Re-building rudder

[tangomoon]

Has anybody got any photos/ information ref rebuilding a rudder - that is removing old fibreglass, welding new tangs, foam shape and epoxy/cloth/fairing. Know the theory but like some pics for reference to on how it's done. Thanks in anticipation.

 

[Pasarell]

Haven't got any picture myself but Maurice Huffey of Blaxton Boats built me a new rudder and stock last year. Might be worth contacting him for any information and he always seems ready to talk and help
www.blaxtonboats.com

 

[Spuddy]

I did it cos shaft had developed a narrow "neck" through corrosion. Had no info on what internal tangs etc so excavated from one side with angle grinder ( insert H & S warning). Found no tangs but shaft bent round prop cutaway so same effect. On starting to rebuild went to some trouble to get shaft chocked up to correct alignment. Not much filling with foam or fairing required for me but used epoxy throughout along with glass cloth and colloidal silica for fairing. Silica is *$&* hard so for larger area maybe there's a better choice. If oldsaltoz comes on then do as he says. You need to get the rudder dry and to control temp in working area. When glassing, try to get as much done in one shift - so layup the next layer when previous still green. Leave it too long and the waxy surface means washing off for a decent bond which means drying again. Errm, for some reason it's desirable to get higher glass to resin ratio than using polyester resin.

 

[oldsaltoz]

G'day Tangomoon,

We need more information, your Bio is a bit scant.

Is the rudder skeg mounted? lift up? balanced? all glass? perhaps a picture.

It's around 2300 hrs here and I'm off on a trip most of tomorrow with a 0530 start so you have plenty of time to respond.

Will do my best to help if you can advise me on boat size and rudder type.

Avagoodweekend......

 

[tobble]

I'm about to embark on what sounds like a similar job on my sabre 27. the rudder is a GRP shell formed around a frame consisting of the rudder stock with three tangs welded so as to run fore and aft along the rudder. according to the owners association in times of hardship Marcon (bless 'em) welded mild steel tangs onto the s/s rudder stock. According to literature from the association, it is a straight forward but involved process: split the rudder open and separate the 2 sides, dig out the sludge that used to be foam, cut out the tangs from one side and get repairs done as required to metal work, then reverse the process: heavily glass one side bak on to the frame and patch the thing back together. Oh, then re fill with this type stuff:
http://www.cfsnet.co.uk/acatalog/CFS_Catalogue__2_Part_Polyurethane_Foam_Liquid_61.html
leaving holes for expansion...

I was also wondering about improving the design of the tangs while I'm about it; either
a) replacing with angle s/s tapered accordingly
b)get the tangs doubled up to form a triangle, or
c) get the tangs doubled AND have an extra strut dividing the tang

the logic being that the rudder takes a hell of a lot of load on occasion, and the maximum bending force is acting on the weakest point - the weld... so I thought it'd be a good idea to improve on the strength of this. The only issue I can think of is it would make the thing a bit more tricky to get back together.

comments?!

 

[oldsaltoz]

G'day Tobble,

Splitting the rudder will save you a lot of work, you need to establish what side if any has the tangs glassed onto it, tapping the side of the rudder about the centre should give you an indication, one side will sound more hollow, the more solid sounding side will be glassed.

If the think you need to strengthen the tang to stock joint just add gussets cut to the shape of the stock.

Tangs should be located about 150mm from the top (so it can break if you get a large rope between the hull and the top of the rudder.
The bottom tang should be about 25% of the total rudder length above the bottom of the rudder, so that it will break off without causing major structural damage to the stock or it's mountings.

I also like to add a light section of flat bar to the trailing edge of the tangs, this helps when aligning and glassing in.

You should avoid expanding foam and opt for closed cell balloons, spheres or 'Q' cells mixed with an epoxy resin for higher bond strength and much better water resistance; also very easy to sand to a profile if required.

Tip:
Rudders can develop leaks at the point the stock enters the fibreglass, getting a good bond between fibreglass and smooth stainless steel is a challenge; however if you slide two 'O' rings over the stock and add a little Vaseline between them before glassing you have no problems, the 'O' rings hold out the water and the Vaseline prevents any resin getting under them when glassing.

Hope this helps.

Avagoodweekend......