Arima 21 Belly Tank Retrofit

[martin3]

NO,   mine boat is 19 Sea Ranger.

The deck is definitely a different configuration,   but the build lay up should be nearly the same.

Here are some photos of the how I built the removable deck piece.

IMG 0733 shows some of the mold forms I used for the deck pour. Not fancy,  but effective.
Simple plywood, plastic, and duct tape.

IMG 0734 shows some finished foam pour on starboard side. Foam is seen extruding from the cut out.
I was able to get same level of fill throughout entire under-deck,  it is glued together and solid.

IMG 0738 shows the dry fitted cross piece in the deck.

IMG "deck steps" shows the finished pockets for the cross piece.
Sorry,   I did not take any photos of the glass layup of the pockets or the underside of the cross piece.
Too busy working I guess,

To make the pockets,   I first carved off some of the foam to create a basic step.
I scarfed out 1/2" pocket and epoxied in a piece of marine plywood for screw backer.
Once I was happy with the general shape and height,   I glassed it all in.
Both sides laid up exactly the same.  The 4Lb foam makes a good mold for the glass layup.

For the cross piece,  I basically overbuilt the crap out of it
I laminated on a nice piece of 1/2 Marine Plywood as stiffner and then glassed  it up.
Towards the ends,  I laid the glass about 1/2 thick to allow for final grinding adjustment in the pockets.

Final fit of the cross piece took some careful grinding,  PITA actually......but I'm really happy with final result.
Fit is flush with deck and fits together perfectly.

For final installation,   the cross piece was bedded in with 3m 4200 and attached with #14  1.5" SS deck screws.
The deck was so solid before bedding in the cross piece. Now,   it's even stiffer.   
I plan to finally glue and screw down all the deck hatches.
Once everything is all sealed in....It's not going anywhere.

[martin3]

Here is cleaned up shot with the cross piece set in after gel coating the deck.

[Philsfriend]

Why did you fill the small gap under the deck with foam?  Is the only reason why you cut all those holes in the deck?

[Tesoro]

Oh a 19. That worked out well. Nice job. But that cross piece is so close to the front that it really isnt that structural as much as it is a frame for the small hatch opening.

On the 21, having a floor 2 ft longer and no additional cross pieces other than one smack in the middle, I would not consider cutting it out to enable to insert a longer tank as you cant really replace it back to original strength.

[martin3]

Why did you fill the small gap under the deck with foam?  Is the only reason why you cut all those holes in the deck?

The holes were cut to access the under deck VOID.
That gap is supposed to be 100% FOAM filled between your deck and Lower hull.
That picture was after I removed all the original 2lb foam.

Most of the foam in my boat was water logged.
I knew the deck was suspect when I bought the boat.   
To the extent the foam had failed was a surprise. 
From the helm seats to to the engine well, my deck was completely disconnected. 
My deck was simply laying on top of the wet foam,  not glued together at all.
Literally,  you could lift it up 2 to 3 inches. NOT GOOD!

The only way to save this boat was to re-pour all the foam,  it had to be done.
I had 2 choices,    cut off the deck and start over or try to access the VOID space.
The deck itself was 100% structurally sound,   so I did not want to cut it out.
6" Milwaukee Hole saw to the rescue.  i drilled the 6" holes about arms length apart.
I spent  weeks digging out the old foam.
It was major PITA.....but I was able to remove nearly 100% of the old wet foam.

After thoroughly cleaning the areas, I used 5.5 gallons of 4lb Structural marine Foam to re-pour it all.
By pouring it the way i did was able to fill the under deck much better than factory.
There are no VOIDS under this deck.   It glued back together perfectly.
The plugs were glued back with a little bit of foam,  then glassed in.
I used 8 inch Air sander (36 grit) to flatten all the plugs and prep for gel coating.

[martin3]

Oh a 19. That worked out well. Nice job. But that cross piece is so close to the front that it really isnt that structural as much as it is a frame for the small hatch opening.

On the 21, having a floor 2 ft longer and no additional cross pieces other than one smack in the middle, I would not consider cutting it out to enable to insert a longer tank as you cant really replace it back to original strength.

Tesoro,

No doubt,  the cross piece in the 21 is much more structural.... based on the location.
In my humble opinion,   the same concept could be done to create a removable deck piece on the 21.
The deck and hull layup is the same,   albeit 2 feet longer.

The pockets I made are exactly the same thickness as the deck hatch openings.
They are perfectly tied into the deck.
The cross piece itself can likely hold 1000 lbs of weight after all the stiffening i did.
Once it was bedded and screwed in.....forget about it. 
The deck cross piece is stronger now than it was ever was.

The biggest gain in structural support was making sure the foam poured all the way over the the
stringer,  locking in the deck all the way to the edge. I was amazed how many VOIDS were present.
I assume this was done at time of the build,   it looked like the FOAM injection did not expand as well as it should have.

I can literally jump as high as I can and slam on the deck.....it doesn't move.
SOLID!

I have been on new Arimas.....the deck in my 30 year old boat is WAY stiffer than a new boat.

If someone opened up their 21 and did the same technique,    I would imagine the foam pour to make the pockets would be
a structural improvement in itself. I would not be surprised to see some VOID space be found at the edge of the deck in that
location. VOID space equals flex in the deck.

Once the the beefed up cross piece is bedded in with adhesive and screwed down,  it should be stronger than original.
The cross piece controls side to side movement,   keeping the deck flat plus giving support for walking on it.
Most of the structural support comes from the FOAM sandwiched between the 2 layers.

I have been messing with boats and fiberglass my whole life.....I suppose I see things differently than most people.
Difficult yes......but not impossible by any means.

[Tesoro]

For sure that project is not for a first time fiberglasser/gelcoater but could be done with careful studying and test practice. The problem with that retrofit on a 21 is that it will look like one if not carefully done. In your case you had to redo the whole floor surface where an original floor has the molded in non skid pattern.
I would assume that your boat was left parked out in the rain with the plug in for a winter or two.

[martin3]

For sure that project is not for a first time fiberglasser/gelcoater but could be done with careful studying and test practice. The problem with that retrofit on a 21 is that it will look like one if not carefully done. In your case you had to redo the whole floor surface where an original floor has the molded in non skid pattern.
I would assume that your boat was left parked out in the rain with the plug in for a winter or two.

Tesoro,


I do suspect you are correct,   the boat was stored wrong by the 2nd owner of my boat.
When I found it.....it was stored bow down with the plug in it.

Plus,   the idiot had installed rod holders on the gunnels right behind the Skip top frame.
They cut the top of the liner to get enough clearance for the body of the rod holder.
This allowed water to pour into the under deck.
I had to fix those as well.