Rudder rebulid: what to use as filler instead of foam?

[lost soul]

I have my rudder of and am about to open it up for a rebuild job.

The standard procedure is to use expanding 16 pound foam as a rudder fill. At least that is what I have found in my research.

Anyone have any advice for a different material that would not absorb water and not be too heavy?

thanks!!

 

[Crazy Dave Condon]

How about a photo or two so anyone who is going to respond will be in a better position knowing what you are dealing with. A picture is worth a million words.

 

[dlochner]

The trick is to keep water our, not always an easy task given the different rates of expansion between fiberglass and the stainless steel shaft.

A structural foam core might be worth considering. Sandwich Core Composite Materials

 

[lost soul]

Here is a picture from the last time it was rebuilt, in 2001. I just brought the rudder home and it awaiting surgery.

 

[PaulK]

Looks like the method you suggest- using expanding foam- doesn't work very well. The photo shows all sorts of space that the foam didn't expand into. Water gets in and... there you go. Though it would be more work, getting non-hydroscopic foam boards and shaping them to fit in the space might work better.

 

[lost soul]

Paul, that picture was when it was under repair. More foam was added and the holes filled. I have only 2 pictures. Will post the other one here.
The black was vinylester fairing compound. The rudder was then reglassed over with a vinylester layup.

 

[Jim 5757]

FWIW there's a good video on YouTube.

 

[rgranger]

...(snip).... Though it would be more work, getting non-hydroscopic foam boards and shaping them to fit in the space might work better.

Yeah.... I was thinking that might work well also.... and you could fill in the little spaces with a touch of expanding spray foam. Foundation foam board would probably last a very long time and does not absorb water.

 

[Skipperdan]

try Extruded Polystyrene Insulation use the spray foam to glue it in. Then fill in any small gaps. The trick is to make sure you do not have any voids. you can then fill or coat it with sure seal a water proof paint. Get all the wood out. Then epoxy the skin back on.
Your other option is to leave it hollow and not use any water absorbing materials PVC stringers with a channel to the bottom. Then just drill a hole in the bottom. Or if you have lots of money... https://ruddercraft.com/index.php?route=common/home. Mine was $1,200.00 with tiller complete, but I do not have that kind of money so I made my own tiller and repaired my rudder and attach points. I sealed everything up and fared the rudder.

 

[lost soul]

Thanks Yawl,

I will post a few pictures when I get it open......

 

[lost soul]

I opened the rudder today.... Here are a few pictures. I will go for expanding foam, 16 or 20 pound.

 

[Skipperdan]

At this point your foam is serving no purpose. Just leave it out. Clean and sand everything down to fiberglass. Clean and paint the steel members. use rigid poly foam 2" or 3" strips going horizontal to make a good framework. maybe 12" on center or one in between each member and one on each end. Epoxy them in with mat so they are rigid. This gives your rudder its shape and strength. Leave a passageway for water to go through. make a framework around the edge also. The rudder now should be solid with no flex. Now epoxy the cover on and drill a hole in the bottom to let any water escape. you could use a fairing epoxy mix on top of the framework you made to fill any voids as you put the top back on. Once you have a mold (the old rudder) the foam serves no purpose but to hold the water in. Make it water proof inside and out and forget the foam.

Dan

 

[dlochner]

Here's a link to the Boatworks Today video on rebuilding a rudder.

I wouldn't compromise on the foam. While the fiberglass skin carries most of the load, it is the foam that provides the stiffness. With empty spaces the glass can flex and break the bonds with the foam strips. Rudder experience tremendous loads, it would not be good to compromise the strength.

To keep the water out, use a good flexible sealant at the rudder post to rudder joint. Carve a little well around the rudder post and fill with liquid Lifecaulk. This will seep down around the post and fill any voids at the top of the rudder. Finish caulking with regular Lifecaulk.

 

[Westcoaster]

I'd recommend two things. One is to use solid material from the rudder armature out to skin depth. That eliminates crushing foam as some cheap rudders do. Second, I'd use Airex foam or similar, non water logging, as it were, to shape the rudder. It is more work than expanding foam but is IMHO the correct way to do this job and one I've used with good success.

 

[Skipperdan]

The foam strips are just to form the fiberglass in the form of a beam. If you do it correctly it is stronger than the bond to the foam. The fiberglass goes over and an extra 3" on each side. Just like you would make a brace on a Kevlar canoe

 

[Loyalist]

I say go with a water "resistant" foam of your choice. You can use a water resistant epoxy to join the foam as you work it. Do not use solid filler as the rudder will not only lose floatation but also put much more stress on all parts of the steering system.

 

[lost soul]

I have decided on using a 16 pound expandable urethane foam. Most likely I will use US Composites foam. Now I just need to find the cheapest source.

Thanks guys. I will continue to post pictures.