Reply With QuoteThe kit including 3200 for the plans, cost me $31,250.00 inc gst . This was a Christmas special. According to Spirited, the standard price for the lot is $34,250.00Originally Posted by chris69
The MDF all goes. It is replaced by 4 composite bulkheads, the main BH is the aft cabin wall, then the forward cabin wall, the transom and one about 2 feet back from the bows, the anchor locker and the deck locker sit forward of this bulkhead.
The kit including 3200 for the plans, cost me $31,250.00 inc gst . This was a Christmas special. According to Spirited, the standard price for the lot is $34,250.00
The engine requirements all depend on what you want from the boat. Obviously it's very easily driven, and will perform quite well even with a pair of 40's.
However, I've never driven a horsepower I didn't like, so I'd max it, AS LONG AS the weight of the larger engines isn't negatively effecting the trim fore and aft or adversly lower the tunnel height. I'd reckon given her quite slim sponsons she'll be a little fussy with weight and its placement.
Great project mate, all the best with it!
I replied to his once, don't know where it went. The MDF all goes. It is just a building jig and gets replaced by 4 bulkheads and one fore and aft frame made out of the composite panels.
Thanks, Within this family of primarily catamaran sailboat designers the catchphrase is "light is right" so it will be very interesting to see the comparison between a pair of 97kg 40HP Hondas and the pair of 163kg 60HP Suzuki power plants. That's a total weight difference of 132Kg on the very very back end.
Just a little one, the Sandy Strait. Stitch + glue construction. A basic boat for a "pilot project" to see if I will still want to build a bigger boat down the track...
Yamaha F70 is only 120kg
I wouldprobably opt for a couple of 40s. Most lightweight semi displacement hulls don't appreciate being driven too hard rough water. I would be happy with 18-20 knots average cruising speed and offshore I could have the troll lines out all day. I'm looking foreward to seeing the finished product. If the designers could have sneaked another 2-3' length for the same beam it would have opened up a few more possibilities for internal fitout without much more weight
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That's smart. Lots of unfinished projects about.
Yes, I've got a spread sheet with the specs on 40 50 and 60 hp from honda, yamaha, mercury and suzuki. But I did sneak in an extra column in the Yamaha's for a 70. The problem is this continual growth in expectation which automatically happens when you look at a 50 after looking at a 40, the 40 never looks as good again (and so on etc.) I first strayed into stink boat territory a long time ago at the Sydney Boat Show. There, I saw an Arvor 20, made for North Sea conditions and sporting a single 85 hp yanmar diesel inboard. As a sailor, that setup seemed so logical to me: plenty of power, reliable, cheap to run etc. I'm just not sure I need to go 40 knots, or want to divert the funding to get there and sustain it.
Upon reflection, i think you're on the money, and I don't think 30+ knots really suits the "character" of the boat you're building.
You've got plenty of time to consider your options before you're ready to bolt some egg beaters on it. I certainly wouldn't be buying engines now and having their warranty evaporate during your build.
Hello Stevemid,
Congratulations on the project, I bet you took a deep breath.
To help with the motor choice I would ask the following;
Where and how do you intend to use the boat?
eg. will you be crossing bars? travelling long distances?
What sort of loads will you be carrying?
The smaller motors may struggle to lift the heavily loaded boat onto the plane.
How important is speed to you? or is an easy 18 knot cruise more important.
After looking at the website I would offer the following comment, the hulls really do flatten down aft. My Webster Twinfisher is very similar and if I drive at lower speeds( 14-18 knots) and keep the flat aft sections in the water the ride is very good, but if I drive fast enough to lift the falt stern sections out the water she does pound on the flat sections. This only happens in bigger waves that actually lift the whole hull.
By comparison the Noosa cats and Kevlacats carry the deep V all the way aft.
The fuel capacity is very low at 150 litres.
If you add more tankage be very careful about upsetting the fore and aft trim.
The bridgedeck clearance of 430mm is very interesting, most cats that size have the tunnel almost touching the water at rest. If your boat does in fact sit high it may be sensitive to trim fore and aft when at rest, because most cats have the tunnel in contact with the water which stiffens them up fore and aft and prevents pitching.
The displacement figure seems very optimistic at 1200kgs.
It may weigh that empty but add motors, batteries, fuel, passengers, esky full of ice, snapper leads etc. I would expect a loaded weight well over that.
For example a similar Kevlacat has a dry weight of about 1400kgs empty.
Motors 180 kgs
Batteries 30 kgs
Fuel 100 kgs (150 lt = about 100 kgs)
Passengers 300 kgs
Esky full of ice 40 kgs ???
Snapper leads 10 kgs ???
Tools 10 kgs ???
Which adds up to 650kgs approximately.
As you can see actual displacement = boat + load may be quite a bit more than 1200kgs.
Did you go for a test drive before purchasing?
If so how did it perform?
Yes fair enough, shooters call it "calibre creep" ending up looking at elephant guns to shoot rabbits ! Not knowing much about cats it's easy to assume a 23' needs a fair bit of motor to push it along.
Since the F70 came out with such a weight advantage over it's competition I've been hoping to see some lighter 4 strokes in the smaller end of the range. A 70kg 4 stroke 30hp would be sweet for my Sandy Strait.
Crocodile, thanks very much for putting the thought into your reply.
Usage: Id say this boat will spend most of its time in Sydney Harbour being used for cruising/camping/fishing, venturing further off shore as I gain experience with this type of boat (heaps of sailing off shore previously.) There’ll be many trips up to Broken Bay (15 NM north, no bars to cross) I’ll probably do a couple trips per year trailering up the NSW coast, and 1 trip per year to Qld to fish inside the reef and on the reef. Hopefully, this would involve anchoring out at the reef for a week or so at a time.
Your comments regarding weight are right on. The designer’s estimate of weights include two categories: Lightship weight retains only enough fuel and water for basic operations, nothing else. So the 1200 kg includes the fitout only: motors, tankage, batteries, fridge, cooker, electrics, wiring, etc. Payload includes everyhing else that you bring on the boat, this he estimated to be 500kg to achieve the estimated performance. My payload estimate (not including ice)
2 Crew 80
Water 100
Fuel (2X60) 85
Food & bev 50
Personal gear 30
Total: 345
For me, comfort and economy outvote speed. I’ve been thinking that if I were able to get 17 knots cruising at 4000 RPM the BF 40’s would be draining about 5.5 L/hr. On 60 L tanks that would give me a max range of 185 nm (This would get me to the Swains and most of the way backI could double my fuel to 240 L, the weight would go up another 85 KG and max range to 370 (less the penalty for the extra weight.) Do people carry spare fuel in Jerry cans?
I did not get a test drive as there were only two other boats under construction at the time I was thinking about this. One has now been launched has twin 60hp Suzuki’s on it and he said he achieved 29knots WOT - The Suzukies weigh in at 163Kg each as opposed to about 100 Kg for the the Hondas 40’s which were put on the 2nd boat built but not yet launched. The one thing about composite boats is that they are built light and they have to stay light to perform. They cannot become a home for everything everybody and anybody “might” need. Thus the engine choice includes weight, fuel economy at cruise and fitness for purpose. For me going through this thought process now in more detail, smaller might just be better.
Again, Crocodile, thanks for provoking the thinking. Anything flakey in the above? What about jerry cans? (I knew there was something I liked about diesel!)
Hello Stevemid,
If you are going to cruise the NSW coast you will be crossing plenty of bars.
My thoughts are that you can never have too much power when crossing a bar.
Have a look at these Honda websites;
http://marine.honda.com/pdf/props/Al...BF40%20EFI.pdf
http://marine.honda.com.au/Fuel_Consumption_Reports
If you are buying 40's you might as well get 50's for the same weight and very little
extra $$$$.
A 50 at 4000 rpm uses between 7.5 to 10 l/hr.
That is about 30hp being produced. A 4 stroke about produces about 12 hp for every gallon
used, look at the bulletins and see for yourself.
60 hp (at cruise settings) is not very much to push a boat of that size and weight.
Two 50's will use a total of about 18 lt/hr (at cruise settings) which when drinking from
120 litres is an endurance of 6.7 hours X 18 knots = 120 nautical miles with no reserves.
If you mean the Swains off Gladstone, they are about 150nm NE of Gladstone = 300nm return.
I would want a 50% margin for error/ bad weather etc. That's 450nm of range, which is a
lot of petrol, your boat when loaded with that much petrol may not be able to plane.
Also that much petrol in jerries would make me very nervous, built in tanks are a much
better idea.
Your weight table is again a bit optimistic.
Two persons weigh 170 not 85. I think you would benefit from doing a very rigorous tally of all the items that you will put on the boat. You may be surprised what it all adds up to.
Check that the existing boats are carrying that sort of load.
I know that the composite boats are extremely light, but that is only the structure.
All boats still need motors, batteries, petrol, steering, anchors + chain + winch, hand
rails, furniture, bunk mattresses, toilet + holding tank, water, tools, spare prop,
electronics, glass windows, fishing tackle, snorkeling gear, not to mention XXXX beer.
Was the completed boat loaded or was it "artificially" light?.
For mine I would be chasing a run in the completed boat and bringing plenty of ballast, human or otherwise, to simulate a well loaded boat.
I would be paying special attention to its behaviour at medium speeds of around 15 to 20 knots.
I am not trying to be pessimistic only conservative and rigorous.
There is nothing worse than a sluggish speedboat that needs to run the motors at max rpm at all times.
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