller dia prop.

 

[ids987]

Gear drives are working because a bigger diameter prop is more efficient than a smaller dia prop.

Ken,

That was one of my points last time I posted on the subject as well (I believe it is well proven), but I wasn't really sure if this still applies with surface drive - due to the other factors in play (eg cavitation, unloading due to prop lift etc).

To add confusion to this though, in the same boat (submerged drive at least), generally you would run much the same diameter prop (on a gearbox and direct), but the gearbox setup will obviously run much more pitch. For example, a typical . 45 direct drive prop is a Mocom 1919 (approx 49 x 55mm). My geared (1.5:1) Picco .45 runs a Mocom 2028 (approx 50 x 77mm), and yes, I know that 77 is less than 55 x 1.5, but the revs are greater, and I am confident in my own mind that the boat would be significantly slower - even just for out and out straight line speed, in a direct drive setup.

The diameter question is what prompted my question, because the Octura X4xx props have a fixed diameter/pitch ratio. I believe that if you go bigger on the diameter as well as the pitch - if the diameter was already enough for the boat, you are loading the engine more, with little gain (again I'm not 100% sure if this applies as rigidly to surface drive). I thought maybe (for example), if a direct drive boat is running a 4xx series prop, maybe a 6xx series prop would work better for the same boat and engine with a gearbox, with the higher pitch to diameter ratio.

Yes, the gearbox will allow you to run a larger diameter prop as well, which (as Dave pointed out), enables you to run a bigger boat at comparable speed to a smaller, direct drive boat - with the end result that the smaller boats have to contend with your wash. Gearboxes have been in common use in the UK since the 80s at least, especially in .21 classes, and the same hull is often specified for .21 geared, or .40/45 direct drive.

Ian

 

[Terry Keeley]

I like it so far cause I can run as fast as most in heat racing set up much tighter. Running high 40's wet to the bow with X450's and X447/3's.

Been playing with trying to go faster for SAW and am running cut (47mm) 1650's with a little cup and a V947, hoping to get in the mid 60's if I can get rid of the %$#@@!! china walk! :lol: