Aluminum Semi-Displacement Catamaran Build

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
Very nice project!


Sorry I didn't comment while you were in the planning stage, but let me offer a comparison with the Island Packet Cat 35' that I owned for several years. That boat had a beam of 15', a center hull for breaking waves under the bridge and also for lowering the cabin sole to also lower the cabin roof so you could easily see over it from the center helm position near the transom (it was a sailboat after all).

You shouldn't have that problem with your pilot house helm position and your cabin height is much taller than mine.

Your weight target seems entirely achievable, maybe a bit conservative. My boat weighed about 18,000 lb light ship (measured on a travellift). Yours is longer but narrower and doesn't have the center hull or mast so you should easily hit the weight of 22,000 lbs.

My boat was really a full displacement hull, even though the hulls were narrow so the 1.34*sqrt(lwl) rule doesn't really hold it butwas very inefficient. It took full power from its twin 27 hp Yanmars to hit that value. It should be able to almost do that on one engine if it were an efficient full displacement hull.

Two things caused that I believe: the drag of the center hull and the relatively heavy weight for its length. So keep the weight down as best you can.

Post some interior renderings when you have them.

David
Another comparison is our Endeavour 44 catamaran trawler, which is 44’ loa x 18’8” beam. The layout with forward queen is similar, except with the greater beam, we have room on each side of the bed, and the head is down 2 steps in the starboard hull, but very roomy with a walk in shower.
Your layout looks like it is galley and saloon up on the same level, which is nice. The Endeavour has a very large saloon, with galley down on port, another head and shower to port forward of the galley, and two queen berths aft in each hull. Amazing what another 6’ allows in a boat!
Endeavour also made a 36 catamaran trawler.

I’d love to see photos when your boat is finished
Jack
 
I’d love to see photos when your boat is finished
Jack

Jack, will do. I'm heading down next week for another inspection. I'm crossing my fingers that we will be ready for sea trials early November. They have made more progress in the last 4 or 5 weeks than in the previous 3 months. So I'm cautiously optimistic.

I'm a downeast boat guy. So when I looked at boats in the 36 to 38 foot range, I had certain accommodations in mind. I've been able to fit a lot more creature comforts in this boat at a similar LOA and not too much greater beam. I'll probably still use her the way I would a downeast boat (i.e. I was never looking for a livaboard trawler). I certainly could have bumped up the size and fit more in - but I'm at the upper limit of what I want to operate/build/maintain/pay for.

We'll see how it goes. This is likely my last "big" boat. I'll post some more photos next week.
 
6 months late and counting...

There are a few really top notch folks working behind the scenes and they are serious about doing their best work...there's just not enough of them.

Nevertheless, here's a couple update photos for your viewing pleasure.
 

Attachments

  • 11_7 Bow.jpg
    11_7 Bow.jpg
    139.2 KB · Views: 144
  • 11_7 Bow 2.jpg
    11_7 Bow 2.jpg
    120 KB · Views: 117
  • 11_7 Stbd Side Deck.jpg
    11_7 Stbd Side Deck.jpg
    109.1 KB · Views: 114
Great looking boat, especially the forward rake Pilot house.

Thanks, that really appealed to me in some brutish, utilitarian way. But brutish and utilitarian is how my wife describes me anyway.

I did ask for some sexy wood trim on the interior. I like the way it's looking if we can just get it over the finish line.
 

Attachments

  • 10_23 Cabin 2.jpg
    10_23 Cabin 2.jpg
    106.7 KB · Views: 104
  • 10_23 Cabin 3.jpg
    10_23 Cabin 3.jpg
    108.4 KB · Views: 95
Appreciate the pics. She is going to be a beauty! There is a simplicity about these boats that is appealing.
 
Nice looking to be sure.

Beautiful .. not so much.

Fwd slanted windows look OK.
But other angles look better.
 
Nice looking to be sure.

Beautiful .. not so much.

Fwd slanted windows look OK.
But other angles look better.

Too bad Marin isn’t here to give us a lesson on “Wannabe windows” (meaning forward raked windshield). They were a real rubbing point for him and I loved having the most ridiculous set of all!

Regardless, this is a fantastic project that only $$$ prevent me from undertaking myself. Envy is not a sensation I experience very often.
 

Attachments

  • 141248FD-3C65-4FDC-85EE-013E6D205151.jpg
    141248FD-3C65-4FDC-85EE-013E6D205151.jpg
    59.7 KB · Views: 67
Last edited:
Larry,
HaHal looks like a baby animal say’in “me too” “me too”.
Kidding aside it’s clear you’ve got more volume in the upper cabin.
But vertical or slanted back would look better. Most would find it “old school” and not like the notion of not being cool. Being cool, vogue and/or mod like others is most important.
But it fits your boat nicely. I really do like your boat/windows Larry.
 
Looks like she is coming along nicely. As a member of the forward raked window club, I approve!

Ted
 
What’s wrong with forward raked windshields? I love the forward raked panels on the front of our flybridge. It cuts out reflections at night and when it is raining it keeps most of the rain water off the front panels.
 
Wait...wait...we may have reached a new phase - they are pulling wire!
 

Attachments

  • 11_12 Helm.JPG
    11_12 Helm.JPG
    96.2 KB · Views: 69
  • 11_12 Wiring.JPG
    11_12 Wiring.JPG
    109.2 KB · Views: 80
  • 11_12 Electric Panel.JPG
    11_12 Electric Panel.JPG
    119.1 KB · Views: 74
Pulling wire is a good thing.

Is that a spot light on top of the PH? Have you had one in that position before? How did it work at night in regards to glare with the light shining overhead?

A previous boat had one on the bow pulpit that I used at night to light up the dock when pulling in. I am considering putting one in the position you have, or way up top on the arch but concerned how well it will work.
 
Last edited:
Is that a spot light on top of the PH? Have you had one in that position before? How did it work at night in regards to glare with the light shining overhead?

I've had a light on the pilot house before and it was fine. Particularly if you are looking at something on one side or the other. Now whether this light will create a problem with reflections on my aluminum remains to be seen. Most of the horizontal surfaces will have non-skid paint that should handle the reflection, but I'm sure I'll still have refraction (I think that's the right term).

Frankly, I'm not a big fan of spotlights. They are necessary equipment, but I try not to use them and often a handheld from the side deck is preferred if you can do that.
 
Hotwork is almost done and wire is going in everywhere. The question now is whether we'll launch before Christmas or sometime in 2020. It could go either way at this point.

I have to admit, as pissed off as I am about the delays in construction - there are some dedicated guys working there. As a former Army guy, I'd much rather talk to someone in the bilge about what's going on, and every one of them has taken a lot of pride in their work. All the guys I talk to are embarrassed my boat is over 6 months late, they say they are dying to see her in the water, and they seem to have an attitude of "you're not going to have any problems from any of the work I did!"

I like that in people.
 

Attachments

  • 11_21 Hot Work.jpg
    11_21 Hot Work.jpg
    143.6 KB · Views: 112
  • 11_21 Winch 2.jpg
    11_21 Winch 2.jpg
    110.3 KB · Views: 120
In custom boat building, 6 months late can be considered well ahead of schedule. I've watched a number of custom builds go on (including my own) and 'on schedule' is extremely rare. On mine two years turned into 5. The only important thing is will you be happy with the result.
 
What’s your ground tackle setup?

Hmmm...I wondered when that subject would come up. I guess no time like the present.

Obviously from the photo I'm using a Lone Star Marine 12v winch.

I've specified a Rocna 25 with 50' of 5/16 chain and 150' of 5/8" three strand. That should not fill up my spool, but I don't know how close it will come to filling it. Once I get delivery I will go ahead and add enough 1/4" Dyneema to fill the spool.

My displacement is around 25,000# fully loaded (possibly less) and frankly, I had a bit of trouble calculating the frontal surface area. I have a lot of freeboard when viewed from the side, but that tunnel made it a bit challenging to calculate. I think I'm good on rode, I was between sizes on anchors so I moved up one.

If I got it all wrong, please don't tell me!
 

Attachments

  • 11_21 Winch.jpg
    11_21 Winch.jpg
    101.5 KB · Views: 105
Steady progress...they are finally getting the interior knocked out.

First shot is the dinette.
Second shot is the galley roughed in.
Last shot is some of the toys going on the mast. I'd say they are about 80 - 90% done with electronics and electrical.
 

Attachments

  • 12_13 Dinette 1.jpg
    12_13 Dinette 1.jpg
    75.1 KB · Views: 91
  • 12_13 Galley.jpg
    12_13 Galley.jpg
    81.7 KB · Views: 93
  • 12_13 Mast.jpg
    12_13 Mast.jpg
    107.9 KB · Views: 90
Looking good!

Man, peeking through the rear door, the cockpit area sure looks huge on this boat. Will it be covered?
 
Cardude, sorry for the delay. I'm back into "negotiations" with the builder and that's got all my focus...don't ask...

The cockpit won't be covered - although I've got a plan for a soft cover I can put up during fair weather. The cockpit is large, but not as large as the pics taken through the salon would have you believe. That shot includes the top step down to the boarding platform, which is really not part of the cockpit's usable space.

I'm coming over from 10 years in a lobster boat - so I'd call this cockpit large when compared to most cruising trawlers, but not overly so.
 
Not much is happening on her now. But a couple of sub-contractors are still working on bits and pieces.

Here's pics of seat cushions being test fit and drawer fronts built and installed. I understand the galley is ready to actually be placed in the boat and the "cushion guy" is working on the backs.

Both the carpenter and cushion sub-contractors have been great to work with!
 

Attachments

  • 12_27 Cushions 1.jpg
    12_27 Cushions 1.jpg
    97.7 KB · Views: 83
  • 12_30 Galley 2.jpeg
    12_30 Galley 2.jpeg
    72.8 KB · Views: 76
Hi George, I wish that I could give you some positive news on my build but both the Dec. and Jan. construction goals were missed and we are close to the Feb goal and it seems unlikely that they will make even the Dec. goal by Feb. I am unsure if they have begun the build beyond putting out drawings. Color me disappointed but still mildly hopeful.
 
Back
Top Bottom