Theorical Physics.

[Seadog]

I've got a sort of physics/hydrodynamics question I'd like to ask about water for all you scientifically minded guys.

I found standing water in foam filled stringers, in a 1970 Aquasport 222.  I mean a lot of water!  The stringers were made out of glass only.  Looked like a layer of mat, then roven, then another layer of mat.  

These stringers did not have any signs of holes being drilled into them, and no signs of any structural breach in the construction.

So if that is true - if the stingers were intact with no holes and no breach in integrity-  then my question is: how did the water get in there?

I don't really have a solution to this question, but I have some ideas.  

Whatcha think?

[Jerry-rigged]

My guess - The fiberglass let it thru.  As I understand it, all Ester-based resins are water permeable.  Poly-ester more than vynelester.  Of the common resins, I think only Epoxy is not water permeable.  Epoxy is more expensive, though, so boat builders don't use it.  Do a search on the http://www.boatplans-online.com message board (link on the top right of their home page).  There have been several discussion there about the different resins.

Jerry

[Wilson]

I think that jerry hit it.  You have to have lots of water sitting close to it for a LONG time for that to happen.  But just look at gelcoat and what causes gelcoat blisters.

[JimCt]

Seadog,

  I agree, all glass boats will take up a fair amount of water (make that weight) if left in.  Small boat racers (sail, maybe power too) haul out when not racing to keep them light.  The soaked stringer problem could also be related to the foam used.  A proper spec. closed cell foam (which may not have existed back in the early AS days) will stay dry inside.

Question I've got:  Why were the stringers completely closed up with no drain provision in the first place?

[Seadog]

I thought it interesting that fiberglass laminates are not as non-porous as once thought.  That water can 'seep' thru the glass given enough time, and that water intrusion is not always due to holes drilled.  So the water I found in my boats stringers was probably partly due to condensation that will vary with temperature, barometric pressure and humidity, but a lot of it was seepage thru the glass that accumulated over 34 years.

Jerry-rigged - thanks for the link, that's a good read. I've read that the fiberglass strands, the basic manufactured glass, has not changed much at all over the years.  But there has been huge advances in the packageing of the glass - Double Bias ect, and huge advances  in resin  and foam technology.

Wilson - are gel-coat blisters caused by water intrusion into the tiny air pockets left in the gel-coat?  That would mnake sense.

Jim - That's exactly the question I asked when I found all the water in the stringers.  Why the hell didn't they afford for water drainage out of the stringers?  But then if they would have left in drains, water could have also drained in.  It was probably a design flaw.  Don't know if later Aquasport models were designed any diffferent.

So what does this have to do with re-buildsand everyday use of our boats?  Probably nothing...

[Wilson]

if you allowd water drainage you would also be allowing water intrusion.  The same holds true today, in that, you want to keep all water away from that foam once it gets in there it is TOUGH to get out.

[JimCt]

Here's a dumb question: why is there foam in there in the first place?  Flotation can't be the reason because there isn't enough there to matter.  Judging by all the stringer discussions & repair pix, it's there just to cause trouble.

[Wilson]

It does provide a certain amount of floatation.  if there is enough it will keep you afloat.  Often times it is in there to dampen the noise the hull makes.  It deadens a lot of noise, and provides some structure.  The denser the foam, the more floatation and structure.  It also does a good job of holding gas tanks in place.

[Seadog]

Don't know for sure why the foam is in there, but I think your right, it's not just for floation alone.  I think the foam will also cut down on vibration in the hull, makes for a more solid construction and a better overall ride. I found 15 thirty gallon trash bags full of soaking wet foam in my boat.  That seems like a lot of foam.  All of it in the stringers. And it must of added some lift and buoyancy.  

Some guys I've talked to take the foam out and don't put it back when they do their rebuilds.  To avoid the inevitable water intrusion and having to carry around the extra water logged foam weight, over time. I'm leaning toward putting it back.

[JimCt]

Is there a foam available that can be used that won't soak up water?  Reason I'm asking is when I finally find the 175 I'm looking for (older and therefore affordable) stringer rehab is probably going to be on the list of tasks.  The '86 175 I went to look at yesterday no doubt had stringer problems since it had been sunk.  I'd have bought her but there were too many other problems; squishy deck around the console, transom seperation (stress & probably rot), severe wiring corrosion and a general look of long term extreme neglect.

[Seadog]

Jim - best advise I can give is don't be in a hurry to buy a boat.  Take your time - the right one for you is out there somewhere.  Don't know about your area but around here there are a ton of boats for sale all the time.

Not sure if there is a foam available that is 100% water proof. I've read that even the closed cell foams will absorb some water given enough time.

I'm going to start a new thread with the question you asked earlier: see 'To Foam or Not to Foam'

[JimCt]

Seadog... Just been looking at that 222 in PA on Boat Trader. Seems too good a deal to be true.  He'll even tow it 1/2 way to buyer. Trouble is I can tow a 175 with my Cherokee but a 222 would be suicide.

I don't see many AS available up here.  Maybe spring will fush them out.  But as you say, patience... patience.  Thanks for the sound advice.  Guess I'm jumping the gun worrying about foam.

Cheerio!