Boat Trim Question

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1

Hi All,

I’ve been working to help Soave sail to her rating. I understand my sailing skills are a part of the equation. Working on that variable by practicing.

Last season I focused on sail trim because she was experiencing lots of weather helm.

This season during mast tuning I used wedges to increase forward mast rake by about 3/8" of an inch at the deck level. This moved the top of Soave’s mast about 4" forward.

Weather helm is less this season.

Still focused on getting Soave to sail to her rating, I’ve observed boat trim may be off. (HERE) is a photo showing Soave’s bow her bottom pain is 4.5" higher than the water level. I know someone could have gotten creating with her water line. So I measured from the top of her rub rail on her gunwale to the water level. This measurement is 64"

I did the same in the stern. Water is 1.5" above the bottom paint. And the water level is 44" below the top of her stern rub rail.

If I believe her waterline is in the right place, ( a big if). She’s sitting low on her stern… off by about 3".

I’m wondering how Soave’s trim compares to other NS 33" out there. Best way to compare would be to compare top of rub rail to water level, because all out bouts have had multiple bottom jobs where the water line may have been moved.

Thanks for any insights you can share.

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

2

Hi Rob,

I usually spend 2 days and a night on my boat each week. I’ll try and remember to make your measurements next week. I’m having some health issues, so I have missed a couple of nights in the last few weeks, so I can’t promise for sure it will be this week. Also, I forget things - even things I really NEED to do on the boat. So a private reminder around Wednesday might not be a totally bad idea. :slight_smile:

Given the curved shear and arched transom, it would be helpful if you would post a side view and rear view with little arrows pointing to exactly where you want me to take the measurements. I say exactly where, because your definition of “rub rail” and “gunwale” seem to be somewhat different than mine, so I want to make sure I give you useful measurements.

Are your water tanks full? Filling mine lowers the bow a bit, though my bottom paint line still looks about like yours in the photo even with the tanks full. I’m curious what else you could do about it besides adjusting water tanks if you find that your boat is painted correctly, but not sitting level on her lines.

I would think that filling the water tanks, especially the forward one, might lift the stern bit. But probably not a 1.5”. Any amount of the transom being immersed would probably have a bigger effect on your boat speed than how high the bow sits (within reason, of course.) A small change in bow immersion will affect the water flow around the hull, of course, but probably not a lot given the round lines in our hulls. (I have over 17,000 miles in rowing shells, so I have a lot of experience with trim in long, narrow boats, but not so much in short, wide ones!)

Do you have a lot of extra equipment beneath the cockpit, or hanging on the transom? For example, I looked at one boat (Big Easy, in San Diego) that had a generator beneath the port cockpit seat and a dinghy on davits. I didn’t pay attention to trim at that time, but it seems that would put quite a bit of weight aft. And the generator is on the same side as the water tanks.

Immersion of the transom will affect water flow, but then you also need to add in the effect of turbulence drag due to the water not coming together smoothly at the stern. If there’s nothing you can do about transom immersion, then you probably are wasting your time worrying about the rest of the trim. Overall lightening will probably make a bigger difference. With a cruising boat like ours, there’s not even a lot you can do there. My boat was built for a serious NS racer (it won the 1998 NS Nationals) so it didn’t have anything extra to weigh it down. And the PO didn’t add anything to it but the sail cover. (Which probably messed up the race performance more than adding a generator would have!) It’s hard for me to imagine caring enough about speed to remove extra equipment, but you have different standards and objectives than I do. It’s the beauty of boats that we can so totally personalize them.

3

Rob,

Fundamentally weather helm is a product of heel. “Flat is fast,” as they say.

A baggy or improperly trimmed sail would contribute to the problem, for sure. Maybe you’re not trying to sail high enough when close hauled. I’m sure there could be lots of ways to tweak things, but the thing I’d be most interested to know is how far over you’re heeled.

Ed Cook
Chat-eau, N26c #173
Middle river, MD

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4

Rob, I don’t have a33 so keep that in mind when you read what I have to say. The manual shows the 33 has a 100 US gallon water tank toward the bow. 100 gallons of water weighs about 834 lbs. Are your batteries near the stern and how big is the bank? A big bank near the stern could bring her down a bit at the stern. Do you have a photo of the stern and how full was the water tank when you took the photo of the bow? That could have a big effect on your trim. You could spend some time looking through the Nonsuch Photo Gallery section on the 33 and check how they trim. The 33s I have seen seem to be high at the bow. I must say in the photo you posted she doesn’t look particularly high in the bow. I think dragging the stern would slow you down more than a slightly high bow. Do you have a heavy tool kit you can move from the stern to a forward locker?
Mark Powers

5

Thanks for that, Ed. I know it was meant for Rob, but I’m happy to learn wherever I can.

6

I’m having trouble understanding what comparing distances above the water line, even at comparable points, would tell anyone.

I could see how that would be informative if every boat was set up the same, sailed the same, and complete information about their performance was available. Otherwise, I’d need some help grasping how those comparisons would get turned into useful information.

As evidence that weight distribution matters, I can offer that my boat went bow-down by about 2.5” when my diesel was out and the electric engine hadn’t yet gone in. Also, I’ve been following discussions since 2017, and I have yet to hear anyone saying that their boat performed equally on port vs. starboard tacks. Again, all the posted explanations come back to weight distribution.

It seems to me that, in line with what several people have already said, the boats do better if they’re not squatting at the stern.

The best thing to do is to experiment with stowage that affects boat trim, and see what stowage arrangements improve/diminish an individual boat’s performance.

– Bob

7

We’re all different. I think Rob likes numbers. If it makes him happy, then there is value in that. Maybe they will be useful or maybe not, but they seem easy enough for me to get if I know exactly where to measure from. Oh, and if I can do it while on the boat. I really only have convenient access to the port side without moving the boat and I do represent quite a bit of moveable ballast…

8

Apologies if my question came across as critical. I really am curious how these sorts of analyses work.

My weight is about 55% of a Westerbeke 21’s, so you probably don’t want me measuring while on the boat, either.

– Bob

9

Hi Ed,

Prior to adjusting my mast rake weather helm was very noticeable starting at about 12 knots of wind. Required 7º of rudder to hold course. Heel would be sightly less than 5º.

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

10

HI Mark,
Soave’s forward tank is empty. Her battery banks is under the berth in her aft cabin.

I know from racing small boats the effect of moving crew weight forward or aft can have on boat speed. I’m trying to figure out is Soave’s boat trim is out of spec or if at some point in her past her waterline was incorrectly measured during a bottom job. Before I start moving stuff to impact trim I want to compare Soave’s trim to other NS 33’s.

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

11

Hi Brian,

( Here ) is a photo showing the point I’m measuring to to compare boat trim. I’m dropping my tape measure till it touched the water and measuring to the top of the vinyl rub rail.

My first step is to try to figure out if Soave’s waterline as defined by her bottom paint is correct. If it is, I’ll know she’s not sitting in the water as her designer intended.

I’m thinking before I “fixed” my weather helm problem by changing mast rake, maybe I should have checked boat trim.

I’m currently carrying a heavy plow anchor and 200’ of chain on Soave’s bow. I’m contemplating dropping it at my slip before heading out to race, but loosing that much weight will push trim even further out of spec ( according to my bottom paint waterline).

Rob…

12

Bob,

You are correct. My approach only works with boats from the same mold and it only tells me if I’m starting from a trim point that is what the original designer intended. I’d like to start experimenting from a known starting point and have an objective way to track changes.

The boat I have the most experience with ( Flying Scot ) weighed 1200 lbs. Skipper and crew added about 350 lbs. We could ( and did ) adjust boat trim frequently during the race by sliding forward and aft. Trim affects more than just hull shape in the water…. it changes the relationship between your upper foils ( sails ) and your lower foils ( keel and rudder ). Similar to the way mast rake works.

Soave weighs 15,350 lbs. So crew position doesn’t have much of an impact. A big plow anchor and 250’ of chain sitting on the bow does have an impact. But according to my waterline, Soave is already light in the front. I figure I ought to understand trim before I loose the anchor and chain.

It’s a process to understand enough about a boat to be able to coax the last 5% of speed from her. You don’t know what works till you try. Comparing with other boats helps you prioritize what ideas to try first.

Rob

13

No worries…. critical thinking is important.

Measurements from a different model of Nonsuch will not help me, no need to measure your boat, unless you want to compare with other NS26’s

Rob…

14

On our 33 the boat seems to be low in the stern. I am basing this on the fact that the water pools aft of the scupper drain.

15

Hi Blake,
Soave also pools in that spot after rain. I guess this is a hint that our trim is different from what the designer intended. It’s also a very good way to measure trim at least while at rest.

Another thought is maybe forward/aft trim changes while wile underway. Next time I’m out I’m going to check if Soave’s trim shifts forward under sail… because with the mast so far forward the driving force from the sail probably adds forward, side, and downward forces where the mast is attached to the hull.

Maybe I shouldn’t focus so much on trim at rest… its trim while underway that matters.

16

I think the designed placement of the deck drains was off. On 33 #8, the water pools aft of the drains with full water tanks and lots of anchor chain in the chain locker. This is with no one on board (empty cockpit).

Ward Woodruff
N33 #8 Margery
Niantic Bay, CT

17

Ward,
I have the same problem with deck drains. It’s an annoyance as the gutter must be constantly cleaned. Michael Passero
Born To Run, 33, #42

18

Don’t get a lot of rain here, but when I wash the boat the water all seems to drain well. My boat actually has two drains on each side. Perhaps this was to correct the pooling problem in earlier boats?

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19

Hi Brian,

When I read the first phrase of you post, It Never Rains in California started playing in my head.

A couple folks have mentioned that on light race days they make sure their front tank is full to help lift the stern out of the water. It will be interesting to measure how much the tank can impact fore/aft trim.

Rob…

20

Rob, I just knew you would get around to play with the water level in the tank. :innocent:

Mark Powers