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I have put 4 coats of epoxy on my douglas fir rudder for my Weekender.  I plan on painting the rudder box, so I used cloth on the box, but no cloth on the rudder.  The rudder looks so pretty I don't want to paint it.  Assuming my rudder won't get a lot of direct sun, I presume I am okay with just leaving it bright with just epoxy?  Also, for final coat, if I sand with 100 grit up to 300 grit, will it remain clear or do I have to put on the last epoxy coat perfectly and not sand?  BTW - I LOVE my rudder.  It turned out so perfect and beautiful. 

If you go bright you had better add some varnish to it to protect it from UV rays. They are brutal to epoxy and will quickly degrade your finish.

Keith

Yup, varnish it.  Also, that will make it look great after the final sanding.

Unless you use a 2,500 grit paper, you'll knock the gloss off an epoxy or varnish surface, requiring another coat to restore the shine.

For most paints, varnishes and surely epoxy, don't use finer then 320 grit. Above this grit the surface doesn't have enough 'tooth" to hold subsequent coatings.

Painted surfaces can get by with 120 grit if applied with a full bodied paint (not LPU's). For a really smooth job go to 220, but under a few coats of paint, noting more is necessary. For clear work, again 320 is the limit when sanding. You can get smooth results with this grit. For finer results you can scrape the surface, but this takes some practice to do right.

I would be hesitant about putting a painted or varnished board in a 'glassed rudder box. The 'glass will chew (literally) though the paint or varnish is short order exposing the board.

Rudders take a beating and should be sheathed if possible. My usual route is to make them from tough, completely inert materials, like all 'glass, metal, composite, HDPE, etc. these are unaffected by moisture, scratches, dings, etc. and will last a long time. Wooden boards look nice the first season, then require progressively more and more repairs as time goes on.

At least the portion inside the box should be sheathed, so that 'glass rubs against 'glass. A neat trick I use to reduce the friction inside a kickup rudder head (box) is to use a piece of Teflon or other material like HDPE between the board and the rudder head cheeks or inside the box. These materials are "self lubricating" and keep friction down. The lack of friction permits the board to live longer, so long as you don't bash the leading edge into stuff.

I guess I don't understand - I have a bright finished rudder in a glassed rudder box and have had no issues what-so-ever.

this is the glassed box


and in this pic you can see the rudder is brite mahogany.



I did not varnish it. I epoxied it and left it at that because varnish is too much of a headache for a part that is underwater IMHO
At no time has the "glassed" rudder box presented any kind of issue.

a.

Thank you for all the insight.  I did not realize you can varnish over epoxy.

for the canoe i built i had three coats of epoxy and then about 5 coats of varnish over that with a sanding inbetween.  while most people would agree with Paul we sanded the last few coats with 4000 grit paper on the sander and let me tell you that the thing GLOWED.  it could be the type of sander we used and/or the paper but we had no adheasion problems with the varnish not having enough tooth.  we have done the same with other projects and finishes and still had no problems.  i also admit that this was probably overkill but we just could not stop ourselves.  we used the Festool ETS150 and their Platen sanding pads. 

on a side note, the woodwork on the clorox bottle we only sanded to 400 which was plenty for the wood to shine and since i am just using boiled linsed oil for a nice had rubbed look it is just fine.

yeah varnishing over epoxy works just fine. Here is how I did my companionway door.

I took old redwood that had been in the yard and ripped it on the bandsaw into smaller planks (thinner)


and then I epoxied them onto the plywood



and shaped them





and then glassed them



and then varnished over that



it has held up really well

you can see it on the cabin roof in this photo taken last week on the lake



it isn't show finish quality but it gets the job done and looks salty

a.

Wow Adla that is beautifull, Great job and a really great idea, thanks for sharing it with us.

  Brian.

Here is another shot - a couple of things to keep in mind:

My boat is intentionally finished kinda rough to look like a nice old boat

I am sloppy with paint

But here is a shot with the dog and the companionway door - it has mud and spray on it..but when wiped down...it is rather shiny still.



I got the idea from someone else kind of...I liked Bob Smalser's 3 piece door he built for a Hartley...but this sort of a very modified take on his idea..

a.