Sanding rough interior of fiberglass hull

[TrentePieds]

I rather agree with Neil. But you are in it now, aren't you?

However, there is a material called "expanded vinyl". Half a century ago "high end" Scowegian yachets like the "King's Cruiser" had their interior lined with it, and it not only looks nice - it is ivory white - but it is easy to keep clean, and it also has insulating properties so you don't get condensation driving down the insides of your hull. It totally hides small imperfections in the substrate.

It is applied with a spray can of 3M adhesive deftly wielded.

D'ye think that might be worth considering?

TP

[Steve Bean]

" Fiberglass dermatitis " is the term for what you want to avoid by not sanding the fiberglass. Inhaling the dust isn't good either.

[Spot]

For Salty Blonde's scenario, wouldn't getting off the carpet adhesive and any surfacing agents from the original layup be essential before applying a fairing compound?

[Chotu]

Originally Posted by Spot

For Salty Blonde's scenario, wouldn't getting off the carpet adhesive and any surfacing agents from the original layup be essential before applying a fairing compound?

100%. It’s not going to be a fun project at all.

I have the same to do in many areas this winter. The shower being the worst. No carpet adhesive residue for me but an awful lot of surface area and sanding.

A solvent should remove his carpet adhesive fairly quickly.

[wingless]

My Festool RO150FEQ vacuum sander is my go to tool for all sanding operations.

The vacuum not only makes the operation very, very clean, but it also greatly extends the abrasive life.

[Benz]

I'm going to disagree with everyone and say that once the glue is removed, you need to sand with 80-grit in order to get a surface that primer and fairing compound will adhere to well. You don't have to go nuts on it, but removing a hundredth of an inch will not affect the integrity of your hull. And anyone who's ever sanded glass knows that burning through even one layer of biax with 80 grit, unless you gouge the edge of the sander in, is a hugely time-consuming task.
I recently did the exact job you're contemplating: sanded the inside of a catamaran hull, primed with 2 coats of 545 primer, then rolled on 2 coats of Awlgrip. I recommend against spending a lot of time fairing--what a thankless, dusty task! A quick smooth-over of the laminate, 2 coats of primer (intelux pre-kote?) and paint. I like Kirby's marine enamel--really nice stuff, and affordable.

[Chotu]

Speaking to Benz’s comment:

You know, it’s probably one of those cases where we all picture something different because none of us know what the glass he’s talking about looks like.

Sanding before fairing compound could very well be important. All depends on what he’s starting with. If it’s smooth, it needs some tooth sanded in. If it’s chopper gun or rough hand laminate probably not. Maybe they even used peel ply.

We’ll never know the right approach without some pics.

[smj]

Originally Posted by Chotu

Speaking to Benz’s comment:

You know, it’s probably one of those cases where we all picture something different because none of us know what the glass he’s talking about looks like.

Sanding before fairing compound could very well be important. All depends on what he’s starting with. If it’s smooth, it needs some tooth sanded in. If it’s chopper gun or rough hand laminate probably not. Maybe they even used peel ply.

We’ll never know the right approach without some pics.

A Gemini would probably be rough hand laminate woven roving?

[Clivevon]

Trente pieds got there before me. You are doing what? For why? Sounds like an awful waste of effort To me. Honestly. Dont do it. Forget the sander. There is a boat material designed for the job you want. Generally called headlining. It is a foam backed ivory coloured vinyl you stick onto the underside of the ceiling usually. There are firms that can do a very nice job of stitching panels of the material together to fit the compound hull curves but if you want to DIY then a good alternative is to make up separate panels To fit by stapling the material around thin board, Then glue panels to hull or if you want them removable, use velcro tape to attach them. Keep the lines of the panel joins horizontal. For a really classy look, You can then screw thin Varnished teak battens over the joins if you want.... Worked well for me. Much nicer looking than any paint job & a lot less hard work.

[dbcreed]

I suggest you consider Hull Liner - you have quite a few options, and the fabric is both easy to install (particularly forgiving to curves and rough surfaces) and attractive.

I purchased some of this and used 3M headliner adhesive to nicely cover lots of inside hull real estate: https://www.dltcorporation.com/category_s/343.htm

Sailrite has a wide selection from which I imagine you could find a good color & feel: https://www.sailrite.com/search?keywords=Hull%20Liner They also have 3 videos showing installation.

I agree with the comments about avoiding sanding the fiberglass, and if you want a smooth surface via applying fairing compound, then sanding (then repeating), you're in for quite a job if tackling a significant area.

Good luck!

[tpkas]

Before choosing a painted finish rather than a carpeted finish consider any condensation issues that may arise.

To get a smooth finish over raw fibreglass in the past I've squeegeed a coat of polyester resin and filler and then applied "peel ply" (nothing more than a 100% polyester shower curtain!) to get a finish that then required relatively light sanding to get an acceptable finish.

Brian

[Chotu]

Originally Posted by tpkas

Before choosing a painted finish rather than a carpeted finish consider any condensation issues that may arise.

To get a smooth finish over raw fibreglass in the past I've squeegeed a coat of polyester resin and filler and then applied "peel ply" (nothing more than a 100% polyester shower curtain!) to get a finish that then required relatively light sanding to get an acceptable finish.

Brian

This is a smart idea. All you have to sand in this case are the bumps. Unless there is also fairing to do.