CR 13 build

[Guest]

I am considering building a Corsair13 in Australia but I have a couple of questions before I buy the plans.

1. I sail in Moreton Bay which has a lot of sandbanks, so I was wondering if it is possible to install a pivoting centreboard instead of a daggerboard to limit damage to the boat when I hit a bank. If not possible can the daggerboard case be made to withstand a grounding?

2. Looking at the pictures, the mast seems to be stepped into the hull through the foredeck. Can it be just fixed the the top of the foredeck in the manner of beach catamaran masts? The mast is held up by the shrouds and the forestay. I realise I would need some strengthening under the deck. I have sailed other dinghys with that arrangement. I will be fitting a gunter sail to it. I was thinking water down the hole from waves, and maybe damage to the deck if a shroud let go.

I would greatly appreciate your advice, as I am really excited that I have found a boat that seems just right for me and am keen to get going with the build.

[Brocky]

I posted this before as a guest but now I can do it as a user.

I am considering building a Corsair13 in Brisbane, Australia but I have a couple of questions before I buy the plans.

1. I sail in Moreton Bay which has a lot of sandbanks, so I was wondering if it is possible to install a pivoting centreboard instead of a daggerboard to limit damage to the boat when I hit a bank. If not possible can the daggerboard case be made to withstand a grounding?

2. Looking at the pictures, the mast seems to be stepped into the hull through the foredeck. Can it be just fixed the the top of the foredeck in the manner of herons, pacers, etc? The mast is held up by the shrouds and the forestay. I realise I would need some strengthening under the deck. I have sailed other dinghys with that arrangement, but I also have to consider rigging it on my own as I will be doing much of the time. Maybe it is easier with a keel stepped mast, I'm not sure. I will be fitting a gunter sail to it. I was thinking water down the hole from waves, and maybe damage to the deck if a shroud let go.

I would greatly appreciate your advice, as I am really excited that I have found a boat that seems just right for me and am keen to get going with the build.

Ian

[Jaysen]

1. If built to spec, the dagger will attempt to pop up when grounded. Note “built to spec” and “attempt”. This means you have to make the dagger trunk with adequate clearance and use light wedge, shock or weight to keep the dagger down. I prefer wedge on my v12.

2. If you want a deck stepped mast your looking a structural changes that few here will be able to assist you in making. I would be trivializing the effort to say “you can” (you actually can). My hon at response is “you shouldn’t, if deck step is a requirement select another design”.

I would advise against any stays on a small boat. They are a hazard unless you really know what you are doing. Nearly all the real injuries I’ve personally seen while sailing involved something with a stay (chainplate gashes, bone broken on stay, people caught on stats and sheets). Granted bigger boats. Unless you’re racing, and proficient enough to do it, I don’t think the risk is worth it.

[Brocky]

Thank you for taking the time to reply so promptly.

Neither of my proposed mods are essential, I am just looking at ideas which might suit my wants. I certainly don't want to do something that will compromise the design, and I am nowhere near experienced enough to radically change the design, such as building a support structure for a deck stepped mast that might work, I thought I might be able to just bung it on the deck with a bit of support. My boat building experience is limited to a two-man canoe that I built last year (successfully) and my sailing to a 14ft catamaran, as well as a dinghy many years ago. So I really appreciate someone like you who knows a lot more and can give helpful tips and advice to a beginner like me.

It's interesting that you used the expression 'attempt to pop up' for the daggerboard. You don't sound too convinced that it will all the time. A dagger would definitely be easier to build and I suppose a centreboard can jam just as easily as a daggerboard, so maybe I'll leave the decision as a question for now and address it when I get to it during the build. I've just bought the plans so I'm committed to building this boat.

As to your comment about stays, all the pictures I see on the site of the corsair13 have shrouds with a bermuda rig so are you talking about some other sort of stay like spreaders or something? In the years that I sailed the cat I never had a shroud let go, and I sure put them under pressure at times, but they were always in good repair, and professionally prepared. I don't intend to race the boat, just cruising my local waterways.

Thanks again,
Ian

[Jaysen]

I may have looked at the wrong design. If the plans have the mast using stays then that design complication for moving to deck stepped is reduced. The f the mast is free standing moving to stays … lots of work.

The temptation is to put a compression post under the deck, and attach a mounting bracket to it. The difficulty is that the current supports in the deck are expecting the majority of the lateral force to go to the keel step. The decking is only stiffening the mast and providing a second support (Jacques and I had this general discussion years ago regarding keel vs deck step). Jacques suggested that deck stepping would require thicker and wider reinforcement at the mast partner across the board. I’m some cases an additional bulkhead.

The dagger will pop up 100% of the time unless you jamb it too tightly. That’s my sin ever. dang. time. I tend to sail more aggressively (because I’m stupid) so need that sucker to stay down. Between its natural floatation and the wide box, it naturally sits at 50%. Once I get to about 75% of hull speed the dagger assume “this moron is going to hit something” and starts chickening out. After the third time I lose my patience, smack the wedge with the radio and then run into oysters, mud or sand. Every. Dang. Time.

The dagger will attempt to save you from yourself. Just don’t be me.

[Brocky]

Haha, fortunately i got all my need for speed out of me when I had the cat, a 14ft Maricat. We used to enjoy tearing around blowing away all the slow monohull dinghies, then a couple of Nacras would turn up and make us all look rather silly. Now in my senior years at 71 ( and hopefully a bit more wisdom), as I want to sail moderately, with a comfortable seat, and be much drier, the daggerboard will probably survive multiple strikes on sand. So I will probably stay with it. What sort of clearance do you suggest either side of the board so it is less likely to jam?

Regarding the mast, yes I was just thinking of downforce, but lateral forces on the mast would be significant especially with a big sail attached to it. I have the plans for an 11ft Heron dinghy that I was going to build with a deck stepped mast, and it has quite an elaborate structure under the deck to support the mast, not just a post under it. So yes, I'm convinced. Thank you.

I must be getting keen, I've started clearing out my shed to start building.

Thanks for your advice, it's helped me get started.

Ian

[Jaysen]

Jacques should have designed a 1/8” lateral and 1/2” longitudinal clearance (1/4” and 1” respectively). He and anticipated some noise damping in the longitudinal. Just build to the plans and you will be fine.

I appear to still be in my youthful stages (50) because I can seem to be under sail without trying to get another 1/2 knot out of whatever hull I’m in. I won’t be sailing much anymore but I don’t see that changing too much any time soon.

Give your 2x the space you think you need. I built outside, under a tarp. The number of times I felt cramped due to a tool or material proximity was ridiculous. I’m don’t know how these guys build in small spaces.

[Brocky]

Thanks for those guide measurements. I'll certainly do some outside to reduce the dust, but my shed is a fair size so should be ok.

Nothing beats a cat for sailing thrills (and spills), it's great fun sailing hard and pushing the limits, that's what makes it such fun. If you didn't get enjoyment out of it you wouldn't put up with all the bad bits, eh.