Which one out of these small multi-hull designs will be the best for my needs?

[Eli]

I think it's important to remember these are just estimates. The Siren has never been built and probably no one has weighed any of these boats. Designers uses different methodologies to arrive at estimated dry weight, so comparisons are not very meaningful. The total displacement is meaningful because that is estimated from the volume under DWL, but load capacity is not accurate because one must subtract the inaccurate dry weight from the loaded weight at DWL.

A more meaningful method to compare the carrying capacities of the boats is to add up the volume of the plywood from the materials list and multiply it by the density of the plywood you intend to use. Subtract that number from the displacement at the designed waterline and you will have a more meaningful comparison of load capacity.

There are some designers who actually use this crude methodology and admit to it. The assumption is that the plywood scrap is equal in weight to all the other components (solid wood, epoxy, paint, fittings, rig etc). Even if two designers use this same crude methodology, they may arrive at a different estimated weight because they may use a different plywood density in the calculation.

Can you share the plywood materials list for the Duo1000 and the Siren?

Sure:

Siren 8.4

Plywood (Gaboon) 9mm 56 sheets
16mm Durakore panel 6 sheets
Fibreglass Unidirectional 450gsm 85 metres
Unidirectional 900gsm 30 metres
Double Bias Tape 600gsm 100 metres (150mm wide)
Triaxial 580gsm 85 metres
Double Bias 450gsm 12 metres
200gsm biaxial 25 metres
Oregon (or Hoop Pine) timber 150x50 2.0 lineal metres 7
5x75 2.5 lineal metres
200x25 8.0 lineal metres
75x20 8.0 lineal metres
Cedar timber 20x20 30 lineal metres

Epoxy resin 240 litres (may be more depending on technique)
Filler lightweight 5 kg
Filler filleting compound 25 kg (nominal)
Paint primer 16 litres
Paint top coat 16 litres


DUO 1000

Plywood 8 mm 2,5x1,22m = 67 Sheets
Plywood 6 mm 2,5x1.22m = 28 Sheets
Plywood 4 mm 2,5x1,22m = 17 Sheets
birch plyw 4mm = 24m2

Oregon pine:
25x25mm 200 m
25x35mm 520 m
25x50mm 130 m

Glass cloth 225 grams/m2 330m2 Glass covering
Bi-axial glass 450 gr/m2 13m2 beams
UD glass 550 gr/m2 4m2 aftbeam
Epoxy/hardener 250 kg
Silica 3 kg
Glass spheres 8 kg
UD carbon 300gr/m2 50mm 40m rudder, daggerb
Foam 70kg/m3 10m2 bridge deck

 

[Eli]

I think you've answered your own question. Among these three designs, Woods Eagle 24 does everything you want it to do and is substantially easier and cheaper to build and maintain than the other two.

I will point out that there are a lot of catamaran designs in this size range without centerline bridge deck steering stations, and there's probably good reason for that in terms of optimal use of the available space in a relatively small cruising multihull. I am happy to suggest a few designs easier and cheaper to build than even Eagle 24, some trailerable, if you'd like.

Sure, that would be nice.

 

[cluttonfred]

Sure, that would be nice.

OK, then let me ask what are your actual requirements in terms of how many people you'd like to have sleep onboard and for how long at a time? I imagine you are only looking at multihulls, but is it only catamarans or would trimarans or proas also work?

 

[waterbear]

Thanks for the material lists.

Also be aware these designers probably expect you to be building in okoume/gaboon plywoods such as bruynzeel or joubert, which are not cheap. If you use a cheaper plywood such as meranti you may see your plywood weight increase by 25-50% which cuts into payload capacity.

Admittedly my plywood weight estimate doesn't really work, perhaps this is only used by designers of very small craft and not multihulls. I added a somewhat arbitrary fudge factor of 1.5 and it now works pretty well. Here's my formula.

(Cubic meters of plywood)*(Plywood density)*(Fudge factor of 1.5)= Dry weight of the boat.

I'm using 450kg/m^3 for okoume, let's see how this works...

Eagle

0.92 m^3 of plywood equates to 622kg of boat weight. This is pretty close to the designer's estimate.

Siren

1.52 m^3 of plywood plus 75 kg of duracore gives us 1087kg estimated boat weight, which is again pretty close.

Duo 1000

2.61 m^3 of plywood gives an estimate of 1761kg boat weight. This is a little further off, but also pretty close. Building this boat in birch ply (as is specified for some panels) would add another 575 kg to the dry weight, and result in a grossly overweight boat with significantly reduced load capacity.

Gypsy

1.52 m^3 of plywood gives us 1087kg. This is way less than the designer's estimate of 1800kg. I'm not sure what's going on here, but it suggests Gypsy is going to be a lot lighter than the duo1000, despite a having a higher advertised dry weight. Gypsy is also 4000kg at DWL, so is probably the king of carrying capacity in this group. This also means you could build in a cheaper, heavier ply and still have good load capacity.

This is of course a very crude comparison, but I do think it has some validity and is useful for making comparisons.

 

[guzzis3]

At my other computer I can right now using this machine a bit anyway.

You have options. Just some thoughts:

Wizard / Sango

Ply. No not fold, just normal. Easy to build, very good to Sail, good accommodation for a family.

Eagle 24 with cutting. Galley in hull. Double bed in the cutting. Family can sit on a double bed and eat we try. Toilet in one hull. Three singles. To race better for Dagger board.

Sailing Catamarans - Saturn - 8.8m hard chine performance cruiser with central cuddy https://sailingcatamarans.com/index.php/designs-2/3-25ft-to-30ft-catamarans-designs/173-saturn

Instead of Siren 8.4, DUO 1000 consider Saturn

Money and time to build about Similar. Good accommodation. Very good sailing boat

2c...

 

[Eli]

OK, then let me ask what are your actual requirements in terms of how many people you'd like to have sleep onboard and for how long at a time? I imagine you are only looking at multihulls, but is it only catamarans or would trimarans or proas also work?

The design parameters - a vessel that is fun to sail and race during weekends, and is also able to
take a small family for a few weeks per year cruise in the Mediterranean, during the summer season.

The boat would accommodate a couple and 1-2 kids for a few weeks at most together with some basic amenities
like shower, toilet (wet head ), and a small fridge in the galley.
The solar system of 2KW panels, 5KW Lifepo4 bank, 4KW backup Generator and 50L fuel, add additional 175kg.
This additional weight is being offset by a large margin by the fact that there is no need to carry fuel for the outboard (electric),
no need to carry gas for cooking (induction) and heating(electrical). Everything is provided by Solar.
I also intend to use synthetic rigging which should offset the weight further.

I have looked at Tris. At 30ft range a trimaran have less accommodation than a similar Cat and has a wetter ride.
Kurt Hughes has some nice designs, but I prefer the open deck of a catamaran. Catamaran has also the most surface for
solar panels. An important point these days and one of the major factors in favor of catamarans.

I also did look at proas - in Particular Rob Denney's Harryproa cruiser 50. I like the design and the advantages it brings in terms of speed and safety.
I would build one of those, and intelligent infusion seems like a nice technique to learn. However, the design is still being refined, with few
first hulls now being built. I am waiting to see actual build time figures and costs, which for now seem higher than initially estimated
when met with everyday reality and the rising costs. Once the first few ones will be bult in Fiji, the actual costs and building times will be more precise.

That leaves the homebuilt plywood Catamaran designs as the most sensible option for a budget family cruiser.
However, I would be happy to be proved wrong.

Regards,
Eli.

 

[Eli]

Thanks for the material lists.

Also be aware these designers probably expect you to be building in okoume/gaboon plywoods such as bruynzeel or joubert, which are not cheap. If you use a cheaper plywood such as meranti you may see your plywood weight increase by 25-50% which cuts into payload capacity.

Admittedly my plywood weight estimate doesn't really work, perhaps this is only used by designers of very small craft and not multihulls. I added a somewhat arbitrary fudge factor of 1.5 and it now works pretty well. Here's my formula.

(Cubic meters of plywood)*(Plywood density)*(Fudge factor of 1.5)= Dry weight of the boat.

I'm using 450kg/m^3 for okoume, let's see how this works...

Eagle

0.92 m^3 of plywood equates to 622kg of boat weight. This is pretty close to the designer's estimate.

Siren

1.52 m^3 of plywood plus 75 kg of duracore gives us 1087kg estimated boat weight, which is again pretty close.

Duo 1000

2.61 m^3 of plywood gives an estimate of 1761kg boat weight. This is a little further off, but also pretty close. Building this boat in birch ply (as is specified for some panels) would add another 575 kg to the dry weight, and result in a grossly overweight boat with significantly reduced load capacity.

Gypsy

1.52 m^3 of plywood gives us 1087kg. This is way less than the designer's estimate of 1800kg. I'm not sure what's going on here, but it suggests Gypsy is going to be a lot lighter than the duo1000, despite a having a higher advertised dry weight. Gypsy is also 4000kg at DWL, so is probably the king of carrying capacity in this group. This also means you could build in a cheaper, heavier ply and still have good load capacity.

This is of course a very crude comparison, but I do think it has some validity and is useful for making comparisons.

Thanks for the detailed comparison.
The Gypsy is 2400kg loaded (the confusing number is 4000lbs empty, on the design page).

 

[Eli]

At my other computer I can right now using this machine a bit anyway.

You have options. Just some thoughts:

Wizard / Sango

Ply. No not fold, just normal. Easy to build, very good to Sail, good accommodation for a family.

Eagle 24 with cutting. Galley in hull. Double bed in the cutting. Family can sit on a double bed and eat we try. Toilet in one hull. Three singles. To race better for Dagger board.

Sailing Catamarans - Saturn - 8.8m hard chine performance cruiser with central cuddy https://sailingcatamarans.com/index.php/designs-2/3-25ft-to-30ft-catamarans-designs/173-saturn

Instead of Siren 8.4, DUO 1000 consider Saturn

Money and time to build about Similar. Good accommodation. Very good sailing boat

2c...

This is very close to what I was thinking as well, a stretched Eagle with a hard top and a bench with table, that converts to double bed.
Toilet and shower (wet head) in Starboard front, instead of bunk.
Galley in Port hull, together with a small sitting Nav station 1m wide in Port hull forward, instead of bunk.
Aft bunks stay the same.
This configuration can sleep 3-4, with amenities for few weeks cruise.
The hard top can be closed with soft enclosure on the sides in weather.
The stretched hull adds some buoyancy, partly compensating for weight of the hard top and the additional supplies.

 

[cluttonfred]

The design parameters - a vessel that is fun to sail and race during weekends, and is also able to
take a small family for a few weeks per year cruise in the Mediterranean, during the summer season.

The boat would accommodate a couple and 1-2 kids for a few weeks at most together with some basic amenities
like shower, toilet (wet head ), and a small fridge in the galley.
The solar system of 2KW panels, 5KW Lifepo4 bank, 4KW backup Generator and 50L fuel, add additional 175kg.
This additional weight is being offset by a large margin by the fact that there is no need to carry fuel for the outboard (electric),
no need to carry gas for cooking (induction) and heating(electrical). Everything is provided by Solar.
I also intend to use synthetic rigging which should offset the weight further.

I have looked at Tris. At 30ft range a trimaran have less accommodation than a similar Cat and has a wetter ride.
Kurt Hughes has some nice designs, but I prefer the open deck of a catamaran. Catamaran has also the most surface for
solar panels. An important point these days and one of the major factors in favor of catamarans.

I also did look at proas - in Particular Rob Denney's Harryproa cruiser 50. I like the design and the advantages it brings in terms of speed and safety.
I would build one of those, and intelligent infusion seems like a nice technique to learn. However, the design is still being refined, with few
first hulls now being built. I am waiting to see actual build time figures and costs, which for now seem higher than initially estimated
when met with everyday reality and the rising costs. Once the first few ones will be bult in Fiji, the actual costs and building times will be more precise.

That leaves the homebuilt plywood Catamaran designs as the most sensible option for a budget family cruiser.
However, I would be happy to be proved wrong.

Regards,
Eli.

Thanks, Eli, that sheds a lot of light on what you're looking for. I guess "budget family cruiser" means different things to different people, but you clearly need bunks for four adults as kids have a tendency to grow if you feed them. Mine are all young adults now and the two boys each passed me in height at age 15, though I am still a little taller than my daughter. As for the rest, many multihulls are relatively limited in their weight capacity for a given length, trimarans even more so than catamarans, so given your requirements you have to go pretty big.

I guess my image of a cruising catamaran is something much more modest like the original Wharram Tiki series. In fact, you should definitely take a look at the Tiki 30, which even has an optional deck pod. The plans are expensive but overall it's a proven, ocean-capable design and plenty big enough for your needs. While 30' long I doubt it would be harder or longer or more expensive to build than the Woods design. Similarly, the late Thomas Firth Jones had a couple of designs worth considering, Brine Shrip and Dandy II, that are a little more spacious than the same size Wharram boats. There are many more out there, but I suspect that you'll find most of my suggestions too spartan for your taste.

Lastly, I am not sure that your all-electric solution makes a lot of sense in terms of weight or economy in a small cruiser. By getting your cooking, hot water, and propulsion from the panels and batteries you've greatly increased that need and cost and then you still have a generator and 50l of fuel anyway. A couple of big solar panels and a large Jackery/Goal Zero/etc. power station would cover all your lights and electronics and such and could also be tied in to the alternator on your outboard for extra juice when the engine is running. Your 50l of generator fuel will run a 9.9 hp 4-stroke for 10 hours or a 6 hp one for 20 hours and an ordinary 6 kg kitchen-size butane gas bottle (and a spare) will run a nice gas cooker and a small tankless hot water heater just fine.

 

[waterbear]

Thanks for the detailed comparison.
The Gypsy is 2400kg loaded (the confusing number is 4000lbs empty, on the design page).

Good point. Although if the gypsy were built open deck the carrying capacity would be a lot better without the deck pod. But you also say you want 4 bunks and a wet shower, which is difficult to shoehorn into an open deck catamaran in this size range.

I disagree with cluttonfred's suggestion of the Tiki 30, because it's so small inside. No standing headroom, etc. At least you can stand up inside Gypsy.

You might also consider the Waller TC750, which is a bridge deck boat the size of Eagle. This boat has very cleverly packaged a standing head with shower, a double berth, two single berths, a standing kitchen and a dinette. And it doesn't look bloated. The downside is the boat is narrow for trailering.

I also have an off the wall suggestion: Bolger AS39 monohull. I just saw a thread about this elsewhere, apparently the first was built singlehandedly in 6 months out of 70 sheets of plywood (although they didn't say what thickness), and was later "sailed in the Mediterranean, the coast of Africa, across the Atlantic and extensively among Caribbean Islands" before being lost to a lightning strike.

 

[guzzis3]

Bolger AS39 to big ??

Tiki 30 no!!!

Waller TC750 7500 but hard to build ??

Eli: 25'. 28', 30' now Harryproa 50 ???

 

[waterbear]

Bolger AS39 to big ??

I mentioned the AS39 as more of an interesting data point than a suggestion - I don't expect Eli would actually want to build one! That said, how do you define "big?" Interior Space? Sail area? Weight? Cost? Slip fees? Time to build? Number of Sheets of Plywood? As an example, at my local marina the slip fees for the AS39 would be $439, while the Duo1000 would cost $459, because there is a 20% surcharge for catamarans. I believe the fee used to be 50%, which would make the difference pretty dramatic.

If Eli is motivated and effective then the Duo 1000 can be built. It's best to be motivated, building to plan and not sweating the details. Otherwise it's best to build the simplest boat that meets your needs to maximize the odds of finishing the build.

 

[waterbear]

I found something else interesting. The Woods Tamar is similar to the Duo 1000 (both are bridgedeck plywood cats with similar overall dimensions), but utilizes about 9% more plywood by volume. However, the dry weight of tamar is estimated at 3,000 lbs, vs 1,600 for the Duo. This suggests either the weight of tamar is very conservative, or duo is wildly optimistic, or somewhere in between.

 

[Eli]

Thanks, Eli, that sheds a lot of light on what you're looking for. I guess "budget family cruiser" means different things to different people, but you clearly need bunks for four adults as kids have a tendency to grow if you feed them. Mine are all young adults now and the two boys each passed me in height at age 15, though I am still a little taller than my daughter. As for the rest, many multihulls are relatively limited in their weight capacity for a given length, trimarans even more so than catamarans, so given your requirements you have to go pretty big.

I guess my image of a cruising catamaran is something much more modest like the original Wharram Tiki series. In fact, you should definitely take a look at the Tiki 30, which even has an optional deck pod. The plans are expensive but overall it's a proven, ocean-capable design and plenty big enough for your needs. While 30' long I doubt it would be harder or longer or more expensive to build than the Woods design. Similarly, the late Thomas Firth Jones had a couple of designs worth considering, Brine Shrip and Dandy II, that are a little more spacious than the same size Wharram boats. There are many more out there, but I suspect that you'll find most of my suggestions too spartan for your taste.

Lastly, I am not sure that your all-electric solution makes a lot of sense in terms of weight or economy in a small cruiser. By getting your cooking, hot water, and propulsion from the panels and batteries you've greatly increased that need and cost and then you still have a generator and 50l of fuel anyway. A couple of big solar panels and a large Jackery/Goal Zero/etc. power station would cover all your lights and electronics and such and could also be tied in to the alternator on your outboard for extra juice when the engine is running. Your 50l of generator fuel will run a 9.9 hp 4-stroke for 10 hours or a 6 hp one for 20 hours and an ordinary 6 kg kitchen-size butane gas bottle (and a spare) will run a nice gas cooker and a small tankless hot water heater just fine.

You are probably right about the weight economy in a small cruiser. It would make more sense to build the smallest design that actually fits my needs, rather than try to adapt and overload a light displacement design affecting its performance and safety.

There is something comforting about solar, knowing that you do not depend on any port for your needs - indefinitely. Being able to cook, heat your water, power instruments and enter and exit marinas
without need for fuel is also a great safety factor. There is also the added benefit of sailing and motoring in absolute silence, no gasoline smell on board, no scheduled services (except a small backup genset), no engine oil and filter changes, etc. That being said, I also recognize the weight and money savings, not speaking about simplicity of a small outboard with an alternator. For those who just want to get on water without spending fortune and time it is a great option.

 

[Eli]

Bolger AS39 to big ??

Tiki 30 no!!!

Waller TC750 7500 but hard to build ??

Eli: 25'. 28', 30' now Harryproa 50 ???

According to Rob, a Harryproa "Cruiser 50" can be bult at home in 1500-2000 hours and around 100k $USD.
Not much far from Wood's and Bernd's 30ft +/- designs.
I like the idea. However, till the few ships being built now are completed, we do not have the actual numbers.
The C60 being built professionally at Ballota is getting close to 500k + $USD for a finished boat.

I like how Wharram designs look, there is something romantic and magical in them. However, for actual sailing - I prefer the performance and safety of a modern designs in the likes of Woods, Shuttleworth, Bernd, Waller etc...