Straight prop shaft

[Mark]

On a rigger how bad does the boat perform if you use a solid prop shaft, in other words no flex drive?

 

[Flyin Rat Sass]

well, You lose one of your primary tuning points,and if the shaft is angled down you'r defeating a lot of work that went into designing the prop.then there's that whole vibration thing.Just have to ask why, would you consider using one?

 

[Mark]

No, not considering it, just wondering how they run. Was thinking they would want to jump out of the water because of the angle.

 

[Flyin Rat Sass]

It would defeat the sole purpose of a "rigger"---go fast!!!

 

[not2bright]

i know a guy that has a 1/8 scale barhdal that is straight shaft and the thing hauls butt, the fastest 1/8 scale i have seen

 

[Flyin Rat Sass]

Many scale hydros do benifit from the added lift provided by the prop angle,in fact some rely on it.

 

[EatMyShortsRacing]

Straight shaft will have a lot less power drain on the engine than a flexdrive assuming you have installed the shaft correctly. Yes that can have an impact on your shaft angle but apply a little ingenuity and you may just come up with a solution that gives you the best of both worlds

EMS Racing What about winged keels?

 

[_laxmasta2039]

wouldnt a down-angled shaft make it nose-dive, not come up? :unsure:

 

[Ian Inverarity]

That depends on the props....

 

[Mark]

If you shaped the blades taking the angle of the shaft into account the prop should run like a horizontal shaft shouldn't it? As long as it's a surface prop.

I just think that a flex is a big drain on power. Why are so many people running them.

Perhaps Andy Brown could answer this and the prop speed question I was asking.

 

[Mike T.]

You would essentially be turning the development clock of RC model boat design back to 1959. For many reasons, the flex drive became an instant success and nobody looked back.

 

[Hap Mulvany]

One of the most sucessful riggers of all time the Crap Shooter used a hard shaft. Ask Marty Davis

 

[EatMyShortsRacing]

And you all seem to have missed the point....

How about a combination of both??? There are a few ways to achieve this but look under the back of my gear Drive .21 Rigger and you will see one version. The Flex shaft is less than 6 inches long and the strut is well over 6 inches. Try using the flexdrive to handle the bends only and use solid for the rest... Best solution.

EMS Racing Making too much sense?

 

[Mark]

EMS,

That sounds like the best solution although people will say that you have to make the bend in the flex tighter and this will rob power and cause more wear, but you use this idea and for you it must work. Do you get more wear?

Something like a coil that binds as energy is put through it like a flex drive can only be tested with special equipment because the power robbing effects increase with more torque or energy and speed, so you can't make a reasonably judgement by just spinning the prop with the collet of the engine loosened off. I'm curious to know the outcome of such a test.

 

[EatMyShortsRacing]

Mark,

Well the sharper bend is not always required. My 21 hydro does have a gear drive allowing the shaft to be much lower that for direct drive so it does have only a very gentle bend in it.

Secondly is it the bend or the coiling and binding in the shaft tube that creates more drag and power loss?

Another version could be a straight shaft from the engine to just before the strut and have a small amount of cable taking the bend then connecting to the stub shaft???

Hmmmmm

EMS Racing Dont ask what mark IV is!!!

 

[Kris Flynn]

the FE guys are getting into straight shafts...a smaller diameter shaft can be used, but other than that i dunno about the rest of the benefits...there was an article in RCBM i short time ago on it...

Kris

 

[Mark]

Hey EMS,

That's what I was thinking how your 21 was setup.

Kris,

Smaller shaft? Maybe. Hollow shaft? Maybe. Titanium shaft? Maybe. But how you gonna weld or solder it to the flex drive.

 

[Don Templeton]

To answere the first question, many of the solid shaft outriggers up thru the early 80's like the Crap Shooter were built with an air dump in the back to reduce lift. I also have seen many riggers with a solid shaft to a second universal just ahead of the strut which flattens out the prop.

While these were 80mph boats and the flexes are running up to the 120's I still sometimes wonder what speeds we would be at today if the flex drive had never come along.

Just my thoughts,

Don

 

[Kris Flynn]

Mark, to tell you the truth, i dont know anything about it...

http://www.rumrunnerracing.com/feforums/sh...=&threadid=9517

Maybe some helpful info on that thread?

or this page

http://www.geocities.com/jwohlt5362/HardwarPage.html

Kris

 

[EatMyShortsRacing]

Hey this reminds me of two boats...

One is the Dr Jock Racing "Sticker". It was made for straight line and was longer than my twin 90 boat. THis was a 45 boat. The boat was very long so the straight shaft had a very low positive angle. Obviously the longer the boat, the shallower the prop angle.

Second is from my Multi-boat (FSR) days when I went to square drive couplings so I could lay the solid shaft a little flatter and used a 2 inch piece of square drive attached to a ferrule to do the bend at the engine.

EMS Racing How many boats has this man owned???