Minimum cruising cat-size & cost

[Manie B]

In calm water (like a dam) calculated motor should give at least 10 knots

you need 3x that for the actual boat at least

so if calculations show 5hp buy a 15hp
fourstroke 30% lighter on fuel what i found personally

[Richard Woods]

Thank you for having my designs high on your list.

You cannot go wrong with a high thrust 9.9hp Yamaha on a 9m catamaran. We even had one on our 34ft Romany and could cruise at 5.5knots under power. But that boat was at the top end of size for a single engine. However I also used one on my 28ft Gypsy and my 30ft Sagitta. It worked great on those smaller designs.

You want a minimum cruising cat, so you will have to accept that sometimes you cannot sail or motor as fast as you'd like.

I think you will regret not having standing headroom in at least the hulls. If nothing else it means the freeboard is low so the boat is wet to sail, and there is also a greater risk of bridgedeck slamming. Both of these lead to discomfort at best. I assume you want to enjoy your cruising??

I think it unlikely that you will find any professional designer willing to "check over" your own design. I wouldn't do it. For two reasons: 1) it makes me liable for any of your design faults. 2) It would take me so long it would be cheaper for you to buy one of my stock designs.

You do have to think about insurance, certification (if needed) and resale value when designing your own boat.

Hope that helps

Richard Woods of Woods Designs

www.sailingcatamarans.com

[marshmat]

Originally Posted by Richard Woods

You cannot go wrong with a high thrust 9.9hp Yamaha on a 9m catamaran.

I keep hearing good things about these small Yamahas. My only concern would be that if you're in an area where Yamaha dealers are hard to find (admittedly, there aren't many such places), spare parts and warranty coverage may be sporadic.

I think you will regret not having standing headroom in at least the hulls. If nothing else it means the freeboard is low so the boat is wet to sail, and there is also a greater risk of bridgedeck slamming. Both of these lead to discomfort at best. I assume you want to enjoy your cruising??

Agreed.... at least a small area of standing headroom in the hulls would be quite desirable. Low, slim racing hulls don't seem appropriate for something you'll be living aboard for months at a time.

I think it unlikely that you will find any professional designer willing to "check over" your own design. I wouldn't do it. For two reasons: 1) it makes me liable for any of your design faults. 2) It would take me so long it would be cheaper for you to buy one of my stock designs.

The way I see it: if you have the engineering knowledge to design a small boat (and I only deal with small boats- smaller than Richard's, at least), you don't have much need for a designer's help, and if you don't have the engineering knowledge, the designer essentially has to treat it as starting a custom design from scratch. I can't take responsibility for work that isn't mine.

Originally Posted by Alex.A

Basically if i were to buy plans, at present it is between Woods and wharram....

Both well known designers; you've certainly realized by now that Woods boats are a bit more spacious and modern, Wharrams tend towards the rustic, simple and time-tested. Choosing a boat is really a matter of personal taste and preference, more than anything else: it's an emotional decision, so go with what fits your style and makes you happy.

BUT am getting that desire (disease) to self design.
YES - i have read the thread on why not to....... and wouldn't go into it without much thought,learning and getting the idea's checked by someone who knows what they are doing.
Present design has between 1.3 and 1.4m in hulls but fear it may be too little..
Fanie - looks like i may be designing for elsewhere if plans go well......

Designing can be a lot of fun, if you like thick books full of equations and long essays on design tradeoffs. (As an engineering physicist, I find this sort of stuff relaxing.... small craft design is something I do just because I like it, but I doubt I'll ever make a full time job out of it.) If the idea of spending thousands of hours to learn how it all works isn't appealing, it's probably better to find a designer whose philosophy and approach match yours. A good one should be able to take whatever sketches and preliminary drawings you have, combine them with his/her engineering knowledge, and come out of it with a custom design that looks and performs the way you want it to.

[Alex.A]

Thanks guys - designing is a fascinating process and is teaching me exactly how much does go into creating a finished boat!!!
Even if i dont design one - i like learning the how and why of things and while complex math isn't really my thing, it is teaching me a lot about boats, which will allow me to make informed decisions in the future.
And all you people out there giving time and info on this (and other) forums - thank you very much!!!

Speed not so much the issue as saftey and being able to get out of trouble if needed.
Freeboard at 1m to 1m10 / deck 1m up and beams 90cm - more than 10% of length! Freeboard is low.... but can be upped along with headroom.
Hulls are narrow - hull beam 70cm at wl =12.85 and flared going up to 1.2m.
9m loa - 7.5m at wl. Beam 5.4m = 60%.
I like double enders...... and rounded - quarter circle.
Headroom idea is that in ok weather or anchoured i will have full headroom.
But am at the beginning of this all and no doubt it will develop and change lots as i go.......
And simplicity/low cost are more complex than i would have thought....

[Richard Woods]

I have never had any problems with the Yamaha outboards except the time I was hit by lightning. I have had 5 of them, starting in 1985. So no need to worry unduly about spares

A good starting point when designing anything is "use your eyes and plagiarize"

Based on you initial requirements, from months ago, a boat that would suit you would be my 28ft Gypsy. That is a hugely successful boat with a couple of Pacific crossings to its credit, plus many offshore trips.

So I would start with that as a baseline and modify it to suit your own needs

Good luck

Richard Woods of Woods Designs

www.sailingcatamarans.com

[Alex.A]

I do like the gypsy.
The wife wants to know what being hit by lightning was like?

[Fanie]

I have never had any problems with the Yamaha outboards except the time I was hit by lightning. I have had 5 of them, starting in 1985.

Hits by lightning or Yamaha's

If it's hits by lightning you should consider a different religion maybe.
If outboards, give the poor things oil, they'll last longer

The wife wants to know what being hit by lightning was like?

Enlightning ?

[Fanie]

I was hit by lightning once. I was on the phone with a customer when I was hit. I just saw a flash and when I 'woke up' I was lying in the chair on my back with the phone on my chest. No clue how long I was out.

That's why I suggested to Richard consider changing religion.
I now believe when there's heavy weather, stay away from wired telephones

[Richard Woods]

You can read about my lightning experience on the Articles pages of my website

Richard Woods of Woods Designs

www.sailingcatamarans.com

[catsketcher]

Here is a good talk by a sailor from Australia who circumnavigated using Yamaha 9.9s. His boat is a 32 footer stretched a little. As for finding spares, Chris (the featured sailor) says it is much easier to find outboard spares and petrol than diesel spares and diesel.

http://www.seawindcats.com/index.pl?page=584

cheers

Phil

[Richard Woods]

Rush is another Australian circumnavigating catamaran (33ft Crowther) that used a single 9.9 Yamaha.

You are right about the oil. The first high thrust models had a fail safe design flaw, later rectified. You had to change the oil every 50 hours, not because there was less of it, but because the viscosity changed

That doesn't seem to be a problem now

Richard Woods of Woods Designs

www.sailingcatamarans.com

[cavalier mk2]

I found the ultralight nylon/plastic prop to be good for a extra 1/2 knot on the Yamaha high thrust we use on my Vagabond mk2. We can go over 7 knots flat out when light but usually cruise at 5 1/2 to 6 for economy. I ran the formulas and with that prop there is almost no slip which was a new one for me. The best thing about them is they are easy to work on if you ever have to. It will still make good headway into a rising wind.

[cavalier mk2]

I better send in this correction before the nitpickers come after me. The ultra light prop was on our first 9.9, We haven't gotten around to reinstalling it since installing a 25" shaft version which is a neat option to look for. We kept the same prop depth but raised the motor height to keep the power head out of the spray. I've run outboards without the Yamaha's reduction gear but the prop is always functioning with lots of slip and headwinds slow the boat down more. If you can't find a 9.9 high thrust you should look at bigger 4 strokes. The gas used in a 2 stroke will weigh the boat down !

[oldsailor7]

Originally Posted by Alex.A

Hi - sorry for not posting more details or sooner - have been away. 9m is my limit - licence and build space. I would prefer to build in ply because it is what iam used to... not entirely essential though. The reason for building is mainly that there are few 2ndhand cats in South Africa of this type and they are bloody EXPENSIVE for what you get!!!!! Lots of expensive condomarans but that isn't what i want. I prefer cats for many of the reasons already stated.

I will be sailing mainly with wife and young child so handling is an issue - type of sailing will be coastal 99% of the time but the area i sail is quite hectic - hence wanting a capable cat!! Cruising from tip of Africa up East coast mainly but also atlantic side.
Speed isn't such an issue. Doesnt have to demount though could be usefull.
Time for building isn't an issue as self employed and work from home but cost is.... and buying materials as i need them would be better than borrowing money to buy complete boat.
We live simply and therefor a simple boat is fine. Dont need masses of space or gadgets/luxuries.
I am blessed with a reasonble woman!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
A bridgedeck isn't essential but protection from weather is!
I sail small cats and to me 9m feels big but am confused by the mix of replies to size/saftey. What can you all tell me about the difference between transom and canoe sterns? Internal space and loading vs saftey? Want transom hung rudders and outboard - say 9hp.
Also minimum practical sails - as with boats - sails are EXPENSIVE here - as is everything else......
Thank you all for your knowledge and idea's.

Sounds like a Buccaneer 24 would suit you just fine.
There is a great pic of Samnz B24 on a weekend cruise with two couples on board, on the B24 thread. We've done coastal cruising with three on board. The loo is best positioned under the head of the forward berth.

And small is less expensive.

[rob denney]

Originally Posted by Richard Woods

Thank you for having my designs high on your list.

You cannot go wrong with a high thrust 9.9hp Yamaha on a 9m catamaran. We even had one on our 34ft Romany and could cruise at 5.5knots under power. But that boat was at the top end of size for a single engine.

www.sailingcatamarans.com

Maybe for a cat, but Blind Date, the 15m near sister ship of the proa in the video has recently fitted a single 9.9 Yamaha. Does 8 knots.

Rob