76' 170 Rebuild

[MJB]

I've cut the tops off the stringers 3/4 of the way forward till I found dry foam.  Now I'm looking at pouring foam once I have repaired a couple delam spots -- any recommendations on density (#2/4/8) for the stringers??  Any recommendations on foam suppliers??

[LilRichard]

2# will be fine.  I would suggest FGCI, only because I know them... but there may be suppliers closer to you.

[MJB]

LilRichard,

Thanks for the info, I thought #2 foam should be fine.

[MJB]

Finished up the rough glass work on the transom 2 weekends ago.  Last weekend I spent Friday afternoon and Saturday morning grinding the inside bilge from the transom forward to the storage lockers.  Ground out the delam spots along the stringers and got that ready to glass.  Prepped the aft portion along the stringers ready to rebuild the stringer sides that I had cut out.  

During all the grinding I found that the center stringer was in worse shape than I thought.  The 3/4' piece of ply running the length of the boat to the bow was glassed in but not very well originally.  Water had gotten into the ply stringer and it is wet and in some places the glass has delaminated from the ply.  

Structurally should I remove the old stringer and replace??  Or is it good enough, doesn't provide any strength, no need to replace, just glass over the bad spots??  The glass holding it in place seems to be solid.  

Also, wondering why when the boat was made that stringer is not the same height all the way up the length of the bilge??  If I do replace the stringer I think I should be able to get away with a uniform height keeping it just below the fuel tank coffin.

Here's a couple pics of the 18" of the stringers I replaced this past weekend at the transom.  I glassed in a couple of 1/2 rounds of 3" PVC pipe to allow for water draining along the outsside to the inside of the stringers.  I plan to put a bilge pump to take care of any water.

 



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[RickK]

Looks good Mike  8)
Are you saying that there was wood in the stringer system?  Should not have been any wood there.

[MJB]

Rick,

The 3/4' piece of marine plywood runs down the center of the hull from the transom up to the bow.  Not the stringers on either side, those were all foamed in.  I had too cut out a piece about 24" long and it was wet but not rotten.

[MJB]

If you look at my first post and check the second or third picture you can see that piece running down the center.

[fabuck71]

Like this one:



Mike, that was a great idea to leave those tops of the stringers in, I had a hell of a time leveling off my tops of foam.  Damn I wish I would have thought of that.  Oh well, next time.

[LilRichard]

I actually added a stiffener to the middle of my hull (it's not really a stringer - not big enough to qualify).  Having extra support in the middle is not a bad idea - so you may wish to put one back.  Your call.

Here is what I did:




Note the half round PVC down the middle... it is covered in 3 layers of 1808.

[RickK]

I see that piece - hmm, I wonder if that is the actual keel and they glass over it to give it a stout rounded edge?  
Doesn't look like it is used for anything else - maybe one of our builder members can help us out here?

[fabuck71]

On my 19-6 it is flat in a couple spots, looks like it was used to rest the fuel coffin on.

[MJB]

I can't claim that idea about cutting the stringers that way....I saw one of the member's do it that way and "borrowed" it!!  That's what's great about this site, everyone is willing to share info.

Back to the center piece -- the fuel tank coffin did not rest on the top of the center piece at all, there's at least a 2" gap between each.

I'm not real certain it provides any strength, maybe it was only used during it's initial manufacture.  I've seen some other pics of other 17s and they seem to change construction techniques over the years.  

It would be easy enough to replace but I'd hate to waste cloth and resin for no real reason.

Anyone else with any thoughts??

Mike

[MJB]

Sorry, no pics, but have done some more work.  I opted to remove the center piece of plywood and have added two layers of 1708 down the center as well as fixing the delaminated sections on the port stringer.  This has really strengthened the bottom of the hull along the center since it was pretty thin.  

Poured 2-part foam last weekend into the stringers, didn't have quite enough so will finish that this weekend.  This has added quite a bit of rigidity to the stringers which is good.

I'll get some pics and add those this weekend.

Couple questions:
1.  Transom Drain -- any recommendations on manufacturer or type/size?

2.  The original deck was not actually sitting on the stringers, there was about a 3/4" gap.  AS put this "putty" like mix/adhesive down and set the deck on top.  I'm thinking of laying 3/4" strips of plywood the length and width of the stringer and glassing them to the stringer and then when I put the deck/sole back in will lay down some glass on the stringers and lay the deck/sole on top and then screw the deck/sole in place.  Then glass over the topside deck/sole.  How's this sound??

[LilRichard]

You can use whatever drain you choose, but may I suggest that you put an oversized PVC "sleeve" in before the drain.  Rough up the PVC and glass it in with some thickened resin and you'll be sure your drain never allows water into the transom should it loose the seal around the edge.  

Personally I like a brass garboard drain... just what I have always had.

As to the wood on top of the stringers - sounds like a good thought.

[MJB]

Sorry about the pics, I have to download and haven't had a chance.  I'm finally in the "put back" phase of this rebuild having finished the stringers and adding strength to the hull keel on the inside.

Now I'm starting to plan for the deck sole replacement.  I'm going back and forth between exterior plywood and marine plywood -- my checkbook says save a few bucks and go with exterior, but I keep thinking marine plywood.  Any thoughts??  How about thickness??  Seems like the old deck/sole had 1/2" (might be 3/8") if I remember correctly, any recommendations??

I've been looking through a bunch of different rebuilds and have gotten alot of good information, but haven't yet found (maybe I haven't looked hard enough) a good way to secure the fuel tank in the coffin.  The old tank had the straps with screws that went thru the coffin and into the stringers which over time wore bigger holes into each.  I want to avoid that problem all together.  Should I still go with straps and find a better way to anchor or is there another method??

And finally, I want to do all I can to prevent water from getting into the deck/sole -- anchoring the console -- previously it was anchored to 3/4" trim under the console and that trim was screwed to the deck.  Is there a better way??

I know, bunch of questions but I don't want to get too far down the road on the rebuild and wish I did something else.  Appreciate any feedback/input and I will get the pics up soon.