CONTINUOUSWAVE

Just bought [a 2010 170 SUPER SPORT]. I did not notice [the hull] damage [shown in Figure 1] before I purchased the boat as-is from a Boston Whaler dealer. They delivered 2010 170 SUPER SPORT to me in the water, and I immediately moved it on my lift. Then, a few days ago, I loaded the boat on the trailer to take it home and do some upgrades and work on it.

Think I will need a good fiberglass guy to grind out, apply fiberglass and gel coat [to repair the damaged area].

Q1: are there any special concerns with this-type [repair] work [on a Unibond hull]?

Q2: how could this damage have happened?

To me, the damage [to the keel] looks like somebody beached [the boat] on [a boat launching] ramp.

The damage to the hull at the forward quarter of the keel (seen in Figure 1) is quite unfortunate. For advice on making repairs, see the article in this forum at the top of the index listings which will lead you to three good reference articles on hull repair:

Advice on Repair of Unibond Hulls
https://continuouswave.com/forum/viewto ... f=6&t=9254

I suggest you read all three linked articles to get a better idea of how to make a proper repair.

In all cases, the first step is to let the hull dry out and for any water already behind the gel coat and laminate to be allowed to drip out and evaporate.

Because the area of damage is part of the running surface of the hull, you should take some immediate steps to prevent further ingress of water into the hull laminate and possibly into the foam interior. For example, if you intend to continue use of the boat before making a repair, apply some quality duct tape that has excellent adhesion and is reasonably water resistant to cover the damaged area. If you are not going to use the boat, get it out of the water and let the damaged area dry.

ASIDE
I am very surprised that an authorized Boston Whaler dealer sold this boat "as-is" knowing that the damage would required immediate repair in order to avoid further harm to the hull.

Because the damage is not in a highly visible area, a repair does not need to perfectly cosmetic and undetectable. On that basis you could very likely make a good repair yourself that is not particularly invisible to the eye, but will stop any ingress of water into the hull laminate and foam. My own preference for making a repair like this would be to buy the WEST System K-105 repair kit for about $60, and also to read their pamphlet on repair of fiberglass hulls with epoxy resin.

The damage looks as though it may have been caused by the trailer. I would examine the trailer carefully to rule that out. It could also have been caused by "power loading" when the trailer has not been in sufficiently deep water.

I agree that then damage to the keel could have been caused by the trailer. I had similar damage when my trailer bunks were set a bit too low. On certain boat launching ramps [the angle the ramp descended into the water caused] the keel [to be able to ] scrape on the front crossbar of the trailer during the loading. [As a remedy for this problem with this trailer on those certain ramps,] I slightly raised the trailer bunks and also installed a plastic skid guard on the trailer’s front crossbar.

If you just want [the repair to be] water tight and [the boat to be] ready to run then I would use the [WEST System Fiberglass epoxy repair] kit Jim recommended.

If you want [the repair] to look pristine and gel coat over it, you will have to stay away from epoxy and go with a polyester resin underneath the gel coat.

Cala wrote:If you want it to look pristine and gel coat over it you will have to stay away from epoxy and go with a polyester resin underneath the gel coat.

Wrong. You are repeating old myths. You can apply gel coat polyester resin over a surface of cured epoxy resin with excellent outcomes, as long as you properly prepare the epoxy surface. I have personally done this and the repairs have stood up for over twenty years. I describe the process in an article:

The Epoxy Cure
https://continuouswave.com/maintenance-logs/epoxy/

There is no doubt it can be done. People who insist it cannot be done are just not well-informed about using epoxy resins.

For advice, listen to an episode of WHALER RADIO that was recorded and posted 26-years ago in which the use of epoxy resins to make repairs to Boston Whaler hulls was discussed:

https://continuouswave.com/whaler/radio ... tPart1.mp3

https://continuouswave.com/whaler/radio ... tPart2.mp3

Also see a recent youTube presentation from WEST Systems in which the strength of new gelcoat bonds to cured epoxy surfaces was tested:

Can You GELCOAT OVER EPOXY? We Tested It!
https://www.youtube.com/watch?v=UUxzWEAZ8Vs&t=119s

Can you apply gelcoat over top of epoxy? We’ve put together three tests involving polyester fiberglass panels and WEST SYSTEM Epoxy fiberglass panels. Those tests include the following.

-Feather Edge Test: Sanding through the gelcoat with progressively finer grits will show whether it feathers out cleanly or starts to flake and chip at the edge. This simulates what you'd need to do when blending a gelcoat repair into the surrounding surface.

-Flex Adhesion Test: By scoring hash marks into the gelcoat and flexing the panel until it snaps, we can see if the gelcoat lifts or peels away from the laminate. This tells us how the gelcoat holds up under stress, like bumping into a dock or taking an impact on the water.

-Tensile Adhesion Test: Metal studs bonded to the gelcoat surface are pulled off with a PATTI meter to measure how much force it takes to break the bond. The failure mode is what matters here. Did the gelcoat let go, or did it hold on tight enough to pull fiber up with it?

Stick around to see how each panel held up and find out whether this long-standing boatyard rumor actually holds water.

Using epoxy resin for repairs produces a stronger bond and better waterproofing than using polyester laminating resins for the repairs.

To me, the damage to the hull surely looks like if was from the trailer.

On my 190 NANTUCKET I had similar keel damage caused by the trailer. The existing trailer was due for replacement, and I ordered a new trailer. The problem with the trailer causing damage to the keel fiberglass and gel coat did not recur with the new trailer.