|Topic Review (Newest First)|
|02-23-2009 02:07 PM|
It depends on the nature of the foam
"open cell" foam means that the air-filled areas will interconnect and not be completely sealed off by plastic. This allows water, air or any other fluid to migrate through the material.
"closed cell" means that the voids are separate, distinct and don't allow direct communication with ea. other - hence moving any fluid through the foam is very difficult.
|02-23-2009 01:47 PM|
Thanks for all the input so far. Regarding buoyancy, I dont think it a huge issue as the areas being repaired relative to the overall size of the rudder are small. Were talking adding a coupple of pounds to a rudder that weighs hundreds of pounds ( and is still attached). I am starting to lean twd micro balloon mix.
A ? for crissake - you state the foam absorbs water, but then so dous the foam that was from the factory. Am I missing something painfully obvious?
|02-23-2009 01:17 PM|
Makes me want to scream!!!!!!!!!!!!!!!
No you can't use Great Stuff foam as it is open cell and will absorb water.
You can buy closed cell foam liquid to pour into the rudder, but usually you can buy it only in gallon sizes...and it isn't cheap.
You could TRY to make a female hole in the rudder area, the make a male piece to fit it using foam from HD or Lowes. Then glass over the area AFTER removing all the bottom paint.
|02-22-2009 10:45 PM|
|scottyt||if you want to fill with epoxy, you can fill it with micro ballons mixed, you can get it as light as you want, then cover it with glass and epoxy for strength. but the point of using foam for neutral buoyancy is a good idea. but you could also fix it with epoxy like i said and try to float it, if its close leave it alone, if its light drill some holes and epoxy in some lead. if its a little heavy there is not much you could do.|
|02-22-2009 09:28 PM|
|billyruffn||You might want to speak with the rudder OEM -- the foam may be necessary to "balance" the weight of the rudder, i.e. to give it neutral bouyancy. Replace foam with solid epoxy and the bouyancy will be effected. I'm no expert in this area -- just a thought. Ask someone who knows.|
|02-22-2009 09:25 PM|
I know MAS epoxy from watching Latitude & attitudes TV never saw it in a store though. ( never really looked) and being in NJ all t he time you would have thought I would have seen it.
They say its the best!
|02-22-2009 09:07 PM|
Interesting piece of info, thanks.
Yes I am using epoxy. MAS to be specific. No VOC, no blush, nice New Jersey company. Excellent products.
|02-22-2009 09:00 PM|
The only thing I can help you with is to tell you to be sure you have epoxy and NOT polyester Resin. Polyester will eat thru just about all foams.
A quick story. I saw a boat that had been holed and sunk. It sat under water at the dock for an entire winter. It was raised in the spring and they filled all the holes with the spray foam from home depot and then moved the boat. The guy that was working on it said they used spray foam all the time when raising boats.
So thats my story on foam.
|02-22-2009 08:52 PM|
The rudder on my 1983 Mason 43 had some hollow sounding spots and some evidence of delam in the lower edge. My instincts tell me that the areas I am talking about are small enough relative to the overall area of the rudder that nothing done would probobly be OK, but thats not really my style.
I drilled holes and ground (grinded?) away the crappy parts. Now in some areas the foam core seems to have vaporized. Also there appears to be cells within the rudder such that any water intrusion - only found on the lower edge in the rear - seems to stay local. I built clever little clam shell from garbage that have allowed me to let them stay open in the cool winter air without me wondering if water is getting in.
My questions and pardon if they are stupid. For the voids, can I use the foam stuff one finds in 'home improvement ' stores before doing the glass work. Research indicates the stuff does not absorb water. Is it better to use thickened epoxy? Straight epoxy? From there I am using standard techniques, but read somwhere that the binders in mat are not epoxysoluble. Is it OK just to alternate the layup with different weight rovings, alternating bias?
None of the repairs are near the top where the shaft enters the rudder, but one is near the bottom where her lower pintle exits. Near, not on. No signs of stress fractures exist anywhere. First all paint was removed and the gel coat sanded.
Any other thoughts or tips are appreciated.