Trying to design my own cat.

[Guest625101138]

Dragging a transom is slow, turbulent and looks very ugly - that is why rocker is introduced in the after sections (often more rocker than the forward bow to amidships sections) to get the transom clear. Canoe sterns that drag are not quite so bad as wide transom designs - but dragging any transom, repeat, slow and ugly. Most boats are overloaded hence more transom dragging - then it becomes a Catch 22 situation, more weight, more drag requiring even more rocker to get the overloaded transom free, then because of more weight and designed in more rocker to counter weight, more pitching. Round and round in circles we go. The only solution is to have a clear view of what you want and then stick religiously to it, no compromising, no excess weight and junk carried aboard, get the drift? Weight is the dirty word. Keep that down and your boat will sail sweetly. That is why everyone here has been telling you you can't carry a big crew on your small boat. And no matter what you say, if your boat sails like a dog, you and your friends will not be happy. Have I repeated myself? - quite possibly.

Gary
I can relate to most of what you say. The point on the canoe stern is incorrect though. Think about, if it was such a detriment to performance you would never consider having a bow deeper than the waterline. Canoe sterns offer the most efficient form for energy recovery.

If you want to see efficient hulls then take a look at rowing sculls. They offer the best speed for power input irrespective whether they carry 2, 4 or 8 rowers. No flat raised transoms amongst this lot.

Taking some logic from your points above and the correct understanding of a canoe stern you can deduce that an overloaded hull with a canoe stern will be more tolerant of the overloading than a hull with a wide flat transom. Maybe Richard is onto something.

Canoe sterns have recently been rediscovered with power cats so it could be Richard will set a new trend amongst sailing cats.

The older cats with canoe shaped were built in a time before composites were well developed and sails could develop the efficiency they can today.

Rick W

[masalai]

See Richard, we got all sorts of advice coming - all because you typed - - whatever - - a catchcry or two occasionally does work wonders.... and I bet there will be more advice coming....

[Guest625101138]

See Richard, we got all sorts of advice coming - all because you typed "....." - a profanity or two occasionally does work wonders.... :D:D:D:D:D:D and I bet there will be more advice coming....

I am not responding to the profanity. In fact I was put off by it in a public forum no matter how it was disguised. Just felt obliged to put the case for canoe sterns on efficient hulls.

And don't take that to mean I do not like raised wide transoms on sailing boats. I do not have enough experience with either type in a range of conditions to offer advice from experience.

I know a wide stern will power better above hull speed but I figure that is not where Richard wants to operate. He can buy a kite board if he wants to go fast under wind power.

Rick W.

[Gary Baigent]

Rick
The Australian C Class Quest cats had canoe sterns but even compared to today's designs in higher technology materials, those boats were still very light - and they went through the water with very little disturbance - but remembering English criticisms of that period, they observed the Aussie boats pitched too much. Now those Quests had very little (to almost zero) rocker if I remember correctly, the hulls were race boat fine and yet they did not handle UK sea conditions as well as the broader transom MacAlpine-Downie designs. Going further back with fine (asymmetric) hulls, canoe sterns were the CSK designs from Hawaii - and they had considerable rocker - and they pitched badly also in certain sea ways. Your point of canoe bow and immersed canoe stern being fast on rowing skiffs: okay, correct but I personally do not like deep bows on sailing multihulls - they can overcome or tend to affect steering if the bow is immersed too far - but I accept your point of the canoe stern (and pointed it out earlier) being less of a problem than a dragging transom design. Why am I writing this round the merry-go-round stuff - as long as it works, there are no rules. But the operative word is "works" - and the broad, asymmetric sterns of Richard's design are going to turbulate.

[Guest625101138]

Gary
Agree that some flat sections fore and aft will help with damping pitch. I think there is good prospects for horizontal foils to do it more effectively.

I have not followed how the asymmetric hulls developed. I can understand the value above the waterline, been on a beach cat with asymmetric hulls and have played with asymmetric model hulls but I do not know what Richard aims to achieve.

Rick W

[masalai]

Rick, firstly thanks, - - - I think Richard, on an earlier post, implied, it was to get maximum effective beam on a 10 ft overall width build - if I have read and understand correctly....

[Richard Atkin]

Been away for a bit. Thanks for the replies everyone.

Just to be clear, I haven't done any analysis on the hulls I have drawn. It's just a sketch. When I said I was conclusive, I meant that there was nothing more I wish to conclude without the help of a NA. The only big unknown remaining for me is the final hull shape.

My proposed hulls are asymmetric on both the longitudinal and transverse axis.

1) The longitudinal asymmetry below waterline, is just a result of the flaring of the tunnel walls, and the desire to keep a wide floor to stand on. I thought a bit of longitudinal (hope I'm using the right word) asymmetry shouldn't hurt too much. In fact, it might help to stop the boat slipping sideways when it is heeling slightly...thus minimising the need for dagger boards.

2) As for the asymmetry on the other axis (wider stern and narrow bow), this was just a wild guess, based on comments made by Gary, and stuff I have read about canoes. As I mentioned in a previous post, paddled canoes go faster when the max. beam is slightly aft of centre. Couple this with the notion that a thin bow and fat stern will help the hull to negotiate waves, then the obvious experiment is to try it out. However, modern asymmetric canoes are powered by the alternating motion of paddles, so the reasoning for their shape could be irrelevant to my design.

3) There are two reasons for the asymmetric flaring above the waterline. The first reason is to maximise the BWL, as Masalai pointed out, within California's 10 ft trailer restriction. The second reason is that I wanted to devote the flaring to the tunnel, to maximise the boat's ability to lift up over the tunnel waves, which will be bigger than the waves on the outside. This is important because my clearance is little more than a foot. The centre of gravity must be kept low, the BWL must be kept wide, and the bridgedeck pounding must be kept to a minimum.

Gary has pointed out that the fatter stern will create turbulence, so the elusive equation is: total hull drag vs performance in waves. Remember, I am not trying to design a competitive boat. This performance equation is impossible for me to work out at this stage. This is why I have shown all my guesswork.....to see if people say "Richard, you're an idiot"....or "Richard, it is definitely worth testing". Good to see it hasn't all been "idiot".

Rick, do you feel like whipping up a visual suggestion? (I like watching your sketches popping up here and there in other threads). If not...I understand. I just thought there's no harm in asking. Obviously, I would need to take into account your lack of knowledge with waves. Perhaps I, or the NA will need to build and test two models - one similar to mine and one similar to Gary's.

Just one other thing....those of you who feel like you are repeating yourselves....please don't think I am being ignorant. I never skip-read anyone's comments.

[Richard Atkin]

I think I was supposed to say vertical axis...not longitudinal...sorry. You catch my drift.

[Richard Atkin]

Bloody hell, I keep getting mixed up with the different axis names, and axis directions. Again, I apologise if I have got it wrong.

[masalai]

Don't worry about it, you know what you mean and all the following posts will identify and clarify things hehehe (masalai is in a cheeky mood again/still)

[Fanie]

Actually a transom is a nice thing to have if you hang a little outboard on it. Most sailboats have a stern suitable for an outboard, the shape of it doesn't have to cause any drag and you don't have to sacrifice hull shape either. You just add the outboard since it is the secondary propulsion for emergencies. So what if the outboard isn't going to be as fast as it can.

One thing you may take into consideration regarding the amount of displacement your hulls have. Let's say you have 1000kg of total displacement. You load your stuff and the crew gets aboard, so let us say you have 400kg of added weight.

When you travel at speed (doesn't have to be fast) and you approach a wave, then the weight of you vessel as well as the added weight has a tendency to resist any sudden movement in any other direction than what it is going into already. The result is that the hull may dig into the aproaching wave, and what gets it out and over the wave is the force of the residual bouyancy the hulls may have.

If you travel down a wave and you now have to go up the next, if it is steep, the change in direction may double the weight of the whole boat, and cause the boat to sit in the water much deeper untill bouyancy has overcome the change in gravity. Don't know if this makes any sense. It is easier to catch a brick falling from two feet up than cathing one from ten feet up.

I have seen you mentioned the width it has to be to be towed legally, that is limited (I have the same problem). This leaves only two options, you could make the hulls higher... or you could make them longer... or a bit of both. Longer hulls are faster than short hulls - nothing to do with racing.

The length of a towed object is not as much limited. If it's very long it may require a longer car port or garage. I recently saw a small truck that was very long. Closer inspection I saw it was one they used to transport gliders in.. you know, those aeroplanes without engines :rolleyes: Nobody thought it was funny, even longer vehicles exist. So towing a longer boat is not a problem.

Making the hulls high could cause a worsoning effect on pitchpolling. I always consider the worst case in both directions, this gives one a feel for where you are with what you have... from too high to too low, and then what am I prepared to live with.

A boat will always try to go right through a short choppy wave.

BTW, my hulls have flat bottoms for waling on also. It is terrible to walk on a round surface.

[Richard Atkin]

Hi Fanie.

I have already thought about that stuff and came to a compromise. The BWL is less than half the length. If the hulls were much longer I would be starting to get into weird proportions and I would be a bit concerned about handling problems. Also, I'm not sure how a long narrow tunnel would effect waves in there. Could be a nightmare.

I accept that 6 people on a boat my size is probably asking too much in choppy conditions. If I can have a boat that can take a big load on a lake, and take a smaller load in the chop, I can live with that. It doesn't have to be the perfect boat for all occasions, as long as I get some good adventures from it. As I said, I might have two boats.

After reading Gary Baigent's comment again about the stern turbulence, I think he was referring to the flow being faster on one side of the hull than the other. It would not be hard to make the underwater hull symmetrical and maybe it would be good to give it a knuckle...maybe not. Maybe I will have rocker and transom. Maybe not.

I think people are probably getting tired of this boat!!

Well...I've learnt a huge amount from all the generous people in this forum (including you)....and especially Rick Willoughby. I've also learnt a lot about California real estate, marine conditions, marina rules, beach rules, road rules etc etc etc. When I am there I will talk it through thoroughly with a naval architect and I will be able to understand what he is talking about.

[Richard Atkin]

The photos below show the cave, and the view from inside the cave that I lived in for 9 months when I was 'camping' in Sydney, about 8 years ago. I had run out of money, so technically I was homeless (without the whiskey bottle). However I could have gone back to NZ any time I liked, so I was not desperate. I just really enjoyed living there!
It's a tiny cave on a small cliff face at Tamarama beach. The nights were usually very hot, but I got used to it. I slept under a net to keep out the mosquitos that lived in rock pools around the cave. It was actually very comfortable.
I wasn't concerned about being stabbed because the area is quite safe.
Only my shampoo was stolen. Might have been another homeless dude!
I used public toilets and showers (cold) nearby.
After a while I started to make friends in Sydney, and could have moved out, but the cave gave me privacy and tranquility when I wanted it....so I kept sleeping there. Weird huh?
Every morning I would be woken up by the sun and I would roll out of my bed and jump straight into the ocean. The water was always warm. I felt like a cave man.
I ate food from christian charities. The food was the surplus food from restaurants - stuff that was made for the previous night. Absolutely delicious...and there was always too much!! Sydney-siders are extremely generous to the homeless. I never considered myself homeless, and at first I felt a bit guilty about eating the food....but after a couple of first class meals, my guilt disappeared. My stomach became judge and jury.

It was an interesting time. Australia has beautiful long summers. If I couldn't live in Los Angeles, Queensland was my second choice. I spent some time there too (in a house).

[catsketcher]

Hello all,

Richard, for a day cat going narrow is not a problem. You have to be mindful of the considerable weight the crew will have and the large effect this will have on stability. This means you can go for a narrow cat and use crew weight.

In fact the second cat to sail around the world - World cat - was a CSK design and they were very thin in todays language but excellent boats. The early off the beach cats by CSK like Manu Kai were about 3:1 length to beam and fab boats.

In fact if an assymetric hull, thin, double ended cat is what you want you must read about Rudy Choy, Woody Brown and the CSK mob. They designed and sailed great cats starting over 50 years ago. So Richard - get onto Amazon and buy a copy of "Catamarans Offshore" by Rudy Choy. It will serve you very well. A slightly smaller Manu Kai may be a great boat for you and you will be doing your bit for keeping multihull history alive. In fact Rudy Choy and Woody Brown built a half size -19ft - version of Manu Kai - the first modern cat. You may be able to get lines for it on the Yahoo groups CSK forum.

Remember to stand on the shoulders of the giants

Phil

[Fanie]

I can see why you had to roll out of bed :D

[Richard Atkin]

Phil, that's very interesting. Just when I thought I've gone as far as I can, something new (old) comes along. I'll check it out. Thanks.

[Richard Atkin]

Fanie, yeah there wasn't much headroom....always dry though, even during a couple of big storms. If I wanted headroom, I would sit on the boards you can see beside the bed. I would put a mirror and my shaving stuff on the ledge that hangs over (top of pic). A very well designed cave :D I had a few caves to choose from. That one was the best.

[Fanie]

Something like the bridal suite :D He he... not much headroom. Sounds a bit like Richards cat :p

[rayaldridge]

Richard, with my little beachcruising cat Slider, I designed a little more rocker into it than would be appropriate for a speed-oriented boat, but I needed to do it in order to get sufficient displacement from my fine hulls.

This means Slider is probably slower than she could be, but on the positive side, she tacks as easily as a monohull, and I attribute that at least partially to the rocker.

Ray

http://slidercat.com/blog/wordpress/

[Richard Atkin]

I have decided to buy a monohull. It will be better for dealing with California's choppy and light air conditions, with large payload, and easy to rig and slide onto a trailer. It will be big enough to take 8 adults and gear.
OK its going to heel, and it won't feel like a cat, and I won't beach it, but it will still be great fun to sail to Catalina island and survive the trip. Definitely don't want a big cat.

If I have the storage space, I will still get my 'canoe-cat' drawn up and built, but it will be for sheltered waters only. It will probably be about 25 ft long, 10 ft wide, double-ended, no rocker, symmetrical below the waterline, and a whole lot of fun.

This post is not exactly fascinating, but as the thread is about to die again, I thought I should just disclose my final final FINAL decision. Thanks to everyone for helping me get to it.

[rayaldridge]

Richard what kind of trailerable monohull is going to be big enough to take 8 adults and their gear to Catalina?

Ray

http://slidercat.com/blog/wordpress/

[masalai]

something like a "Court 750" I raced in in WA....?

[Richard Atkin]

um....all the trailer sailors I've looked at so far have 5 or 6 berths. Is there one that can take 8 adults?? Or are there towing restrictions? Do I have to rip out all the furniture and throw the engine and anchor overboard?

PLEASE tell me there is a trailable monohull that has a decent payload.

[masalai]

On the 750, all the bunk cushions were removed and swags rolled out to sleep around the camp-fire, after it served its purpose as cooking place....

[bobg3723]

Hi Richard,
I've been catching up with your past posts and a thought occured to me. Correct me if I'm wrong whether these fit your requirments:
1. You want to be able to sleep at least two adults and a couple of munchkins.
2. Not too concerned about performance for six individuals mucking around in.

Howza bout a trailerable cat/tri switch hitter to suit one or the other?
Two hulls for point #1. A slip-on third hull for the gang on point #2.

With aluminum tubes already designed for in the plans for this cat, I'm sure you can attach a removable central pontoon...er hull for a party barge to leasurely cavort around in with a crew of six or seven. Here's a before and after shot of what a 'Duo900 Frankenpontoon' might look like that I've butchered up in a paint program for you. And here's a link to the designers website.
http://www.ikarus342000.com/DUO900page.htm

Regards,
Bob

[bobg3723]

Heck, even a 9 meter water weenie for the third hull would be even more portable. Just inflate and pile on the bodies.:cool:

Cheers,
Bob

[Ikarus342000]

Hello

As designer of the DUO 900 are strictly against any changes on this design.
A-symmetrical catamarans are very weight sensitive. This boat is meant to stay light. So do not fool around with the design without consulting me.

Bernd Kohler
K-designs
France

[bobg3723]

My apologies Bernd. Thank you for correcting my foolish lack of understanding of the Duo900's design parameters.

Sincerly,
Bob

[bobg3723]

Hypothetically speaking as it relates to symetrically shaped hull forms, could not the bridgedeck beams of a catamaran be so designed to accept a third hull to function as a degraded performance trimaran? One might wonder why bother, but the idea is to take a high performance catamaran of light displacement and modify it to accept more displacement in trimaran mode. This might come in handy for when a group of extra passengers might be accomodated onboard on a family outing 'on the lake' with the increased displacement capacity of the added third hull that would normally be beyond the safe operating limits of the light displacement cat alone. Is this paradigm wrong?

[rayaldridge]

A good tri will have much wider overall beam than a cat of similar length.

Of course, if you built new beams, as well, it might work. This is the essence of the kits that were or are sold to convert a beach cat into a tri.

Ray

http://slidercat.com/blog/wordpress

[bobg3723]

That part about having to increase the beam overall makes things not too much more complicated to excecute, on the face of it. But on further examination, the added expense of another set of properly engineered crossbeams along with the added central hull does force one (me, in particular) to ponder whether it made more sense to stick with a higher displacement design from the very start. A cat to tri retrofit does stray from the KISS principle....

Note to self:
What I learned today: Try not to make a silk purse out of a sow's ear.:( :D


BobG

[Richard Atkin]

Hi Bob and Ray and Mas and French dude Bernd

I've given up on the whole idea of making a small heavy cat for choppy seas. No matter how you build it, the reliance on lateral stability means it will always feel like a washing machine when sailing in 2 or 3 ft waves, especially in light wind...and that is very typical conditions in LA. The 'gliding cat feeling' that I enjoyed in the past, was always on a very flat sea. It's taken me a while to wake up to this point.

I realise that a monohull with that 'stupid' big lead keel dragging through the water is not such a bad thing after all. I won't say no to the nice big cosy cabin too.....and slightly better payload. I will enjoy the 'mono feeling' instead.

I'm looking at pocket cruisers at the moment. As much as I like the fresh open deck feeling of a small cat....I am also attracted to the opposite. Super-cosy, very strongly built offshore pocket cruisers appeal to me (even though they are incredibly slow). A good one will get me and about 5 other people through really shitty conditions....so it could broaden my sailing experiences. Maybe I will develop an appetite for bad weather.

I will have two boats if my LA property and my bank account will allow it. Mono for the rough, and cat when it's flat. That way I get the best of both worlds.

[rayaldridge]

I feel the opposite way, Richard. When it's rough, I like the idea of being aboard a boat that won't sink, and doesn't beat me up until I get too tired to make good decisions.

One thing I haven't understood about your design efforts is your urge to take so many people sailing at the same time.

Ray

http://slidercat.com/blog/wordpress

[Richard Atkin]

Ray,
I agree the sinking factor is a big negative. But I have no intention of sailing from one country to the next.

Not sure why you think a monohull will beat you up any more than it's multi equivalent. Monos are less weight sensitive aren't they? More immediate reactive buoyancy? Surely that makes them better for dealing with large wind waves, if we are talking about small cruisers. When a cat is big enough, the waves are not so much of a problem...but I don't want big.

As for so many people...
a couple is very romantic,
4 people is like inviting your neighbours over for a cup of tea,
6 people is a small gathering...the boat starts to feel very lively, but it's not really a party
8 people makes the boat feel closer to a party...you start to get multiple conversations, and couples can be with each other away from the crowd without looking like snobs.

I want all those options. I like camping with many people.
Up to 6 is more realistic though

[Leo Lazauskas]

[QUOTE=Rick Willoughby;219650]Gary
If you want to see efficient hulls then take a look at rowing sculls. They offer the best speed for power input irrespective whether they carry 2, 4 or 8 rowers. No flat raised transoms amongst this lot.
/QUOTE]

Yabbut, the speed of the hull changes very dramatically during a rowing stroke, so a transom isn't a very good solution. You aren't comparing apples with apples.

Leo.

[Guest625101138]

[QUOTE=Rick Willoughby;219650]Gary
If you want to see efficient hulls then take a look at rowing sculls. They offer the best speed for power input irrespective whether they carry 2, 4 or 8 rowers. No flat raised transoms amongst this lot.
/QUOTE]

Yabbut, the speed of the hull changes very dramatically during a rowing stroke, so a transom isn't a very good solution. You aren't comparing apples with apples.

Leo.

Leo you would need to provide more information for me to get your point. I was defending the efficiency of canoe sterns against comments inferring their inefficiency.

Are you implying that if a rowing scull could be operated at fixed speed then it would have a wide stern? I am interested because my pedal boats operate at fixed speed - virtually continuous thrust.

Rick W.

[ropf]

I want all those options. I like camping with many people.
Up to 6 is more realistic though

Richard, don't give up - just start from the right end! Buy a small boat, mayby a sailing dingy with a tent.

All it need is to keep you afloat and allow some kind of movement. Dont care abot speed, pitching, pointing or whatever.

Then go out and sail for some months. This will change your mind completly about what you want and what you need. Always look out how the different boats behave under different conditions.

Now you have a idea what kind of boat you really want as well what all the design numbers an computer generated pictures mean in practice.

You are ready for the next one. You will find boats of all classes and styles in the second hand market and usually cheaper than building by yourself.

You are now sailing again. In the evening on anchor you may start to draw your dreamboat.

The only place to design a boat is a boat!
good luck
ropf

[Richard Atkin]

Ropf,
The only boats I have ever sailed are the P class, Phase2, Sunburst, and hire cats. I did many years of sailing when I was a kid. I am not completely new to the ocean, but I have never sailed a larger boat.
I agree with you though....I need to start sailing again. Getting past the worst of winter now, in Wellington, I'd like to get on the water soon.

[Butch .H]

Richard get the mono cats suck!

[Richard Atkin]

NASA designed a space shuttle with wings....the worst concievable design for re-entering the earth's atmosphere. They did it because they thought that the idea of picking up a little capsule in the ocean 'sucked'. They might tell you that the wings were for war strategy reasons, or national security, or something like that....but I think they just thought the floating capsule 'sucked'. :D
Now they have gone back to the more sensible design. Well, they are trying to, but they keep getting confused between imperial and metric.

[rayaldridge]

Ray,
Not sure why you think a monohull will beat you up any more than it's multi equivalent.

Well, I'm relying on my experience offshore in both kinds of boats. Although there are legitimate reasons to pick a monohull over a multihull, comfort is not one of those reasons. I think any fair-minded person who has sailed on both kinds of sailboat in rough conditions will admit that multis are a lot more comfortable.

This is the point in the discussion where a monohull true believer will usually chime in about how intolerable the quick motion of a cat is compared to the slower motion of a monohull. That's nonsense.

The two main reasons that monos are less comfortable than multis are:

1) Monos heel. It's been substantiated by the U.S. Navy that heeling leads to a swift decline in crew efficiency. It's hard to live in a room that's constantly oscillating violently.

2) Monos roll. This is the motion that leads to seasickness for most folks, which is a debilitating condition. The slow sickening roll of a mono in a seaway can be gotten used to, of course, but usually not on a day trip to Catalina. It generally takes several days. Even after you get used to it, it's still an exhausting exercise to deal with, hour after hour, day in and day out.

I'm not sure you're thinking this party concept through. Try having a party for 8 in a broom closet, because that's about how much room you'll have on a trailer sailer. If a party in a broom closet is still fun, then you have extraordinary friends.

My opinion is that it's far better to have the party on the beach after the sail. When you're sailing, immerse yourself in the sensations of sailing, because that's really why you're out on the ocean in a sailboat. There are more comfortable ways to get to Catalina.

Ray

http://slidercat.com/blog/wordpress

[Richard Atkin]

Hi Rick,
I have been looking at your solar boat design. It has features that contradict Gary Baigent's advice to me. Your hull is not only double-ended...the stern is actually thinner than the bow. I'm guessing this is not ideal for pushing through choppy waves. Maybe your design won't pitch badly because you don't have a big tall rig, and your boat is very light. Maybe it doesn't matter if your boat pitches because it is not relying on sails. And maybe it does matter because the flat vertical face at the stern will cause a lot of drag if it keeps burying.
Maybe you should go for a wide transom just to make it more sea-worthy. Have you done any assessment on how it will perform in waves?

[Richard Atkin]

Ray, I take your point, but I think you are referring to catamarans that are demountable. I think my little cat is going to roll like a small planing mono dinghy. It won't fly like a Hobie. I am keen to get it built if I can. If it sucks on the open sea, it should still be fun on the lakes.

I'm not concerned about many people in a tight space. It's never been a problem for me before :D Have you ever been squashed in a tent with many others? No big deal. If you have a big space, but people are still squashed together, then I can see your point.

[Fanie]

Hello Richard,

A feller that looks at mono's from cats is confused... frustrated and at witt's end :D

Have a look here -

http://www.go-catamaran.com/avent28.php

This is a demountable boat that is designed to handle up to 8 people (sharing :D) and this is also the thing I had in my minds-eye that you were looking for.

It is the right size, easy to handle and would be safer than a smaller cat.

[rayaldridge]

Ray, I take your point, but I think you are referring to catamarans that are demountable. I think my little cat is going to roll like a small planing mono dinghy.

Why do you feel that way? My little cat Slider doesn't roll at all, and is highway legal, with fixed beams. Of course, to be fair, she's only 16 feet long. Four adults would overload her.

Ray

http://slidercat.com

[Fanie]

I've been trying to get Richard to go for a spin on someone's rig so he can get a feel for it, but no, he would rather theorize about the capabilities and how it would feel on the water.

My suggestion is still to go on two or three different size boats and cast your vote on what you want then. I just bet you'll fall in love with something like I posted in my previous thread.

You can always excersise your voice singing on the boat. Worst that can happen is the guy can throw you overboard :D

[ropf]

I am not completely new to the ocean...

Richard, i didn't want to piss you, sorry. The point is, you enjoy your snuggy tent because it is dry, warm, it d'oesnt shake (exept to an earthquake), you can always go out and erect to your full size... and the tent doesn't need to sail windward.

There are some trailerable cats able to carry weight of 6-8 the people. But after some hours you will hate them. And of course fully laden they don't sail well. So i think rayaldridge is right - coose a boat for quick sailing, carry some camping equip and make the party on the beach.

It's mutch more fun if your friends have their own boats. You can sail in fleet or even do a matchrace to an quiet beach, enjoying the campfire as well the snug and dry tent. A sailing boat serving as comfortabe transporter as well as party ponton will be *very* big.

with regards ropf

[Richard Atkin]

Hi All.

I'm not at my wits end and I'm not pissed off, and I'm not confused. Just still trying to make up my mind.

Ray, I was thinking of what it would be like to sail a small cat through 2 to 3 ft waves for 12 hours, getting from Long Beach to Catalina. I imagine it would become tiring, and my adventurous shipmates might lose their enthusiasm.

I don't want a demountable cat, Fanie. Lots of reasons. One of those reasons is that I want to rig a boat in 10 minutes.

I've been thinking of another idea. A wide flat monohull with no ballast. The crew of 6 could sail it like a dinghy, using crew weight for stability. If it capsizes, a large carbon fibre ladder could be attached to the centreboard well. Some people could climb the ladder, which would create a very effective ballast for righting the boat. The hull would be flat enough to provide some initial stability.

A boat like this would be extremely light and strong, and ideal for dragging up on to a beach. It would provide better accomodation than a cat, and would be much better for handling the weight of 6 adults.

I haven't got time to pursue this idea at the moment, but it might be a good option.

Cheers

[masalai]

For that 12 hour PLUS sail?????? "....cat through 2 to 3 ft waves for 12 hours, getting from Long Beach to Catalina...." - the song says "...27 miles across the sea..."

[bobg3723]

Hello Richard,
Twelve hours back to port, sounds like an an Avalon to San Diego leg at arond 60 nautical miles or so as the crow flies. At monohull speeds, that sounds about right.

Regards,
Bob

[Gary Baigent]

Richard you turncoat
Maybe you could consider one of these: the Cox's Bay skimmer, 5.5 x 2.25 metres, free standing wing masted schooner rig, water ballasted (when you need it) 120 kgs boat weight empty (maybe) and could carry 5 people - but it is a day boat with however two mean quarter berths forward. Now who is the turncoat.

[bobg3723]

Richard,
For what it's worth, my uncle once took his 17' Hydroswift I/O powerboat (this was in the 70's) across the strait to the Channel Islands, chaperoned by a friend following in another powerboat.

He said he'ld never do it again. The way he put it sounded like it got hairy out there for him. He didn't explain exactly what, but the Hydroswift was not up to the job.

Regards,
Bob

[Richard Atkin]

Hi Mas,
yeah, it always takes longer than people predict. Get caught in some chop and the wind is dying.....

[Richard Atkin]

Gary, I am very interested in that general design. You've got me more excited about the whole idea of doing something like that. Maybe just a tad bigger, and a proper, but small low cabin. 3 couples so no-one has to leave the wife behind.
I still want to talk to you in future when I am ready to start designing or purchasing the final design. Maybe you would be interested in designing a new one?

[Richard Atkin]

Bob,
power boats have the wofting stench of satan. I don't like them :D

cheers

[bobg3723]

Richard,
I agree wholeheartedly. Dinosour juice is noxious. :(

But I think the expected sea conditions out in the Channel Island straits in differing seasons will no doubt guide your design accordingly. I prefer a multihull myself (to me, speed means having more time to spend frolicing at my destination), but a cleverly designed unballastesd lightweight daysailer with the displacement capacity for six souls on board and their gear that's managable to portage up the beach is of interest to many of us. I don't feel designing such is too tall an order to achieve. But I'm no naval architect. Far from it. :D

The Channel Islands can be a great way to get away from it all that's also accessible by ferry and you can also get groceries in Avalon. I guess it's our version of Fraser Island. Getting there and back is not too long a journey for a two or three-day weekend.

We all want you to blaze the trail, man, and write a song about the adventure! :D

Cheers,
Bob

[Gary Baigent]

Richard
The CCS design could easily be enlarged to 6.5 metres, in fact my Belgian sailing mate is talking semi-seriously of one - but maybe it is just Belgian beer talk (which is the best around, by the way). He has done the mini-Transat in a 6.5 (came fourth) and likes the idea of a lightweight version. But he wants a single rig; that is not a problem.
However I like the low 6.5 metre double rig on the 5.5, a lot of sail area down low and should make the boat plane like a crazed looney reaching and running. Beating to windward, the after rig can be cranked to windward to get it out of the disturbed air of the forward rig - and then centred on other points of sail after that.

[Richard Atkin]

Thanks for the words of support, Bob. I look forward to blazing the trail! :D

[Richard Atkin]

Gary,
I am almost sold on a Skimmer 6.5 already. The 5.5 looks well built. It looks strong. I like the stayless wingmast double-rig idea. All that power without the heeling. I don't mind the compromise with windward performance.
On a freak day....it might be possible to plane in a straight line for the whole 22 miles....WOW. That would be amazing. (well....I can dream).
I know that glass over ply is strong....but what is the chance of water getting in and making the wood rotten and heavy? Would it be a bad idea to make the boat fibreglass foam sandwich? And what if the foam absorbs water....is solid GRP too heavy?
I asked about this another time, but I didn't get an answer about the reliability of different building techniques. I don't want to build it myself.
I want a professionally built, long-lasting, low maintenence boat if that's possible.

[Gary Baigent]

Whoever started up the weird fantasy of water soak age into closed cell foam was inhabiting Pluto, and the far side of Pluto at that. Swerve away from that nonsense. Similarly, two coated epoxy and glass/carbon over ply will not soak water either. As for strength, epoxy/glass over thin skinned tensioned ply is a very good, low tech and therefore reasonably priced way of getting a light boat that will last probably as long as you will. However if you plane at 15 knots into offshore California rocks or reefs as in your dreams .... well, few materials can handle that - maybe steel .... but then that is a hopelessly heavy material for small boats. IMHO laminates of solid glass is also too heavy - but foam/epoxy glass/carbon sandwich is an excellent and lightweight way to build - but more expensive than the bent ply combinations and also slower. You can have a tensioned ply hull formed in less than a week - but it is more art than the established way of boat building and therefore does not appeal to the average conservative mariner. Check out the Gougeon's book on this subject.

[bobg3723]

Gougeon Brothers is a must have in anybody's collection. In fact, all the popular plywood boat building books on Amazon dot com for that matter.

Gary,
You Kiwi's have a world of experience traversing some truly hairy seas between Kiwiland and Oz in skinny multi's. Give us your assessment of what would be the minimum requirements for a daysailer to sail across the Channel Island straits in either a mono or multi, if you would please? :?:

Regards,
Bob

[Gary Baigent]

Bob
No way am I going to give advice on this subject - I haven't crossed the Tasman in a light multi - but have done some very wild coastal sailing here in a Newick 36 with foils named Mokihi (Maori for a lightweight raft) - and also on some light cats and tris. The Newicks are not that light (but still light enough) but they are real sea boats that do everything well, not nose bleeding top speed but fast on all points of sail - you cannot go wrong with his above 30 foot designs, again that is just my opinion.
This subject (light multis offshore) can be very controversial - but people have crossed seaways in all sorts of multihull craft.

[bobg3723]

Gary,
What do you know about some of the Malcom Tennent designs like his Great Barrier Express for example?

Bob

[Gary Baigent]

I used to have an altered (by me) Tennant 32 foot Bamboo Bomber named Supplejack - there are some jpegs of it in the back blocks of this site (Pahi cat). And I was around when the first Great Barrier Express (Richard Pilkington's) was launched. They are excellent designs. The local multihull club has introduced an 8.5 class based on a one or two steps-up-the-ladder performance version of the GBE - and the class is strong with fervent loyalists keeping the class very much alive. IMO they did not go far enough into introducing a more performance oriented class - but I'll say no more having incensed them enough already. The new 8.5's are very quick especially Dirty Deeds. The GBE's have to be heavily modified to keep up - therefore any original models have become almost obsolete for racing. If you can be bothered ploughing through this stuff, here is a bit of the early history of Tennant and Given designs:

24. open wing deck design
AUSTRALIAN MULTIHULL DESIGNER Lock Crowther had appeal in Auckland with some Kraken 33 and 40 racing trimaran designs plus his racer/cruiser 40 foot catamarans being built here. Local multihull designers like Young (still interested despite early bad press), Ron Given and Malcolm Tennant had gained recognition
few larger cruising catamarans. Given designed his own 36 foot lightweight racing catamaran Tigress in 1971, an open wing deck design like an enlarged Paper Tiger; it looked extreme and observers were impatient to see it line Given, Tennant had drawn larger designs but his examples also took time to build; multihull sailors invariably had little money and usually built their own yachts. Tennant had earlier built a few Australian B2 Class Stingray catamarans and tried unsuccessfully to get the class established here; then he designedcruising 36 foot catamaran named Vorpal Blade – but the owners took a decade to construct the boat. In 1972 he published his ideas on a 9.8 metre high performance wing masted catamaran he named Bamboo Bomber which had flared and stepped hull topside shapes with blister cabins fore and aft of the central cockpits; the boat looked a bit weird and spacecraft-like and nothing came from it. However in late 1972 I asked him to redraw the concept, clean up the lines by discarding the stepped cross section hull shapes and the result was an attractive and very modern (for those days) racing design – two examples of which began construction soon afterwards. Both yachts Supplejack and Superbird were launched in 1977 and were built in tensioned ply like large versions of the (then) Olympic class Tornado. Both wing masts ended up heavier than intended and made the light platforms pitch in some sloppy seaways and light winds – but given sufficient wind power to drive through waves, both yachts were very fast. Continuing loosely to the Bamboo Bomber theme he had first shown in Sea Spray, Tennant drew a clean looking, aft cockpit, blister cabin 8.5 meter racing/cruising catamaran named Great Barrier Express - which Tennant said was inspired by a Hawaiian beach cat developed Mickey Munoz. Compared to the second version of Bamboo Bomber, Great Barrier Express had more rocker in hull underwater profile (for easier tacking) and sloping transom hung rudders which could be lifted, whereas Bamboo Bomber rudders were fixed down and under hung. The latter rudders also sloped and had skegs – retrospectively bad mistakes - as too was the sloping GBE rudder design – which tended to lift the sterns and push down the bows when sharp helm movement was made - later versions had vertical rudders to counter that problem. The original Great Barrier Express built and owned by Richard Pilkington was launched in early 1977 beating the Bamboo Bombers into the water. The cat had sensational speed and quickly became known as a giant killer; it was also instantly popular and went into production at Pilkington’s boatyard.
The original group of Given, Tennant and Fay had broken up by the early 1970’s; Given and Fay, who had collaborated on the Paper Tiger had split over disagreements with the design when it went into production which culminated in a court case. Then Tennant’s Great Barrier Express and Given’s Gulf Tiger competed for the quite lucrative fast cruising/racing catamaran market – and earlier friendship quickly evaporated. The Great Barrier Express hull was based closely on tensioned ply Bamboo Bomber and was round bilged while Given’s Gulf Tiger continued his Paper Tiger theme with hard chined hull cross sections. The GBE was more
performance oriented with the elliptical shaped cross section hulls having less wetted surface area than the flat sided, chined Given design. The after sections of Gulf Tiger were almost flat like a planing hull dinghy. The two also differed in rig design; Given aiming his Gulf Tiger to the average sailor by keeping the rig simple with a non-rotating mast and similar (although spreaders were much wider) to bendy, fractional setups of New Zealand dinghies – while Tennant drew a rotating mast and a high aspect ratio B Class catamaran-type rig for his design, making it higher performance and requiring some extra skills to handle. Given supporters were adamant that large spinnaker carrying Gulf Tiger would be the faster yacht – but were proven wrong.
Many club members considered open wing deck, lightly constructed multihulls outrageous and that these designs were nothing more than overblown day sailers with afterthought accommodation – which was correct. Duncan Stuart, who owned Kraken 40 Krisis, cracked, “If you close your eyes when on Supplejack’s deck and step onto the tramploline, you can’t tell any difference.”
With the success of the Great Barrier Express design Tennant was pressured by people with a non-surfer-type philosophy into making a larger hull design with more accommodation. So Tennant drew the Turrissimo version which was more inflated in hull crossection, higher wooded and slightly longer than the GBE. After the sleek lines and minimalist earlier surfer inspired boat, Turrissimo appeared gross to some eyes but Tennant had listened well – if people thought accommodation more sensible than balanced aesthetics, then he was going to give it to them – and fat Turrissimo turned out to be a faster sailer than its appearance belied.

[Gary Baigent]

Sorry I messed up some areas of the cut and paste - but you get the gist.

[bobg3723]

Hey Gary,
I've been diligently going over some pictures of hull to beam connections and the one thing that always gave me pause for thought was the the connections themselves. They appear to my eyes as some sort of clamping affair like that on construction scaffolding and I can't help but wonder how tremendous a racking effect would exert upon that juncture. This leaves me somewhat more concerned for the integrity of the beam at that point than I am about the bending modulus central to the tube. To my eyes', something more substantial is what's called for. I don't know...maybe of a solid spade-shaped pad to distribute the torsional load down into the hull structure seams a prudent design step.

If the connection had some sort of give like that of that you would find in timber lashings, that's not too bad. You would have to gain stiffness by haveing four or more crossbeams. But solid clamps on the end of two beams doesn't have the sort of give a rope lashing has, and so more surface area for the connection would be needed, like a buttressed Cypress tree in the swamp, sort of connection.

I don't know. What say you?

Regards,
Bob

[Richard Atkin]

Gary, thanks for the information about building materials. It might be quite some time before I email you (depending on how things go with my non-boat related plans), but I would like to discuss with you a larger Skimmer in the future if you are available.

Thanks again for all the advice and earlier suggestions.

[Gary Baigent]

Bob
If you look at Tornado tubular beam/hull connections you will see they are very carefully done with the clamps fitting perfectly with no gaps or hard spots and resting on bases that also are carefully done and which spread the loads through frames below the connection areas. There is another method making moulds by glassing over the tubular beams (which are wrapped initially in plastic to stop adhesion to the alloy) so the beams are solidly set to the hulls in sleeves which in turn are set over bulkheads or ring frames - these spread the loads throughout the immediate area of the hulls - and work fine. Or you can build wing shaped composite beams that do a similar job.

[bobg3723]

Gary,
Thanks for the description on how the beam ends are bedded. Well I guess tubular stock aluminum crossbeams have had several decades on its track record.
Are aluminum crossbeams an easy to order item for multis that are no longer manufactured, let's say as a owner installed replacement part? Or does one need a naval architect to sign off on a custom spec'd replacement? Just curious.

[Gary Baigent]

Bob
I'm not ofay on this, getting alloy beams where you live, (most new multihulls have stopped using alloy by the way) and because the beams on my boat are composite wing shaped ones that are carbon/glassed solidly into the floats as well as into the main hull - and I recommend this way instead of using alloy. But you could hunt down some local mast sections and maybe even get some extruded oval beams (it is still possible to do so in Auckland) but with mast sections you end up with the unnecessary luff track - or you could build some carbon ones ...... or get perhaps a broken set of Volvo 40's carbon beams and patch them up - bad joke. As you can gather I'm not someone who employs marine architects to use their expertise in telling me what to do - I'm just a suck and see kiwi bloke, mate.

[bobg3723]

Bob
or you could build some carbon ones ...... or get perhaps a broken set of Volvo 40's carbon beams and patch them up -

Yeahbut that'll take too much duct tape! :D

Seriously though, the largest displacement cat I've seen so far with what I believe to be alloy tubes are Dakota 33's, and my interests are in the demountable crossbeam variety trailer cats with all up dry weight displacements of 4000 lbs.

I guess its the sign of the times when companies like Seawind for example discontiued thier S24 with alloy crossbeams, like this example with a "Walmart" harbor tent. :D

I think it's kinda slick, actually! :)


Regards,
Bob

[rayaldridge]

Deck tents can be pretty slick, and you don't even have to have a big cat to make them useful.

http://slidercat.com/blog/wordpress/wp-content/gallery/slider1/tent.jpg


Ray

http://slidercat.com

[bobg3723]

Hi Ray,
And that's the beauty of a cat with a wide tramp. Its nice having a double duty tent for both the tramp or shore with a full stand up height. The owner custom canvased his floor on this one it seems.
I own the exact same style tent pictured on that Seawind 24. Mine has an expanding accordian steel frame. Zippered screened windows and a rainfly on top. Completely sealed floor. Set me back $100 for a display model. I'm contemplating doing the same for my Duo900. The outboard on the Duo is designed to attatched to the aft crossbeam so I'm hoping I can design the area between the two hulls to accomodate my harbor tent without too much rearranging of running and standing rigging components.
Your videos of Slider I've seen so far (I haven't seen all) show you camping onshore. Have you spent any nights in that tent situated on that tramp along the shore yet? What's it like?

Best,
BobG

[bobg3723]

Ray,
The design I've concieved would entail having the tent fame standing at half its original height in stance (the corner legs are telescopic), and completely encapsulate both cockpits in a custom made tent giving access to both hulls. If my rig were a sliding gunter, I could haul it up, loosen the jaws and lower it hozontal and fasten a tarp as a sun awning /rain fly over most of the tramp area. I won't have the standing height like the guy did with his, but I can lounge with tons elbow room and plenty of shade and mesh screened windows and screened ceiling under the rainfly.

It shoud be more comfortable up on the tramp where the breeze flows freely and it'll alleviate my claustrophobia, too. :)

Regards

[rayaldridge]

Your videos of Slider I've seen so far (I haven't seen all) show you camping onshore. Have you spent any nights in that tent situated on that tramp along the shore yet? What's it like?

Best,
BobG

Yes, we have spent a night or two in the center deck tent.

A couple months back, my daughter and I sailed down to Navarre, which is about 20 miles west of here. We were actually planning to go all the way down to the National Seashore, but it started blowing pretty hard in the afternoon, and we elected to get into the lee of the causeway by Navarre Beach, and have a rest. Unfortunately the Air Force is still rebuilding the picnic grounds there, and the beach was mined with No Trespassing signs. We decided to go around to the other side of the causeway, where I hoped to find a little shelter under the curve of the beach.

We anchored next to the boat launch, which gave us access to nice bathrooms, but it was fortunate we'd brought the deck tent, because there was no camping ashore. This is unfortunately often the case along this coast these days; just about every foot of waterfront belongs to someone.

The center deck is actually cedar duckboards, which I learned to like when we had our Wharram cat. The tent covers the center deck and one cockpit, leaving the other cockpit as a porch, so you can still get in and out of the tent easily. The seats are movable, so you can put both in the covered cockpit facing each other, and have a civilized place to sit inside the tent. Add a folding table and two can sit down to dine, under cover, in a 16' open cat.

I think you're on the right track with your big tent. That wide-open center deck or tramp is a great advantage open bridgedeck cats have over other boats. Why not make use of it?

Ray

http://slidercat.com

[bobg3723]

Ray,

That's a pretty common complaint I hear from many others on the water who had to contend with the endless miles of 'No tresspassing' on coastal frontages and causways. Man, it does suck, too! :mad:

I supposed I have to be a very well traveled water hobo to find all the desirable secretspots. :) Hey, that was part of the fun pursuit when I was crisscrossing the country back in the day with a dog eared copy on Free Camprounds in hand. :D

I remember one night I spent in a public campground up in northern Minnesota when a 'derecho' like event blew in. And although I was among a mature stand of trees, those (I would estimate) 60+ MPH winds made for a nervous nights sleep. I kept having these morbid fantasies about the next days headlines reading "Camper found crushed to death under last night's storm".
More about these infrequent winds at this site:
http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm#risks1

That made me think more about designing into the plans for my Duo900 a capable harbor tent to hunker down in. I've been through a 'liquid white-out' along the shore of a lake once before. It was mildly scary at first and I was on land at the time on a pickup bed camper with plenty of daylight, but it was nowhere as scary as the sound of the tree limbs ripping and crashing to the ground with an ominous thump nearby in the darkness of the evening. But, people have drowned from getting entangled in tents coming loose taking them into the water, so that is of concern, too.

If I hadn't yet beat a hasty retreat to someplace on land away from flying and falling objects, I think I'd prefer a multihull (one without bow tramps to catch air) than a rolling monohull in conditions like these. The frame of the tent I picked up is a collapsing accordion steel truss, and it would be on-the-water removable, yet securely mounted into a bolted receptacle on the cabin sides, with the canvas given access to both companionway doors, in case I had to make a hasty retreat for one of the hull cabins.

I can picture a scenario where if I had to make a life or death decision to beach the craft, I would be more suited in a catamaran and beach it at ramming speed (the Duo900 has no dagger boards) and wade ashore like a scalded cat.

Worst case scenarios aside, harbor tents make alot of sense. My own personal Northwoods camping experience has spurred me to ponder this more.

Best,
Bob

[Richard Atkin]

Lol...you guys sound like a couple of catamaran advertisements. I like the tent ideas. Don't forget though, Gary's Skimmer can do the job too, but with more people, and will have a similar speed in light air. (that's my advertisement).
I said earlier in this thread that I would never defend a monohull. I really am such a turncoat :D

[bobg3723]

Rich,
Nah, just guilding my personal golden calf. :D

Me personally, I wouldn't defend one design over another. They're all good at something there, Benedict Arnold!. ;)
Here's some racing scows for you:
http://www.youtube.com/watch?v=XrMUEIb-pDc

Good fun!

Best,
Bob

[Richard Atkin]

Wow. Never heard of the E Scow and A Scow until now. Looks like quite a handful. Interesting to read that it is over 80 years old.

thanks for the post, Bob

[bobg3723]

They cut off the sharp end, cause it would only add weight when catching air. :p

Their shape reminds me of hydrodynamic femenin napkins without the wings. :D

Someone was giving an 18' racing scow in town away for free. I almost bit, but went for a 17' cuddy cabin shoal keel tub with trailer and gear for the price of the trailer. You'ld be surprised at the $1000 to $3000 bargains you'll find among the 24' and less plastic boats.

Best.
Bob