bottom barrier coat

C

C-Wolfe

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Sep 16, 2020
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Location
Anchorage
C Dory Year
2008
C Dory Model
255 Tomcat
Vessel Name
Valhalla
So I crawl all over (and bellow) my boat and never notice this

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What is the best way to address this? I'm guessing sanding the whole bottom then a barrier coat and new bottom paint. Any short term solution, I was really looking forward to go out in the next couple weeks. We still have a few feet of snow on the ground and a few inches forecast for the next day or two so not something I can consider doing anytime soon. I haven't call anywhere but I'll be surprised if I can find anyone locally that can do it before late summer early fall at best, that's just the reality of living in Alaska. I would appreciate any advice for short and long term solution for this. Did I or would I possibly do damage to the core by having used the boat in that condition? I have removed a good amount of hardware to epoxy fill and reset and so far all the core shaving that came out while drilling have been looking nice and dry, Aldo I didn't do any near those spot.
 
Your gelcoat is wore down to the laminate layer. To do repair properly, it would take putting the boat on stands, get two quarts of gelcoat, MEK hardener, some wax additive, and green tint coloring for gelcoat. Mix up gelcoat with no wax. Roll out or brush 3 coats of unwaxed onto exposed areas. Do not sand between these coats. Top the final coat with the wax additive. Sand and fair in. (lots of youtube video's on this) Then fix your trailer bunks, by moving the middle bunks more forward, and replace your bunk carpet with softer thicker carpet. Your boat has been trailer-sailed a lot. This is just normal ware and tare on the hull no core damage to be concerned about.

Mark
 
Thanks Mark.
I think for now, or once it get warm enough, I will lift the boat to repair the gelcoat where needed so I can use the boat. Later this summer/fall when temperature is more appropriate, I would like to do a more through gelcoat repair, then epoxy barrier coat and new bottom paint. Let me know if anyone see something wrong with this plan.
But while I'm at it, should I look into making any adjustment to my boat/trailer setup? Should the bunk be more flush with the transom? Any height adjustment I should consider to improve on the scouring of the bottom I'm having? The picture don't show it very good but I have plastic sleeve covering the board instead of carpet, it look like a good product but could this be part of my probleme, they tend to move a bit at every launch/retrieve. they are easy to push back in place but always a bit off once I get back home. I saw other trailer with those, they are usually screw in place on the side, something I could do at the ramp once the boat is in. the water but they is often other boater waiting for me to get out of the way.
Thanks
 
I have to disagree with "Waypoint" here. I base this on over 50 years studying boat osmosis, and construction of fiberglass boats, in the US, Europe (Med and Baltic) and Caribbean.

There is absolutely no reason to re-gelcoat the boat's bottom. Eposy is a 3x better barrier to moisture absorption than is gel coat (or the next best compound vinyl ester resin). Polyester resin is most permeable to water, although light colored gel coat is slightly better than just plain resin. When a boat is "peeled", then no gel coat is applied. Epoxy resin over the bare peel or a layer of cloth is laminated in place, and then more layers of epoxy, with barrier material.

However if this boat is going to be used in AK, there is minimal risk of osmosis. If a boat is laid up in let's say Finland, and then taken to the Med, there are significant risks, but not the other way around! (Osmotic blistering). Actually Osmotic blistering is extremely rare in C Dorys. I have seen more cases of blistering due to poor layup/gel coat spraying, than due to osmosis in our C Dory boats.

Without looking further at the boat's bottom, I am not even certain I would attribute this to abrasion from the trailer. These isolated areas could be where the boat was supported when painted in the past.. We don't know if there was an epoxy barrier coat to begin with. If the boat was painted on the trailer, then these spots being bare would be expected.

Is the boat going to be in the water all season long? What is the history of the boat? (Where was it used in the past, and any history of known blistering.

The "bare" area you see there is not a risk to water penetration into the core.

If the boat was not going to be kept. in the water, I would just go ahead and use it as is. Later you can consider If it is worth the considerable cost to have the bottom sanded, a barrier coat and then bottom paint. Once a boat has bottom paint, it is best practice to remove all traces of that paint before epoxy barrier coat is built up.

If the boat is going to be kept in the water, then I would put on a coat of ablative bottom paint and use it this season. You can then put the boat into a heated environment to do work in the fall.

Media blasting (Sand blasting is a very definite NO!) for a C Dory. Dry ice, or bicarbonate blasting can be reasonably safely done--if there is someone who is an expert in this type of blasting. Use of ground up walnut shells and similar is also too abrasive for the C Dory's bottoms.
 
Yes, your trailer bunks should be even with the back edge of the transom. Colby
 
Bob, Thanks for your response.
C-Wolfe was originally purchase in Anchorage Alaska and have no reason to believe it ever went out of state, I am the second owner, previous owner passed away so I got very little history on this boat, also no log book. Hour meter had 1400 hrs when I took possession of the boat so it was used a good amount, I added about 150 hrs since. I have no plan to go out of AK. The boat is kept on the trailer when not in use, outing are normally 2-5 days. The bottom paint is past due to be redone but i don't have any growth on it so it's been kind of low on my priority list.
The spot are fairly square so I think you might be onto something when you mention been on block on the trailer when painted last. My thought was the gelcoat was done at factory but I don't know if it was redone or repair in the past. The forward part have some superficial scratch like you would expect from someone that will occasionally beach the boat, might be a reason to need deeper repair near the transom.
I'm thinking of hitting those spot with a coat or 2 of epoxy just for peace of mind and making a plan for a full bottom paint in the fall as you mention.
Colby, I think I should start with getting a tongue weight then decide if I just move the boat forward by moving the bow stop or extend the bunk. I probably will have more questions before I make up my mind.
Thanks
 
I think the main problem that started the hull erosion is your bunk carpeting. Indoor/ outdoor carpeting the carpeting that is installed on your trailer bunks now will get as hard as 80 grit sand paper after being dinked in saltwater for years. So when your trailer is going down the bumpy roads it vibrates the bunks just like a palm sander. This is what is happening to your hull. Try to replace your bunk carpet too. I just replaced my bunk carpet with this cudacarpet.com bunk carpeting. Pretty soft stuff. One more thing to add, make sure that you are using rear tie downs. Be sure they are tight. The less movement the less sanding action on the hull.
 
This is really soft bunk carpet. https://cudapowersports.com/ Wanted to send the proper link. I redid my trailer with this 3 months ago. Not cheap, but it's thick, and is made for trailer bunks. Had great reviews, so far so good for my baby!

Mark
 
Agree that new bunk carpet is in order for this trailer. At the same time, you want to inspect all of the fittings on the trailer. AK has a 5,000 lb trigger weight (boat and trailer) for brakes. Depending on what truck you using, I would want brakes especially if any mountain driving is involved, even if the boat and trailer are less than 5,000 lbs.

In many tens of thousands of miles and over 60 years towing boats I have never noted a "sandpaper" effect on aft trailer bunks....When you are hauling the boat out the bunks will be wet; any material trapped in the carpet will be squeezed out. IF possible the trailer should be washed down with fresh water after each dunk. A good tie down system keeps the boat from moving laterally, as well as fore and aft. If I am launching at shallow entry angle ramps regularly, I will have "Slicks" on the forward 1/3 of the trailer bunks. On some trailers and set ups, an extra keel roller can help loading and unloading.

When you put carpet on the bunks, use Monel Metal staples. I use either an air or electric (solenoid) stapler. SS staples will rust out, Monel metal will not.

I always use a ratchet strap over the cockpit area, even when using rear tie downs (Ratchet Straps, from towing eyes to trailer frame.). Put the strap just forward of the stern cleats. This way it will help to keep the boat from riding forward in an emergency stop. (This is in addition to the chain &/or tensioner from bow eye to top of trailer pole tongue (The trailer should have an eye bolt at this point.)

It would be fine to put a coat of epoxy over any fiberglass visible (even though outer polyester layer is intact) areas. With the cold waters a few days in the water should not be an issue. The summer temperature will be only a little above 50*. (Vs the 88* water in the Fl. Keys, where in a week there is significant growth). On our RIB when we were cruising AK, we would put a "sacrificial" layer of cloth and epoxy, with last layer having powdered aluminum mixed in each year on the areas showing wear from pulling up onto a beach, or even routine unloading.

Have a great season enjoying the boat!
 
thataway":21w1qvmd said:
Agree that new bunk carpet is in order for this trailer.

I have plastic cover over my bunk with carpet wrapping the end of the wood. The plastic cover will slide a bit during launch/retrieve, will be easier to adjust with boat off, I need to make that more of a priority on next launch or if I lift the boat.

At the same time, you want to inspect all of the fittings on the trailer. AK has a 5,000 lb trigger weight (boat and trailer) for brakes. Depending on what truck you using, I would want brakes especially if any mountain driving is involved, even if the boat and trailer are less than 5,000 lbs.

The trailer do have surge brake, not my favorite but for now they are doing what they are supposed to do. Tow vehicle is a chevy 2500HD crew cab, long bed with class V hitch. Tow very nice.

In many tens of thousands of miles and over 60 years towing boats I have never noted a "sandpaper" effect on aft trailer bunks....When you are hauling the boat out the bunks will be wet; any material trapped in the carpet will be squeezed out. IF possible the trailer should be washed down with fresh water after each dunk. A good tie down system keeps the boat from moving laterally, as well as fore and aft. If I am launching at shallow entry angle ramps regularly, I will have "Slicks" on the forward 1/3 of the trailer bunks. On some trailers and set ups, an extra keel roller can help loading and unloading.

I do have the standar bow strap from the winch plus safety chain and 2 rear tie down. I also add a wide-heavy duty ratchet strap between the forward cleat and the raise part over the V berth, not a bad idea to add another one over the cockpit as you mention, at least for longer/bumpier ride

When you put carpet on the bunks, use Monel Metal staples. I use either an air or electric (solenoid) stapler. SS staples will rust out, Monel metal will not.

I always use a ratchet strap over the cockpit area, even when using rear tie downs (Ratchet Straps, from towing eyes to trailer frame.). Put the strap just forward of the stern cleats. This way it will help to keep the boat from riding forward in an emergency stop. (This is in addition to the chain &/or tensioner from bow eye to top of trailer pole tongue (The trailer should have an eye bolt at this point.)

It would be fine to put a coat of epoxy over any fiberglass visible (even though outer polyester layer is intact) areas. With the cold waters a few days in the water should not be an issue. The summer temperature will be only a little above 50*. (Vs the 88* water in the Fl. Keys, where in a week there is significant growth). On our RIB when we were cruising AK, we would put a "sacrificial" layer of cloth and epoxy, with last layer having powdered aluminum mixed in each year on the areas showing wear from pulling up onto a beach, or even routine unloading.

Have a great season enjoying the boat!

Thanks, I have enjoyed this boat very much the last 2 season, looking forward to the next one if it ever come. we just received about a foot of snow which put us over 100 inches for the season. Not that unusual for here but we normally have a few warm spell in early and late winter, that didn't happen this year, still lots of snow on the ground
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Anyone familiar with this contactless moisture meter? (Bob) :D

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I sanded and added 4 coats of Interlux Interprotect 2000E on the damage spots. My intention is to do the whole bottom this fall.
I did just a few reading from the bottom with the moisture meter, I was getting average of about 12% forward of where the core end and average of 14% near the transom. I set it on hardwood but I'm not sure that is the setting I should be using. Like I said, it was just a few reading, I need to go back and do a more thorough assessment but I want to make sure I do it right.
Thanks for any help.
 
I have two of the cheap meters: The same Ryobi you have, and I usually use it on "Hardwood" setting. I also have a "General" which is the same principle and readings are the same as the Ryobi.

What you are looking for with one of the cheaper moisture meters, is relative wetness. I believe that the meter uses capacitance to measure the relative wetness of the material.

The minimal difference between areas you measured is not really significant. What you did is fine.
 
Thanks Bob. I figured the difference was not enough to create concern but wasn't sure if I was using the right setting for the C-Dory bottom.
 
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