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Springy Side Decks- Reinforce?

bigd14

Contributing Partner
Blogs Author
I'm in the process of correcting core damage to the side decks, from below. The starboard side is complete, but the port side remains. I'm loathe to remove the galley so I am limiting my repairs to the easily accessible areas, although I suspect the water damage does include the inaccessible areas.

But, to my question. The side decks are quite wide, and have a lot of unsupported area that flexes considerably underfoot (easily observed from below). The port repair helped a bit with this, but the springiness remains. There are no cracks in the gelcoat or fiberglass but it just seems this area flexes more than it should. So I am wondering if I should I add a longitudinal stringer in the middle of the side decks "while I am in there" to help reduce flex? Or is this simply a fools errand? After all it was designed this way and it has lasted 30+ years.

Any and all advice welcome.

Thanks.

Side Deck Core Before.jpgSide Deck Core After.jpg
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Yes and ... No...

Our model has wide side decks also.
And there is a bit of flex when I walk on them -- at 210# it might be just me! :rolleyes:

Having sounded them several years ago with a meter and found them dry, I believe that it's just the limits of how much deflection or flex you get with xx number inches of width. Coring is a nominal half inch, so the "I beam" effect is going to be limited by this thickness.
One crude test would be to cut out a piece of 5/8" ply to your deck's unsupported width, lay it between two other pieces of wood (1 X 3 would do fine) and stand on it and carefully measure the deflection.

A bunch of years ago when I was working under both side decks to add big G10 plates to each stanchion and pulpit base, set in thickened epoxy, I contemplated adding a "cross brace' of a piece of honeycomb. Having tired of laying on my side and working overhead, I decided not to. Like your observation, our deck seems strong enough for almost 3 decades, so the basic engineering/layup schedule must be OK.

No wrong answer, and if you are going to reinforce the span, doing it in conjunction with another under-deck project is probably the best time to do so.
(Just another "while you are there" potential addition to the project list.)
:)
 
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bolbmw

Member III
Nice job on the repair!

For what it's worth I have not noticed flex on my decks. I am 190 lbs. I do have a gelcoat crack or two near chainplate bases or around sharp corners, always where there is a sharp angle such as around the chainplate base.
 

tenders

Innocent Bystander
That’s a nice-looking repair, and a hard-fought battle with gravity, I’m sure.

I’ve done four core repairs on my boat, from above, on areas both smaller and larger than what you’ve done, and they don’t flex at all. I think what you’re seeing is the result of two phenomena from having gone in from below.

1 - There is still “wiggle room” in the fix in the form of adjacent core material not being firmly bonded to the new material, weak core material near the repair but not part of the repair, and new and old core that is not (or is no longer) firmly bonded to the upper skin (the deck). This probably can’t be prevented.

2 - The upper skin, the deck, has been flexing for years and has undoubtedly lost some of its original rigidity. It’s still in place, and remains flexible after the repair. (I’ve noticed this in my fixes from above - the removed deck has become really wimpy and not even suitable for repurposing as backing plates.) The lower skin, through which you made the repair, is far thinner by design and was only ever intended to provide shear strength (I think that’s the term) rather than stiffness. I don’t see how you get around this with a from-below repair, unless you use a very stiff core replacement like G10, but that’s going to get expensive and heavy very quickly. My from-above repairs don’t have this problem because I replace the upper deck with 3/16” G10 which is rock-solid stiff, and it’s epoxied to the surrounding deck with layers of glass tape built up inside a 2” bevel. In the process of creating that bevel I dig out as much spoiled core beyond the hole in the deck as possible, and stuff it full of new core.
 

bigd14

Contributing Partner
Blogs Author
All good points, thank you. Tenders, I too did a core repair from the top, and it was more solid, so you are may be on to something, although the side decks were not as wide. However, touching the non skid which is in good condition is forbidden on this boat. So I may very well add a stiffener to reduce some of the flex. That is likely the best compromise for doing the work from below.

Thanks
 

bigd14

Contributing Partner
Blogs Author
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Stiffener1.jpgStifferner2.jpg[/FONT]

[FONT=&quot] [/FONT]
[FONT=&quot]Procedure: Mix up some neat epoxy and spread it under the deck. Let cure until tacky (I used fast hardener and a heater to speed up the process). Mix up more epoxy, wet out stiffeners, except for the gray felt area in the middle of the underside. Stick the stiffener into place in the tacky epoxy. The dry felt grabs the epoxy. Tape into place with Gorilla Tape, then work the fiberglass part of the stiffener against the underside of the deck with rollers, brushes, squeegees, etc.
[/FONT][FONT=&quot]Installing Stiffener.jpg[/FONT][FONT=&quot]Stiffener install closeup.jpg[/FONT]

[FONT=&quot] [/FONT]
[FONT=&quot]Here is the final result. I have not measured deflection, but the decks feel much better now than they did. Its messy because I added some fiberglass cloth between the two pieces of stiffener, and over the tapered end on the left side of the photo.
[/FONT][FONT=&quot]Stiffener Installed.jpg[/FONT]
 
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Kenneth K

1985 32-3, Puget Sound
Blogs Author
Lookin great! If I lived closer I'd drive down there to see it in person and pick up some pointers on tools and fiberglass repair from you.
 

bigd14

Contributing Partner
Blogs Author
Epoxy fun.jpg

Hi Ken here is a photo of my setup for most work
Paint rollers (for spreading neat epoxy)
Epoxy roller (blue handle, optional for wetting out fiberglass cloth)
Chip Brush (not shown, for painting epoxy, dabbing air bubbles out of cloth, etc)
Epoxy
Stir sticks
Cups
Thickener (I mix this outside since its bad for the lungs)
Flexible Spreader (not shown, useful for jamming thickened epoxy into crevices)
Gloves! Double or triple them up, then when one gets messy you can peel it off an have another glove right there at the ready.

Contact me back channel and I can expound upon any of these items!
 
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Kenneth K

1985 32-3, Puget Sound
Blogs Author
Yeah, great. I was planning on PM'ing or calling you before I start the actual FG repair. Haven't done this kind of work since 1995 and I was only partly satisfied with my results back then. At least it's an "invisible" area under the headliner so it only has to be strong and not pretty.
 

Nick J

Sustaining Member
Moderator
Blogs Author
Looks familiar

That looks fantastic. The stringer is a really elegant solution. One of the things that helped me do the overhead fiberglass work was to wet out the glass on the table, roll it up on a 8" diameter pvc pipe, then unroll it overhead. Still a sticky mess, but it seemed to prevent the glass from falling while I got it in place.
 

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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Nice Repair

Very high on the Elegance Scale. :)

When I put epoxy (bi-ax, and mostly G10 plates) under all the stanchions and pulpits, I made soft pads using a piece of scrap plywood with an inch of cheap-o upholstery foam on top, and wrapped in cling plastic or for a smaller one just a plastic ziplock baggie over it. Pushed them up tight with one or two wood props tensioned with C clamps (a 1 X 3, paired with another piece, and moved up tight, awkwardly using the other hand to tighten the clamp.)

I also found that most of the time a piece of cloth or bi-ax would stay up after being sqeegied flat.

Not what I would call fun, and nearly impossible to have too many pieces of plastic sheeting or drop cloths. Lots of vinyl gloves. Great use for several years' accumulation of cottage cheese, butter, and yogurt plastic containers. Those various-size aluminum "loaf pans" are good for wetting out larger pieces.

After the temporary whining, however, the result is euphoric satisfaction!
:egrin:

After all, keeping the boat in "newish" condition with the regular investment of labor and some $ is the only way most of us can own a high end production sailboat with the performance and livability of an Ericson.
Most of our maintenance and restoration tales pale in comparison to the maintenance nightmares of my friends of newer Hu____s and their ilk.
And when they get (temporally) done, the underlying structure is still weak, thin, and wobbly.

Not like I have an opinion, of course....
:rolleyes:

About those stiffeners, Great Idea!
https://www.jamestowndistributors.com/userportal/show_product.do?pid=57774

Wish I had known this years ago.
 
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Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Those clever stiffeners look much like the factory stringers--which I suppose were wood? (Please excuse the original panel mess)

1-IMG_0440.JPG
 

toddster

Curator of Broken Parts
Blogs Author
Very interesting! Are these things flexible enough to get them into position around a tight corner? I need to add a couple of stringers to the inside of the transom to support the wind vane and other COTB toys, and have been trying to figure out how to get long pieces of wood in there without cutting even bigger holes in the liner...
 

bigd14

Contributing Partner
Blogs Author
Toddster the stiffeners are somewhat flexible. The foam is stiff and will break if you bend it more than about 30 degrees or maybe less. But they would conform to a gentle curve. They cut easily with a utility knife. Loren I too used a board with a foam pad attached jammed under the repair to keep it all in place
.C1468627-1B2A-4B5C-9384-C399C0E601CB.jpg
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
One thing not to lose sight of is that the strength of the finished shape is totally dependent on the "box" beam created by the cured glass and resin. You could put in shorter pieces of foam, end to end. The time and material saving with the purchased form is the built-in "fillet" and ready-to-glass fabric layer already on it.

I have seen this type of "ribbing" done with cardboard tubes (like inside the paper towel roll) cut in half and glassed over. Whether your form is air, foam, or oak lumber the shape and thickness of the box 'beam' that you create is where you get the stiffness you seek.
 

toddster

Curator of Broken Parts
Blogs Author
Yes of course, and another issue, which originally caused me to contemplate wood core, is incorporating backing plates for external hardware. But considering that the job under contemplation will have to be done at arms length through awkward access points, and follow a concave surface, these inexpensive pre-assembled forms seem just the ticket. I see they also offer wider "plank" shaped pieces.

(It might be overkill, but the idea is to prevent any potential "oil-canning" under the force of the bolt-on auxiliary rudder. )

arcturus COTB.png
 
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