How can I simplify my house boat design for easier construction?

Tying up a houseboat to land is done with stern ties. A large and very beefy, well backed cleat is placed on the stern on each outboard hull side. Then there are long ropes that lay on the rail/gangway sides. Then you throw the loose and to the land and the hulls are bows to lnd. Then you tie off on angles to rock or trees.

dock tying is no different, but tying off to land is done as described; you always have someone at the helm when the other guy is tyng off

the ropes are like 3/4" and about 100' long

 

Your comment about a boat interior being like a house fails to recognize economic realities. Unless you have quite a bit of $$, most boat spaces are very expensive.

My boat is going to come in at over $5000 usd per linear foot and I did all the main labor. And you fast forget tradeoffs. A high ceiling and square corners means lots of windage, even underway if the front ceilings are high.

Boats are lots of tradeoffs.

If I recall correctly, one of the billionaires has a boat and a helicopter pad boat. Apparently, he didn't want the helicopter landing on the big yacht?

 

Re 'drawing up a concept of what I want so that I can get a price estimate on building it', you will still need to produce a fairly detailed general arrangement design, including a structural midship section so that you can get just a rough initial estimate of the weight of materials that will be needed.
Nobody is going to commit themselves to telling you that they could build you the hull for US$ X00,000 based on a 'back of an envelope' sketch - it needs to be fairly detailed, with an honest estimate of the weights.

Re your sketches above, they do remind me of your old Hurtigruten coastal ferries - even the colours with the orange hull and white superstructure.
We have quite a few of your old ferries trading between the islands of the Eastern Caribbean - here is a typical example.
ADMIRAL BAY II (Ro-Ro/Passenger Ship) Registered in St Vincent Grenadines - Vessel details, Current position and Voyage information - IMO 6519053, MMSI 377952000, Call Sign J8PB3 https://www.marinetraffic.com/en/ais/details/ships/shipid:469701/mmsi:377952000/imo:6519053/vessel:ADMIRAL_BAY_II

And re how you don't like curved walls in boats, then maybe your best bet is to adapt an existing ferry design, where you have most of the enclosed accommodation in a 'house', and not so much down in the hulls (?).
Have a look at this 46' ferry design by Malcolm Tennant -
Ferry - 46 - Tennant Designs https://www.tennantdesign.co.nz/product/ferry-46/

This is very similar in many ways to what you have sketched above.
If you like something like this, your best bet would be to buy a set of plans from the Tennant office. And adapt them a bit (not too much!) to suit your own Statement of Requirements. Talk to the design office first, and tell them what you propose to do - they will give you an honest opinion as to if it is viable or not with their design.

Here is a link to one of Malcolm's 'yacht' (as opposed to ferry) designs - but this has more accommodation in the hulls, and less in the deckhouse.
Ragtime - Tennant Designs https://www.tennantdesign.co.nz/product/ragtime/

Here is another example of what I think might come close to what you have in mind - it has long skinny hulls, but they have been very carefully engineered by Kurt Hughes.
Kurt Hughes Multihull Design - Catamarans and Trimarans for Cruising and Charter - 50' Cruising Catamaran https://www.multihulldesigns.com/designs_stock/50pwrcruisingcat.htm

You could also have a look at this 'Sea Shanty' design by Schionning -
Sea Shanty Power Catamaran Series - Schionning Designs International https://schionningdesign.com/designs-sdi/sdi-sea-shanty-power-catamaran-series/

I think that you can see where I am going, re the links above - I think your best bet is to buy an existing design that is nearest to what you have in mind, and then adapt it (hopefully not too much) to what you want it to do for you.

But be aware that US$ 200,000 is not going to get you very far with any of the designs in my links above.
And you will most certainly not be able to engineer your design to be cheaper to build than these existing designs.

Also be aware that for a big heavy boat, outboard motors become less and less attractive or viable, as they simply don't have the torque required to push the boat through the water.
Fallguy's Skoota is 32' and has outboard motors, but it is a big jump up to say a 45' cat that would probably weigh 3 or 4 times what Fallguy's cat weighs.
Note also that Fallguy has basically spent US$150,000 just on materials to build his boat, with him putting in all the labour.

 

I got about 20k in unskilled labor just to have some help during hard projects and one-two days a week.

 

I just came across these folk in Portugal who build power catamarans - their 12 metre yacht seems to be similar to what you have in mind.
I am not too sure though what it would be like travelling along the coast of Norway if the sea is rough.
https://nazarethboats.com/boats/aquacruise-1200/#info

Here is one for sale on Yachtworld -
2021 Planus Nautica Aquacruise 1200 House Boat for sale - YachtWorld https://www.yachtworld.com/boats/2021/planus-nautica-aquacruise-1200-3810416/

 

category C, inshore
capable of seas to 2M
Force 6 winds 22-27 kts

the problem with winds of 22 knots is power and windage; the boat needs sufficient power to quarter

 

It's not so much the wind I'm afraid of as it is the waves. I wouldn't want them crashing into the house. If they smashed their way in, they could flood the house floor and create a terrible "free surface effect" where all that water sloshes to the low side and causes a capsize.

With some hull behind the house, there is some buoyancy to raise the back of the house up out of the way of the on rushing water.

For the engine hp I said would be adequate, I was assuming a displacement of about six metric tons. This would fit nicely with a 12 m length and a 4 m beam.

Adding 3 m to the length will surely increase the displacement, but the twin 30 hp will give you about 40 to 45 hp of continuous duty.

Going by the lower number, and assuming you will need 5 hp per metric ton, you could go up to an 8 mt displacement.

Everything is going to weigh something. And the weights will add up quickly. The big structural decision will be whether you want the house to be an integral part of the hull structure, or you want it to simply sit on top of it.

There are good arguments for either one. If the house is part of the hull structure, it will look less like a house and may have cross beams you will have to step over. But such a choice will also mean less windage per given wall height, and likely less building cost and weight.

With the house simply built on top, all the cross beams will be beneath the house floor, and there will be space under it to place heavy objects, such as batteries, that you may not want to put in the hulls.

The disadvantages are:

1.) that you would be now building a double structure, the hull, then the house. This will certainly come with added structural weight.
2.) that the floor of your house will be at the shear line or slightly higher. Your walls will go up from there. This will mean more windage, short walls, or maybe both. It will also mean less ultimate stability, as the weight of the house, and everything in it, will be higher up. The side walls of the house can be less than 2 m high, as you need not stand near them, but this will dictate your interior layout to some extent. Sitting and laying areas would be near the side walls. Standing ones would be more near the center.

If the floor plan is to extend to the sides of the boat, a means of getting from one end to the other, through the house, must be provided. I would go with a door at each end that lined up with the other.

I also envision a grated deck at each end of the house, that is at least 1 m wide, that runs from shear to shear. These would provide an at least reasonably quick access to the hull decks on either end of the boat. You will need this access for tying up, casting off, and boarding.

I would go with deep "V" hulls that go about 1 m deep to:

1.) provide lateral resistance (as the house walls produce plenty of sail area), and
2.) produce a slower pitching motion an prevent pounding.

These may have actually less whetted area than hull with a different sectional shape with keels added.

 

I wonder if @LandFish is getting a bit disillusioned - the Forum has not seen any sign of him since Saturday.

Landfish, if you are still keen on building this houseboat, I still stand by my opinion that your best bet is to buy a set of plans for a design that is proven - please don't try to design the whole thing yourself.

 

LandFish,
Good advice from Bajansailor.
A proven design, that fits your needs, will save you money, time, sweat, friends, and much more.

 

Thanks! The illustration makes it easy to understand.

Yes I've noticed. I have to make a lot of compromises, but I accept that and will try to find a good solution anyway.

That actually makes a lot of sense that boat builders don't want to give an estimate based on a concept that is not fully designed. I thought maybe they could do the weight estimations and correct the hulls for me so that it could be a functional boat, but this is probably not the case then.

Wow I didn't think there is actually a boat that looks so similar to the drawing I made. Also great that it is possible to buy the design plans and talk with their designers about it.

Thank you so much for this and all the links, it is very enlightening.

Doesn't the website say this boat is category B? Is that better or worse than C?

Wow that sounds really scary, thank you for informing me about this!

Your whole post is very interesting to me, thank you so much for this! I really haven't considered any of these aspects.

Haha, I don't give up that easily. Don't worry I am still here, I just had a busy weekend.

Yes thanks for this, slightly modifying an already working design seems to be the way to go for a novice like me! I will survey the used market first and see if there is something I could live with first and as a last resort modify an existing design plan and get it built.



I knew boat building would be a long and complicated process, but I still feel like I underestimated it. You guys are really cool for showing me the reality of it all and teaching me a lot of things I didn't know!

 

Trouble is, small ferries like this do not seem to come up on the second hand market very often.
I had a look around the Ocean Marine site (they deal in commercial boats) but couldn't find anything suitable.
I did see this very neat 'little' electric catamaran though. A hull form like this would probably work well for what you have in mind.
But be aware that if say 50% goes on the electric propulsion and other outfit, then that is still at least US$ 150,000 just for the aluminium hull.
https://www.oceanmarine.com/detail....6&category_current=18&category_current_sub=46

Here is a nice Malcolm Tennant 45' power cat for sale - but she is US$ 250,000 and is located in Fiji.
You might get some good design ideas from her though.
2007 Malcolm Tennant 45 Catamaran Motor-Yacht, Lautoka City Fiji - boats.com https://www.boats.com/power-boats/2007-malcolm-tennant-45-catamaran-motor-yacht-7505030/

Have a look also at this BDF thread from 15 years ago - this gentleman had fairly similar ideas to what you are proposing.
Affordable, long-term liveaboard? https://www.boatdesign.net/threads/affordable-long-term-liveaboard.8294/

 

The linked boat I looked at said Category C. Category B is a near shore vessel, capable of 20 miles out or farther in fair weather.

Nothing more frustrating than marketing arguing with itself. The blurb said Cat C rivers, the spec sheet says B.

 

tbh, I wouldn't take her 20 miles offshore, ever

 

Nice! This is almost the same size as I was going for.
What if the hull is made out of fiberglass instead of aluminum, wouldn't that reduce the costs significantly?

Cool! I'll read through the thread, seems like there could be some good hints in there.

Huh? Thats so weird that they cant even get their specs straight. I'll assume its the worse category then based on what you said.



I found this boat second hand for about 78k usd. Not a cat, but it has been used for whale safari and such, so it looks pretty sturdy.
And inside seems to be pretty wide and ferry-like. Lots of work needs to be done on the interiors tho, but this might work out.
Im mostly worried about fuel costs of such a big craft. Its has two mega engines which look like they are pretty high cost:
BB Brødrene AA https://www.finn.no/boat/forsale/ad.html?finnkode=198605206

 

I don't think so - not unless you have access to a ready made mould, as otherwise you have to build a male mould, and do lots of filling and fairing.

Re the link to the former ambulance boat, now engaged in whale watching - be very careful when you have to admit that

as the costs can easily get out of hand.

And these large two stroke Detroit diesels have a reputation for being thirsty beasts - not such a big issue where diesel is 'cheap', but I doubt that it would be 'cheap' in Norway. They would be fine if you don't go out to sea with the boat very much, but if you have ambitious cruises planned (you do have a wonderfully long coastline to explore) the fuel costs could get rather expensive (unless you pootle along very slowly).