Effect of being at waterline and fore/aft imbalance - SailNet Community

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  #1  
Old 12-11-2008
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Effect of being at waterline and fore/aft imbalance

Well, we've loaded everything on Pelican. At this point, our stern is AT waterline, and our bow is an inch above it. We're going to try to move some stuff around, but I don't know how much of a difference it will make. Most of our storage is in the stern, with little available forward.

What's the effect of being bow up, and how can I expect our boat to handle when it's AT waterline vs. the 2" above waterline it used to be?
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Old 12-11-2008
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Labatt,

The hull form of your boat is similar to ours, and I can say emphatically that trimmed stern down is undesirable on our boat. In my experience, this is true of most boats.

If you can shift some heavier gear out of the stern and closer to mid-ships, I think you'd be doing yourself a favor. If that's not possible, try to draw from your aft-most water tank first, so at least you'll be mitigating the aft-trim somewhat.

Also, the boat may trim differently with sails set and some heel, so you might want to get someone to snap a few photos of the boat under sail to see if it's truly dragging the stern.
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Old 12-11-2008
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It depends on the boat... In most multihulls, having the boat a bit heavier aft is actually desireable in many cases. In the case of your Passport 40, I think you need to rebalance the stowage plan a bit—or just keep your wife and kids stuck up in the v-berth.
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Old 12-11-2008
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Labatt, to answer your question,

heavy stern will point worse, but run better downwind.

Also will cause more leehelm. It's not critical, as you are not going to race..don't worry..safe travel

Alex

Last edited by Giulietta; 12-11-2008 at 08:13 PM. Reason: wrote weatherhelm instead of leehelm.sorry
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Old 12-11-2008
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Do you have all your anchors and anchor chain in the bow? A full anchor and chain complement may take care of any trim issues.

You should consider that being low on the waterline may produce some surprises down the course. The first is the probablity of hull staining...the cruiser PO of my boat raised the waterline six inches for this reason. Various items desined to be normally above the water line, may now be below the waterline, either permanently or when heeled. Suspects should include the rudder thruhull/bearings, various points in the head including the toilet bowl itself, the sinks. You should look through the boat carefully to imagine what difference six or eitht inches of water level might make...or check with other owners who have lived with such loading.
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Old 12-11-2008
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Quote:
Originally Posted by Giulietta View Post
Labatt, to answer your question,

heavy stern will point worse, but run better downwind.

Also will cause more weatherhelm. It's not critical, as you are not going to race..don't worry..safe travel

Alex
Yes. THat is correct. I will also add that tacking becomes a bit more tedious. BUT YOU ARE A CRUISER AND A LIVEABOARD.... DON'T FRET IT!! You should have seen our waterline. We had it raised FOUR INCHES on our 380, and did the same with our 400. It is no big deal. Just thank God you did not buy a catamaran!!

One thing we did to help offset some of it was to varnish our can goods and put them in the bilge in a container. That will take them out of the galley and make them more centerline.

Or... buy a really big freaking anchor (smile)... or... tell your wife you need to buy more stuff to level out the boat! Learn to use your dissadvantages to your advantage!!!!

Brian
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Wouldn't overloading the stern move the boat's pivot point (center of lateral resistance) aft? That's the way it works with ships.

And wouldn't this then cause less weather helm and more lee helm (assuming the center of effort on the sails is the same)?

Also more drag, since the stern is generally fatter than the bow.
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Originally Posted by Cruisingdad View Post
Yes. THat is correct. I will also add that tacking becomes a bit more tedious. BUT YOU ARE A CRUISER AND A LIVEABOARD.... DON'T FRET IT!! You should have seen our waterline. We had it raised FOUR INCHES on our 380, and did the same with our 400. It is no big deal. Just thank God you did not buy a catamaran!!

One thing we did to help offset some of it was to varnish our can goods and put them in the bilge in a container. That will take them out of the galley and make them more centerline.

Or... buy a really big freaking anchor (smile)... or... tell your wife you need to buy more stuff to level out the boat! Learn to use your dissadvantages to your advantage!!!!

Brian
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Old 12-11-2008
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As others have said, if you're bow-heavy you increase weather helm, and if you're stern-heavy you'll increase lee helm. If you have Annapolis Book of Seamanship there's a great explanation of the physics behind this (p 84-85 in the 2nd edition). With only an inch difference, you can probably compensate by trimming the sails.

Next time you haul, you might consider raising the waterline, so you have an inch or two of bottom paint to keep barnacles, algae and other slime from attaching.

Assuming you're leaving this weekend as planned? Wishing you fair winds - Dan
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Old 12-11-2008
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Add beer. How about getting a few dozen of those Heneken kegs? They are handy to have, and easy to open and dispense. And they would be a welcome sight at any anchorage. You could put them way up in the bow or strap them on the deck far forward.

And when they are empty, you can use them as temporary bouys.
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