SuperCat 20 Sailboat Repair

[gte718p]

A couple of months ago I moved to Hawaii. It is a hard life, but someone has to live it. One of the first things I did was pick up a sail boat. It is a 20 Ft Boston Whaler SuperCat. In the early 80's Boston Whaler attempted to jump into the beach catamarans market that was and is dominated by Hobie. They bought a small company and started making beach cats. They made amazing boats, but did not have a long run. The original designer bought the company from Boston Whaler and is still making cats under the Aquarius brand.


The boats name is Tuna Patrol

Last week I was out sailing and I screwed up reading the channel marker. Rather embarrassing as it was in my home port and waters I have sailed many times. I ended up hitting a rock with a good bit of speed. Thankfully the boat was okay, but I screwed up one of the dagger boards pretty good. I did a decent job fixing, it but eventually I will need to replace it. I called Aquarius and the dagger boards run $3k a piece.

Daggerboards are not rocket science, just basic hydrodynamics and composites so I am going to make my own.

I started by picking the foil I want for minimum drag.

Then I drew it up in Fusion 360.

The next steps will to be build the internal skeleton structures. They are either going to be balsa or carbon fiber. I'm going to cover the skeleton in foam and carve it with a CNC router. Finally I'm going to wrap the daggerboard in two layers of carbon fiber.

 

[twowheels]

Who knew Boston Whaler made cats? I'm familiar with their monohull sailboats, but never seen a cat. Great project - I'm following!

Tim

 

[Bondo]

Ayuh,.... Resize yer graphics, as right now yer post is unreadable,...

 

[6PTsocket]

Doesn't a cat have 2 dagger boards? Shouldn't the new one match the other one? You are are not always running with one out of the water.

Sent from my SM-G900V using Tapatalk

 

[gte718p]

Ayuh,.... Resize yer graphics, as right now yer post is unreadable,...

It wasn't bad on my computer monitor, but on my tablet you are right it is unreadable. I'll fix it eventually.

Who knew Boston Whaler made cats? I'm familiar with their monohull sailboats, but never seen a cat. Great project - I'm following!

Tim

Boston Whaler only made cats for about three years. Thankfully the hull design and support has continued. I just fell into one, I wasn't looking for it, but they have a cult following. They are amazing boats to sail. I have never been on a boat that points so well.

Doesn't a cat have 2 dagger boards? Shouldn't the new one match the other one? You are are not always running with one out of the water.

Sent from my SM-G900V using Tapatalk

I'm changing the design of the boards so I am only going to make one at first. If I'm happy with the design I will make the match. I generally only sail with one board down anyway. If I'm lifting a hull that can be a little interesting, but he hull shape is very forgiving and tracks we'll without the board. It is actually common to sail the smaller Supercats without the daggerboards.

I do still have a repaired matched OEM set for racing. These will be my general cruising boards.

 

[6PTsocket]

It wasn't bad on my computer monitor, but on my tablet you are right it is unreadable. I'll fix it eventually.



Boston Whaler only made cats for about three years. Thankfully the hull design and support has continued. I just fell into on, I wasn't looking for it, but they have a cult following.



I'm changing the design of the boards so I am only going to make one at first. If I'm happy with the design I will make the match. I generally only sail with one board down anyway. If I'm lifting a hull that can be a little interesting, but he hull shape is very forgiving and tracks we'll without the board. It is actually common to sail the smaller Supercats without the daggerboards.

I do still have a repaired matched OEM set for racing. These will be my general cruising boards.

I was a mono hull guy, myself. I had a Tanzer 22. The keel was 1200 lbs of cast iron. The boat would break before the keel. There was a keel/ center board version but it wouldn't point up for squat. I had a friend who bought that one and actually brought it back to the factory and they switched keels.

Sent from my SM-G900V using Tapatalk

 

[gte718p]

So a little progress has been made. One of the dagger boards is repaired. I didn't realize how badly I had damaged the other dagger board. I was on the board yesterday and realized that the second daggerboard as well as the rudders are urgent need of repair. Hopefully I will remember to to take pictures this time.

Not much progress on the new boards. I did finish the CAM work. However the machining time is horrendous. Almost 8 hours I'm limited in tool size as the router table uses a little bosch routers as the power head. The Machinery Hand Book doesn't appear to cover foam cutting. Anyone have experience in routing foam? I'm finding conflicting numbers for feed rates online. I'm really hoping to push the feed rate to get the machining time down.

 

[gte718p]

I'm about 90% done with repairing one of the dagger boards. I didn't take any pictures of it, but I rebuild the bottom edge using filled epoxy, allied two layers of glass to the bottom and leading edge, and painted it. I'm going to apply a top coat of epoxy and it should be almost as good as new.

I took the boat out this weekend, but didn't realize how badly the other dagger board was screwed up. I didn't wear through the glass on this one, but took several chunks out it and a lot of deep scratches.

I gave the board a good sanding with 80 grit to ensure that the epoxy has a good surface to bite to. I'm using West Systems 105 resin with the 206 hardener. That gives me a work time of about 20 minutes in my climate. Unfortunately it also gives me a 10 hour dry time. I do 5 minutes of work and then have to wait till the next day. A full repair takes maybe 30 minutes but it has to be spread out over a week.

The can in the middle is epoxy filler. It basically thickens the epoxy so it stays were you put it. I absolutely love the stuff. I'm actually using the wrong filler, but it is what you I had. You can basically mix the epoxy up to be like bondo. You can get everything nicely filled and smooth and then sand and feather it in to make a strong perfectly smooth surface. The 403 is actually for structural bonding. 406 or 407 would be a better choice as they are much finer, but sometimes you go with what you have.

This is what it looks like waiting to dry. In 10 hours, I'll sand and blend everything and do the other side.

 

[gte718p]

What hole?

Everything is filled and sanded. Unfortunately I sanded a little to deep in on spot and had to do one more quick epoxy coat. Tomorrow is paint and then I will top coat both boards.

 

[IndyGarage]

Kauai? My wife and I were there a couple months ago.

3K for a daggerboard seems like they really don't want to make them anymore.

Your repair looks good. Question - I thought in your first description the daggerboards were snapped off or something. What you are showing is a ragged leading edge. Will it really affect your boat handling very much?

 

[gte718p]

Kauai? My wife and I were there a couple months ago.

3K for a daggerboard seems like they really don't want to make them anymore.

Your repair looks good. Question - I thought in your first description the daggerboards were snapped off or something. What you are showing is a ragged leading edge. Will it really affect your boat handling very much?

I'm on Oahu.

The newer version of this boat (which is almost identical) is a purpose build racing catamaran. Everything is carbon fiber from the mast to the hull and even the dagger boards. It is unfortunately like having a Ferrari. Parts are expensive because they can and people will pay.


This dagger board was actually not in horrible shape. Originally, I though it was just scratched and dented and I wasn't going to have to do any work to it. However, the hole actually pushed through the glass and into the core. Couldn't leave it like that or it would delaminate. The other daggerboard took the blunt of the strike. It was actually missing pieces and the core was exposed. I had to lay glass on that one, I just forgot to take pictures.