Electric dink options for your Catamaran

[tp12]

Good Morning from overcast Sydney.

One part of the 'going electric' debate that I haven't really looked into yet is the electric dink. For me, it will need to meet the following requirements:

1 - capable of planing with 4 adults
2 - able to do the shopping with 2 adults
3 - dive/fishing/spearfishing tender for 2, added bonus for 4
4 - anchorage/area exploration - needs a decent range

Is anyone doing it now with a configuration that they/you think will meet those requirements? Or most of them? What are the options? Battery size/life is a big consideration for me here but it's something I don't yet have my head around in terms of options/range etc.

Ta muchly

Edited to add:
5 - Recharge from the mothership (yes,I've seen the other thread)
6 - Some form of independent charging capability - not expecting big things here

[BigBeakie]

Originally Posted by tp12

Good Morning from overcast Sydney.

One part of the 'going electric' debate that I haven't really looked into yet is the electric dink. For me, it will need to meet the following requirements:

1 - capable of planing with 4 adults
2 - able to do the shopping with 2 adults
3 - dive/fishing/spearfishing tender for 2, added bonus for 4
4 - anchorage/area exploration - needs a decent range

Is anyone doing it now with a configuration that they/you think will meet those requirements? Or most of them? What are the options? Battery size/life is a big consideration for me here but it's something I don't yet have my head around in terms of options/range etc.

Ta muchly

Edited to add:
5 - Recharge from the mothership (yes,I've seen the other thread)
6 - Some form of independent charging capability - not expecting big things here

Here is what we have done. This is probably smaller than what you'd want if you want to regularly carry 4 adults, but this was designed for the 2 of us to take our SCUBA gear.

It has flat front deck with dive ladder, under deck is plenty of storage for anchoring gear, personal effects etc. There are locking side inside panels to store mast & sails/fishing rods etc. We'll be using the e-Propulsion Navy 6 (which I have tested ) with 2 x Valence U27-24XP in a battery box that serves as a perfect seat for rowing. The battery box lifts in and out via the davit dinghy lift winch. Batteries are charged by 2 x 350w solar panels that come off our davit to go on the tender as a sunshade bimini cover ( when we're not sailing).

Beaching keels have insert bushes to take axle for beach wheels to pull it up on shore.

It should be a credible sailing tender that rows very well and can be pushed by the 6kW electric on battery at "planing speed" ( given that cats don't plane) with 2 adults, and move along quite reasonably on solar alone for unlimited range as long as the sun is shining.

[tp12]

Originally Posted by BigBeakie

Here is what we have done. This is probably smaller than what you'd want if you want to regularly carry 4 adults, but this was designed for the 2 of us to take our SCUBA gear.

It has flat front deck with dive ladder, under deck is plenty of storage for anchoring gear, personal effects etc. There are locking side inside panels to store mast & sails/fishing rods etc. We'll be using the e-Propulsion Navy 6 (which I have tested ) with 2 x Valence U27-24XP in a battery box that serves as a perfect seat for rowing. The battery box lifts in and out via the davit dinghy lift winch. Batteries are charged by 2 x 350w solar panels that come off our davit to go on the tender as a sunshade bimini cover ( when we're not sailing).

Beaching keels have insert bushes to take axle for beach wheels to pull it up on shore.

It should be a credible sailing tender that rows very well and can be pushed by the 6kW electric on battery at "planing speed" ( given that cats don't plane) with 2 adults, and move along quite reasonably on solar alone for unlimited range as long as the sun is shining.

I think it's pretty close to meeting my requirements, if it doesn't already. I assume you're planning on removing the battery box for charging in the cockpit/similar from the bank? Or just charge from the two panels?

I love that it sails and rows and is stable. I'd be pretty keen to see how you get on with it. It could be a lot of fun in its own right. It'd be a great fishing platform.

[valhalla360]

Everything but planning is easy. If you want planing, you run into the energy storage problem.

I've thought, a cat hulled dingy with long narrow hulls (think like a hobie) wouldn't take a lot of power to get decent speed. You could add solid bimini that folds down when not in use that holds solar panels.

Assuming a 14' by 6' dingy (hanging off the back of a 40-45' cat with a 20' beam)
- With a couple HP (say 1500w), it should be capable of around 10mph.
- The bimini should be good for maybe 500w of solar...so assuming 4hr at the rated output, that's 2000w-hr per day. (if the batteries are dead, you could still limp along at 500w as long as the sun is out).
- A couple 200amp-hr batteries will hold around 4800w-hr...figure about 2500w-hr usable or about 1.5hr at peak power. If you drop back to 500w, you have around 5hr of run time for tooling around canals or if you want to troll for fishing purposes.

This seems a viable self contained system with minimal maintenance required and quite functional.

[BigBeakie]

Originally Posted by tp12

I think it's pretty close to meeting my requirements, if it doesn't already. I assume you're planning on removing the battery box for charging in the cockpit/similar from the bank? Or just charge from the two panels?

I love that it sails and rows and is stable. I'd be pretty keen to see how you get on with it. It could be a lot of fun in its own right. It'd be a great fishing platform.

Thanks, yes it ticks all the boxes we gave the designer. He sells the plans.

The plans are excellent and it only took me a day to cut out the strongback and stations from the 16mm MDF, and put the frames all together the next morning, so it's pretty staraightforward. The 10mm infused panels will be done at the yard on the big table and then glass taped together on the stations.

The batteries live in the battery box at the transom of the Freeflow 50 and charge as part of the house bank, and then can be disconnected from the house and moved into the dinghy where they are charged by the removeable panels. The panels are 325w by the way, not 350w as I stated earlier.

Will be very cool to be able to sail around some of the lagoons, eh?

By the way, the rationale for this electric dinghy was that several cruisers who dive told us they would be in fantastic remote anchorages and would run out of petrol (gas) for the outboard. The idea of being really independant for longer periods of time in remote regions, and be able to explore long distances running on solar, well that was something we wanted to try.

[tp12]

Originally Posted by valhalla360

Everything but planning is easy. If you want planing, you run into the energy storage problem.

I've thought, a cat hulled dingy with long narrow hulls (think like a hobie) wouldn't take a lot of power to get decent speed. You could add solid bimini that folds down when not in use that holds solar panels.

Assuming a 14' by 6' dingy (hanging off the back of a 40-45' cat with a 20' beam)
- With a couple HP (say 1500w), it should be capable of around 10mph.
- The bimini should be good for maybe 500w of solar...so assuming 4hr at the rated output, that's 2000w-hr per day. (if the batteries are dead, you could still limp along at 500w as long as the sun is out).
- A couple 200amp-hr batteries will hold around 4800w-hr...figure about 2500w-hr usable or about 1.5hr at peak power. If you drop back to 500w, you have around 5hr of run time for tooling around canals or if you want to troll for fishing purposes.

This seems a viable self contained system with minimal maintenance required and quite functional.

Yeah I think you're right; a cat dinghy seems the way to go for propulsion purposes and has a lot of other benefits, too. I've been spoiled a bit having access to my mate's BRIG, which hammers! It's like a sports car.

Thanks for the post.

Originally Posted by BigBeakie

Thanks, yes it ticks all the boxes we gave the designer. He sells the plans.

The plans are excellent and it only took me a day to cut out the strongback and stations from the 16mm MDF, and put the frames all together the next morning, so it's pretty staraightforward. The 10mm infused panels will be done at the yard on the big table and then glass taped together on the stations.

The batteries live in the battery box at the transom of the Freeflow 50 and charge as part of the house bank, and then can be disconnected from the house and moved into the dinghy where they are charged by the removeable panels. The panels are 325w by the way, not 350w as I stated earlier.

Will be very cool to be able to sail around some of the lagoons, eh?

By the way, the rationale for this electric dinghy was that several cruisers who dive told us they would be in fantastic remote anchorages and would run out of petrol (gas) for the outboard. The idea of being really independant for longer periods of time in remote regions, and be able to explore long distances running on solar, well that was something we wanted to try.

It's a new design you commissioned? I'd expect that you'd have done a lot of that thinking already. Just being able to sail around as well is a huge bonus and yeah, I reckon having a little sailing boat like that to get around in would be a giggle. The local kids will get a kick out of it, too. Nice dinghy!

[BigBeakie]

Yeah, we came up with a bunch of ideas and the designer drew it up. Actually, he's a Naval Architect who know multihulls, so we're pretty confident in the design performance.

[sailhand]

It will be interesting to see how this new design goes. I had talked to torqueedo at one stage when i sailed down to sydney a few years ago. My design planes with a 3hp so torqueedo were fairly confident that they would achieve planing speeds and seemed very keen. however after discussing torqueedo motors with the former dealer in australia i decided to explore other avenues.
To see my dinghy planing with the 3 you can google magic carpet 3.5 and check it out on youtube. The specs on your new design state the dinghy weight as 85kg is that correct. For a sailing rig i suggest a hobie bravo style rig with a free standing rig and sail furling around the mast. This furling ability would be hugely advantageous on a tender with the ability to stow the sail at a moments notice, not to mention furling.
one of my designs has been rigged for sailing but as yet i have not sailed on it so cannot pass comment. It is good to see more cats being developed for tenders, they have their shortcomings however i believe they are excellent in this role if designed properly. By the way is your axle system similar to mine.

[BigBeakie]

Originally Posted by sailhand

It will be interesting to see how this new design goes. I had talked to torqueedo at one stage when i sailed down to sydney a few years ago. My design planes with a 3hp so torqueedo were fairly confident that they would achieve planing speeds and seemed very keen. however after discussing torqueedo motors with the former dealer in australia i decided to explore other avenues.
To see my dinghy planing with the 3 you can google magic carpet 3.5 and check it out on youtube. The specs on your new design state the dinghy weight as 85kg is that correct. For a sailing rig i suggest a hobie bravo style rig with a free standing rig and sail furling around the mast. This furling ability would be hugely advantageous on a tender with the ability to stow the sail at a moments notice, not to mention furling.
one of my designs has been rigged for sailing but as yet i have not sailed on it so cannot pass comment. It is good to see more cats being developed for tenders, they have their shortcomings however i believe they are excellent in this role if designed properly. By the way is your axle system similar to mine.

I did not discover these when I was searching, which is too bad. They look great. And light at 45kg!

Are you using 10mm foam panels? Is there any issue with durability in heavy chop or getting bumped if you build that light? Ours has 200gsm double bias spec'd in the infused panels, which sounds like it might be a fair bit heavier than what you've used?

Yes re the wheels, my idea was to find the balance point with gear, and then insert stainless tube through the keels, into which the wheel stub axle would fit. Yours look like they work really well.

I really liked your duckboard transoms too, very handy.

[FlyingScot]

My plan is to supplement the 15 hp Yamaha Enduro with a 2-3 hp Torqeedo. New model coming out this year to replace the 1 kw version with 1.1 kw and no gears. It's virtually silent. I've yet to test one on my AB aluminum 9.5 ft RIB.

My brief research showed the cost/weight/hassle of a larger electric setup would not be worth it.

I hope you find something to fit your needs.

[sailhand]

Hi big beakie, i used 400gm2 glass on 10mm foam, 15mm in the bridgedeck. The hulls are resin infused solid glass 3600gm2 in the keel and turn of the bilge and 1800gm2 for the rest. There is nothing else, no bulkheads frames stringers foredecks lockers hatches etc.. yes the transoms are fantastic for snorkelling/diving as they are basically flush with the surface of the water when you push on them. There is a line behind the motor which runs between the hulls and serves multiple roles as liftpoint for davits, towing bridle for towing other vessels and ladder for boarding from the water along with the help of the outboard leg. We basically slide our backside onto the transom with our legs in the water and get all the gear off and throw it in the boat, then just stand up and stroll in. It does work really well for deepwater acess, its definitely the best weve used, the takacat is probably a close second by all accounts with the seal flop technique over the front. The first of the foam prototypes was built from flat foam panels like your dinghy. We hand laminated one side of the panels, attached them to the temporary frames and then glassed the outside in one hit. After that we turned the hull over and taped inside. Again we used 400gm2. The weight savings with infusing cored panels is not that great if you use grid scored and perforated due to the amount of extra resin absorbed in the core. We decided to make a mold and infuse solid glass hulls and they are really tough. We made hulls that ranged in weight from 6 to 8.5 kg each. The super light hulls were actually slightly porous as we really cut back on the resin, too much obviously. When we tried to float the lightest hulls out of the mold we got tiny areas of condensation like moisture appearing, upon investigation we discovered that it was porosity. Actually one of the really annoying things about the dinghy is that the solid infused hulls ring like aluminium with the ripples on the water. The old foam core hulls would hang on the painter in dead silence, oh well cant have everything. If you hit the solid hulls with a hammer really hard you will end up with a very nasty lump in your forehead when it bounces back at you. They are "Tough"!!!!! We wanted to make them solid to simplify any repairs but so far no leaks. The dinghy has done a lot of work, not so much lately weve been renovating a rental property, and had no leaks as yet. We dont even have any bungs in it at this stage. The current dinghy is 6 or 7 years old and the foamcore one before that for 4 years. Not much we'd change. Try not to build in hatches and seating etc it is far better to be able to configure things as required. Check oc tenders they have done basically the same as us, moveable seating and storage in soft bags. We use shade cloth for storage bags as it lets the content dry and not go mouldy. This is a much better system as you dont have weight. Once you put in hatches, weight, then you fill them up, weight, and cart it all around with you. It just didnt make sense to me. I can empty it out in a couple of minutes and fill it up with mud castnetting prawns. Wash the selfdraining deck with a bucket or two of water and fill it up with water containers and do a water run, then lay out as many seats as i need and trim the boat and head into town. its that versatility in the single platform with amphibious ability that we were trying to achieve. I think the great tender debate is about the various roles required of a single small vessel as much as it is about the type of vessel itself. I think oc tenders, like us, recognise that need and prioritise it the same as us. Sure you can get something faster but is it light, can you lift the outboard and stow it easily and move it up and down the beach etc. There is an endless number of roles these vessels are required to fill and my main advice fwiw, not that much really, is the age old adage, Keep It Simple Stupid. The last bit of which refers specifically to me.

[tp12]

Great post. Thanks for the insights into your thinking and the process, as well.

[44'cruisingcat]

Originally Posted by BigBeakie

Yes re the wheels, my idea was to find the balance point with gear, and then insert stainless tube through the keels, into which the wheel stub axle would fit. Yours look like they work really well.

I really liked your duckboard transoms too, very handy.

No need to use stainless tube, the Magic carpet and another dinghy of Bob Oram's design have simply glassed in heavy wall conduit to slot the axles into. Axles are pulltruded solid glass rod.

Another idea is to fit short sections of this tubing vertically into the coamings fore and aft, which gives a place to store the wheels when not in use and also lets the wheels serve as rolling fenders on the dinghy. This also greatly reduces one of the concerns of hard dinghies, that of them bumping boats when coming alongside.

[SteveSadler]

Ive seen a 14' sailing cat inflatable in the Med that could work but I doubt any outboard electric motor on the market today will push any tender over 6 kts. A cat tender has no advantages here as a 12' cat with 4 people is like taking 50 people on a 35' cat and expecting a 20kt sail.
If it could it would need a larger battery than the mother ship has to go a mile.
Planing (15kts) 4 people takes 20hp on a 12' rib. Cats are still limited by hull speed and much more limited with weight.

[sailhand]

Steve has definitely hit the nail on the head here. Two people and gear in a cat dinghy under 12ft and thats about it for planing easily. I am what some people might be inclined to consider somewhat portly and justifiably so. At 108 kg im not exactly the pin up boy for Jenny Craig. With myself and another person of similar displacement shall we say, its pretty much the limit for us easily planing with a small motor. In saying that however one of my friends, who owns a 62ft oram catamaran, and both our partners went for a run in my dinghy and planed the three of them with a 5hp. Obvoiusly there total displacement was around the same displacement as me, aparrently a function of a shorter waterline length and a considerably diminished beam on their part. I apparently have been blessed by the powers that be. I seem to be one of those lucky models, not a fashion one, with an expandable beam. This is apparent to any poor unfortunate sod who has sat through possibly the worst production currently uploaded on youtube, my video, and suffered the visual onslaught of the final image in said production. Sorry counselling services are not provided, if you are suffering ptsd as a result of viewing this image then seek help from the appropriate source.
Monohull dinghys have far better load carrying capacity in a given size generally speaking. They have other disadvantages though such as stability and self draining options in these small sizes. They usually go faster in the planing version however they probably dont ride as well as a cat in most cases. Like ive always said its a compromise and with all attributes on a linear scale its the individuals environment and preferences that they will use to plot their optimal requirements on these scales to derive their ideal solution, ie: fast slow, light heavy, big small, soft ride hard ride, stable unstable. To be truthful it was a careful analysis of as many different attributes of the perfect tender to suit our needs on this type of scale that lead me down the design path I chose. Self draining was a big one for me as well as a small cheap outboard that was fairly fuel efficient. I do not generally carry large heavy loads, myself excluded obviously, so that was not a priority however it was still a necessity to occasionally carry 300 litres of water or 6 or 7 people so i still wanted that capacity it just wasnt a priority. It is very much a form follows function design proposition a tender otherwise half of us, dare i say possibly predominantly the male half, would have a formula one single seat hydroplane with 200hp on the back for a tender. We'd get there in a hurry and it would be outrageous fun but completely useless for anything else. And who knows maybe next week i will see someone doing exactly that, but if thats where their priorities, knowledge, capacity and beliefs take them then all power to them, pardon the pun, and for being nice i think i should get the first test drive.
Cheers