Best blade to cut fiberglass?

[kjdunne]

I will be re coring the deck panel that covers my fuel tank. I am looking for recommendations for the best tool and blade to cut the fiberglass on the bottom side of the panel. It is a fat 1/8 inch or so at the deck plate holes. I have a multi-tool, reciprocating saw, jig saw, assorted hand saws, angle grinder, etc. to choose from. I would like to leave as much of the vertical part as possible to tab to.

 

[kcassells]

google it...
Already sounds like a mess. Is it wet and so why? Million tools but why do you have to make the repair in the 1st place. Water intrusion?

 

[gm280]

A multi-tool works amazingly well in some places. It cuts pretty quick and very clean. It just depends on what you are doing... JMHO

 

[dingbat]

Cut up a hot tub a couple weeks ago.

Jig saw /saw all was too slow. A cut off wheel was too dusty. Circular saw with regular wood blade made short work of the project. For places the circular didn’t fit, a timber saw worked just as well

 

[kjdunne]

kc - water intrusion, the plywood was not sealed at the deck plate holes and the deck plate screws had no sealant. The fiberglass was porous along one outside edge of the plywood core, too. Resin starved it looks like. 23 year old Sunbird.

gm - a multi tool blade for wood? Or some other type?

dingbat - not sure I can trust myself with a circular saw for this...need to think more on that!

 

[sphelps]

Use the small thin metal cutting blade on your angle grinder . I haven’t found any other blade that cuts it as well ..
‘But that’s just me ...

 

[dingbat]

dingbat - not sure I can trust myself with a circular saw for this...need to think more on that!

set the saw to cut 1/4” deep and go at it.

A 4.5” cotdless would be ideal

 

[gm280]

This is a perfect example of how people like their method to do similar jobs. Everyone of the previous suggestions will do the job. If you own any or even all of the difference tools suggested, try each one and decide for yourself which gives you the better performance. Again, there really isn't one perfect answer to do things. But the neat thing about this site is how you will get so many options to do things. Then you can pick the one you like...

 

[dezmond]

Your original post sounds like you want to “peel” the wood off the fibreglass panel correct? If that’s the case why not just make a new panel?

 

[harringtondav]

These are inexpensive, and work well making a clean cut in fiberglass. I used it to core a hole in my pal's deck for a powered anchor chain windlass. I started from the fiberglass side for a perfect circle cut with no break out splinters.

Mine is missing it's pilot drill. It chucks up in a 1/2" hand drill.

 

[archbuilder]

If I understand your question correctly I would choose the angle grinder and cut off wheel. It sounds like you are wanting to cut off the back skin of the panel? The multi tool works well but is a bit slower on my experiance. I have used a circular saw also, very quickly but it can also cut the wrong thing very quickly. Ask me how I know lol.

 

[kjdunne]

I used the multi tool with a wood / drywall blade (because that's what I had). It made a nice thin cut and the best part was no dust cloud! The dust just collected along the cut.

It did wear out the blade.

The fiberglass came free of the rotted wood easily, stayed adhered to the dry wood.



Used a wider blade designed for "wood with nails" as a powered scraper to get the rest of the wood off. Lo and behold, it was not plywood, but end grain balsa core. Nice to know Sunbird used a quality product, too bad the workmanship to install it was lacking...

Underside ready for grinding to get to clean glass...

Topside is a nice diamond pattern non-slip gel coat, that's why I want to re core instead of try to make a new panel from scratch.

To be continued... maybe as a new thread...gotta get back to the paying job!

 

[kcassells]

Looking good. That tool is perfect. Sand out all the old stuff. Wipe out with acetone prior to installing anything. Also WET out the new wood, edges and fill any exposed voids. You're on a roll.

 

[kjdunne]

The grinding is done! Used a belt sander with 36 grit for most of it. Not as fast as the angle grinder, but not as big of a dust cloud either. Finished with the 4 1/2" angle grinder with 50 grit disc. I decided to take off the ridge - fillet that was left after I took off the bottom fiberglass skin.
The next decision is 1/2" or 3/4" marine plywood. I have both leftover from an earlier project. The 3/4" is what I used for the work table the panel is on. The 1/2" is the same size.

The old core was 21 1/2" wide, which left room for tabbing along the sides. ​I need to check to make sure the 3/4" won't be too thick for the panel to be flush with the deck if I make it closer to the full width of the panel.
The plan is to seal the plywood both sides and edges with epoxy, then use thickened epoxy to adhere it to to fiberglass panel. Will I need to cover the bottom side with cloth if it is sealed with epoxy? If yes, which type? What tabbing should I use, if any? I plan to use West System epoxy with 206 hardener. What is best for thickening it for gap filling between the wood and fiberglass?

 

[AShipShow]

I would at a minimum tab it in with 1700 bias, but personally, I would just do a layer the whole thing to really seal it up and give it some stiffness.

 

[gm280]

Yes, the multi-tool does eat blades. But don't throw them away. With a little jeweler's file, you can very quickly make those blades like new again. I do it a lot and doesn't take much time either. Just an idea...

 

[kjdunne]

Going with the 3/4", sealing edges and faces with epoxy. Thickened epoxy to bond the wood to the fiberglass panel. A layer of 6 oz cloth on the bottom and 4" fiberglass tape to tab all edges. Am I missing anything?

 

[gm280]

Going with the 3/4", sealing edges and faces with epoxy. Thickened epoxy to bond the wood to the fiberglass panel. A layer of 6 oz cloth on the bottom and 4" fiberglass tape to tab all edges. Am I missing anything?

Looks good to me. But don't fall into that category of thicker wood is better mentality. Seems we all think that using thick wood will make for a more solid hatch. And it actually does. However, once you apply the fiberglass and resin coats, it stiffens up thinner wood very solid and the reduced weight is realized. If I had to redo my boat project, I would go with thinner wood most everywhere but the transom. JMHO

 

[kjdunne]

Thanks GM, I understand your point. Hard to shake the "if some is good, more is better" mindset sometimes, LOL. It will certainly be solid and outlast me!

 

[kjdunne]

Here's how it turned out... 2 coats of epoxy on the plywood, then thickened epoxy on the fiberglass with a v notched spreader. Clamps, a couple of 5 gal buckets of water and 4 10lb barbell plates to weight it for a 24 hr cure. Was able to do it inside since epoxy does not stink you out of the house. Had to promise the Admiral the unused bedroom will get a full makeover after this... A coat of epoxy on the bottom, a layer of 6 oz cloth applied while wet, more epoxy to completely wet out, 4" tape to tab all around. I found the West System 105 resin and 206 slow hardener very easy to work with, and recommend using their pumps to measue with, Every batch was perfect. It's not a show boat finish, but it will only get seen by bilge critters anyway.
I'm pleased for a first timer working with this stuff. It is certainly waterproof and very strong, overbuilt, I won't need to worry about it ever again. Thanks for watching.