Corsair 13 Power version tested

[proman_11]

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?

[Jerry-rigged]

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

[jacquesmm]

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

[Jerry-rigged]

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

[jacquesmm]

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.

[retrosub]

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.

[ks8]

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!

[gk108]

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.

[proman_11]

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.

[ks8]

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!