Auxiliary or Main Engine?

[ponapay]

Not so long ago it was unusual to have an engine designed to power yachts for any reason other than to berth when the wind was light. Now we mostly have powerful engines, but how powerful should they be?

I fitted a replacement engine recently to my 38ft plastic traditional shaped ketch. It replaced a 36hp engine and the new one is rated at 50hp. A new prop was fitted and she has now become much more manoeverable in harbour - even astern.

The problem is now that I expect her to go faster into wind when under power. I sailed from a port with forecast N5-6 winds, they prevailed for the 15 miles to the open sea and then gradually increased - possibly funnelled by an offshore island - until the wind was up to 55 knots. I had reefed well down and was debating a return to harbour - to the relief of my crew - but to go back the way we came out was no longer possible, the wind had veered to provide a blast straight at the shallow bar and narrow entrance making it unwise to attempt entry at that point. I turned downwind for a 5 mile pasage to the south before an exciting beam reach west to the southerly entrance. On turning to enter through a group of islets we encountered a head wind of up to 60 knots and short sharp seas, we were under power and now with no sails up. My vessel has external halliards and a roller reefing genoa. Our maximum speed into wind was 1.8 knots. As soon as we got a lee the speed increased to the usual 6.5 knots.

Am I expecting too much of her to make better head way in such conditions?

<hr width=100% size=1>

 

[oldharry]

In a word - yes! 50hp is non too much power for a what appears from your description to be a fairly heavy hull. However, I guess too that many yachts would not have made up against a 60 knot wind and head sea at all, and would have had to wait for things to settle down a bit.

<hr width=100% size=1>

 

[Chris_Stannard]

You may have forgotten that the pressure of the wind increases with the square of its velocity. Put more simply a 60 knot wind will give 16 times the wind resistance of a 15 knot wind. You do not say whether you boat is lightweight of heavy dispalcement but with a short sharp sea, and the boat slamming, I would guess you were lucky to be going anywhere.

<hr width=100% size=1>Chris Stannard

 

[LadyInBed]

1.8 knots sounds about right to me. Any faster and I reckon thing would feel very uncomfortable, for the crew and the boat.
As for big engines, to have a lot of power to hand is comforting, but you don’t have to use it just because it's there.

<hr width=100% size=1>