attack angle

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dwilfong

Well-Known Member
Joined
Jul 1, 2008
Messages
5,979
Ok setting up my first rigger (Kep"s 21) a few questions.

Attack angle is the angle of the ride surface not the top of the sponson?

Dose the angle of the top of the sponson make a difference?

What is a good place to start with the angle?

Bottom of the tub should be flat with setup board?

Hight of tub off board make a difference?

Dose using square drive set up change thrust angle and change setup?

I know a lot of questions but being a newbie could use all the help I can get.
 
Ok setting up my first rigger (Kep"s 21) a few questions.
Attack angle is the angle of the ride surface not the top of the sponson?

Dose the angle of the top of the sponson make a difference?

What is a good place to start with the angle?

Bottom of the tub should be flat with setup board?

Hight of tub off board make a difference?

Dose using square drive set up change thrust angle and change setup?

I know a lot of questions but being a newbie could use all the help I can get.

OK, some very good questions:

Attack angle is the angle of the ride surface not the top of the sponson?

That is correct, it is the bottom of the sponson as it attacks the water.

Dose the angle of the top of the sponson make a difference?

Yes, the top of the sponson is a part of a wing. It can lift, push down or be neutral. I set the top of the sponsons on my boat so that it has 3 degrees of angle to push the sponson down on the water.

Bottom of the tub should be flat with setup board?

Correct, you will want to place some blocks under the tub so that it is paralell with the table and zero your angle finder on the boat.

Hight of tub off board make a difference?

Yes, in very rough water the bottom of the center section will hit the waves if the clearance is too small. I like to have 3/4" on 21's and 7/8" on 45 & 67's and 1" on twins.

Dose using square drive set up change thrust angle and change setup?

No, it does not. The standard flex setup acts like a solid rod, so the thrust is exatly the same. I love square drive though, because of the ease of cleanup and less friction.

These are some VERY good questions, unusual for someone new at the hobby.

Suggest that you look at this setup article: http://rcboat.com/setup.htm
 
A lot folks will argue;BUT on a especially a 21 the square drive is key.. less friction, less useless load on the engine. You want to load the engine with the prop not shaft drag. .21s will not forgive you the least for anything that takes power away.. only because they don't have the "extra" power the bigger engines do. This is the most technical class you can run, the fun part is the challenge. Another thing to take into account is WEIGHT. Pay attention to detail on this. Remember the less boat weight the more prop you can pull. (in my opinion).

Norm Doerr
 
I got it of the board tonight finely after all day shimming it and making blocks to put the boat on.

Weighed the boat ready to run on my great grand fathers balance scale still has the 1932 cert stamp on it from PA.(all I have right now). 3lbs 6oz.

Thanks for chiming in it was perfect timing and great info,Just what I needed.
 
David, I'm no hydro guy by any means, but I will say-

Anytime !!!

Marty is offering advise , listen carefully,

his boats run VERY well.

He has offered me much advice in the past, and I have listened well-

but I don't always remember what the master has shared :blink:

I need a prop class refresher course Marty ;)

Andy
 
Believe me I was very surprised and honored that he offered his advice. I am like a sponge and take in every thing.

Every thing I have learned has come of international waters.

RC Boating is very addicting.
 
I got it of the board tonight finely after all day shimming it and making blocks to put the boat on.
Weighed the boat ready to run on my great grand fathers balance scale still has the 1932 cert stamp on it from PA.(all I have right now). 3lbs 6oz.

Thanks for chiming in it was perfect timing and great info,Just what I needed.
Is that weight ready to run?
 
Dose using square drive set up change thrust angle and change setup?
No, it does not. The standard flex setup acts like a solid rod, so the thrust is exatly the same. I love square drive though, because of the ease of cleanup and less friction.
Marty,

Would you please elaborate?

I would think that square drives are a more "mechanical" means of connecting the crank to the propeller.

Regards,

-Buck-
 
I got it of the board tonight finely after all day shimming it and making blocks to put the boat on.
Weighed the boat ready to run on my great grand fathers balance scale still has the 1932 cert stamp on it from PA.(all I have right now). 3lbs 6oz.

Thanks for chiming in it was perfect timing and great info,Just what I needed.
Is that weight ready to run?
Yes that is ready to run with batt. The scale may be off a little may be 3oz one way or the other.

CG is 1" behind the turn fin.
 
Last edited by a moderator:
Dose using square drive set up change thrust angle and change setup?
No, it does not. The standard flex setup acts like a solid rod, so the thrust is exatly the same. I love square drive though, because of the ease of cleanup and less friction.
Marty,

Would you please elaborate?

I would think that square drives are a more "mechanical" means of connecting the crank to the propeller.

Regards,

-Buck-

Buck:

http://rcboat.com/sqdrv.htm

A couple of tips on this. After you solder on the tapered brass piece using StaBrite, put the completed flex with soldered on tapered brass piece on a short piece of 3/16/ shaft. Put it in the lathe and hold the unsupported flex end in a short piece of brass tube so that you can hold it. Turn on the lathe and spin it and place a torch on the soldered connection just until the solder melts. When it melts the shaft will go completely smooth. Let it cool and you are ready to go.
 
I got it of the board tonight finely after all day shimming it and making blocks to put the boat on.
Weighed the boat ready to run on my great grand fathers balance scale still has the 1932 cert stamp on it from PA.(all I have right now). 3lbs 6oz.

Thanks for chiming in it was perfect timing and great info,Just what I needed.
Is that weight ready to run?
Yes that is ready to run with batt. The scale may be off a little may be 3oz one way or the other.

CG is 1" behind the turn fin.

Weight is IMPRESSIVE.....
 
I got it of the board tonight finely after all day shimming it and making blocks to put the boat on.
Weighed the boat ready to run on my great grand fathers balance scale still has the 1932 cert stamp on it from PA.(all I have right now). 3lbs 6oz.

Thanks for chiming in it was perfect timing and great info,Just what I needed.
Is that weight ready to run?
Yes that is ready to run with batt. The scale may be off a little may be 3oz one way or the other.

CG is 1" behind the turn fin.

Weight is IMPRESSIVE.....
I put a lot of thought in to the weight as i built the boat.

Luna for the tub sides

Home made eng mounts with fiber washers

Speedmaster ruder with cut down mount

Speedmaster strut cut down blade and small one sided mount

Carbon wrapped boom tube with solid carbon rod in sponson and in tub section

home made pipe mount

Phenolic tub covers with polycarbonate cowl

thin tin on tank build

And of course my own lite weight bat pac

It is all in the details every little bit adds up to a lot.
 
A lot folks will argue;BUT on a especially a 21 the square drive is key.. less friction, less useless load on the engine. You want to load the engine with the prop not shaft drag.
I would like to hear more on how a square drive would have "less friction" that a properly set up conventional collet. You still have a stuffing tube that the flex cable runs through & shaft bushings in the strut and even add the drive dog making direct contact against thrust washers at the back of the strut which does not happen on a conventional collet set up. As far as the cable at the motor once it's under load the squared end is bound in the collet. But hey, I'm always open to new thoughts or ideas so I'm all ears on this one............... :)
 
Last edited by a moderator:
A lot folks will argue;BUT on a especially a 21 the square drive is key.. less friction, less useless load on the engine. You want to load the engine with the prop not shaft drag.
I would like to hear more on how a square drive would have "less friction" that a properly set up conventional collet. You still have a stuffing tube that the flex cable runs through & shaft bushings in the strut and even add the drive dog making direct contact against thrust washers at the back of the strut which does not happen on a conventional collet set up. As far as the cable at the motor once it's under load the squared end is bound in the collet. But hey, I'm always open to new thoughts or ideas so I'm all ears on this one............... :)
Heck I am far for an expert or even experienced with RC boats,but hear is my 2 cents.

Teflon is its own lube so I am using lead Teflon bushings and a pure Teflon thrust washer.

I am using a flex shaft soldered on to the stub shaft and a Colet up at the eng with a small gap for cable shrink.

As far as the square Collete as the shaft shrinks it will slide in the Collete and unload the eng.

Spray a little Prolong in the tube and of you go.

I can feel the difference with my hand on the drag. Not much HP with the 21.
 
Last edited by a moderator:
A lot folks will argue;BUT on a especially a 21 the square drive is key.. less friction, less useless load on the engine. You want to load the engine with the prop not shaft drag.
I would like to hear more on how a square drive would have "less friction" that a properly set up conventional collet. You still have a stuffing tube that the flex cable runs through & shaft bushings in the strut and even add the drive dog making direct contact against thrust washers at the back of the strut which does not happen on a conventional collet set up. As far as the cable at the motor once it's under load the squared end is bound in the collet. But hey, I'm always open to new thoughts or ideas so I'm all ears on this one............... :)
What kind of drive system does the worlds fastest .21 Hydro have ?
 
A lot folks will argue;BUT on a especially a 21 the square drive is key.. less friction, less useless load on the engine. You want to load the engine with the prop not shaft drag.
I would like to hear more on how a square drive would have "less friction" that a properly set up conventional collet. You still have a stuffing tube that the flex cable runs through & shaft bushings in the strut and even add the drive dog making direct contact against thrust washers at the back of the strut which does not happen on a conventional collet set up. As far as the cable at the motor once it's under load the squared end is bound in the collet. But hey, I'm always open to new thoughts or ideas so I'm all ears on this one............... :)
Heck I am far for an expert or even experienced with RC boats,but hear is my 2 cents.

Teflon is its own lube so I am using lead Teflon bushings and a pure Teflon thrust washer.

I am using a flex shaft soldered on to the stub shaft and a Colet up at the eng with a small gap for cable shrink.

As far as the square Collete as the shaft shrinks it will slide in the Collete and unload the eng.

Spray a little Prolong in the tube and of you go.

I can feel the difference with my hand on the drag. Not much HP with the 21.
I'm no expert either but:

Being smoother when it's just sitting on the table turning it by hand is one thing. What happens when you spin the drive dog at 25000 rpm while being pushed up against the Teflon for a period of time? I don't think it will last long before the Teflon is machined away by the drive dog??? I'm asking as I don't know.

-Buck-
 
A lot folks will argue;BUT on a especially a 21 the square drive is key.. less friction, less useless load on the engine. You want to load the engine with the prop not shaft drag.
I would like to hear more on how a square drive would have "less friction" that a properly set up conventional collet. You still have a stuffing tube that the flex cable runs through & shaft bushings in the strut and even add the drive dog making direct contact against thrust washers at the back of the strut which does not happen on a conventional collet set up. As far as the cable at the motor once it's under load the squared end is bound in the collet. But hey, I'm always open to new thoughts or ideas so I'm all ears on this one............... :)
Heck I am far for an expert or even experienced with RC boats,but hear is my 2 cents.

Teflon is its own lube so I am using lead Teflon bushings and a pure Teflon thrust washer.

I am using a flex shaft soldered on to the stub shaft and a Colet up at the eng with a small gap for cable shrink.

As far as the square Collete as the shaft shrinks it will slide in the Collete and unload the eng.

Spray a little Prolong in the tube and of you go.

I can feel the difference with my hand on the drag. Not much HP with the 21.
I'm no expert either but:

Being smoother when it's just sitting on the table turning it by hand is one thing. What happens when you spin the drive dog at 25000 rpm while being pushed up against the Teflon for a period of time? I don't think it will last long before the Teflon is machined away by the drive dog??? I'm asking as I don't know.

-Buck-
I have polished the strut and drive dog. Don't need it to last long washers are 12 for $.05 have lots of spares.

Hope to try today will let you know.

worked pretty good with a dremel hooked to it, pulled as hard as I could didn't miss a beat.
 
A lot folks will argue;BUT on a especially a 21 the square drive is key.. less friction, less useless load on the engine. You want to load the engine with the prop not shaft drag.
I would like to hear more on how a square drive would have "less friction" that a properly set up conventional collet. You still have a stuffing tube that the flex cable runs through & shaft bushings in the strut and even add the drive dog making direct contact against thrust washers at the back of the strut which does not happen on a conventional collet set up. As far as the cable at the motor once it's under load the squared end is bound in the collet. But hey, I'm always open to new thoughts or ideas so I'm all ears on this one............... :)

Weeeeeel :) If you take two of our boats, one with standard cable and one that is square drive and spin the entire assembly without the engine in them. The square spins easier. You can see and feel how free they are. This excercise has convinced a majority of the folks who come to the shop and want to know. I have no solid scientific reason why .. I can tell you that there is a least half the stuffing tube on the square drive boat, the stub shaft is polished and the lead telfon bearings reamed perfectly straight to match. also the ferrule is soldiered on the cable straight on centers.

Clear as Mud eh :)
 
A lot folks will argue;BUT on a especially a 21 the square drive is key.. less friction, less useless load on the engine. You want to load the engine with the prop not shaft drag.
I would like to hear more on how a square drive would have "less friction" that a properly set up conventional collet. You still have a stuffing tube that the flex cable runs through & shaft bushings in the strut and even add the drive dog making direct contact against thrust washers at the back of the strut which does not happen on a conventional collet set up. As far as the cable at the motor once it's under load the squared end is bound in the collet. But hey, I'm always open to new thoughts or ideas so I'm all ears on this one............... :)
What kind of drive system does the worlds fastest .21 Hydro have ?
No clue.. at least which .21 is the worlds fastest. I can tell you the fastest 21 I know of runs a square drive. :)
 
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