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Transom holes Polyester vs Epoxy

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A-K

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Hi All.

I have 3 holes from a transducer I recently removed. Sounds like Polyester is the material to use because gel coat will stick to it.

Can someone recommend a polyester resin and gel coat kit?

My gel coat color is the new white.

Thanks for the help.

AK
 

A-K

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I'd like to try and fix it right the first time. So I'll most likely pass on the screw trick.
 

DanLovingood

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A_K,

I would use epoxy instead of polyester, especially below the waterline. I was alway told that polyester does not bond to wood as well as epoxy and will eventually fail. I have made many repairs with epoxy and gelcoat with no problems getting the gelcoat to adhere. Wet out the hole with unthickened epoxy first, then fill the hole slightly below flush with thickended epoxy (I would use colloidial silica as a thickener for this repair), then lightly sand after cure and add matching gelcoat to obtain a flush repair followed by wet sanding with progressively finer grits and then polish. I prefer West System products and always keep some on hand for repairs just such as this.

Cap'n Dan
 

A-K

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Thanks Dan!

I have bottom paint on my boat. Would it be better to just use the epoxy and paint over ?

Or should I epoxy, add gel coat, and touch up paint?

Would epoxy and paint only prevent water intrusion?

Sorry for the stupid questions. I just try not to assume to much and don't like to leave things to chance.
 

DanLovingood

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With bottom paint, you could skip the gelcoat and just touch-up with the bottom paint. In this case I would fill flush with epoxy, let cure, and sand smooth before touch-up with bottom paint. Epoxy is an excellent barrier to water intrusion but does not hold up well to UV exposure usually requiring some kind of UV protective coat if exposed. Bottom paint would provide that UV protection for the epoxy. The initial wet-out with unthickened epoxy allows the epoxy to infiltrate into the wood core and provides an almost bulletporrof bond with the thickened epoxy. Colloidial silica is generally used for epoxy adhesives and dries very hard and is difficult to sand, so don't get too carried away with overfilling. I barrier coated the wood furniture on my 1990 1800 with epoxy (2 coats) followed by 2 or 3 coats of spar varnish (for UV protection) and it held up for about twenty years.

Cap'n Dan
 

A-K

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Well just so happens I have the west systems epoxy in my shop. But I need new pumps because they “gel”ed up over the winter ... so new pumps on order!

Thanks again!
 

pelagic2530

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X2 to everything that Cap'n Dan said. For small repairs like this, epoxy is the way to go. MFRs use poly due to the lower cost, and the good adhesion to the gelcoat giving them a nice clean finish. Gelcoat will adhere to epoxy in small areas, just make sure to sand the surface so as to give it a "profile" to increase adherence. No reason to go back to poly for the majority of repairs.
 

sailmaster

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All good advice. The old saying in the boat shop when bonding something was if you had a choice between polyester or paint use paint. I use WEST Epoxy because it is highly reliable. Too many use it for the wrong reason. Only epoxy specific fabrics will work with it for example. Using gel coat below the waterline is not best practice for a boat that is not drysailed Polyester gel coats are not waterproof. Epoxy and vinylesters are. Do not get too enamored with gel coat, it is just paint and not all that great as paints go. It has some nice attributes about repair ability and manufacturing but it is not the be all end all in the narrative.
2 biggies for your repair.
A Dry it out Fan works best with time. Heat Lamps not as much
B Wash off repair with detergent and water before epoxy to get off any water/polyester goo film and then after sanding epoxy repair to remove any amine blush that will stop bonding and curing of gel coat or paint. I use a citrisolve 50:1 reduction first and final clean with windex. ( Citrisolve will remove paint in high concentrations and take the oil out of your skin ) Orange ZEP Stuff from home depot

That said if the "new white" is vinyl ester it sticks better and is highly water resistant
 

warthog5

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Use a countersink on the holes...Flare the holes...and it will clean the glass. carefully tape around each hole. Fill with thickened epoxy or polyester... Use Cabisol to thicken it. A razor blade makes a good spreader for small stuff like this. Skip the gellcoat and just paint it.

You sure spent a LOT of money on new West System pumps.....I haven't used West System in 15yrs...at least.
 

pelagic2530

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Would using 4200 or 5200 be acceptable for filling small screw holes? I’ll be changing my transducer soon and have to fill the old ones. Thanks
You CAN do it that way, but it's not the right way to do it. All sealants will eventually fail, and especially in below-the-waterline applications, this leaves your transom core vulnerable to water intrusion and rot. So at best this is a temporary fix, and temporary fixes have a bad habit of becoming permanent and being forgotten about until they cause a problem.

Filling the holes per Warthog's and Cap'n Dan's descriptions above is the only permanent way to do the repair. Additionally, when you mount your new transducer, be sure to over-drill the holes, fill them with epoxy, and re-drill your mounting holes in the "plug" of epoxy that creates. That way, your core is protected from water intrusion into the new fastener holes. Sealing those holes on final installation with 4200 or 5200 (I use 4200, as transducers do need to be replaced from time to time) is also a good practice.
 

DanLovingood

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For installing a transom mounted transducer, I would recommend not drilling any holes below the waterline. Instead use an epoxied on mounting system such as Sternmate or Stersaver. I mounted a big, honking Totalscan transducer on my 1800 using the Sternmate and have been very pleased with it. It eliminates the need to drill and offers a greater range of adjustability for getting your 'ducer just right. If you are handy, you could fashion your own similar to the Sternsaver with 3/4" or 1" thick starboard.

Cap'n Dan
 

sailmaster

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You CAN do it that way, but it's not the right way to do it. All sealants will eventually fail, and especially in below-the-waterline applications, this leaves your transom core vulnerable to water intrusion and rot. So at best this is a temporary fix, and temporary fixes have a bad habit of becoming permanent and being forgotten about until they cause a problem.

Filling the holes per Warthog's and Cap'n Dan's descriptions above is the only permanent way to do the repair. Additionally, when you mount your new transducer, be sure to over-drill the holes, fill them with epoxy, and re-drill your mounting holes in the "plug" of epoxy that creates. That way, your core is protected from water intrusion into the new fastener holes. Sealing those holes on final installation with 4200 or 5200 (I use 4200, as transducers do need to be replaced from time to time) is also a good practice.
nice tear out article in this months Professional Boatbuilder dealing with fastening to cored materials
 

sailmaster

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For installing a transom mounted transducer, I would recommend not drilling any holes below the waterline. Instead use an epoxied on mounting system such as Sternmate or Stersaver. I mounted a big, honking Totalscan transducer on my 1800 using the Sternmate and have been very pleased with it. It eliminates the need to drill and offers a greater range of adjustability for getting your 'ducer just right. If you are handy, you could fashion your own similar to the Sternsaver with 3/4" or 1" thick starboard.

Cap'n Dan
are they still mounting transducers inside the boat. Used to do it for Lowrance back in the day
 

DanLovingood

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are they still mounting transducers inside the boat. Used to do it for Lowrance back in the day
sailmaster,

That is how my 1800 was set up for its for its first 20+ years of life. It originally had a Hummingbird transducer epoxied to the inside of the bottom hull. I switched to a Lowrance unit around 2012 and instead of drilling holes in the transom for that 'ducer, I built a small tank out of 4" pvc epoxied inside the bottom hull, cut to the angle of deadrise so the transducer would fire straight down. I then mounted the transducer to the bottom of a 4" pvc threaded clean-out plug, filled the tank with antifreeze and screwed in the new transducer (it was small enough to fit inside). In 2018 when I rebuilt the boat I switched to a Simrad Go7 XSE and wanted all the structure scan capabilities which forced me to go to the transom mount. You can still mount transducers to the inside of the hull provided the hull is solid fiberglass with no core to block passage of the sound waves.

Cap'n Dan
 

sailmaster

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sailmaster,

That is how my 1800 was set up for its for its first 20+ years of life. It originally had a Hummingbird transducer epoxied to the inside of the bottom hull. I switched to a Lowrance unit around 2012 and instead of drilling holes in the transom for that 'ducer, I built a small tank out of 4" pvc epoxied inside the bottom hull, cut to the angle of deadrise so the transducer would fire straight down. I then mounted the transducer to the bottom of a 4" pvc threaded clean-out plug, filled the tank with antifreeze and screwed in the new transducer (it was small enough to fit inside). In 2018 when I rebuilt the boat I switched to a Simrad Go7 XSE and wanted all the structure scan capabilities which forced me to go to the transom mount. You can still mount transducers to the inside of the hull provided the hull is solid fiberglass with no core to block passage of the sound waves.

Cap'n Dan
when I was doing the lowrance installs we used polyester not epoxy and only cabosil as a thickner as it is harder and less flexible than epoxy and gave a better picture. presume the stuff today is way way advanced. on the other side I had a customer who spent the second world war sailing a K boat ( 128 feet long with teak decks that leaked terribly ) listening for uboats with a microphone in a bucket dragged over the side. They got some and called in airstrikes from Millville NJ NAS
 

SEA YA

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You CAN do it that way, but it's not the right way to do it. All sealants will eventually fail, and especially in below-the-waterline applications, this leaves your transom core vulnerable to water intrusion and rot. So at best this is a temporary fix, and temporary fixes have a bad habit of becoming permanent and being forgotten about until they cause a problem.

Filling the holes per Warthog's and Cap'n Dan's descriptions above is the only permanent way to do the repair. Additionally, when you mount your new transducer, be sure to over-drill the holes, fill them with epoxy, and re-drill your mounting holes in the "plug" of epoxy that creates. That way, your core is protected from water intrusion into the new fastener holes. Sealing those holes on final installation with 4200 or 5200 (I use 4200, as transducers do need to be replaced from time to time) is also a good practice.
Thanks for the input, much appreciated.
 

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