Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 07-05-2015, 11:50   #1
Registered User

Join Date: May 2015
Posts: 1
Replacing rotted rudder with marine grade plywood coated in fiberglass

I am in planning stage to rebuild my rudder. I've watched videos on fiberglassing process. My dilemma is in choosing weight if fiberglass and amount of layers for durability. My plan is to sandwich 3/4 " plywood then use original as template. Original is 1 3/4 " thick which leaves room for 1/8" shell of fiberglass. Any help or direction would be greatly appreciated.

Shore Footed is an appropriate Handle since I've owned boat for about a year and have yet to be able to take her out of the slip!!!
__________________

__________________
Shore Footed is offline   Reply With Quote
Old 07-05-2015, 13:37   #2
Senior Cruiser
 
DeepFrz's Avatar

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Winnipeg
Boat: None at this time
Posts: 7,930
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

I urge you to use high density foam rather than plywood. Any leak and the plywood will wick the water through the whole rudder. Sorry can't help you with the layout but there may be info. on that on the West website.
__________________

__________________
DeepFrz is offline   Reply With Quote
Old 07-05-2015, 14:52   #3
Guy
Registered User

Join Date: Feb 2013
Location: So. Oregon, USA
Boat: Seafarer36c
Posts: 4,308
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

That is not very much fiberglass. It probably would leak and ruin the rudder. Some 1" foam board from the lumber supply and a 1/4" of fiberglass on each side would be better.
__________________
Guy is offline   Reply With Quote
Old 07-05-2015, 15:05   #4
Moderator
 
Adelie's Avatar

Join Date: Feb 2010
Location: La Ciudad de la Misión Didacus de Alcalá en Alta California, Virreinato de Nueva España
Boat: Cal 20
Posts: 4,628
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

Is the rudder inboard or outboard?

Marine ply is a bad choice, too much of the wood grain runs the wrong way.
__________________
A house is but a boat so poorly built and so firmly run aground no one would think to try and refloat it.
SailboatData
Adelie is offline   Reply With Quote
Old 07-05-2015, 17:24   #5
Registered User
 
rognvald's Avatar

Join Date: Jan 2011
Location: Summer: In the land of Wooly Mammoths
Boat: Pearson 34-II
Posts: 2,252
Images: 2
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

And how do you attach the rudder post to the plywood? And what prevents torsional twist of the rudder under sail?
__________________
"And those who were seen dancing were thought to be insane by those who could not hear the music."
Friedrich Nietzsche, Thus Spake Zarathrustra
rognvald is offline   Reply With Quote
Old 07-05-2015, 17:42   #6
Registered User

Join Date: Mar 2011
Posts: 253
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

This will never work, Google boatworks today rudder rebuild and there is a great video. You can use the old one as a mold basically and fill with foam. Plywood will get soaked and rot. Dry rudders are a rare thing.


Sent from my iPad using Cruisers Sailing Forum
__________________
shamrock is offline   Reply With Quote
Old 07-05-2015, 18:00   #7
Registered User
 
xeon_tsd's Avatar

Join Date: May 2011
Location: "Out There" (mailing Austin TX)
Boat: Lafitte 44
Posts: 419
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

Quote:
Originally Posted by shamrock View Post
This will never work, Google boatworks today rudder rebuild and there is a great video. You can use the old one as a mold basically and fill with foam. Plywood will get soaked and rot. Dry rudders are a rare thing.


Sent from my iPad using Cruisers Sailing Forum
^^^^^^ exactly what I was going to post...

Here is the link well worth following on youtube.

__________________
hopefully I will keep this updated.... http://svchapaai.com
xeon_tsd is offline   Reply With Quote
Old 07-05-2015, 18:16   #8
Registered User
 
Nicholson58's Avatar

Join Date: Jan 2011
Location: Live aboard
Boat: Camper & Nicholson58 Ketch - ROXY Traverse City, Michigan No.668283
Posts: 3,466
Images: 83
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

Quote:
Originally Posted by Shore Footed View Post
I am in planning stage to rebuild my rudder. I've watched videos on fiberglassing process. My dilemma is in choosing weight if fiberglass and amount of layers for durability. My plan is to sandwich 3/4 " plywood then use original as template. Original is 1 3/4 " thick which leaves room for 1/8" shell of fiberglass. Any help or direction would be greatly appreciated.

Shore Footed is an appropriate Handle since I've owned boat for about a year and have yet to be able to take her out of the slip!!!
Others will suggest foam or balsa fill. Both are NOT water proof materials and both have a positive permeability. Given enough time, they will become saturated. Neither of these materials will maintain a bond to the skins once wet and neither one, especially foam has a great shear strength. I would not use either system for any structure that was meant to be always submerged. We live in the north. One only need walk the yard in the spring as the weather warms to see split & dripping rudders where the freeze expansion has burst the skins & wrecked the fillers.

I researched the problem when I rebuilt my rudder. The blade is 3o X 60 and 5 inches thick. I was able to leave the bare edges attaché while the guts and remainder of the skin was hacked away. New glass was built up using US Composites 635 THIN epoxy resin and 48 oz Fabmat. This was applied to the SS armature and the stock. The rudder was placed on the floor over my lower half form. This form was (starting at the rudder) 7-mill polyethylene release film; 1/8" flimsy plywood; layers of foam rubber & slats of wood. The procedure was to form the above system against the lower surface using the wood slats and foam rubber so that the upper surface where the skin should be would be level.

Next, I filled the rudder cavity with syntactic foam made from the same 635 THIN resin mixed with 3M microballoons also from US Composites. The mix is 3 gallons of epoxy with 10 gallons of balloons. Use large plastic buckets & a drywall mixer in a heavy drill. Hang on to the bucket so it does not spin and start slow. The mix is like Kraft Marshmellow cream. Pour this into your mold and let it cure. The resin noted is extremely slow and even a thick pour will not overheat. It will take 4 days or more to be able to sand or grind without wrecking your media.

The cured strength of the syntactic foam is about 3000 psi compressive. Your skins will bond to this filler better than anything else you can imagine so the final strength of the structure will be massive.

Remove the lower form & film. You may find low areas of void that need to be filled. Use the same stuff. For leveling and fairing, I used a 9-inch right angle grinder & 40 grit disk from Home Depot. For eying the level, I sued an aluminum bar as one would use a concrete screed. As you drag it over you working surface, black marks will be left behind at the high points.

I could have applied the skins myself but preferred a pro job with a vacuum bagger. Instead of buying the stuff, I found my local yard was know for this & could do the job for less than it would cost for me to buy the tools. I furnished heavy carbon fiber cloth. Three layers made for a really strong finish. The syntactic foam is very light weight and will never, as long as we live, become waterlogged.

My photos include a number of shot of this project.
Member Galleries - Cruisers & Sailing Photo Gallery
__________________
Nicholson58 is offline   Reply With Quote
Old 07-05-2015, 18:29   #9
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,366
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

How big a boat? 1/8" fiberglass seems very thin. Non pourous lightweight epoxy filler is a good way to go. Regular foam will soak up water even worse than epoxied plywood.
As mentioned... you need tabs welded to your shaft. Or is it an outboard rudder? If it is I would go with the plywood.... or wood of some sort.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is online now   Reply With Quote
Old 07-05-2015, 19:11   #10
Registered User
 
dpddj's Avatar

Join Date: Jul 2011
Location: Maine, USA
Boat: Leopard 40
Posts: 266
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

Same questions as Cheechako - how big is the boat?
DO NOT PUT WOOD internal to your rudder if it is to be submerged most of the time. There is a zero probability that water will not again get inside.
I just rebuilt the two rudders on my cat. I laid up a mold from one of the original ones, faired it better than new and proceeded bit by bit as I had time. Combination of eglass, vinyl ester and epoxy products. Dropped 10# per rudder (more gin tankage available). Contrary to what some posters have stated, there are foams that will not absorb water and are structurally perfect for this application. Stay away from EPS and many urethane foams. Especially foam rubber .
I would have machined direct molds on one of my CNC machines but I was too lazy to create the 3D CAD file needed. Besides, sometimes old techniques are more fun.
Have fun - it's only messy for the duration.
__________________
dpddj is offline   Reply With Quote
Old 07-05-2015, 21:32   #11
Registered User

Join Date: Mar 2012
Location: Aus
Boat: Owner Builder
Posts: 115
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

If you choose to go with ply ?
Despite the above posts then paint the ply
with a epoxy like international everdure
This is a very thin ie. watery consistency
Epoxy that will soak into the ply
Keep painting multiple coats wet on wet
Do not let dry until finished.
The end grain will soak up a fair amount
Keep painting as long as it soaks it up
This will deeply penetrate the ply especially
the end grain, it will be slow to completely harden
but can be glassed over while still wet (best)
Make sure every screw-bolt hole, ALL exposed
Ply is sealed.
If done properly the ply should be sealed for life
& will last even underwater.
Even the interior ie, if using more than one piece
of ply should be painted before glueing
Be a pedantic old granny about complete coverage
I have tinber rudders glassed over that are 15yrs old
with no water inside.
Despite all the nay Sayers it is possible with care.
Rebate the top of the rudder or where ever the shaft exits
About 6mm or 1/4" & seal with long life caulking
Eg sikaflex 295 this should be enough to be able to
flex with any expansion/contraction & stop water
Wicking down the shaft & prevent crevice corrosion
In the shaft
__________________
BriaF is offline   Reply With Quote
Old 07-05-2015, 23:17   #12
Registered User
 
UNCIVILIZED's Avatar

Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

Some tips, as we have no idea what kind of rudder, or for what boat & application you're building it for.

You can directly bond fiberglass cloth with epoxy to a stainless steel, or aluminum rudder shaft. And to this, you can bond various types of internal rudder structures.

The methodology, as well as things to watch out for are well documented in many places on the WEST System site, in addition to multiple other composite resources.
But,... regardless, do yourself a BIG favor & download the (free) classic book, On Boat Construction via the WEST System site, along with their user guides. Also, their other resource is Epoxyworks magazine. Again, free for download, with searchable archives, describing various project builds, just like on the main WEST System site.

Pretty much every composite supplier, & manufacturer have how to publications, as well as videos, & tech help lines. That, & if you get stuck at some part in the process of rebuilding things. You can come here for some answers, or better yet, go to BoatDesign.net Forums
They're all about building, & fixing things which float.

As far as wood, if you're fixed on using it, you're best bet in terms of making sure that it survives for a while, is to use thing stuff. Like thin sheets of BS 1088 Okume plywood. Say 3-4mm, and use a vacuum system to pull the epoxy through each piece, so that there's no air space left in the wood.
Then, laminate them together (under pressure or vacuum) to get whatever thickness it is which you desire.

You can use things like a clear penetrating epoxy sealer, this one for example Clear Penetrating Epoxy Sealer but as long as there are spaces in the wood that water & air can get to, then things can rot.
That's just reality.

To get some ideas as to how some of the "pro's" build/rebuild rudders, take a bit of time looking around on this site. CCI Marine composite fabrication | Competition Composites Inc.
They've been around/playing this game for a few decades, & a good bit of their stuff is pretty decent. I say a good bit, as in/for some applications, you really need to be an experienced engineer to say how well X will work for a specific job.
But being a business, it's in their best interest to keep their customers satisfied, so have a look at some of their techniques.

Albeit, IMO, there are far better ways of building a rudder than to "secure" a stainless steel blade structure in between 2 glass skins, using only high density foam as the "structural attaching" component. Meaning that which is the primary attachment between the rudder stock & blade skeleton, & the skins.

Frankly, there's a LOT which goes into designing & building a quality rudder, but no one here wants to read a (technical) book on the subject, so... that said, I'll shut up, & wish you well on your project.

Good Luck!
__________________

The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
UNCIVILIZED is offline   Reply With Quote
Old 07-05-2015, 23:46   #13
Registered User
 
crazyoldboatguy's Avatar

Join Date: Apr 2014
Location: Chicago
Boat: Alden auxiliary ketch 48'
Posts: 858
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

I had an older edge glued rudder made of mahogany. It was deteriorating (not rot, just the glue joints opening up in a few spots).

I decided to cover it in fiberglass, knowing that it was not the best. It is a deadwood attached hinged rudder on a Pearson Triton. The original wood rudder is nearly 50 years old. Granted, it lived in fresh water all its life but 50 years is a long time.

Anyway, the key to sealing wood underwater is to do it right. After the old rudder was covered in glass, I made sure EVERY hole in the rudder, along with the total surface area, was coated in the required 6 layers of Interlux 2000e water barrier coating. Every fastener hole was slathered ALL THE WAY IN with this material.

I have used this rudder for over 10 years. ZERO evidence of ANY incursion of water into the wood. Any water getting in would have caused swelling and splitting of the rudder inside the fiberglass. There is no evidence of this.

I wouldn't make a rudder using foam to fill same. Boats in the northern climes are not always stored in a heated building (mine is). Any water getting into the foam will freeze and crush the foam, creating voids and trouble.

I may make a new rudder out of steel and fill same with oil. The oil would prevent corrosion inside the hollow form. Who knows - that may just work.
__________________
Outside of a dog, a book is a man's best friend.
Inside of a dog, it's too dark to read.
crazyoldboatguy is online now   Reply With Quote
Old 08-05-2015, 05:42   #14
Registered User

Join Date: Feb 2010
Location: UK, Middle East, Australia
Boat: Angus Primrose One design 45ft And Duncanson 34 Mk2
Posts: 197
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

Check these guys out...
Jefa Rudder bearings
__________________
nauticalnomad is offline   Reply With Quote
Old 08-05-2015, 06:03   #15
Certifiable Refitter/Senior Wannbe
 
Wotname's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: Van DeStat Super Dogger 31'
Posts: 7,331
Re: Replacing rotted rudder with marine grade plywood coated in fiberglass

Marine ply is fine for a rudder if properly built (and maintained).

FWIW, my ply rudder is still giving good service (touch wood) after 40 years of being submerged.
__________________

__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Reply

Tags
fiberglass, marine, plywood, rot, rudder

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Locating Marine Grade Plywood Helbent Construction, Maintenance & Refit 2 05-01-2015 13:39
Grade 30 vs Grade 40 Chain ? stevensuf Anchoring & Mooring 15 23-01-2012 18:31
Marine Grade Plywood for Hatchboards ? SvenG Construction, Maintenance & Refit 8 19-09-2010 01:31
Which Do You Select: Marine-Grade or Consumer-Grade ? RubyBishop Marine Electronics 21 01-02-2010 20:25
rotted decks Wahoo Sails Construction, Maintenance & Refit 6 16-03-2006 06:18



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 10:25.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.