newbie question - shaft seal

[t_boy]

Hi,

I'm building my first boat . As I don't have any experience I don't know how to seal the prop shaft. I think it should be simple so I am looking for easy DIY ideas.

Any help or information is welcome.

Thanks

T_boy

[mahoon]

Hi T-boy and welcome.

There are many more qualified to answer than me, but here's how I did it on my boat.

You will need a brass tube slightly shorter than the prop shaft (to allow enough room for prop shaft to connect to prop and engine/gearbox. This tube is called a stuffing box or stuffing tube (historically it was stuffed with all manner of items to attempt a waterproof seal). The stuffing tube should be fitted with bushes or bearings at both ends to aid keeping water out and reduce friction between shaft and tube.

Stuffing tube should be filled with either a water-repellant grease or lubricating oil - I think it's a matter of personal preference which, but I wait to stand corrected on that. If choosing oil, a small junction is commonly made with another small brass tube at right angles, so that the oil can be topped up occassionally.

Once you're happy with you shaft and tube arrangement, the tube should be allowed to exit the boat via a drilled hole that's tight on the tube without causing it to distort. Allow the tube to protrude a small amount from the hull and apply enough waterproof adhesive around it to cause a complete seal. I used epoxy resin which is ideal.

The same should be done on the inside of the hull where there's usually more room to apply more expoxy than on the outside. Give it as much epoxy as space will allow.

Bear in mind that you will have to have the alignment between prop shaft and engine fixed before glueing the stuffing tube in and you will want to ensure there's the minimum amount of deviation from a straight line between the shaft on the engine and the prop shaft, to keep vibration to a minimum. A universal coupling joint or stiff flexible tubing is usually used to connect the motor shaft to the prop shaft and these both allow for a small amount of misalignment, but the straighter you keep the line, the less vibration, less friction and more power you'll have going to the prop.

With motor and prop shaft connected and epoxy fully cured, you are ready to attach a prop and undergo first sea trials :)

If water ingress occurs, it can hopefully be remedied with the reapplication of more epoxy to the right area.

Anyway, that's how I did my boat and water ingress via the stuffing tube and prop shaft is at the bottom of my list of worries :)

Note: stuffing tubes are also commonly used for the rubber - only they are mounted vertically not horizontally.

Although I have not made a stuffing tube (as they are readily available to buy at reasonable prices), I have googled several others' home-made attempts that are just as effective.

Hope that helps and I'm sure any glaring errors or omissions I've made will be corrected in subsequent replies. Happy boating :)

Edited to add:
Depending on the length of the prop shaft and tube, it's often a good idea to support the tube with some kind of bracing inside the hull. This will help to further reduce vibration.

[WAXER128]

Alot of good info from Towboat Joe.
http://www.towboatjoe.com/shafts.htm
Waxer

[Brooks]

If the shaft and tube are long, say over a foot, the grease may provide too much resitance for the motor to handle. This happened with a steam powered tramp model, and we had to flush out the grease with lighter fluid. Oil would have been a better choice in this situation, I think.

[toesup]

As I don't have any experience I don't know how to seal the prop shaft.

Welcome to the boat forums t_boy
Most comercialy available prop shafts / tubes come with bearings on ether end of the tube. The tube / shaft can be shortened to suit your model and the bearings (either brass or bronze) can be re-inserted in to the ends of the tube. This allows some space round the shaft (inside the tube) for oil or grease which stops any water from entering the boat up the tube, and should provide very little friction as the shaft has bearings at only two points on its length.
Make sure you have the shaft / tube assembly lined up with the motor / prop position before epoxying the tube in to the hull.

[johnmca72]

http://www.ntxbg.org/pgOnTheWays/pgStuffTube.htm

JM

[Umi_Ryuzuki]

Another version...

http://www.rcgroups.com/forums/showthread.php?t=437771

[t_boy]

step by step I'm revealing the art of modeling.... :)

however I wonder shoud I use a motor with gear box?

Motors(200,500) run 6000rpm (average) , Isn't too much rev? May be If I use gear box to lower rpm and increase torque ?



N.B. It's going to be a bait boat with 2 motor, 1km range at 433Mhz. 6 ch.


Thanks,

t_boy

[pkboo]

T-boy, planning to take the binoculars I see :) You´re not building a speed boat so you want to lower the rpm, you will increase torque and eliminate heat problems by putting a gearbox in between. GL -» Eugène

[toesup]

however I wonder shoud I use a motor with gear box?

Motors(200,500) run 6000rpm (average) , Isn't too much rev? May be If I use gear box to lower rpm and increase torque ?

N.B. It's going to be a bait boat with 2 motor, 1km range at 433Mhz. 6 ch.


Yes, a gearbox of 2:1 or 3:1 should lower the revs and give you more torque.. however, i doubt you will be using full throttle all the time, so you wont be running at the full 6000rpm all the time..

You will certainly need VERY good eyesight or binoculars to control your boat at 1km (3280ft, 0.6 mile).. Even the professionally built boats have a range of only 600m (2000ft)..:p
Bait boats have been discussed here before.. can you see an object, say 3ft long at that distance?.. and be able to say which direction it is going?..
Also, will your radio have that range?.

[E-Challenged]

If the upper end of prop shaft tube is above the water line and shaft is fairly close fitting, you don't need to worry about water coming in. I soldered a 1" 1/4 diameter brass tube to the brass shaft tube then drilled a hole in the shaft tube. Put a few drops of 10w/30 oil in the tube before days run. Grease puts too much drag on the shaft and bogs the motor down excessively. ( In my experience)

[toesup]

N.B. It's going to be a bait boat with 2 motor, 1km range at 433Mhz. 6 ch.


http://www.anglingtechnicsbaitboats.co.uk/

[t_boy]

http://www.anglingtechnicsbaitboats.co.uk/

600 quid?.... I calculated 60-90 EURO if DIY, mostly servo, motors , shaft and prop. Hull is cheap, RC is 15 Euro. No speed control, I just don't need it.
No rudder, the two motors are enough( tank like steering) , IMHO.


Well, I won't use it at 1km range , 100-200 meters is more realistic distance. Binocular is a must ! :)
If I put a microcontroller I can use a radio-telemetry to get exact distance, but I don't think it's necessary.

Many thanks for everyone, it is very helpfull information sealing the shaft etc.

I know I face a problems putting all together, but not impossible.


10x

T_boy

[toesup]

600 quid?.... I calculated 60-90 EURO if DIY, mostly servo, motors , shaft and prop. Hull is cheap, RC is 15 Euro. No speed control, I just don't need it.
No rudder, the two motors are enough( tank like steering) , IMHO.

Well, I won't use it at 1km range , 100-200 meters is more realistic distance. Binocular is a must ! :)

I know I face a problems putting all together, but not impossible.


Yeah, the ready built / hull bait boats from the UK are VERY expensive.. and i agree a DIY version could be made for considerably less.
A speed control is a must if you want precise placement and manouverablility in order to place your bait in the right position. How are you planning on 'switching' your motors on and off if you are not using a speed control?.

Even 100- 200 metres range is being over optimistic. At that distance, seeing what a (say 3ft long) boat is doing left / right is going to be fairly difficult, but the far / near dimension (even with binoculars) will be nearly impossible. Try placing a 3ft long object at this distance away from you and then gauge its distance from other objects...

I'm both a boater and a carp fisher.. so..
Some things for you to consider.
The current record for casting is some 215 yards / metres held by a sea angler using sea fishing equipment and weights. If you can cast this far using carp rods / reels and weights, you should be at competition level!

A top of the range (carp) reel i looked at earlier today will only hold 250 yards / metres of line. With your current equipment, can you cast nearly ALL of the line from the reel?
Try measuring your best casts, i doubt if it will be any more than 50 - 100 yards / metres.. unless of course you are using deep sea fishing equipment.

Even though these forums have seen a large number of bait boat 'wannabees' recently, we have yet to see pictures of a boat actually take to the water and perform a bait drop.
No, its not impossible.. Can we get some pics as you progress with your build please.

[Hoghappy]

Even though these forums have seen a large number of bait boat 'wannabees' recently, we have yet to see pictures of a boat actually take to the water and perform a bait drop.



I resemble this remark! :p

Actually...radio gliching aside...my tug is ready to tow a bait out and release it...if I can do it with a buoy, it can do it with a baited hook/bobber, plastic worm or other lure too. It's just too hot to get out and fish! 106 forecasted again today for the 5th time this week :eek:

Those UK baitboats appear to be designed to drop "chum" into the water, not place a baited fishing line, which is what I am interested in doing.

Capt. Slick

[t_boy]

Yeah, the ready built / hull bait boats from the UK are VERY expensive.. and i agree a DIY version could be made for considerably less.
A speed control is a must if you want precise placement and manouverablility in order to place your bait in the right position. How are you planning on 'switching' your motors on and off if you are not using a speed control?.

Even 100- 200 metres range is being over optimistic. At that distance, seeing what a (say 3ft long) boat is doing left / right is going to be fairly difficult, but the far / near dimension (even with binoculars) will be nearly impossible. Try placing a 3ft long object at this distance away from you and then gauge its distance from other objects...

I'm both a boater and a carp fisher.. so..
Some things for you to consider.
The current record for casting is some 215 yards / metres held by a sea angler using sea fishing equipment and weights. If you can cast this far using carp rods / reels and weights, you should be at competition level!

A top of the range (carp) reel i looked at earlier today will only hold 250 yards / metres of line. With your current equipment, can you cast nearly ALL of the line from the reel?
Try measuring your best casts, i doubt if it will be any more than 50 - 100 yards / metres.. unless of course you are using deep sea fishing equipment.

Even though these forums have seen a large number of bait boat 'wannabees' recently, we have yet to see pictures of a boat actually take to the water and perform a bait drop.
No, its not impossible.. Can we get some pics as you progress with your build please.


Well, I will not cast by hand - this is reason I build a bait boat. It could transport the lead and rig along with bait ( that's even better than casting).
Of course first drop will place a marker, so later drop will be easy using a binoucular.

Insted of ESC I will use 2 motors (left and rigth) in START-STOP mode, so steering shoud be easy, by switching either motor.

Now I want to be exscused for irrelevant topic but : A bairunner reel has capacity 0,30(mono)/200m. , even 50% more if braid ( I saw a 6500 model that accept 600yds of 30lb braid !!!) . The bait boat will drop the rig and spod. Ready!

This is exactly what I need. As soon as I get result I will share it.
Some delay may rise with prop and shaft delivery, because I have to order them from UK.

Any ideas are welcome.

Great thanks,

T_ boy