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Installing a Drive Tube

Old 05-31-2009, 03:05 PM
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rcbif
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Default Installing a Drive Tube

Ok, I'm building an 18inch boat as seen here
http://www.scale4x4rc.org/forums/showthread.php?t=35141

and soon I'll be getting to the part of installing the drive tube or stuffing tube thing. Yes this is my first boat.......I was wondering if this would be an ok shaft for my boat?
http://www3.towerhobbies.com/cgi-bin...?&I=LXCSZ1&P=7
The brass tube is the stuffing tube, with the flex shaft inside, correct? And the brass tube gets exoxied into the hole in the hull? Is there a method to the madness of creating the crazy enongated hole in the hull? Thanks for any help, this is my first boat build and I am enjoying it, and would appreciate any other comments/sugestions!
Old 05-31-2009, 04:21 PM
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Default RE: Installing a Drive Tube

Does it actually need a flex shaft?
Whatever shaft, it needs to go through the bottom of the boat (statment of the obvious time), but this means a hole in the main beam down there the same width as the outside of the tube.  This will reduce the stength there, so frame doublers will be needed in that area.
Old 06-01-2009, 03:58 AM
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pompebled
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Default RE: Installing a Drive Tube

Hi rcbif,

You have a few options:

1) Underwater prop; doesn't 'need' a flexshaft, but the flexshaft can be used to make the propshaft run parallel to the keel, you'll need a strut to hold the propshaft in position.
2) Surfacepiercing prop, the propshaft exits through the transom and the prop is only submerged one blade at the time, this is the faster option of the two.A strut is optional.
Again, a surface drive on a non stepped hull doesn't require a flexshaft, a solid shaft will do nicely, provided the motor is in the front half of the boat, so a long shaft gives you a shallow propshaft angle.

Regards, Jan.
Old 06-01-2009, 10:35 AM
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Default RE: Installing a Drive Tube

I usually cut a slot in the hull long enough to accomodate the angle of the shaft and cut the keel slot as well.Test fit the shaft then use doublers on the keel for strength.Tape the hole as best you can on the outside of hull then use epoxy to seal the slot and glue the tube in place.
Old 06-01-2009, 01:44 PM
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rcbif
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Default RE: Installing a Drive Tube

Cool, thanks. The shaft I posted earlier isnt supposed to be in stock for a while. What else could I use for a shaft and tube that is about 7inches long and under 15bux and can be coupled to a 540 motor?
Old 06-01-2009, 06:05 PM
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Default RE: Installing a Drive Tube


ORIGINAL: rcbif

What else could I use for a shaft and tube that is about 7inches long and under 15bux and can be coupled to a 540 motor?
Try one on here..
http://www.harbormodels.com/site08/m...propulsion.htm

8" long and $15... HAR2021-2023

Or

Would one of these be suitable?
http://www3.towerhobbies.com/cgi-bin...FVSEARCH=SHAFT

Old 06-01-2009, 08:15 PM
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rcbif
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Default RE: Installing a Drive Tube

Do these stuffing tubes use rubber seals to keep out water? or grease and seals?
Old 06-01-2009, 08:51 PM
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Default RE: Installing a Drive Tube

Teflon tube inside of the brass to keep clearances fairly tight aeound the flex cable along with generous applications of marine grease is how I do it generally.
Make sure you anneal the brass tube so it's easier to put a bend into if needed.
HTH
Steve
Old 06-03-2009, 07:48 PM
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rcbif
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Default RE: Installing a Drive Tube

Should the motor be mounted at the COG? Was just wondering, cause the cog on my boat is a bit farther back than the build I'm following to build mine?
Old 06-03-2009, 09:40 PM
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Dan S
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Default RE: Installing a Drive Tube

have everything in your boat (empty fuel tank) but don't mount the engine.
than move the engine so you get your CG where you want it.
depending on hull and preference (this varies with everyone) anywhere between 30 and 35%

Dan.
Old 06-03-2009, 10:24 PM
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rcbif
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Default RE: Installing a Drive Tube

Thanks for the reply. I'm considering the aquacraft nitro hammer rudder, as no other ones are in stock, and I dont want to order elswhere to save on shipping. Is there is big diffrence between performance between an offset mounted rudder verses one mounted one in the center?

one I'm looking at, would probally have to use the bracket
http://www.aquacraftmodels.com/boats...6xxai02l-b.jpg
how done in thread I'm following
http://www.theoaks.ca/hullrear.jpg
Old 06-05-2009, 11:36 PM
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Default RE: Installing a Drive Tube


ORIGINAL: ghostofpf1

Teflon tube inside of the brass to keep clearances fairly tight aeound the flex cable along with generous applications of marine grease is how I do it generally.
Make sure you anneal the brass tube so it's easier to put a bend into if needed.
HTH
Steve
Steve,
The teflon tube in the stuffing box is something most builders have gotten away from. It has been proven that it actually causes more drag than running in the brass alone.
The biggest reason is that when the teflon gets a little thin or hot it will bind up around the shaft in a tight ball and make it lock up and twist off in the collet and be nearly if not completely impossible to get the flex shaft out.

Daniel
Old 06-11-2009, 08:56 PM
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rcbif
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Default RE: Installing a Drive Tube

My stuffing tube is in . Just have one more question. My transome is 1/8 thick. Some of the screws that came with the rudder, and turn fins are 1/4 long. Should I cut down the screws? let them stick through the other side? Or make anchor plate out of another peice of 1/8 ply to give the threads more wood to grab?
Old 06-12-2009, 06:32 AM
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Default RE: Installing a Drive Tube


ORIGINAL: rcbif

My stuffing tube is in . Just have one more question. My transome is 1/8 thick. Some of the screws that came with the rudder, and turn fins are 1/4 long. Should I cut down the screws? let them stick through the other side? Or make anchor plate out of another peice of 1/8 ply to give the threads more wood to grab?
Go for the anchor plate. Then the worst thing that can happen is a stronger transom.

Old 06-18-2009, 12:59 PM
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Default RE: Installing a Drive Tube


ORIGINAL: danielplace


ORIGINAL: ghostofpf1

Teflon tube inside of the brass to keep clearances fairly tight aeound the flex cable along with generous applications of marine grease is how I do it generally.
Make sure you anneal the brass tube so it's easier to put a bend into if needed.
HTH
Steve
Steve,
The teflon tube in the stuffing box is something most builders have gotten away from. It has been proven that it actually causes more drag than running in the brass alone.
The biggest reason is that when the teflon gets a little thin or hot it will bind up around the shaft in a tight ball and make it lock up and twist off in the collet and be nearly if not completely impossible to get the flex shaft out.

Daniel
Actually in my experience the "teflon vs brass" camps are pretty evenly divided and I for one would only run bare brass (with a ton of grease to keep water out )is if I was SAWracing. In SAW racing (Straight A Way) the boats are only in the water relatively briefly so any water intrusion is at a minimum.
For sport running or even running ovals I will continue with the teflon as water intrusion can affect a boats handling during a prolonged race. I have only had failures of flex cable outside of the stuffing tube but will keep an eye on things as you suggest.I normally replace the teflon every year anyway as a maintenance item and have yet to see any signs of undue wear
thanks
Steve

Old 06-19-2009, 09:18 PM
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rcbif
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Default RE: Installing a Drive Tube

Do I need to allpy any type of selant to the screws that hold the hardware onto the transome?
Old 06-20-2009, 03:14 AM
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Default RE: Installing a Drive Tube

Hi rcbif,

I just looked at the pictures of your build on the other forum.
The way the propshaft is positioned will give you an awkward hybrid between subsurface and surface piercing drive, which will most likely not work well.
The propshaft angle is too steep for a surfacepiercing drive, which will force the bow down, making the boat run very wet, which in turn will draw a lot of current as the motor will struggle to get the hull on the plane.
Overheating will be an issue.

Using a solid shaft for a surface piercing drive requires a long shaft, so the motor sits in the front half of the hull and the propshaft exits through the transom, not the bottom.

A slightly shorter shaft would work fine for a subsurface drive, motor way up front and the propshaft would have to exit the hull in the last half of the hull, the prop would sit under the hull, not behind it
.

You may have to rebuild the drive system, as I fear this will not work, at all...

I use thin self adhesive rubber foam between the hardware on the transom to make a watertight seal, silicone will work aswel, but the foam allows removal without breaking the surface of a wooden hull.

Regards, Jan.
Old 06-20-2009, 02:29 PM
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rcbif
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Default RE: Installing a Drive Tube


ORIGINAL: pompebled

Hi rcbif,

I just looked at the pictures of your build on the other forum.
The way the propshaft is positioned will give you an awkward hybrid between subsurface and surface piercing drive, which will most likely not work well.
The propshaft angle is too steep for a surfacepiercing drive, which will force the bow down, making the boat run very wet, which in turn will draw a lot of current as the motor will struggle to get the hull on the plane.
Overheating will be an issue.

Using a solid shaft for a surface piercing drive requires a long shaft, so the motor sits in the front half of the hull and the propshaft exits through the transom, not the bottom.

A slightly shorter shaft would work fine for a subsurface drive, motor way up front and the propshaft would have to exit the hull in the last half of the hull, the prop would sit under the hull, not behind it
.

You may have to rebuild the drive system, as I fear this will not work, at all...

I use thin self adhesive rubber foam between the hardware on the transom to make a watertight seal, silicone will work aswel, but the foam allows removal without breaking the surface of a wooden hull.

Regards, Jan.
Nope, not a problem, got the final assembly done and it worked great! I used some clear silicon to seal up the screws. I just need a new drive dog, as I enlarged on with a drill but it's slightly off centered. I'll have to find one pre made to the correct size. I tried it out with a dead plane battery and got maybe 8-10 mph at the most. My lake is a maze of seaweed however, so I didnt go crazy with it. Once I get the drive system fixed and secure all the electonics it should work great



Old 06-20-2009, 03:08 PM
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pompebled
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Default RE: Installing a Drive Tube

Great!

Let us know how it runs on a fully charged battery when you've got the drive-dog sorted out.

Maybe a small video?

Regards, Jan.
Old 06-20-2009, 04:22 PM
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rcbif
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Default RE: Installing a Drive Tube

whoops, I meant the universal drive. I need one with a 4mm inner diameter. Cant seem to find one.

this part but in a 4mm inner dia.

http://cgi.ebay.com/CEN-GS093-DRIVE-...ayphotohosting
Old 06-20-2009, 04:29 PM
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pompebled
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Default RE: Installing a Drive Tube

If your motor is properly alligned with the propshaft, a solid coupler is a better solution, quit and more stable.

Don't go drilling these things without at least a drill press, or better, a lathe.

Regards, Jan.


Old 08-20-2009, 02:59 PM
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Default RE: Installing a Drive Tube

I'm building the same boat and would like to make it surface.
How far up the transom would you put the prop on a surface piercing drive?
quote:

ORIGINAL: pompebled

Hi rcbif,

I just looked at the pictures of your build on the other forum.
The way the propshaft is positioned will give you an awkward hybrid between subsurface and surface piercing drive, which will most likely not work well.
The propshaft angle is too steep for a surfacepiercing drive, which will force the bow down, making the boat run very wet, which in turn will draw a lot of current as the motor will struggle to get the hull on the plane.
Overheating will be an issue.

Using a solid shaft for a surface piercing drive requires a long shaft, so the motor sits in the front half of the hull and the propshaft exits through the transom, not the bottom.

A slightly shorter shaft would work fine for a subsurface drive, motor way up front and the propshaft would have to exit the hull in the last half of the hull, the prop would sit under the hull, not behind it
.

You may have to rebuild the drive system, as I fear this will not work, at all...

I use thin self adhesive rubber foam between the hardware on the transom to make a watertight seal, silicone will work aswel, but the foam allows removal without breaking the surface of a wooden hull.

Regards, Jan.
Old 08-21-2009, 11:32 AM
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pompebled
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Default RE: Installing a Drive Tube

Hi Becker,

Welcome to this forum!

Will you be using a flexshaft or a solid shaft?

With both shaft types you'll want the angle the propshaft makes with the keelline as small as possible.
With a flexshaft this is easily achieved, as it's adjustable.

With a solid shaft it takes a bit more planning:

Rule of thumb is to have the propnut at 10-13% of the boat' length from the transom.
To get the propshaft angle as small as possible, a longer shaft is better than a short one, as it allows the motor to be further to the front of the boat.
Drill a hole in the center of the transom, the size of the stuffing tube with the center abour 7-8 mm from the bottom.

Attach the motor to the propshaft with a solid coupler and slide the combination into the hull, feed the stuffing tube through the hole.

If the motor is going to be watercooled (yes!) slide the coil over the motor first.

With the propnut at 10-13% of the hull length, put the boat on its keel on a flat surface.
There should be 2 -3 mm of air between the propnut and the surface.

Adjust the hole in the transom to get this right.

Make a motormount, so the motor is fixed in position and glass in the stuffung tube (roughen and degrease the stuffing tube where the glass will sit).

Regards, Jan.
Old 08-25-2009, 11:39 AM
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Default RE: Installing a Drive Tube

Thank you for the reply!
With the info you gave me I will use a flexshaft so I can adjust it.
And yes it will be water cooled.
Were should the balance of the weight be in the boat?
Old 08-25-2009, 01:44 PM
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pompebled
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Default RE: Installing a Drive Tube

Rule of thumb is between 28 and 30% of the hull' length, measured from the transom.

Regards, Jan.

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