PC24 question for Jacques

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Reid
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PC24 question for Jacques

Post by Reid »

Jacques,

Please see the following question from a customer in Austria:

Hello, I am living at the Neusiedlersee in Austria, which is quite big but has a max depth of 1.5 meters. Due to missing rain, we are facing now the problem that we need boats ( only electrical drive allowed ), where draft incl propeller should not be more than 30 cm. I bought the PC 24 plan 1 year ago, and would like to use it with 2 outboard motors wit 4kw. The load of the EC 24 was to little as we are normally 4 persons on board. Now my question: may it be possible to reduce the draft incl. motor by integrating tunnels into the pontoons to raise the outboard a bit more. Or do you have another plan to propose for my problem. as I purchase the plywood only for the pc24, but did not started yet to build. Thx I was looking at the Seabright tunnel 21 but I am not sure if it might work with an electrical drive, as we are limited to max 10 kw, and I would prefer an outboard solution as it is easier to handle and less expensive. Looking forward to your reply.

Thank you,
Reid
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TomW1
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Re: PC24 question for Jacques

Post by TomW1 »

Reid, I do not know if he has access to Torqueedo electric motors, but they are available worldwide and they have a 6KW 9.9HP equivalent motor. https://www.torqeedo.com/us/en-us/produ ... 62-00.html This would be better and fit the design of this boat. It has remote steering, while the 4Kw would require some rigging to do so. He also doesn't have to worry about draft 30cm is nearly 12in.

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jacquesmm
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Re: PC24 question for Jacques

Post by jacquesmm »

There are much better choices than a PC24 or a boat with a tunnel. Wide hulls like the GF18 would be perfect and work well at displacement speeds with a pair of electric motors 10 KW total.
Another good one would be the GP21 but the GF18 is economical, simple to build and can take a large load: no problem at all with 4 persons.
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Fritz63
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Re: PC24 question for Jacques

Post by Fritz63 »

Thx for your feedback.
Yes we do have Torqueedo in Austria. We are using at the moment an 4kw Torqueedo with a 18 feet displacement boat. Hulldraft is about 11 inches plus motor shaft and propeller we end up with about a total draft of 18 inches. We lost last year 2 propellers due to the low water level. This year the waterlevel sank another 4 inches, that's the reason, why we are looking for a boat, which is able to run in low water levels.
If I look at the proposed alternative plans, the hull drafts are about 8 inches, but including motor shaft and porpeller, it looks at least on the pictures of the study plans, that the total draft incl. motor and propeller is more than 16 to 18 inches. But may be I am wrong.
The PC24 was choosen due to the fact, that because of the low water level, it is really hard to enter or exit the boat in some of the marinas, as the most of them have no floating docks. With Ponton Style boat we think it is a bit easier to climb up because of the higher deck level. May be this explains a bit better, why we are considering such "special" solution. GP21 or GF18 might not meet those criterias.
May be you are able to propose another alternative under the those aspects mentioned above. Thx in advance

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OrangeQuest
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Re: PC24 question for Jacques

Post by OrangeQuest »

Big problem with a prop drive system is the prop needs to be a certain depth in the water or far enough under the hull, so the prop has no chance of sucking air. Outboard mounted on the transom has to be at a certain depth and doesn't matter about the draft of the boat. Let's say the centerline of the pro need to be 18" below the surface, doesn't matter if the hull is in 2", 4" or 8", that prop still needs that 18" of depth.

And no matter the hull and how shallow draft it is the 18" depth for the prop is a fact you cannot get away from. Even in a tunnel the top of the tunnel would need to below the DWL at all times. One solution would be a centrifical pump like a oversize bilge pump. The inlet to the pump could be at the very bottom of the hull and less likely to suck air but a big risk of sucking mud and rocks through the impeller. But the boat could go in shallow water almost the same depth as the hull with less fear of hitting logs and big rocks just below the surface. But not very efficient system. But a Tesla pump could be, but I lot harder to make.
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fallguy1000
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Re: PC24 question for Jacques

Post by fallguy1000 »

I waited for JM to reply.

I disagree with him a bit and Ken lays out why..here are my remarks prepared before Orangequest..basically all about getting the skeg immersed just enough..but not deeper than a hull vee..

My 2 cents...

Honestly, a lightweight pc24 is a good solution. The motor in the middle with a torqueedo is best because it can be tilted up as you enter shore and the crew can move to the back to get you closer to shore. The dual pontoons can get handles or tow hooks with beefy backings if you are short of shore..engine up. The draft of 8" is a compromise and deeper than any full width hull, but a full width hull requires a deeper prop setting, so a good trade.

Try not to get too wrapped up in the tunnel idea. Running a high powered boat up on plane is where the tunnels shine, the engine can be on a hydraulic jack and run in even less water, but those are not options with your power limits. The tunnels offer security from taking out a prop going 25mph on a river, for example.

The ideal would be a mud motor, but wholly impractical and never saw one in electric.

Another idea would be to scale the PC24 up 10% x,y only and this would raise her up some. You'd need to probably put the engine on a jackplate to find a sweetspot. I would expect ppi to increase from 275# to 333#.

Also, building in foam would take a lot longer, but would make her super light and glass needs for your speeds are not much.

If you are subject to width maximums; perhaps move the hulls in...

But the prop on a PC24 I expect to run at less than a foot to the skeg and that is really good. Not sure if the torqueedos have a trim button, but that would be ideal at shore for you.

Another thing to consider is a simple double barge bottom. Instead of worrying about speed or efficiency; you have a designer draw a wide bottom pontoon. That would get you closer to say 4" hull depth, but the engine still needs to be immersed below the cav plate..so the only real gains are near shore where the entire boat floats higher, but the prop can still be in between the hulls.
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jonnymac
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Re: PC24 question for Jacques

Post by jonnymac »

what about the skoota 18 or 20, motor is center mounted so it is going to be as shallow as it can possibly be with a outboard and Woods designs are very power efficient.

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Re: PC24 question for Jacques

Post by jacquesmm »

The Skootas are a good choice too.
I understand what Fallguy says about the motor in the middle having less draft but the hulls will have more hull draft in a twin hull than in a wide barge. You gain a little here and loose a little there. I like the very large reserve capacity of the GP21. It is a matter of personal preference.
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