5200 and painted surface

Head Sail

Head Sail

.
Nov 13, 2013
723
Catalina 34 Tacoma
Looking at the directions for the application of 3M 5200, it says nothing about surface preparation. I.E. scuffing or removing paint. I have a 4"x4" piece of 3/4" plywood I painted on both sides with primer and 2 coats of latex paint. I plan on attaching this plywood to the inside hull to attach a heater. My question is do I remove the paint on the side to be bonded or leave it painted or does it matter?
 
Leeward Rail

Leeward Rail

.
Mar 20, 2015
3,229
C&C 30 Mk1 Winnipeg
Because the 5200 is actually bonding to the paint, not the plywood....The adhesion of the paint to the plywood would be the weak spot unless the paint bonds stronger than 5200. Which i seriously doubt. It is latex.

I would remove the paint. Or use glass and epoxy.

Edit: FWIW I almost always scuff bonding surfaces. That way you get a good mechancial bond along with any possible chemical bond.
 
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D

dlochner

.
Jan 11, 2014
12,842
Sabre 362 113 Fair Haven, NY
The paint has to come off. Latex paint essentially forms a sheet of latex rubber across the surface and does not penetrate the wood fibers or cells.

Why use 5200? Why not use thickened epoxy?
 
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Head Sail

Head Sail

.
Nov 13, 2013
723
Catalina 34 Tacoma
Roland5048 said:
What about 3M 4200 instead? At least you can remove it if need be. Not easy but WAY easier than 5200.
Click to expand
That's a option too. But I have no plans to ever remove it. It will support a diesel heater and want to make sure it stays bonded.
 
Davidasailor26

Davidasailor26

.
May 17, 2004
5,605
Beneteau Oceanis 37 Havre de Grace
You might be able to put thickened epoxy in a plastic bag, cut the corner, and have your helper squeeze the epoxy out like from a pastry bag.

Or get something like six10 epoxy or Thixo that you can dispense with a caulk gun.
 
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Leeward Rail

Leeward Rail

.
Mar 20, 2015
3,229
C&C 30 Mk1 Winnipeg
dlochner said:
If I recall correctly, 5200 is heat sensitive and when warm will soften. That may make it a poor choice for a heater.
Click to expand
- Heat resistance- Due to the decreased value in bond strength at elevated temperatures, we do not
recommend use of this product above 190°
F (88°
C).

The tech docs also list sheer strength for bonding to various materials... Fiberglass 300ish psi vs wood. 500ish psi
 
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All U Get

All U Get

.
Oct 2, 2008
3,810
Pearson/ 530 Strafford, NH
I read your original post and trying to understand the 4X4 inch plywood piece under a heater. How big is this heater compared to the area you’re mounting it in? I would probably use flat stock aluminum, predrilled for four screws or bolts. Pictures help. The heater is a great idea, I’m already jealous.

BTW 5200 is like molasses, it continues to drip/move for hours after you apply it. Watched a rudder assembly once where some 5200 was used on a rudder post. Five different guys trying to lift the rudder into the transom all covered in 5200. Then the old guy sprayed it with water to scim it over.
 
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Head Sail

Head Sail

.
Nov 13, 2013
723
Catalina 34 Tacoma
All U Get said:
I read your original post and trying to understand the 4X4 inch plywood piece under a heater. How big is this heater compared to the area you’re mounting it in? I would probably use flat stock aluminum, predrilled for four screws or bolts. Pictures help. The heater is a great idea, I’m already jealous.

BTW 5200 is like molasses, it continues to drip/move for hours after you apply it. Watched a rudder assembly once where some 5200 was used on a rudder post. Five different guys trying to lift the rudder into the transom all covered in 5200. Then the old guy sprayed it with water to scim it over.
Click to expand
The heater is about 4”x 10”. It will fit in the aft locker which is maybe 3’x4’. It will be mounted on a steel L shaped plate.
E468A0AD-7535-4A53-BAD3-F78560C32014.jpeg
 
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jssailem

jssailem

SBO Weather and Forecasting Forum Jim & John
Oct 22, 2014
22,980
CAL 35 Cruiser #21 moored EVERETT WA
Davidasailor26 said:
six10 epoxy or Thixo that you can dispense with a caulk gun.
Click to expand
:plus:
That is the product I would use for the identified job. I would attach directly to plywood.

And yes... Scuff up the surfaces to get a mechanical and chemical bond.
 
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rgranger

rgranger

.
Jan 19, 2010
12,554
Hobie 16 & Rhodes 22 Skeeter Charleston
Citrus strip on the latex.... let it dry.... put a wire wheel on a cordless drill and brush off the paint once the striper is dry.

Mash this on the back of your wood piece... it is an epoxy putty so it won't drip...

1615831601029.png


and then.... craw back there and mash the wood in place and tape it off with masking tape until the epoxy sets.
 
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Head Sail

Head Sail

.
Nov 13, 2013
723
Catalina 34 Tacoma
rgranger said:
Citrus strip on the latex.... let it dry.... put a wire wheel on a cordless drill and brush off the paint once the striper is dry.

Mash this on the back of your wood piece... it is an epoxy putty so it won't drip...

View attachment 191540

and then.... craw back there and mash the wood in place and tape it off with masking tape until the epoxy sets.
Click to expand
Thanks for the suggestion. I checked out a few You Tube videos on strengt test. Regular JB Weld seem to preform well compared to other off the shelf adhesives for bonding strength (no comparrison was done against the West Systems products). Price was only about $6 compared to $30 for Six10. The WaterWeld looked like it was more geared towards repairing cracks and holes vs bonding. The regular JB Weld looks thick enough to stay on even if applied vertically. Leaning towards JB Weld regular based on price, performance, ease of application.
 
rgranger

rgranger

.
Jan 19, 2010
12,554
Hobie 16 & Rhodes 22 Skeeter Charleston
I've used JB weld on my boats but it is more like gooey peanutbutter and less like play-doh. It might not drip much and you may be able to make a masking tape dam to keep it in place.

JB weld is really tough stuff. I once repaired a cracked oilpan on a Ford Ranger with JB weld. Then tapped a new drain plug hole. I sold that truck five years later and the JB weld was still holding strong.
 
D

dlochner

.
Jan 11, 2014
12,842
Sabre 362 113 Fair Haven, NY
rgranger said:
I've used JB weld on my boats but it is more like gooey peanutbutter and less like play-doh. It might not drip much and you may be able to make a masking tape dam to keep it in place.

JB weld is really tough stuff. I once repaired a cracked oilpan on a Ford Ranger with JB weld. Then tapped a new drain plug hole. I sold that truck five years later and the JB weld was still holding strong.
Click to expand
I used JB Weld to repair an exhaust riser. Ended up with a broken exhaust riser in the middle of shipping lanes with no winds 14 miles off shore. :huh:
 
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Head Sail

Head Sail

.
Nov 13, 2013
723
Catalina 34 Tacoma
dlochner said:
I used JB Weld to repair an exhaust riser. Ended up with a broken exhaust riser in the middle of shipping lanes with no winds 14 miles off shore. :huh:
Click to expand
The high temperature version, if that’s what you used is substantially weaker then regular. At least according to the you tube videos.
 
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