Building 23' catamaran. Build updates

[Apollo]

You made the hobart start by 8mths - well done. Any pics on the water now she is fitted with motors? Also underway?

[Chimo]

Cav plates above the water surface when planning by the sound of the results. Pics please

C
C

[stevemid]

Hi Guys,
Just back from the sea trials. Sorry I was a little lame in capturing the full throttle run, but I did manage to get a 15 sec video grab on my phone which I've uploaded to YouTube at this address:
http://youtu.be/X80zXOIl3UY
Chris and Chimo:

Chris69 Great to here Steve no dout your a very happy man,have you put 2x70hp on it,just going by the max rpm and are you sticking with the engine height?

Yes I am a very happy man. Yes, I went with the 2X70hp Yamaha engines. As to engine height, we installed the motors in the top hole. This raised the cav plate about 55mm above the bottoms of the sponsons. By my calculations and the advice on here this was still going to be a bit low, but I was hoping for some lift from the 70's which I did get. The Yamaha technician was happy to sign off on the engine installation, saying they could come up "a bit" but they weren't developing a lot of spray or mist which would cause problems for the engines. So I'm going to stay at this height for the time being.

The amazing thing about these engines compared to the 40's that I sea trialed on Frank's boat was the amount of lift! At rest, the cav plates are sitting about 150mm below the water. But soon as you get upwards of 3000-3500 RPM's the bum starts to lift. At 4500 where it seems to be most comfortable, it is really planing and the back of the cav plate becomes visible -- not out of the water like on the mercury verado website, but visible. The other thing is there is no turbulence around the legs, just the rooster tails that you'd expect.

Any pics on the water now she is fitted with motors? Also underway?

As I say I was a bit lame in this respect and I'll capture some still images tomorrow. As for pictures underway, I'll need to appeal to an AusFish member either in Sydney or in Broken Bay area to help out. All the areas around the jetties are 4 knot zones, so we can't take movies from the jetty. Plus I'm single handed so that makes taking anything underway a bit tricky. Especially since I've only ever driven a boat like this once before (and that was today!) So any volunteers, just PM me.

Now here's the not-so-good news. The actual weight of the boat and motors is 1250Kg. The designer estimated that figure would be closer to 750Kg. Leaving me 500Kg for personal effects for a total displacement of 1250Kg This means that the waterline estimations(DWL) are off for my build. No big deal but I drew my antifoul line 50mm above DWL. So I have about that showing at the front but I am right on that line at the stern. As I say, mounting the engines in the top hole gave me the engine height I needed on the plane vis the cav plate, however, I'm going to be dealing with green scum on the white bits of the boat. I'll be discussing this with the designer.

Oh, one other thing: When you're going along at 4500 RPM and you punch it, there's still enough power to throw you backwards if you're standing. Even the tech was surprised and this is due to the lightness of the boat and the beauty of those 70's I reckon.


This is all so exhausting but I am so stoked!
Steve

[Shark Poker]

Congratlations Steve.
Hope you take a moment or two to appreciate what you have achieved, instead of worrying about the next little job.
Look forward to seeing the side view photos in relation the the fwd/aft balance we discussed. I still think it will be spot on.
Sleep well tonight mate!
Pauly

[battleon]

Well done Steve, great effort all the way through. I thoroughly enjoyed my cat when I had her and I'm sure you will have some great times ahead.
Congrats!!

[Chimo]

Steve

All in all a really good result but it looks like the addition of some pods would give you the extra bum lift you are going to need as you stack fuel and goodies aboard.

Plus with a couple of pods bolted on you can really hang the motors where they need to go, probably up another two or three or maybe four holes depending on the thickness / size of the pods.

Might as well get it up before you repaint the hull IMHO

As a matter of interest what does the other hull weigh? Maybe there are builders and there are builders. Nuf said about architects of all persuasions.

Cheers
Chimo

PS the transducer probably wont work real well where you have it located.................

[Crocodile]

Well done Steve,
I hope that you enjoy many great days with a boat that you can be proud of.

[The Woo]

Congratulations mate. Having her move under her own power is a momentus occasion.
I look forward to seeing you iron out the to be expected teethings. Plenty of help here if you need it mate.
Well done mate!

[gofishin]

Fantastic Steve! May she give you years of joy
Cheers


Sent from my iPhone using Tapatalk

[stevemid]

Hi Guys,
OK you've borne with me for two years so I went down today to take pics and movies for you. Being a SHS (single handed sailor) has its disadvantages when it comes to taking selfies underway, but I did my best. I'm going to get a helper and get detailed performance figures asap.

Here are the underway movies looking backward:
4200RPM http://youtu.be/vuSAwtY89do
4500RPM http://youtu.be/CzaLFmBoQWA
5100RPM http://youtu.be/fWUEay0r5DU
Thats as fast as I went today. I'd hate to run somebody over looking backwards taking movies.
Here are some side-on pics of the boat with the motors mounted.
Entry Way.jpg40 Litres.jpg40 Litres_2.jpgIMG_1894.jpgFloating On Her Lines Almost.jpgFlushing Engines.jpg

[stevemid]

Steve

As a matter of interest what does the other hull weigh? PS the transducer probably wont work real well where you have it located.................

I didn't weigh Franks boat but I have launched it twice now and I'd say it is heavier however I only ever launched mine off his trailer when mine didn't have motors installed. AND I may have backed the trailer in further for mine.....I did weigh Frank's trailer, however, so it is just a matter of putting his over the weigh bridge which I'm keen to do furthering my discussions with the designer.

Yes, on the launch morning the last thing to do was to sika on a star board piece that I could mount the transducer on however I didn't know quite where to put it so we put that item off till later or the 20 hr service, whichever comes first.

At what level do I want the transducer mounted? It seems if I mounted it at the level of the cav plate, at trolling speed it would be 6" under the surface and at planing speed it would be just skimming the surface. How do you deal with that?
Steve

[mull dog]

It's an absolute credit to yourself Steve. You must be proud and so you should be. I would love to do the same one day when time permits. It doesn't look like its sitting too low in the back end at all. I also love the look of the raised sheer line gives your boat. Looks like a speed racer!

[Chimo]

You mount the transducer with the rear down about 5 degrees so its in clean water flow at planing speed. Its fine to be in deep water at low speed or stationary.

Have you loaded the tanks and got your gear on board so the weight is in the hull? If so its probably not sitting too low and good to see you can lift the motors well clear of the drink when they are up.

When you were doing your runs how far back were the motors trimmed?

Cheers
Chimo

[stevemid]

You mount the transducer with the rear down about 5 degrees so its in clean water flow at planing speed. Its fine to be in deep water at low speed or stationary.

Have you loaded the tanks and got your gear on board so the weight is in the hull? If so its probably not sitting too low and good to see you can lift the motors well clear of the drink when they are up.

When you were doing your runs how far back were the motors trimmed?

Cheers
Chimo

I had 50L of fuel and about 80L of water in when I took the pics. I could have topped the water up to 200L which would bring down the bow and lift the stern some. I put an additional 168L of fuel in the main tanks (cap of 150L each) for the run down to Sydney today and as those tanks are closer to the centre of the boat it didn't affect trim that much.

As far as trim, the gauge has 3 bars showing. The Yamaha tech said the boat liked it there on the plane so I've just left it there as there is heaps other stuff going on. (e.g. The trip to Sydney didn't come off. Seems some FW builder switched the vent and the fuel lines.) Anyway if I put the throttle down the boat seems to jump up onto the plane in a very few seconds, so it seemed fiddling with trim is a fine point for later exploration.)

My priority for now is just to get the boat working. ie make sure that all systems work, then to learn all these new systems: ie, the DSC VHF, the Garmin Combo, the Digital Gauges, etc etc, not to mention working the NMEA 2000 interfaces between all of the above. I kinda know what Jessica Watson went through with 20 tech's explaining the ins and outs of the systems installed on her sailboat just before she departed. Like her, my body's tired (not that my body is like her's) and my brain is saturated. I'd just like to get this thing on a mooring and sleep for a while. (except I haven't put in the mattress yet!!!!)

[fisho64]

Looks good mate!
astonishing though that a naval architect could miscalculate the displacement by about 80%-who was the designer?