CNC Plans not Included

I always show my mates the sig 45 as being close to my ideal boat. Less to build time, less materials and higher performance. The layout has a lot going for it for sure. But it shows how shade needs to be designed in from the start if that is a big consideration on the SOR. An open deck with removable furniture could be good, but some permanent furniture can act as storage too.

One thing I can promise you is that if you can't easily and safely zip up the mainsail bag you will be motoring more than you had planned. Having a hardtop capable of walking on, to zip up a sail bag makes it easy. My last boat had the zip out of reach and made it very unsafe an difficult to zip up the bag. A dreaded chore which meant the main didn't come up for shorter legs around the islands. Philosophy has its role it yacht design, and things that are easy to use get used, things that are hard to use don't get used as often. A walkable hard top to tend the boom (even if only strong enough for one person in a certain area) is a must for me after dealing with the poor design I had. A common prob I see with many designs.

I agree upwind performance to be a priority, prioritised somewhere behind shade. Most charter cats have next to no upwind performance. Obviously the total lift to drag ratio of the boat is what matters here, both above and below the waterline. If the charter cat with its towering super structure remained, but somehow the boat weighed 1/4 as much, like the designs we are talking about would, and had daggerboards, it would suddenly sail much MUCH better will to windward even with the superstructure. But obviously much better again with less supers structure.

If I can find the article by a prominent designer which talked about weight and windward ability I will link it. I think maybe Shuttleworth had an article where he broke down windward performance gains on Dogstar, where you could see exactly how much weight reductions and aero gains each contributed to windward performance? I'm trying to dig it up..

Obviously no one here wants a huge super structure, and a hard top as low as possible, maybe even fitted with removable windows (or maybe even a totally removable hard top for Hamilton Island race week etc at some effort) is not going to result in poor windward performance when you look at the entire package IMO. That being a very lightweight daggerboard boa, with a smaller than average frontal profile even with a hardtop. I think even with the hardtop it should beat racer cruiser monos in upwind VMG in most conditions.

The Voyage day charter cat I went on had a huge stainless tube frame syle full bimini top with canvass. Full roll down plastic available, but the center section below the boom was re-enforced with a kind of board walk for tending the boom. Perhaps an option? Maybe even removable and storeable for storm conditions with significant design work.

 

That is catamarans, higher structure is unavoidable due to the elevated bridge deck with adequate clearance, you really can't go any lower without unacceptable slamming.

 

For sure Dennis, if this were my design (not jorges) I would have elements of the sig45, probably with some form of hard top(s) similar to graingers hardtop between each dodger on each hull. Would have to be remove able for racing as you say.

The windage is more important than the weight when sailing upwind - although weight and windage usually go hand in hand. But thats how catamarans got this reputation by monohull sailers - remeber the old saying cats dont go upwind? The monohulls were normally much heavier for given sailplan, but they didnt seem to struggle upwind like the lagoon style cats - due to the windage. I noticed it on the oram 39C we had - it went great on a reach or run as it was light, easy to see over 16kts without pushing too hard, but upwind it was a dog thanks to the massive lagoon style coach house the previous owner put on it... Its all in the lift/drag as you said, and the aero drag is all 100% negative VMG. So is the leeway - where the hull and dagger boards (or lack thereof) L/D comes into it.

But if you look carefully at the sig45, you will see so many ways in which they have minimised things. Most of the interior doesn't even need fairing as its covered with other "stuff" such as the seating, lighting panels etc. It really does look like a simple, quick to build design. The high price tag is in the carbon and rigging....

Like you, I would also prefer 2x outboard motors instead of diesels. Much cheaper and lighter for a start, tilt them up out of marine growth and harms way, nothing to maintain below the waterline etc If you can budget or justify the electric drives then that would be preferential to diesels also- I also swore I'd never have diesels in a cat again either, such a pain to work on them in narrow hulls. Fine if you have plenty of space... plus they were very noisy in a sandwich boat, light panels really transmit the sound everywhere... Id only consider electric drives if i had a genset - and i havnt needed one of them in my little 35ft boat - even with a scuba compressor aboard, i should not need the weight and cost and maintenance of a genset either... less is more

 

Worlds best score you purchased there! As boats get smaller, people don't, so the bridgedeck on a 39 footer is going to be a large % of drag, especially as the rig was fairly conservative on that boat. In combination with LAR keels I couldn't imagine it being amazing upwind, but I imagine it would have blown away a lagoon 39. A lower weight just means faster speeds, so you will usually get there faster in all directions, and the appendages work more efficiently with speed which further aids upwind VMG. But I totally agree, windage matters. My main point was a lightweight long cat like what we are talking about could tolerate a hardtop while stilling sailing very well to windward.

I have an idea for a hardtop that can be lowered flush with the foredeck toward the front, and allowing sitting head height toward the rear. For visibility you would look over it. For those times you need to do longer upwind passages the reduced comfort will be tolerable.

My last boat had hatches in the cockpit which leaked salt water on the engines. Standard design in many cats. A maintenance Nightmare. I was always in the cramped hot space fixing something. Combined with props that cost $2K+ each. Shaft drive diesel with the engines inside the cabins out of salt waters way, and better access would be a gigantic improvement, but hard to design the interior around. Plus no problematic $ail drive$ to worry about. The expensive props still remain.

I snapped an output shaft on one of my saildrives by wrapping a discarded anchor rode that was cut off when someone fouled their anchor. I dislodged the grapnel anchor and wound it up to the hull until it was slamming on the hull sides. You have probably heard about the lagoon which SANK after a simple dingy painter wrap ripped the engine off its mounts and pulled the leg out, breaching both rubber seals. Sure, better bulkhead design would have saved the boat from sinking, but that would ruin you cruising plans at best.

What a **** setup. No thanks, not for my imaginary dream boat. Anecdotes like this make help those that have not been there and done that to choose on what may best suit them.

 

Higher than what? With a removable hardtop much windage could be avoided.

 

The Grainger drawing shows a hard top with side panels that are pretty vertical. It does look like it would cause some wind resistance.

I was thinking a hard top with tapered edges, no front or back and open on the sides as well. Any kind of flip down, roll down protection would flip up, roll up completely into the top and it would need to be pretty thick core with camber to be strong enough to walk on. My guess is it's about a 13 foot span, might need a couple of supports down the middle.

I don't have the sailing experience, clearly it's not going to be as fast as a racing, catamaran but surely it's not going to slow it down like a charter cat?? Maybe it does need to be removable.

I wanted outboards but I read a lot of opinions where they are a pain mounted on the stern. In a seaway they are always popping up losing bite ... this is me repeating, I have no idea, I run my prop completely above water level with my tunnell hull.

A couple of other issues, you have to carry gas, theft, it's not as reliable as electric, as much work to install and it's not as elegant a solution.

So an electric sail or shaft drive (side mounted) with a keel in front for protection - guess that's what you would call it - is where I am at right now. I've even been thinking that the sail drive should be mounted in it's own sealed area (case) so if it's ever ripped off the hull water ingress would be limited. Ideally the motor and the drive would both bolt to a center flange so they could be removed and serviced without pulling the boat.

That said electric shouldn't give any problems for years and years so maybe not worth it. I saw some videos of a White cat doing pretty good into the wind. I will see if I can find it, the owner is recounting a trip where the bulkier cats just anchored up since they couldn't make any headway and he was able to sail on to his destination no problem.

We are talking about a lighter boat with no front on the cockpit, surely it's going to be as good.

 

You don't mount the outboards on th3 transom Jorge the elegant solution is to have them tucked away in a nook which is scalloped out from the inboard side of the hulls at about 1/4 LOA forward of the transom, usually around the cockpit area so the engines are located under a seat or such like so that they don't intrude into the interior spaces.





View from the front looking aft, neatly tucked in...


Th3 cat shown in there above pics used to have torquedo drives installed. Th3 owner hated them after numerous failures and eventually got rid of them. They were the early versions tho, probably better sorted now, but the problem remains with having enough power to run them. Inevitably you WILL find yourself in a situation where you really want to motor for a significant distance / all day. Such as a rigging failure preventing sailing, no wind -and have to be somewhere by a certain deadline, whether it be getting to the shops for provisions, picking up pasengers, getting back to do some work, emergency situations etc- stuff happens from time to time... and you just don't have enough energy to do that without a pretty big gen set to supply power for propulsion. These are expensive and heavy and noisy. A boat like this only needs a dec3nt solar and inverter setup, with a wind turbine, and you'll always hav3 enough power for anything. Cheap to setup, silent ( save the wind turbine) and lightweight, low complexity... less is more

Save a g3nset and 2 diesels on sail drives, there's nearly a tonne of weight gone already, not to mention saving $50k still in your pocket...

I was th8nking a hard Bimini behind each dodger of the sig45 layout. Kept open in the center where a boom tent could span between each Bimini. Roll down clears for foul weather...

*God I hate typing on a tablet , please ignore all the out of place numbers!

 

I'm not sure where you got the opinion that an electric yacht is more reliable than outboards? This is quite a new application for electric motors and the data is not really there for yachts yet. I know someone who swapped to outboards to GAIN reliability over thier torqueedo setups, granted an older version. The control systems are very complicated with an intricate web of solar, chargers, batteries, gen sets etc. So many more places for failure, and you will struggle to find parts when it does fail. IE just the genset is more complicated than an outboard and the genset is about 1/3 of the componentry in a hybrid system.

Outboard mechanics and whole outboard motors can be found just about anywhere and are easy to swap over, and you have 2 which don't rely on any shared resources to work independently.

Carrying gas? Well a decent dingy needs it unless you are willing to give up planing. Carrying just one fuel is less complicated IMO. With the correct installation of OBs the other issues are just not there. This is how you do it right.

http://www.boatdesign.net/forums/multihulls/outboards-nacelles-51157.html#post700423

That's my friends boat, Schools Out. He experimented with electric, then with a single large OB in the middle. Then just went to the above method that anther friend perfected in his Oram 44 which is well proven.

I think electric motors with shafts could be pretty cool. I'm an electrician, I work in the renewable sector, so it hurts me to say I am yet to see anyone do an electric propulsion system in cruising sailing boat I would deem to be acceptable (for my useage). Please show me otherwise I really want to believe! Many people who tried it find it unacceptable and revert back to fossil fuel like above. But improvements are coming along steadily. By the time you build your boat, battery energy density and cost may be much better.

Recently, on my last trip on Bedar before I had to let her go, I had to return from the Whitsundays to Brisbane against the prevailing 20-25K winds to meet a deadline. Any sensible cruising skipper would have done what I done, that is to motor at 7-8K for 15-24H at a time to reach sheltered anchorages in the short gaps between the opposing winds to cover 550nm. Would the electric system you are thinking of be able to do this? I could do it with one 24hp diesel running at a time, using about 2L of fuel per hour and Bedar is a lot heavier than the boats we are talking about in this thread.

All the other failed attempts of getting adequate range, power, reliability are always done by someone who thinks they can do it better. But IMO the system is heavy, has poor range under battery, is complicated and not reliable, and has low power. Not really good attributes for something that costs an extortionate amount of money.

IMO the best hybrid system is one shaft diesel with pancake gen/motor in one hull, and only an electric shaft drive in the other (yeah use sail drives if you must, I just don't like them ). With this, you could steady state motor under direct diesel power to complete almost 1000nm at 8k with no wind or a damaged rig. The trip I did from the Whitundays to Brisbane would be doable. http://www.hybrid-marine.co.uk/8.html That's what I would have if I wasn't paying for it. Give the best of both worlds.

The diesel would also act a genset, making it useful for more than one task. The other hull with the electric will be used for maneuvering or also covering distance should conditions and energy storage allow it. The hybrid diesel/gen/motor can also be used just as an electric motor. IMO this makes so much more sense than 2 electric motors and single genset. Its asymmetrical, so it puts people off. But is much more versatile, and at the end of the day will propel the boat as long as you can start the diesel in the event of failures in the complicated electrical system. Propel it until the diesel runs out at whatever the HP of the diesel engine is, rather than the pissweak electrical genset power minus losses when the battery is flat. Also this system would be even lighter than 2 x diesels! A gigantic battery bank (cost and weight) will not be a requirement to fill the gap in power for demanding conditions where the genset cant keep up as you will have a real a 40 or 50 hp engine in those times. Yet all the benefits of electric propulsion will still be there!

My cheap arse version of this would not use the megga expensive clutched hybrid pankake motor. Just a regular diesel engine with well designed high output alternator or 3 with chain drive. The other hull would have an electric setup sourced from EV works or similar. https://www.evworks.com.au/. The idea being cruising cat sailors motor with one engine anyway, but you need 2 for maneuvering. This solves that issue and the set up would actually be cheaper and lighter than 2 regular diesels. But at the end of the day, 2 x outboards still seems an obvious choice for weight, cost, simplicity, reliability, maneuverability in shallow water, ability to repair/replace in remote locations and just carrying one fuel on the boat which also powers the dingy. That saves carrying a heap of jerry cans and will save weight too. Schools out actually has the same 20hp engine on thier dingy as the cat. Hows that for carrying spares! Just find any old cheap engine to put on the dingy should you need to put the good one on the mothership.

 

hehe Groper, my post took too long to write.

 

Here is the video of skipper talking about his experience in a White design. Starts talking about going upwind at the 5 minute mark - https://chriswhitedesigns.smugmug.com/VIDEOS--HOW-TO/VIDEO-Atlantic-48/i-RdkGRgC

I read about early problems with Torqeedo but nothing except rave reviews lately. Electric outboards would be interesting. Solar panels and Wind vanes, sure but you still need the heavy stuff, Batteries. I personally would have a genset though it would rarely be used, no wind, no sailing.

I also like well thought out, engineered solutions which is why, despite the crazy cost, I like the Torqeedo Deep Blue Hybrid System. They market it in the same way I see myself marketing my boat.

 

If your really thinking about electric drive you might want to check out this discussion,

http://www.cruisersforum.com/forums/f48/oceanvolt-hybrid-motor-172720.html

 

Do you also believe the marketing about electric horses being bigger than fossil fuel horses?

 

Yeah that thread has good points on both sides. This is not a thread on what is better gas outboard, diesel or electric. That's the beauty of a new build everyone can stipulate their own power.

I understand the reliability of electric motors and the concept of low rpm torque and how that plays in favor of an electric drive. I don't know what you mean by bigger horses compared to fuel. 40HP is 40HP as far as I am concerned.

I like the idea of an outboard because you don't need to make holes below the waterline ... but in that case I would still go with an electric, that is my choice, everyone to their own.

EDIT -- Don't know how well that gas outboard tucks into the bridgedeck, I assume it's going to get wet. Torqeedos are rated for 30 minute submersion at one meter. I like that.

 

I also like the idea of an electric outboard. Mounted like we showed above. I'm not totally against electric. I like to be objective when it comes to performance, and reliability. I am not convinced.

Just about every electric boat propulsion manufacturer blatantly lies about the performance equivalence of thier products compared to diesel engines when comparing power ratings. This is a direct quote from the Oceanvolt site.

They even spelled powerful wrong to avoid litigation?

http://www.boatdesign.net/forums/propulsion/electric-horses-really-bigger-55435-3.html#post772775

The above linked post cuts the BS nicely with evidence. The whole thread is a good read too. I really do love electric power. Like I said, I honestly want to believe, but its not a matter of faith. I think electric power is really good for so many reasons. I'm totally convinced its right for cars with todays technology for about 90% of the population.

 

Well I can't speak for Oceanvolt or that type of marketing. A lot of people now using electric are happy with it.

This was a fun video to watch - https://www.youtube.com/watch?v=bOOhsP6aBEg ... 16 yo dutch girl sails around the world. Between 7 and 8 minute mark she mentions not having wind for 2 weeks and that - It was very frustrating - ))

She also had no desalinator, no fridge!!! GROPER is this your daughter?? lol )) KIDDING!

I could do that when I was 16, can probably do that now, but no thanks ))