Sailing Cat Trim

[jacktheflyer]

I have just replaced the battery bank on my Fusion40 and moved it from midships to aft in the Lazarette. (approx 250kg) In doing that the boat has gone from being slightly bow down to slightly stern down.

Question for the brains trust- Is it better for hull speed and efficiency to have bow down trim or stern down trim.

[GordMay]

Will depend, somewhat, on point of sail, wind and wave conditions.

The ideal fore-and-aft trim would sail the boat on its lines, with the bow and stern “level”.

In light air, trim weight forward, to keep the stern from dragging in the water (which slows you down).
As it gets choppier, move weight back, far enough to keep the bow from plowing into waves.
You also want to move aft as the wind increases. This will give you more stability because the aft sections of most hulls are flatter than the forward sections.
In planing conditions, move your weight even farther toward the stern so the bow will lift up.
Downwind: Bow slightly down. Upwind: Bow slightly up (stern down).

[belizesailor]

Ideally, for speed and saftey, its best to have a cat trimmed level and not loaded below her design lines.

Now...conduct a poll and see how many cruising cat sailors can honestly say their boat is properly trimmed! [emoji6]

[admiralslater]

Gord May is quite right . After years of racin our cats I can attest that in light to moderate winds weight forward is definitely faster. Our boats are trimmed level and we use the crew position to ajust weight for and aft .It can be as much as a knot depending on hull shape

[mikedefieslife]

Originally Posted by belizesailor

Ideally, for speed and saftey, its best to have a cat trimmed level and not loaded below her design lines.

Now...conduct a poll and see how many cruising cat sailors can honestly say their boat is properly trimmed! [emoji6]

I doubt many are running over their cat’s design payload capacity though.

[belizesailor]

I see plenty cruising boats, cats and monos, sitting low on their lines. This is one reason that stern extensions are a popular improvement to cats.

[mikedefieslife]

They maybe low on their lines (hasn't the owner just painted these on anyway), but they doesn't mean they aren't still perfectly within their design capacity.

I think the payload in weight needs to be discussed more but few seem to ever mention it. Instead they just use a generic phrase like "slower if overloaded" with no qualification as to what overloaded is, and normally the designed payload is never stated.

[jacktheflyer]

Originally Posted by GordMay

Will depend, somewhat, on point of sail, wind and wave conditions.

The ideal fore-and-aft trim would sail the boat on its lines, with the bow and stern “level”.


Downwind: Bow slightly down. Upwind: Bow slightly up (stern down).

Thankyou, that is the sort of info I need from experienced sailors. Am I correct in thinking the forward thrust coming from the sail will tend to leverage the bow down as well?