Trim on Nina, Jacques?

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Daddy
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Trim on Nina, Jacques?

Post by Daddy » Mon Oct 17, 2011 1:18 pm

Very happy with the performance of my Nina. Question is, how should she trim at WOT? I posted a pic on my blog and it shows her with more than half of the boat out of the water when she is at WOT. I have one more notch of adjustment to further bring my motor closer to the transom (no power tilt/trim) and wonder if that would bring the bow lower. I imagine this might take some speed off at the top and but would engage more of the hull with the water. That sharp entry on Nina does not have much function when it is way up out of the water. I wont be able to test the results til next summer but would like some advise on the ramifications of adjusting the motor. You can see the pic on my blog if you like. I welcome other opinions as well. Thanks.
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Re: Trim on Nina, Jacques?

Post by jacquesmm » Mon Oct 17, 2011 2:23 pm

That looks like too much trim. I have seen other Nina's and they run flatter.
How much HP do you have there and how fast do you go in that picture?
That boat is designed for moderate speeds and it looks like you go faster.
She is designed to cruise at 18 mph with about 2 degrees of trim.
How is the trim at cruising speed (18 to 20 mph)?

There are ways to improve the trim at WOT but tell me first what size of engine you have.
Sorry if I don't remember, I looked at your blog and see a 25 but is that the Nina?
If it's a 25, bring the engine closer one more notch.
How about the weights? What was the weight situation in that picture: tanks, batteries.
Jacques Mertens - Designer
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Re: Trim on Nina, Jacques?

Post by Daddy » Mon Oct 17, 2011 2:57 pm

It is a 25hp, the speed is 21 mph in the pic. Yes that is Nina in the picture.
1. I made the motorwell opening smaller and added two square feet to the planing surface (and more buoyancy) by doing that.
2. I am using a 6 gallon portable tank under the bench seat and eliminated the 18 gal. tank in front of frame C.
3. I moved the helm forward one foot to offset moving the tank.(result, moving 200 lbs., me, one foot fwd)
4. When at rest the boat is self bailing. When loaded with 4 the scupper is just at the waterline so I need the plug.
5. Put a hard top on the cabin, adds maybe 30/40 pounds.
6. One battery on port side next to motorwellwell (gas tank is stbd)
I was very impressed when she clocked 21 mph.at WOT, 5700 rpm. Did not expect that. Cruises nicely at 4300 but still trims up a lot by the bow. Got many compliments on your design and everyone seems impressed that I can get 21 mph with a 25hp on a boat of that size.
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Re: Trim on Nina, Jacques?

Post by Daddy » Wed Oct 19, 2011 4:56 pm

Jacques, I answered your questions in the above posting and I have one more for you. 2 degrees of trim. How is that measured? Is it 2 degrees from dead level in the water? How would you even measure that? I guess that a slight rise in the bow is OK at WOT but no more? I will move the motor in one notch, after that there is no more adjustment so It will be what it will be unless I add ballast (grand children in cuddy). Can't wait to get her back in the water, boat too. :D
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Re: Trim on Nina, Jacques?

Post by Cracker Larry » Wed Oct 19, 2011 5:03 pm

I will move the motor in one notch, after that there is no more adjustment so It will be what it will be
There are also transom wedge plates available in different increments to change the mounting angle.

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Re: Trim on Nina, Jacques?

Post by Daddy » Wed Oct 19, 2011 9:16 pm

Cool Larry, never saw one of those, am hoping the one notch will do it. I guess if more hull is in contact with the water I will lose some top end speed but I can live with that.
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Re: Trim on Nina, Jacques?

Post by TRC886 » Wed Oct 19, 2011 9:49 pm

What about adding trim tabs to the transom; and/or a "whale tail" to the motor?

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Re: Trim on Nina, Jacques?

Post by Cracker Larry » Wed Oct 19, 2011 9:51 pm

Yes, I bet a Doel Fin or equivalent would help a lot.
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Re: Trim on Nina, Jacques?

Post by Spokaloo » Thu Oct 20, 2011 2:02 am

Put the pin as low as you can set it so that the motor can come down and rest as low as possible. Your boat is light and she will be very apt to plane on the aft surfaces. Over 20mph, Cloud Cap is out of the water from the C bulkhead forward. At 25mph, light loaded like you are there, it's under the helmsman's feet. Once you add some weight you'll have the bow a bit lower.

Sadly the trim plates that go on the motor won't fit on these boats, the well isn't wide enough to swing it, unless you bought one and trimmed the ends off to fit the well.

I find that whatever I'm bringing for the day should be strategically placed for the weight balance, like an aircraft. If it's just SWMBO and I, everything goes far forward in the bow to trim her down. If we are heavy with friends, everything goes aft to keep her from bow steering.

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Re: Trim on Nina, Jacques?

Post by Spokaloo » Thu Oct 20, 2011 2:34 am

28mph, light boat:

Image

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