Model Boat Mayhem

Mess Deck: General Section => Tugs and Towing => Topic started by: Gerryg on October 14, 2011, 03:49:05 pm

Title: prop shafts
Post by: Gerryg on October 14, 2011, 03:49:05 pm

Hi being new to building boats I was just wondering if anyone  can answer a question for me when using a fibre glass hull how do you seal the prop shaft from the water. I know in a real ship you have a packed gland is it the same on a model boat ?

Title: Re: prop shafts
Post by: DickyD on October 14, 2011, 03:55:43 pm

For sealing between prop shaft and hull use two part epoxy resin.

I use Zap Z-Poxy 5 Minute Formula 8oz Set

http://www.cornwallmodelboats.co.uk/acatalog/epoxy_glues.html

To seal larger gaps use P38 car body filler or even larger gaps use P40 car body filler available from Halfords

Title: Re: prop shafts
Post by: Gerryg on October 14, 2011, 05:01:05 pm

Thanks for the info Richard so the shaft just runs in the drilled hole do you need to lubricate the shaft as it's runnig on the bear fibre glass ?

Title: Re: prop shafts
Post by: BlueWotsit on October 14, 2011, 05:07:27 pm

Im wondering if theres a misunderstanding here.

You usually have an outer shaft which is bonded into the hull in the manner described.

Inside this outer shaft / tube  is the running part of the shaft which is usually watersealed and lubricated using various types of grease - personally I use the green gunky grease thats used on bicycles for lubricating gears - this is an ideal silicone based lubricant

Title: Re: prop shafts
Post by: Colin Bishop on October 14, 2011, 05:24:02 pm

There is a huge amount of advice on the forum about prop shafts if you use the search facility from the main forum page.

Use keywords such as propshaft, prop shafts, oiling etc.

Colin

Title: Re: prop shafts
Post by: Gerryg on October 14, 2011, 09:28:35 pm

Thanks guys I have got it now so the prop shaft runs inside a bush glued to the hull !

Title: Re: prop shafts
Post by: Colin Bishop on October 14, 2011, 09:34:35 pm

Not quite!

The propeller shaft runs in a tube fitted with bushes at each end which is fitted and glued into the hull. Some form of lubrication is then used within the tube although nobody can agree what is the best type!

Colin

Title: Re: prop shafts
Post by: DickyD on October 14, 2011, 09:50:44 pm

Photos of some prop shafts.

http://www.cornwallmodelboats.co.uk/acatalog/Raboesch_Precision_Propshafts.html

Title: Re: prop shafts
Post by: craftysod on October 14, 2011, 10:12:21 pm

A very rough drawing of what they do
Mark

(http://i259.photobucket.com/albums/hh293/craftysod/Scan1.jpg)

Title: Re: prop shafts
Post by: pugwash on October 14, 2011, 11:58:20 pm

Gerry it is also possible (depending on the type of ship) to fit the propshaft at an angle so the inner end is above the water
so that you only need a small amount of oil for lubrication only - this is quite common on warship models.

Geoff

Title: Re: prop shafts
Post by: Gerryg on October 15, 2011, 09:26:05 am

Thanks all got  it now.