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  #1  
Old 03-21-2017, 05:09 AM
Danizichi Danizichi is offline
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a little confused...

Hi, I'm an italian guy. Sorry for my bad english. I'm not expert about powerboat. I look for a long time this type of boats: http://www.boatdesigns.com/mobile/9-.../products/347/
http://www.boatdesigns.com/mobile/11.../products/365/
My doubt is if i can use these boat in the sea. I live in sicily, and i will navigate in Mediterranean sea. I search a small speed boat for mariner use, I have got a 15hp engine. Can you help me?
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  #2  
Old 03-21-2017, 06:02 AM
Ilan Voyager Ilan Voyager is offline
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These boats are only for flat water. On sea you are going to have big trouble with the smallest chop. A simple boat with a 6 to 12 degrees V bottom with enough freeboard will do the job for you. The secret is to keep it minimal and light.
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  #3  
Old 03-21-2017, 06:05 AM
Danizichi Danizichi is offline
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What speed boats I can use on sea with my 15hp?
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  #4  
Old 03-21-2017, 07:38 AM
Danizichi Danizichi is offline
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This is the condition in which I will use my boat
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  #5  
Old 03-21-2017, 09:33 AM
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PAR PAR is offline
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These types of boats are intended for smooth, protected waters only. They're aren't remotely suited for any exposed or choppy water. The photo you're showing is just barely suitable and not very far off shore it's unsuitable. Simply put, these boats are run in ponds and small lakes, occasionally on slow moving, calm rivers. Speeds can vary wildly, but generally the 20 knot range is common, with a 15 HP. This speed feels like 50 knots when you're aboard.

The two boats you have selected are also very different. The TNT can take rougher water than the Picklefork, which is a 3 point. The 3 point will be faster than the mono, but it is also a lot more sensitive to sea state condisions.

If you want an idea of how these puppies run, search YouTube for "Cocktail Class Racers". They look fast, but in reality they're only going 20 knots or so.
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Old 03-21-2017, 10:30 AM
Danizichi Danizichi is offline
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I saw the videos, it looks very funny. But this type of boat ("Cocktail Class Racers"), needs smaller engines. Do you know any boat (maybe two-seater) on which to mount my 15hp that can entertain me? My friends have small rubber boats, but I hate them. I have got a kayak but when there is no wind and I can't go sailing it is slow. I would like a boat that is easy to carry, lightweight and fast. For fresh water there are an infinite number of models but for the sea i can not find anyone. I want too much?
My outboard engine is a Betepok, a 1990 engine, but it is new, it never touched the water. I will use the boat in a range of 100 meters-1.5 miles from the coast.
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Old 03-21-2017, 10:42 AM
Scot McPherson Scot McPherson is offline
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Google search for a boat called a Boston Whaler and Carolina Skiff of 17 feet (approximately 5 meters). These boats are probably the "type" you want. Although you may not have these exact boats available, you can use these as a guide to choose a boat. You will only want to use these boats when the weather is kind and there are no waves or chop on the water.
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Old 03-21-2017, 06:29 PM
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PAR PAR is offline
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There's a very good reason you don't see small craft in open water. It's very easy to find yourself overwhelmed by the sea state, farther from shore than you can swim back to. The Cocktail Class is just a specific class of the generally known "hydros" (monohulls), to which there use to be a large grouping of various sizes. These classes are very common any more with the advent of PWC and other, more modern variants.

Speed on the water is just like anything else and basically boils down to power versus weight. A 15 HP outboard has only so much energy available, so the boat and load needs to be light. The easy way to do this is something small, with dainty scantlings. Of course small, lightly constructed and loaded boats take a beating in anything more than a very slight chop. Another avenue of pursuit is a longer boat with a dramatically bigger length/beam ratio. This type of boat is easier to propel, but lacks elbow room and in the longer length, requires more material, so tends to be heavier. Couple this with a car topper requirement and you're very limited in the options you have available to you. A skinny skiff would be the wisest choice IMO, simply because you get some speed, but the boat is big enough to take on some chop.





This is a 12' (3.66 m) design of mine, modeled in "Blender" by forum member Paolo Furani. It'll perform well with a 15 HP outboard though it'll perform much better with a 25. It's big enough to carry more than yourself and can take on bigger sea states, though is still a protected waters craft.
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  #9  
Old 03-26-2017, 05:59 AM
Danizichi Danizichi is offline
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But is it only a rendered project with blender?
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  #10  
Old 03-26-2017, 10:10 AM
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yades yades is offline
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Quote:
Originally Posted by Danizichi View Post
This is the condition in which I will use my boat
That kind of boat are not to be used in open waters (or open sea) but only in limited calm waters with flat conditions.
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  #11  
Old 03-26-2017, 07:26 PM
Ilan Voyager Ilan Voyager is offline
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Par has very well explained.
Lakes do not change rapidly of conditions and their normal state of water surface is flat. Sea is another thing; waves coming from away fetches, currents, and sudden changes of conditions like in summer under a storm cloud. I also remember that in Sicilia the gusts of wind arriving suddenly from the mountains are common.
Once while fishing in a 18 feet sea skiff about one mile from the shore we were caught under a storm cloud, a big black summer cumulonimbus which arrived from nowhere in minutes.
We have been beaten during 15-20 mn in a boiling sea by 30 knots winds. All we could do was praying and surviving. Happily we had a good very stable sea skiff with plenty of freeboard and a sealed self bailing floor plus insubmersibility. We were also far enough from the rocky coast of granite covered of barnacles ready to transform you in ground meat. The main danger in sea is the coast.
The lesson was: look at the sky and not only at the fishing lines, the situation can change for the worst in minutes..You must be very humble on sea, and having the adequate boat is mandatory requisite. A summer day can end in tragedy with the wrong boat on sea.
Forget about a speed boat with a small outboard on sea, but a good sea skiff with the same outboard will offer great fun safely with a better program, as jumping small waves, exploring the creeks, fishing etx...Probably alsp it will cheaper and easier to build.
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Old 03-27-2017, 06:37 AM
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hoytedow hoytedow is offline
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Even 15 knot winds will leave you wet, cold and miserable with 1 meter waves breaking against your 4.75M hull and blowing over the side. Not fun in winter weather.
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  #13  
Old 03-30-2017, 04:55 AM
Joakim Joakim is offline
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I somewhat dissagree with the comments. At least here in Finland we used to have (70's) an "offshore" classes which had 20-40 HP OB's and very light 3.5-4 m V-hulls. The races were run at bigger lakes and in the Baltic Sea where is quite common to have 1 m significant wave height and it can even be 3 m during the racing season, but then they cancel races or race in the archipelago. Now there aren't any that small offshore classes, but there is one which use about 5 m boats and unmodified 50-60 HP OB's. Top speeds are around 50 knots.

Well it can go wrong: https://www.youtube.com/watch?v=jKRLiGe2p6Y

I had one 70's small "offshore" boat in the 80's. It was a 3.8 m TG-Marin. The hull was about 60 kg. I had first a Yamaha 40 with 48 knots top speed and later a Mercury 25 with 33 knots top speed. The latter was not at all optimized, the top speed should have been close to 40 knots.

You could run about 40 knots in a surprisingly big seas. I never tried in more than maybe 0.5 m significant wave height, but the designer who used to race with Mercury 40 in the 70's with this boat told me that he always had hull throttle and the speed just got slower due to propeller being more and more in the air while jumping from wave to wave.

I think you could do 30 knots with a 15 HP OB on this boat. Maybe just 25 with standard propeller. It planes with 5 HP.
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Old 03-30-2017, 10:53 AM
Ilan Voyager Ilan Voyager is offline
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@Joakim. Like I said with the adequate boat...I'll add with the adequate experience.

You're talking de races, with assistance, security boats and tutti quanti. Lots of money even if that looks cheap for a well paid Finnish guy.

It's like jumping the bumps of the forest dirt roads of Finland at 180 km/h in WRC style with a prepared Peugeot 205. Not for a beginner who started the driving lessons one week ago.

With my mate we were able to sail a Tornado modified for raids by a solid force 6-7 with 1.5 meters white waves, to make runs jumping the waves, also to make complete regatta triangles (so all the allures of wind) and come back by our means. But having a security boat and accepting the risk of breaking the cat at the first mistake as we had the financial means...
Those stupidities, or extreme sailing as some call it, are done by guys with a few years of training...Not by a lone beginner on a 12 feet cat from a beach.

Our amiable correspondent is a complete beginner, and will use his boat probably alone in sea with no security team at proximity. At the first problem he will be in a serious maybe deadly situation. Probably he would lose his boat, payed and built by hard work or at least break the drowned outboard. So the answers were done with this elements in mind. He needs a safe, stable boat, thus he will acquire a lot of wisdom after some cold sweats and lots of adrenaline. And also having great fun with no special worries. After, with experience and knowledge, he will decide if he wants to build a very fast small boat, a capricious and delicate beast, and accept to take the inherent risks.
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  #15  
Old 03-30-2017, 03:31 PM
Joakim Joakim is offline
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Quote:
Originally Posted by Ilan Voyager View Post
@Joakim. Like I said with the adequate boat...I'll add with the adequate experience.

You're talking de races, with assistance, security boats and tutti quanti. Lots of money even if that looks cheap for a well paid Finnish guy.

It's like jumping the bumps of the forest dirt roads of Finland at 180 km/h in WRC style with a prepared Peugeot 205. Not for a beginner who started the driving lessons one week ago.
I used races just as an example. With 15 HP on a boat that can handle 40 HP it is a very different boat and doesn't need all that experience.

I haven't raced motoboats, but I have watched a few races. I just check one Notice of Race. The entry fee is 100 €. Not really a lot of money, although quite expensive compared to the very cheap boats they can race with. Some competetive teams still use boat and OB from 80's, which can probably be bought for a few thousand €/$.
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