Electric motors on a Woods Flica 34' sailing catamaran

[nwdiver]

Originally Posted by sailor4life7777

Thanks for the suggestion and looks very interesting! But wouldn't I be able to get the same benefit of this hybrid engine with one electric motor and one diesel motor with comparable thrust? Are there any advantages to the 2 beta engines over the diesel/electric setup?

Thanks everyone for all the thoughtful tips and advice!!!

Redundancy with two systems......

[sailor4life7777]

Thank you so much for the reply I really appreciate it!!

Just out of curiosity were you able to buy the stringers in such a large size? The largest I can find around me is 12' so unfortunately it's a lot of scarfing for me.

I agree with everything you said. Wood does take a lot of time but I heard foam core takes even longer! My understanding is that plywood /epoxy build is one of the fastest ways to build a boat. Please correct me if I'm wrong though!

Originally Posted by Craig Cape Town

Hi S4L. I couldn't figure how to paste pics in pm so I'll just reply here. Please excuse thread drift. I did the wood/epoxy build, as my dad had a woodwork joinery and that's the medium which I had most experience with at the time. Which method are you using?
If I were to build another cat, I'd look for a hurricane damaged hull for reconstruction or use the Derek Kelsall foam core method. Foam core results in a lighter build and glass has greater appeal when it comes time to sell. Wood takes a lot of time (construction, fairing, sheathing and painting).
I was lucky to have other boat builders around who gave me good advice. One in particular, who had just completed a 45 ft Simonis Cat (designer of the Leopard cat), convinced me to make some changes to the origional Woods plan. This is often where home builds go wrong, but having seen the Simonis boat, I thought it was a good idea.
Attachment 228386
I did not like the flat deck surfaces nor the hard chine of the gunnel on the woods cat, so we added curved tops to the bulkheads to reshape the deck and used strip plank to shape the gunnel before glassing over and under it.

Attachment 228387
I continued the stringers about another foot aft of the last little bulkhead to give room for transom steps. On the Woods design there's just a flat panel on the stern.
Attachment 228384
I made the stringers each in one continuous length instead of scarfing them on bit by bit. This made "the rib" cage curve evenly and gave the hull a natural continuous bend. We found that the stringers needed to be forced down onto the stem and the natural curve wanted the stem to be a little further forward. So we made the bow a foot longer by moving the stem forward.
Attachment 228388
This also made the trampoline area bigger. It's really small on the Woods plan. One other reason for doing this is that the woods bridge deck seemed too far forward and at greater risk of bridged deck slamming.
Plywood boxed channels were added underneath and glassed over as bridge deck stiffeners.
Attachment 228385
Here you can see the top of the bulkheads are curved to shape the deck. The extra foot in length makes the fore peak bunk space more useful.

You'll likely get a lot of nay sayers, thinking that you are crazy to build a boat, when there are so many good used boats available. They do have a valid argument. I took quite a knock when I sold as these boats don't have the same perceived value as production boats. If I had worked the same number of hours at a job instead of on the boat, I probably could have bought a used boat with the money earned. The costs add up and if you're doing a home build you need to crunch the numbers and watch you spending. My biggest mistake was renting a warehouse for construction. If you can find a barn or free space, then grab it as the build will usually take longer than you expect. I started by buying cloth and epoxy as I needed, which was quite expensive. Later I bought a 44gal drum of epoxy and full rolls (400ft) of cloth at wholesale prices (half of retail).
Feel free to bounce ideas off of me. Good luck.

[Craig Cape Town]

I made up the stringers by scarfing them together.
The Kelsall kiss method is way faster than wood as you don't have all the fairing to do. Its basically big panels that are tabbed together,something like stitch and glue method.
You can find more info here http://www.kelsall.com/UniqueKSS/WhatIsKSS.pdf

[Double-Wide]

Originally Posted by Craig Cape Town

HI sailor4life.
Another alternative is to use outboards. Here they are on a small cat in Cape Town.

That sort of makes using the aft steps a bit of a problem.

[double u]

so far I have not fully understood what wants to be achieved "going electric" on a bluewater cruising boat:
environmental friendliness?
cost savings?
weight savings?
self sufficiency?

what else?

[Craig Cape Town]

An alternative position is bellow the bridge deck, drop down or in a nacelle.

[tomtriad]

Plan for the worst, hope for the best. Keep it simple and light. All electric sounds great but real world intervenes. Check Jimmy Cornell's experience with an all electric cat and unlimited budget. He packed it in after the maiden voyage crossing from Europe to the Carribean.

Kudos for your optimism, but you need some offshore and passage making experience before spending $$$ on gear. Electric is expensive, heavy (big battery bank needed), and gives you very little cruising range.

Keep it light, keep it simple. Maybe a couple of outboards to start, see if you like passage making. You can refit inboards later. Leave the airfryer home. Think about a wind generator if you want to stay off Grid.

[sailor4life7777]

Hi guys, I've decided that I'm not going to be adding a mast or a sail I plan to use it as a power boat just to cruise around locally around and fish in Ensenada,Mexico so I won't be making any long distance passages.

My plan is to use a 50hp gas outboard engine (that I already have) on one hull and a 3kw elco 5hp electric outboard on the other hull. I plan to install 8x 450watt solar panels for a total of 3.6kw of solar, 2.4kw lithium battery. I want to be able to move slowly with the outboard so I can troll for fish when the sun is out. What do you guys think of this setup?

I plan to put the outboards on the transom of each of the hulls so there would be some weight imbalance issues but I would just need to put the heavier lithium batteries on the side of the lighter electric outboard.

Thanks for any advice or tips I really appreciate all you guys!!

[tomtriad]

The 50 hp is a mismatch. What you need is an extra longshaft high torque motor like a Yamaha 9.9 4 stroke to push you along efficiently at hull speed, around 6 knots.

A shortshaft outboard on the back of a cat will cavitate in a seaway when it hobby-horses.

[sailor4life7777]

Originally Posted by tomtriad

The 50 hp is a mismatch. What you need is an extra longshaft high torque motor like a Yamaha 9.9 4 stroke to push you along efficiently at hull speed, around 6 knots.

A shortshaft outboard on the back of a cat will cavitate in a seaway when it hobby-horses.

Thanks for the input tomtriad!

The shaft of the Honda 50hp gas outboard is approximately 22.5" which I think would be long enough but please correct me if I'm wrong. I plan to only use the gas outboard at around 6knots would that be an issue? I have designed the motor bracket so that the Honda outboard propeller is just below the waterline.

[tomtriad]

Yes. Big issue. Extra-long shaft is 25". Your prop should be at least 1 foot underwater. It will cavitate in even light chop if just under the waterline. 50 hp outboard is too heavy for a light displacement cat. So are the batteries for your electric motor. Do yourself a favor and get Twin 9.9's with extra long shafts. They weigh 98 lbs and are fuel efficient.

[smj]

The Honda 50 comes in long shaft and xl shaft, not sure which one you have. If the prop cavitates and it’s a long shaft you can either lower the mount or get a 5” extension kit.
From my experience you will get approximately the same fuel burn from a single 50hp or twin 9.9hp’s at 6 kts. Difference being the 50 will probably be running at lower rpm’s than the twin 9.9’s.

[sailor4life7777]

Thanks for all the advice guys I really appreciate it. I think I will go with the extra long shaft Yamaha 9.9hp in one hull and then the elco 3kw 5 hp electric outboard in the other hull. The elco electric is 65 lbs and the 2.4kw lithium battery is 50 lbs. The 8 solar panels would be 320 lbs. It would be pretty heavy but remember I'm not putting a mast and sails and all the sailing and extensive passage making equipment so I would save a lot of weight from that.

What do you guys think? Or should I just go with two 9.9hp Yamahas? One of my biggest concerns is rising fuel costs and it would be so nice to have the option to go fully electric.

[fxykty]

Now that we’re full time on the boat and keeping to our own relaxed schedule we have been sailing off our anchor much more frequently. We could use some forward propulsion only when raising the chain so that we’re not pulling the boat forward with the windlass. In light winds no problem, but in more than 10 knots that’s starting to put a lot more load on the chain. (No Sean, with a larger cat, albeit a well sailing one, sailing up onto the anchor isn’t feasible unless there is heaps of room to either side - and many of our recent anchorages in tight sand holes amongst reefs and bombies don’t have much room for wide swings around our anchor).

But starting a pair of diesels for just 5 minutes of operation is not good for them, so I try to avoid that. I find when I do start engines for up anchor then I keep them on longer (in neutral once sailing) to ensure they get 15-20 minutes of running. Electric engines would be perfect for those kinds of really short run times.

For the passage times when we’ve motored for more than a few hours it’s generally been in fairly calm conditions, but I’m not sure any level of battery and solar would allow for more than 3-4 knots of continuous motoring day and night. Hmmm, not sure we’re ready to just sit around, but that could be our recent city lives talking - always in a rush?

Our diesel engines only have 4000 hours on them, so there’s no rush to replace them. Frankly I’d rather spend the re-engine money on several years of cruising. But if we do keep the boat 10 years or more then I suppose electric will be the next engines within our ownership.

[sailor4life7777]

Originally Posted by sailor4life7777

Thanks for all the advice guys I really appreciate it. I think I will go with the extra long shaft Yamaha 9.9hp in one hull and then the elco 3kw 5 hp electric outboard in the other hull. The elco electric is 65 lbs and the 2.4kw lithium battery is 50 lbs. The 8 solar panels would be 320 lbs. It would be pretty heavy but remember I'm not putting a mast and sails and all the sailing and extensive passage making equipment so I would save a lot of weight from that.

What do you guys think? Or should I just go with two 9.9hp Yamahas? One of my biggest concerns is rising fuel costs and it would be so nice to have the option to go fully electric.

Thanks for your advice tomtriad! Does the cavitation plate need to be 1 ft under water or should the bottom of the propeller be 1 ft underwater?