Flooring on an 18' mariner

[Porbeagle]

I am in the process of a total restoration of an 18' mariner.I picked it up last sept. for $200 with a real nice trailer.
Got her home and found that the chine at waterline was cracked on both sides.PO had used roofing tar on plastic
to seal her up.Port side crack was 8' long,Stbd side about 6'.Boat was total stripped,no floor,wiring,or flotation.
I have restored a 15' Jet before I knew this forum existed.I have read most if not all of the Starcraft rebuilds,and I
am happy to have found a group of like minded boaters.OK,I paid $250 at a local welding shop to have the cracks
fixed.Now I'm about to do the transom and floors.I have decided to follow Woodonglass and go with High density
overlay (HDO),I like his reasoning about having to epoxy only the edges of the plywood.also I have not read where
anyone else has used HDO 2 sides for flooring,and I'm willing to be a guinea pig and report back with my results.
I think WOG's idea is golden and I'll also go HDO for the transom.Will send pics as I go.
Question?,For all the reading I have done,I still don't know the floor plywood thickness as it came from the factory?
1/2" ? 5/8" ? (for an 18' Mariner).Anyone know?
Thanks all in advance
Porbeagle

 

[astor]

Re: Flooring on an 18' mariner

Pics needed, especially of the cracks. 1/2" plywood seems to be the factory floor at least in my 87 SS.

 

[dozerII]

Re: Flooring on an 18' mariner

As astor said 1/2"was what StarCraft used, I personally think it is too flimsy and always use 5/8"and some go to 3/4". The extra 1/8"makes a real difference the feel of the floor and does not effect the height of anything enough to worry about when putting the boat back together.

 

[crankbait cowboy]

Re: Flooring on an 18' mariner

ditto on what dozer said, most likely come 1/2 inch, but i also liked the 5/8 inch replacement. actually my 18 ft ss had been redone with 5/8 when i got it, a good stiff floor is a real neccetity.

 

[barato2]

Re: Flooring on an 18' mariner

especially since so-called "5/8" is actually 19/32" most places these days.

i think the deck in my 64 Starchief was 5/8 from factory....replaced one section with 3/4 and it's very close

 

[Porbeagle]

Re: Flooring on an 18' mariner

So I'll go 5/8,thanks guys I , for the life of me, have not been able to figure out which to use.Hard to find 5/8 HDO surfaced 2 sides.
I'll send pics as soon as I can figure out how to post them.Astor,the cracks have been welded... but I'm going to need advise on
how to reinforce the sides as there are no side panels in this model starcraft.I have seen what looks like 4"X6" alu plates riveted
to every rib,then riveted to the sides,then after the deck is installed, rod holders will also help with support.In any case,the welding
has made the chine area soft and will only crack again in future unless I come up with a plan.Any Ideas?
OK,Promise I'll post lots of pics soon as I can.Thank you Dozeril,Astor,and CB cowboy for solving my biggest problem so far
Porbeagle

 

[jbcurt00]

Re: Flooring on an 18' mariner

you dont need 2sided HDO, single would suffice. MDO is a good choice too, and also doesn't need to be 2sided. Esp not for the deck (floor), the 2nd side is going to be down.

 

[SigSaurP229]

Re: Flooring on an 18' mariner

As astor said 1/2"was what StarCraft used, I personally think it is too flimsy and always use 5/8"and some go to 3/4". The extra 1/8"makes a real difference the feel of the floor and does not effect the height of anything enough to worry about when putting the boat back together.

+1

I have done 5/8" on each of my rebuilds, no alignment issues and MUCH MUCH stiffer than 1/2"

If you epoxy it to me it feels even stiffer than if you just spar varnish it.

 

[SigSaurP229]

Re: Flooring on an 18' mariner

Do exactly what BLUEFIN 16 has done in his rebuild add chine bracing the later years have it anyways.

You can see how it was in my 18ss here.

 

[Porbeagle]

Re: Flooring on an 18' mariner

So JBcurt00,MDO is as good as HDO?If so,I'll go 5/8" Mdo, its way cheaper.And plastic side down you say? I'm beginning to like it better that way.Sig Saur (By the way, I have one.)I want to use riveted tabs exactly like in the pic of your boat.I'll look up blue fins thread
and see if he has detailed pics of his repair.My thanks to both of you for the help and I must say,I have followed both of your posts
for some time now and have learned a lot.I'll open a new thread on this restoration soon.Is it better to post in Starcraft or Resto/Rebuild
section? Porbeagle

 

[jbcurt00]

Re: Flooring on an 18' mariner

I'm not sure what plastic you are referring to as being down, but for use as your boat's deck, YES, MDO is a GOOD choice. It'll be less expensive & a bit lighter then HDO.

You only need it to be single sided (1 good face) not 2sided. The good face will have what looks like a brown paper bag outer veneer. This is the side you want to be up once you seal it & put the deck in the boat.

The other side won't be perfect, but once you seal it, and lay it face down in the boat, only you will know it wasn't a pretty, good face. And it won't matter because you sealed it. So you're good.

 

[roscoe]

Re: Flooring on an 18' mariner

I have 2 18' Mariners, a 1973 and a 1981 model.

The 1973, has no spray rail/chine supports, still has the original 1/2" untreated, uncoated ply, forget how many plys.

The 1981, has the support plates along the chine, also came with 1/2" ply, untreated and uncoated. It was rotted through.


I am replacing with 1/2" 5 ply. Mostly because the newer models have the side panels that rivet into the top of the gunnels, the splash well, and the floor. This ply is strong and stiff, and has waterproof glue. It will be coated/sealed before instal.

If I went to 3/4", the floor would be raised, and side panels would not fit.

 

[Porbeagle]

Re: Flooring on an 18' mariner

Just got done reading postings of yours JBcurt00 along with Grandads , blue fins and others.I'm going with 5/8 Mdo plastic side (good side) up.Next,those chine cracks.Grandads problem was cracks in bottom hull,so he slipped an 8' piece under the ribs.He also used an "L" shaped piece 8' by about 14'' on top of the ribs and riveted up the sides.I don't have cracks under the ribs like Grandad,my problem is
that much of the chine (port & stbd) has been cracked and now tig welded up.I wonder if an "L" shaped piece of alu, not as wide as Grandads,with maybe 2 rivets in each rib and rivets above the chines on the boats side maybe 6" above the chine would work? or individual tabs on each rib,riveted to the top of each rib then "L"bent and riveted onto the sides?That way the weld inside the chine
will not be buried.Maybe hard to visualize but I'm hoping to avoid drilling out rivets on the bottom of the ribs or sides.The newer mod that starcraft used (1 tab for every rib like yours Sig Saur) appeals to me but not having to drill out each rib is good.Rather rivet to the
tops of each rib.Flooring goes down like normal.( maybe have to shim stringers so floor has no give). What think you JB, Sig,and everyone
else? TIA Porbeagle

 

[jbcurt00]

Re: Flooring on an 18' mariner

Just got done reading postings of yours JBcurt00 along with Grandads , blue fins and others.I'm going with 5/8 Mdo plastic side (good side) up

I keep correcting you, but you keep saying it. To be clear, there is NO PLASTIC side on MDO (Medium Density Overlay). It looks like a brown paper bag, the overlay is the paper, and isn't at all plasticized. I'm not sure you aren't thinking of melamine, or some other type of man-made plywood.

Check out BlueFin's rebuild, he added LOTS of extra angle & plate to prevent chine & rib cracking. Might do something similar to prevent stressing the welds........

 

[roscoe]

Re: Flooring on an 18' mariner

True, no plastic, but the treated side is resin impregnated, or coated under pressure.

Perhaps we are just dealing with semantics here.

 

[jbcurt00]

Re: Flooring on an 18' mariner

I may be wrong, but I don't think the paper faced side of single sided MDO is treated any different then the other face, other then being smooth/filled prior to application of the paper facing. It's all resin impregnated, correct?

EDIT: I wasn't sure, so I looked it up. It is ALL laid up w/ phenolic resin, but the side w/ out paper ISN'T specifically listed as resin impregnated.

So my apologies to Beagle & Roscoe for my misunderstanding.

As a phenolic resin impregnated face, it could be considered plasticized, as long as we're talking about MDO and NOT some other type of plastic coated board, like melamine or MDF (medium density fiberboard ~ the carp sawdust & glue 'plywood' that most knock-down furniture is made of) that has a plastic face.

This was the 1st MDO brochure I found. Most MDO is going to be similar:
View attachment MDO info.pdf

As long as we're all talking about that ^^^ MDO, yep we're all good, just semantics.................

Carry on, nothing to see here