The tender decks and cockpits are mostly covered (not hard to make them entirely), and scuppers are easy as the floor is above water level. The T60 cockpit is 350 deep x 3m long x 1.4 wide, so the max water it can hold without covers, scuppers, seats, or folding console, is 1.5 tonnes. Not trivial, but designed for and only possible in a flat calm. When it is angled downward, the max water it will hold is about 250 kgs/550 lbs. Again in flat calm. As soon as it starts going up and down in waves, most of it slops out. The attachment at the bows keeps it aligned so it does not hit the boat when going up and down and there is no deck above it to hit. If I was motoring into seas big and steep enough to clear the 1.5m/5' high beams, I would consider changing course 30 degrees and motor-tack to the destination. Not only to keep the tender dry, but to reduce the spray and the drag from the beams.
Operation is by remote control. Either extended cables (petrol/diesel) or with rc (electric). Lifting and lowering is done from the mothership helm position. Attachment/detachment from the tender helm position. The docked tenders are not steered, but can be if crew is available. This would be a calm water exercise, nearing the dock, but probably not worth the trouble with the big rudders. Certainly not worth it with the under deck motor on a tube option.
None of this is cast in stone. We provide the options, the owner chooses what works best for him. We help him optimise it.
Great news about the cheap drives. If I end up paying for the cargo ferry prototype, they will be given serious consideration. Thanks. The Caroute mounted on the side of the toy box or at one end of the cockpit would make docking any size harry very simple. I will suggest it to the owners who are only having tender motors.
On Thu, Aug 15, 2019 at 5:24 PM Rick Willoughby rickwill@bigpond.net.au [harryproa] <harryproa@yahoogroups.com.au> wrote:
Rob
I believe the ideal situation is two liftable electric pods off the inside of each hull. They need a means of lifting clear of the water and a means to lock them down.Stowing the tender within the deck is a neat idea but I consider it a fair weather means of propulsion. Could be a satisfactory means for getting in and out of a marina in good conditions or getting to a beach from the HP. Not something to rely on in testing weather.The 18m proa buries the leading beam when beating into 2m and higher waves. There is plenty of water on the lee side of the deck. It is not difficult for me to picture circumstances where the tender is taking green water. It would need to have a substantial cover to shed water or substantial scuppers to shed water if not covered. It would be applying uplift in waves about 1m high or flogging against the deck if allowed to move up down. Then there is the question of how is it being operated. Does someone need to sit inside the tender and operate the motor while pitching harshly and at odds with the HP it is attached to. Or are there remote throttle and gear cables that can be located on deck"By the way, there are also much lower cost alternatives to the Kraeutler pods for smaller HPs. I had some detail input on electric propulsion for a 24ft 3T displacement mono. He did a lot of testing and made improvements on a Caroute N400-48V thruster. Amazon sell these for $1467. They are rated at 180lb thrust; equivalent to about 9HP outboard for bollard pull. Once the tube is faired and prop of suitable pitch fitted he was able to get 5kts at 1.5kW battery drain. The motors are not very efficient and the direct drive also limits the prop performance, however they give a reasonable result.Torqueedo now have a range of pod drives. The 4kW pod retails for USD5k. I would not be as confident with these as Kraeutler but they are considerably lower cost and I expect there will be a lot of development with them. One submersed permanently will experience problems long before one that is pulled clear of the water when sailing so those fixed in position should be on the bleeding edge rather than any that are not always submerged. Barnacles near seals is a factor in seal life. No barnacles if the pod is not always immersed.RickOn 15 Aug 2019, at 4:08 pm, Rob Denney harryproa@gmail.com [harryproa] <harryproa@yahoogroups.com.au> wrote:It is not idea, as you can't motor sail on one tack and if the tender is away, the mother ship can't motor (mixed blessing), but overall, it is a better solution than either a pod outboard or inboard diesels with all the problems noted in this thread.
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Posted by: Rob Denney <harryproa@gmail.com>
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