Seeking High-Heat Sealant to Bond Woodstove Chimney to Fiberglass

[Billy_Pilgrim]

I have a small woodstove in my fiberglass S/V. There is a small leak on the interior of the cabin, where the chimney exits the cabin. I want to remove the exterior chimney piece and re-seal it to the fiberglass, so see if this helps with the leak. I had planned to use 3M 5200 sealant for this job, though see in the info sheet for this product that they do not recommend using it in applications that can exceed 190 degrees (F). Does anyone have any thoughts on best sealant to use on a chimney hood being affixed to fiberglass?

Thanks!

 

[dlochner]

Are you using a double walled flue? The flue should not be in contact with the fiberglass.

Resins will start to get soft at about 150° and are quite combustible. 5200 would not be a good choice for this application because it is more of an adhesive than a sealant and it will not expand and contract as well as other sealants.

 

[Billy_Pilgrim]

Are you using a double walled flue? The flue should not be in contact with the fiberglass.

Resins will start to get soft at about 150° and are quite combustible. 5200 would not be a good choice for this application because it is more of an adhesive than a sealant and it will not expand and contract as well as other sealants.

Thanks for your reply. I am not certain as to the specifics of the flue, as the woodstove was installed prior to my possession of the S/V---my guess is that all appropriate parts were used, as the woodstove was installed within the last 2-3 years, using parts that appear to be specific for this application. But i am not positive. The exterior portion of the chimney is screwed down into the fiberglass roof, and this is what i want to take off, sand and clean, and then re-set with a new bead of appropriate sealant/bonding material. Do you have any suggestions for best product for this?

Thanks!

 

[JamesG161]

Does anyone have any thoughts on best sealant to use on a chimney hood being affixed to fiberglass?

Check the brand name of the Stove. Call them for installation sealing.
Otherwise, it would not be used on a FRP sailboat.

I can give you a fireplace caulking spec, but it is used for stable, in place Landlubber fireplaces.
Normally the outside temp of Landlubber flues is < 150°F per code.

Jim...

 

[Billy_Pilgrim]

Check the brand name of the Stove. Call them for installation sealing.
Otherwise, it would not be used on a FRP sailboat.

I can give you a fireplace caulking spec, but it is used for stable, in place Landlubber fireplaces.
Normally the outside temp of Landlubber flues is < 150°F per code.

Jim...

Thanks Jim--i am a beginner in all things and do not have any useful knowledge regarding woodstoves/chimneys/flues etc. if i understand (and extrapolate a bit)---a chimney is typically built with a the portion that comes in contact with the roof designed to not typically exceed 150F? (how do you make that degree circle on a computer?) Is this what is meant by the "double wall flue" comment from earlier? There is a pipe that runs up from the woodstove which is encircled by another pipe, and this second pipe is what comes in contact with the roof, and it is also less-hot? Apologies for what may be some pretty dullardly questions.

 

[dlochner]

Thanks for your reply. I am not certain as to the specifics of the flue, as the woodstove was installed prior to my possession of the S/V---my guess is that all appropriate parts were used, as the woodstove was installed within the last 2-3 years, using parts that appear to be specific for this application.

Never assume the prior owner knew what he/she was doing. That will get you into trouble more often than not.

This page has some information on installing a wood stove on a boat or RV.

Installing a Roof Exit Flue System in an RV, Bus, or Van - Tiny Wood Stove

Before you begin Your flue design should be complete, and you should have all the required components on hand. The install kit is the “base kit” that includes the parts that most everyone needs. Since every structure is different, people need varying amounts of pipe in addition to the kit...

www.tinywoodstove.com

 

[Billy_Pilgrim]

Never assume the prior owner knew what he/she was doing. That will get you into trouble more often than not.

This page has some information on installing a wood stove on a boat or RV.

Installing a Roof Exit Flue System in an RV, Bus, or Van - Tiny Wood Stove

Before you begin Your flue design should be complete, and you should have all the required components on hand. The install kit is the “base kit” that includes the parts that most everyone needs. Since every structure is different, people need varying amounts of pipe in addition to the kit...

www.tinywoodstove.com

Thanks very much for this! and yes, assumptions will mire us all in mediocrity, if not downright destruction. it seems that so long as i have the proper flue for my woodstove, 5200 sealant will indeed be an appropriate way to go, as it is rated up to heats of 190, and a flue is not supposed to exceed 150, yes?

 

[dlochner]

Don't use 5200 on anything that might need undoing in the future. The stove flue would fall into that category.

There is a reason 5200 is referred to as the devil's glue and it is probably the cause of more bad language by current boat owners issued towards prior owners. Don't be that guy.

 

[Billy_Pilgrim]

Don't use 5200 on anything that might need undoing in the future. The stove flue would fall into that category.

There is a reason 5200 is referred to as the devil's glue and it is probably the cause of more bad language by current boat owners issued towards prior owners. Don't be that guy.

OK, thanks. Do you have suggestions for a less-demonic sealant that will still withstand the pervasive wet of southeast Alaska?

 

[dlochner]

3m 4200 or 4000 would probably work. Or a structural glazing caulk, like Dow 795 or GE Silpruf. Check the data sheets first.