Boat Builder Central - Builder Forums

Hi Everybody, dont know if you remember the corsiar 13 that I built in a modified version. I made it into a flat floor centre console boat since I had made the wrong choice in buying plans for a sail boat, and at the time when i was 13.5, i had no idea about hulls and thought what looked good would work. Well any way, its been one and a half years, and this is what resulted.

as you can see I installed a center console, and made a flat floor. I took out most of the "frames" and cut down the front frame to suit a seat with a anchor well.
It runs on a 15 horse power 2 stroke

Few comments on the boats performance:
The boat sits really high in the water. It was very stable even with three of my firends on board. We all weighed more than 70 kilos each. I was happy as I didnt have to be cautious about where i walked or where we walked. it was stable all around. Just to emphasis this, me and one of my friends stood right at the starboard side, and it was basically level.

With the 15 horse power, slow manourvering in the docks is hard. It doesnt respond well. With full left turn it moves left very slowly with a wide radius.

Speed: The boat is definately underpower with a 15 horsepower. Its on the verge of aqua planing (im hopeing/thinking). It feels about the speed of a fast sail boat.

Turning at high speed: At full throttle, with three people on board and other equipment, full fuel tank, esce for a seat. towels etc... I was turning fully and she felt very stable. Underpowered again?

Last note: at full throttle the boat reaches deadrise i think its called. the point before planing. I mean i really feel that if i had a little more power, it would drop down. (also when i first put the boat in the water back when i didnt have so much weight it did drop down with the 15. and planed)

Questions for you guys:
Why and what can I do about the bad low speed handleing.
Why and what can I do about the boat not planing.
Can this hull plane? im just wondering hahaha. (although it did plane before im not very certain because that was a while ago. all i remember is my brother telling me to put more throttle on to bring down the bow.)
What do you think about the boat hahaha?

Nice job! Expecally considering it was built by a teen!

I'll let other more "in the know" comment about the boat's preformance, but if the boat bottom was not designed to plane, you may just be out of luck.

Enjoy the boat, and don't stress about going slow.

Congradulations again-
Jerry

Nice workmanship but the hull is a sailboat hull. It is not designed to plane and will not perform well under power, sorry.

Last note: at full throttle the boat reaches deadrise i think its called. the point before planing. I mean i really feel that if i had a little more power, it would drop down. (also when i first put the boat in the water back when i didnt have so much weight it did drop down with the 15. and planed)

FYI - Deadrise is the "V" angle in the bottom of the hull. I'm not sure if there is a name for what you are discribing, but what is happing is the boat is trying to climb over it's bow wave. In a planing hull, the boat climbs over the wave just fine, the bow drops, and off you go. In a displacment hull, the curved bottom kinda sucks in to the wave, making it very hard to climb over. With a lot more power, you may *kind of* get on a plane, but you will never go really fast - the hull will always try to suck down into the water, instead of skiping on top, like a planing hull would.

Take you time, have fun, and enjoy the boat.

And if you can't live with it, you can always build a FS14 for that 15hp

Jerry

What Jerry explains is correct. You have lift in some places, probably the middle aft part of the hull and suction aft and at the bow. You have two forces working against each other and your hull is stuck in between.
Now, the CR13 is almost a planing hull but don't take chances with a bigger engine.

I think it looks really cool, even if it's not performing as you expected.

I bet your low-speed handling would improve if you removed those runners down the bottom of the hull. I'm not familiar with your boat, but if they aren't structural, they probably aren't helping.

It's wonderful that you are starting to use a boat you built, and plainly, you can build a boat!

Maybe soon, as you refine exactly what you want in a *dream boat*, or just a next step, the group here can help you with a model that will better do what you are hoping it to do.

Pushing that hull faster may push you past a safe region of operating the characteristics of that hull. Whatever you may have changed on the interior, you won't change what the underside was designed to do. Enjoy it, nice and slow. You'll probably get maximum (non-planing) hull speed from a 4 hp, and save lots of fuel too. See if you can borrow one to test and see if it is so, even if the test is with a tiller extension.

But of course... we need to see you in the boat, on the water! More pictures!

I agree with everyone else. You do some nice work. I wish I could have built a nice boat like that when I was 15. Heck, I wish I could now that I'm 50. Anyway, enjoy your boat for what it is: an excellent first effort. It may not be a planing speedster, but there may be a silver lining in that little cloud. I'll bet that the stern really digs in when you try to go fast. That means you will probably be kicking up as big of a wake as a 13 ft boat can make. Nice, high profile runners on the bottom to keep it pointed forward...
You may have built a great mini-wakeboarding boat



Be safe, and have fun with it.

Hi Everybody. Thanks so much for your replys. Hahaha gk108 i really like your idea of a mini wakeboarding boat.
So does everyone disagree with my idea to get a bigger engine. It is a 15 hp now, and im thinking of upgrading to a 35.
Could a possiblilty be to add trim tabs? Could that reduce or counteract the sucktion at the stern and push down the bow?
Ill try and get some photos of it on the water, and maybe a quick movie to show you how she runs.

When Jacques, a designer, plainly says what he said...

Now, the CR13 is almost a planing hull but don't take chances with a bigger engine.

... take him at his word. Don't take chances with a bigger engine.

Enjoy the pace of this boat as she is, with the lesson that some laws of boat hull shapes should be respected. Though it won't help your boat plane, it will begin confirming in you those sensibilities which will make you a more seaworthy skipper, and that is very valuable, and something you can bring to every other boating experience for the rest of your life. If your friends nudge you and bug you to see if a bigger engine will get it to plane... well... guard carefully the seaworthiness of your self that you bring to boating, for the safety of your friends also, since you are the skipper now, of a boat your also built yourself.

If you've got resources for a bigger engine, then you need to be asking about the next build, a truly planing hull, as designed!

proman_11 wrote:
So does everyone disagree with my idea to get a bigger engine.

Yeah, it's a bad idea. Changing to a bigger motor gives you two things, more weight and more push (thrust). Obviously, more weight on the stern will never make the bow go down. The direction of all that thrust is going to be pretty much exactly in line with the prop shaft. The trouble is that the prop shaft is already pointed toward the sky and pushing harder toward the sky won't make the bow go down.

These are simplified explanations for sure, but there are bookshelves full of information on why boats are shaped the way they are. Most of it is about displacement hulls. There seems to be a zillion different concepts of what makes the best sailboat hull. Planing hulls don't get as much discussion because they must have a flat surface on the back end of the bottom in the fore and aft axis. About all that's left to talk about after that is how much V the bottom may or may not have.

Trim tabs won't help either. In order for them to have the force necessary, they would create too much drag. Same goes for doel-fins on the outboard.

There is only one way to make that hull drop at the bow while motoring:
Throttle BACK
It's all about those laws of physics. You just can't break them. Even if you try, one or another of those laws will break you first.

Hi everybody. Well, I took the boat out today, along with two other friends. I took some short video clips as well on my mobile im just working out how to put them on the internet. complicated because mobile phones have a weird format.
The boat worked good today, I was very happy with it. We spent about 4 hours on the water trying to get her to plane. Im not 100% sure, but in attempting to make her plane, I left my friends on shore and took her out by my self. From a stand still I slowly raised the throttle and the bow began to raise up as usual. But as soon as I hit full throttle the bow came down a fraction, problebly about half of what it had gone up. The boat seemed to be planing.
She held up really well through the chop. At first I was VERY worried about her breaking apart especially with the hard hits she was taken over the witecaps on the river today. The only visible damage out of today was a few hair line cracks in the filet joints where the anchor well sits. Other than that everything else was solid. Im even thinking of calling her ICEBREAKER. or Dicebreaker for a more symbolic meaning.

JAcquesmm, I know your the designer and I take your comments very seriously. But I am confused. In a previous topic "Alternator in 15hp Mercury" you said
"1. I agree that you don't need an alternator to run those things.
2. About the CR13 not being a power boat, I stand by that BUT IF there is one sail boat that can plane with a motor, it is the CR13. There is no rocker in the aft, we designed the boat to plane easily on sail and to be used as a fast dinghy with outboard. She also has an unusually wide transom. This boat is an exception to the rule, you can add power and plane.
My comment reflected worries about the structure but it looks like you reinforced the transom etc. It will work."
Jacquesmm, is there any possiblility that this hull could take on more horsepower? Im thinking of buying a 30 hp mercury or adding on a 15 to make the boat a novelty boat. What are the risks involved in this? I really believe the hull is underpowered. Please take into consideration that I have added ALOT of weight to the boat with the flat floor, excessive fiberglassing and reinforcements. (Also because i am an amature i wasted alot of epoxy...)

To ks8 you said "Maybe soon, as you refine exactly what you want in a *dream boat*, or just a next step, the group here can help you with a model that will better do what you are hoping it to do. " Im just wondering if what you mean by that? Can a boat be designed just for me? or for a group? I really love the bostonwhaler outrage, the 30ft version, but I want to build a 20-25 ft version. I really want to start over with a boat, I would love to make it a perfect boat haha (seems weird ha?).

Any ways thanks for all your comments. hope you comment more!

proman,
You have a displacement hull. Like all displacement hulls it will get up to a characteristic displacement speed with very little horsepower. But, if you try to go over displacement speed the boat will try to climb it's bow wave but never quite get up on top. You are then using your horse power to keep the boat on that hill of water. To sustain your boat there you will have to run the guts out of your motor. You may even get a little over hull speed but it will take a lot of rpm's and a lot of gas. I don't know if it's accurate but I've heard that to go one mile an hour over hull speed takes a doubling of horsepower. And the next mile per hour another doubling. Even if this idea is hot air you are in a situation where a bigger motor is not going to solve your basic problem. What the bigger motor will do is allow you to cruise around with your bow higher in the air than with a smaller motor.
Displacement speed= square root of the water line times ~1.4
No one has yet found away to get completely around the limitations of the above equation. But, some still try.
Good luck.

Looking at the profile shot of your hull up-side down, there is not much rocker in the hull, but it is there. By sailboat standards, there is not much, but by powerboat standards, it is still way too much. Ask some of the builders around here that have accedently added 1/2" of rocker or hook to an otherwise flat planing hull - the results are always more than the builder imagened.

D your self a favor and buy a few books on boat design. Even of you are not a big reader, with your intrest in boats, I think you would enjoy "The Nature Of Boats". It is a good place to start - it mixes boat design with good story telling to keep it from getting tough to keep reading.

Jerry

I have written on the message board that she can be "used as a fast dinghy with outboard" but that doesn't mean more than 5 or 6 HP and doesn't mean that she is a true power boat. You can clearly see that this is a sailboat.
The CR13 has almost no rocker aft and is a planing sailboat. Given sufficient wind, the boat will plane or more exactly surf occasionally.
What we call planing in sailboats is not exactly the same thing than in power boats. It is the same type of lift but except in extreme conditions, sails will not keep a boat on plane for long.
With that almost straight run aft, the CR13 can also plane under power but not like a true planing power boat.
With a small outboard, a light crew well placed, the boat will go above hull speed but never very fast compared to true planing boats. A small outboard is between 3 and 6 HP but even on the study plans, I write a "very small outboard":
http://www.boatplans-online.com/studypl ... _study.htm
I owned a boat in that style and used her as a dinghy. With a 6 HP, I was going between 10 and 12 mph without much fuss. This is well above hull speed but that's about all the boat will do and only if kept very light.

You drifted far from the original design, sorry. It is clear that the design is a sailboat, not a powerboat with center console.
The added weight, the heavy engine are a problem: the boat is not designed for that, sorry.
I would keep her as a semi-displacement hull. You probably go at around 12 to 15 mph and that's all you will get out of it.

The FS12 and FS14 are true planing hulls. With the HP I specify, they will easily go above 20 mph, probably up to 25 and that is fast for that size boat. They will go faster with more HP, the hull shape can take it but I don't think it is safe. The USCG calculations agree with that opinion.

I have written on the message board that she can be "used as a fast dinghy with outboard" but that doesn't mean more than 5 or 6 HP and doesn't mean that she is a true power boat. You can clearly see that this is a sailboat.
The CR13 has almost no rocker aft and is a planing sailboat. Given sufficient wind, the boat will plane or more exactly surf occasionally.
What we call planing in sailboats is not exactly the same thing than in power boats. It is the same type of lift but except in extreme conditions, sails will not keep a boat on plane for long.
With that almost straight run aft, the CR13 can also plane under power but not like a true planing power boat.
With a small outboard, a light crew well placed, the boat will go above hull speed but never very fast compared to true planing boats. A small outboard is between 3 and 6 HP but even on the study plans, I write a "very small outboard":
http://www.boatplans-online.com/studypl ... _study.htm
I owned a boat in that style and used her as a dinghy. With a 6 HP, I was going between 10 and 12 mph without much fuss. This is well above hull speed but that's about all the boat will do and only if kept very light.

You drifted far from the original design, sorry. It is clear that the design is a sailboat, not a powerboat with center console.
The added weight, the heavy engine are a problem: the boat is not designed for that, sorry.
I would keep her as a semi-displacement hull. You probably go at around 12 to 15 mph and that's all you will get out of it.

The FS12 and FS14 are true planing hulls. With the HP I specify, they will easily go above 20 mph, probably up to 25 and that is fast for that size boat. They will go faster with more HP, the hull shape can take it but I don't think it is safe. The USCG calculations agree with that opinion.

Hahah thanks alot for all the information. Ive finally given in, im not going to upgrade the engine. Im just going to finish her off, use her for calm days of fishing in the river. Ive decided to start a CS23 or CS25. Mum agrees, dad doesnt. Thanks alot again. Have fun boat building guys!

You gained a lot of experience building that boat. The pictures show quality work. Use that experience to build a real power boat now and during the building, take a day off from time to time on your hybrid CR13. It's still a very usable boat.

The Dougster's real impressed with what you built. Good grief, what a first effort! If you keep it goin' on, you're gonna have it goin' on!

No foolin', I like the boat Dougster

A few boats here have been designed based on particulars that several builders were looking for in a boat. I think when Jacques has enough committed builders for the plans for a new design, he designs according to what they are looking for. It can't hurt for you to join some discussions now and then about any ideal you are looking for. But I had been thinking that we could help first with existing designs to better meet your ideals for the next boat. Talk it up and see what happens.

CS23? So let's start. Talk about the particulars. What made you look at the CS23? List some guidelines that you think bring you to the CS23...

Wow thanks alot for all the comments guys. Even at 16, i see that this forum and website has created a very nice community of boat builders and the like. Right now, I am contemplating building a CS25/23 or design and build my own boat around 25 to 30ft. I have been talking to Ron White on email, and he has given me the inspiration to design one. http://www.concentric.net/~knotreel

What are your opinions on this? I am in my final year of school. Yr 12. so I would spend most of this year, reading up, measuring alot of boats down at the yatch clubs, and putting all this to paper. I also hope to learn to use a CAD program to then have plans to start building. I know this is a massive feat, and I know it will take alot of financial and labour value out of me, but I really think its possible. What do you think? Design and build, or buy plans and build? I will post a design I drew of my "dream boat" very soon.

Thanks again for all the valuable comments, prying me away from building a dangerous boat. (aww im really curious about having alot of power on that hull though. could be interesting. but expenisve.)

Jacques is well experienced in this building method and is getting ready to release his first set of plans based on one-off foam sandwiching he has written and huge manual detailing the layup process as well.

I can only assume that he did this because more boats will follow in this method! We all know that Flat wood limits some shapes, that is why many boats are made in a one off strip method (not because it is fun, easy, or cheap)

Before you decide to go this route look hard at the CS 23/25 I am amazed and the Shape when I see actual Pictures you would never know that it was a stitch and glue boat! The bow is beautiful!!! I guarantee you will have a safer, stronger, longer lasting boat that will be easier to build and less expensive to build if you go with something that Jacques has designed.

I have built others boats and have never found a designer who dose so with amateurs in mind when he is drafting! ... Build BIG take LOTS OF PICS

"one off strip method (not because it is fun, easy, or cheap) "
Whats strip method? i assume this is the mold right? and then the foam is stapled onto it? Is it fun! and is it easy! and is it really cheap! YAY! boat building made into a heaven send. Also, the CS25 can be built in foam core right? I dont wanna work with plywood anymore, its really heavy, and not friendly.

"getting ready to release his first set of plans based on one-off foam sandwiching he has written and huge manual detailing the layup process as well. '
Will we be notified soon about the realease date?

thanks heaps.

The strip method involves building forms (much like the form for our S&G boats, but more of them) and then adding long, thin strips of hardwood around them to get the hull shape, then removing the forms and glassing the hull (inside and out).

Fun, Easy and Cheap are in the eye of the boat-builder, but compired to S&G, it is more work( and a much higher standard of craftmanship - no more "gaps are good"), maybe more money (you need GOOD hardwood+many more shop tools), and as for fun - well if wood working is fun, and boat building is fun, then the more time spent building = more fun, right?

Jerry

What are your opinions on this? ......I know this is a massive feat, and I know it will take alot of financial and labour value out of me, but I really think its possible. What do you think? Design and build, or buy plans and build? I will post a design I drew of my "dream boat" very soon.

Nice job on the build. The fact that you completed that at your age and are still ready to tackle another tells me you can do it. You don't need a Dad, do you?

Building takes a lot of talent, patience and perserverance. Good boat design on the other hand takes years of training, engineering school, experience in design, building techniques, boat handling characteristics, and many other sciences. I'm sure you could, in time, design a decent boat. But you will waste a lot of time and materials in trial and error, and may still end up with an inferior product even if your construction is good.

As you say, a boat like this is a major commitment of time and money. My opinion (hey, you asked for it ) is that you would be much better served putting that time, effort and money into a proven design with designer tech support. There is no way you will design a boat that is stronger, lighter, makes better use of materials, is more efficient, more stable or safer, than a boat designed by a professional yacht designer. To build that 30' hull and mostly rig it out will probably cost what? $50K? Those twin outboards will cost you about $32K more. One you buy the bait and beer and fill up the fuel tanks you're looking at $100K and a couple of years work. With that kind of investment, use a professional designer.

Nothing wrong with you wanting to be a designer, take your time, design and build some small boats, take some classes, work up, but don't risk your $100K just yet. Unless you just happen to be able to afford the loss. That would change my advice.

I'm very impressed with your attitude and ethic for your age. Good luck to you whichever way you decide.

I believe I built the first one off design that Jacques designed. It was the PH15.First of all it is not cheaper than plywood. Second it takes a lot of patience. You really need to think it out before you even start.Make sure you read all the notes thoroughly. You may have to flip flop back and forth to get the answers. They are there , you just have to read . cutting the foam is simple. Easier than plywood. The stripping takes patience. Think it out and lay it out before you start the stripping. I can go on and on. Just remember, if you take your time and think it out and be prepared to spend extra money you will do ok.Look in the builders photos back around July 1905 and pics should be posted.

Hi everyone. Well, ive decided that i have to research and think about this more. Design+Build vs Build. I am going to talk to Ron White abit more, about his understanding about boats etc and ask about the problems he encountered and how well his boat turned out. In previous emails he told me that a "speciality boat" design wins in some areas and looses in some, in that the design might favour highspeed travel through rough water than lowspeed travel through rough water. Or high stability at low speed, or high stability at high speed. He means, that a boat design has its ups and its downs. Now its up to me to see if i can design what i really want. doesnt look promising i have to say.

Thanks heaps.

Hi All,

Well the CR13 named SS Minnow was built back when I was 14, and I am now turning 29.

To jacquesmm, 16 years later, and as an engineer, I realise how my comments may have come across as rude or dismissive of your work. Please accept my apology for comments I made as my younger self.

Thank you for supporting my goals as a young boat builder, that boat has created some of the greatest memories in my life. I can imagine it would have been very different if you didnt support what I was doing, and I decided not to go ahead with finishing the boat.

Thank you again and I look forward to sharing some of the stories and an update about SS minnow soon.

Man

Well, you've got to put a few pictures in here... of your dream boat. Is it still on the table?

Great to see you follow up. Welcome back aboard. It was moving to read Cracker Larry's typically honest and supportive post from all those years ago.

Dougster

alright ... what about just one teaser picture from the soon to be released update regarding the 'Minnow'? We don't need the whole update right away (what am I saying? ) -- well -- not yet. But have a little mercy and show us at least one update picture...

or a link to a new thread with that picture? or a new thread with any update about the dream boat.