Daggerboard "Fuse"

[catsketcher]

Way back, about 30 years ago, I was working with one of the best Australian multihull builders. I was a sponge, absorbing everything I could for my own build to come. One thing I heard from the master builder was his comment that people should not use their daggerboards as depth sounders. (It may have been due to the fact that I had to bring in my own daggerboard to the shop to repair it).

My boss said that anyone with daggerboards should build them properly, then cut off the bottom 300mm and then glue it back on, without glass. This acts as a fuse so that if the board hits bottom the bottom breaks.

When I built my boards, about 25 years ago, I followed his advice. I also added lots of unis draped around the back of the board case and made the case out of glass rather than timber.

So just a few days ago I am coming back from 10 miles up the coast where I slip the cat. She is all nice and clean and the bar I cross (which I have crossed many times before) is benign but lumpy due the fast outgoing tide. I am also enthralled by my new Pypilot autopilot. It has been working so well on both trips.

So the boat starts going off course. Now the autopilot setup is new and I haven't got a super quick release. I try to use the autopilot to get her back on course but she just starts heading for the rock walls at a fast clip, (I am fighting tide so the throttle is open). Oh no... so unclip the autopilot and turn boat whilst hoping the boards, which were down for the windward work into the channel, don't hit.

Then a huge BANG! and we head off into the channel as I see rocks in the clear water. I know that we have hit but I get her into the middle and then stop, check the bilges, no worries. but "How could I be so STUPID!"

I moored and swam on the boat. The board was stuck aft in the case and so I led a rope forward from in the water and winched it forward. A wiggle got it free. I got the goggles out and checked the case and hull, no damage whatsoever, but also no bottom 300 mm of the board. The fuse had gone.

When I built the boat, I made the blanks 300mm too long so I would have a head start on putting new tips on. So today I rooted through the shed and got out the blank. It will get a couple of layers of glass over it and then be epoxied back on the bottom again. I also have to do some work on the trailing edge where there is a small scar.

I am pretty chagrined at my stupidity. My testing autopilot drive had lost its drive cog and so the new autopilot could not steer the boat. Even though I had gone over the bar about 60 times I should not have done it under autpilot at all, and I should have retracted the boards to half height, as I usually do, but did not this time. Thanksfully the boat covered for my stupidity and the lining up of the potentials for error.

But for those who have daggerboards made from cedar. It is a good thing to have the bottom "fused".

cheers

Phil

[Tin Tin]

Good idea. Scary way to find out if they work!


I recall some designers put the shock absorber in the bottom of the case like a soft sacrificial wedge.



I hear Catana boards also snap off easily when fully down in strong winds even if they don't hit the bottom.

[Morph]

HI Phil, I always enjoy your posts... and sympathise with your wee incident... I hit the bottom on the very first delivery of my brand new, just out of the yard Pescott in Port Macquarie and put a dent in the bottom of my brand new boards...Ross did the same as your boards and we did not break off the tip, just patch up the dents with a bit of epoxy after pulling the board up.... so many ways sailing humbles us...
two questions: I now have a new-to-me Pescott Summersalt on delivery from Townsville-- very happy with her. What new autopilot are you using? Currently she has a raymarine tiller pilot but it struggles at speed?
Second question: where do you haul out? I assume you know a place where you can work on your own boat? It's very hard to find somewhere around Sydney.
Cheers Phil

[catsketcher]

PM sent

[Chotu]

that’s a great story. Thank you for sharing.

it really shows the importance of having the trunk or case be stronger than the board itself in some way or another and to have some impact absorbing ability.

mine was designed to have a little impact absorber within the dagger board trunk. That was a lot of extra work. I did it differently.

I made my trunk out of very hard solid glass when it was cored in the plans. It gave me a slight weight penalty. But it is really rugged. Much much stronger than the board itself. So my strategy is for the board to break. And then just make a new one using the other board as a plug.