I am looking to downsize from a racer/cruiser to a trailer sailer. But I am also kean on performance, particularly in light winds to make day sailing more pleasant and for weeknight races. Here is my first question: how much performance do I give up with a swing keel design versus a fixed fin keel? For example, reviews for the Ericsson 23 do not seem to distinguish between the swing keel and fixed keel versions, but I suspect I would be happier with the fixed keel, particularly for upwind performance. Thanks!

I think it depends on the swing keel design. Some, like the Pogos, have a weighted centerboard. With the centerboard down, the weight is down low like God intended. Others have a very short ballast keel, with a light centerboard the swings into that. For a given amount of righting movement, the latter type will have to be much heavier.

Most (edit: modern) performance-oriented trailer sailors seem to have a fin keel with a bulb on the end that retracts upwards, e.g. J/70 or Viper 640. There are also a number of trailerable trimarans, which are very quick.

Depends on the trailer sailer. All other things being equal, I would expect a vertical lifting keel to be faster than a swing keel. Multi hulls can be faster than either. I don't think I would be interested in a deep fin keel trailer sailer. Maybe look into the various sport boat designs? I would pay attention to more than keel type, a lot can be accomplished with form stability.

Melges but you have to ask yourself....can you handle it? Well can you OP?

First 24

Give up nothing, go wtih a lifting keel instead of swing.
S2 6.9 (22 foot boat).
S2 7.9 (26 foot boat).
Trailer sail and launch like a motorboat (even better than swing keel).
Performance is stellar.

Think its a slow design?
Look at: Left Coast Dart, B25, J70, Melges 24, U20, and dozens other that I can't think of.

Swing keel is slow(er) than fixed, or wing for sure.. but there are better more trailerable designs out there than swing.

But directly answering the question, it can make a huge performance difference, look at ratings for the Catalina 22 swinger versus fin. These are Portsmouth derived ratings.
Catalina 22 (FK, No Spi) 97.1
Catalina 22 (SK/WK, N/Spi) CAT22 96.3
So there would appear to be a significant difference. The Catalina 22 has a fairly large sampling for ratings (due to numbers made).

Less than a second per mile is significant? What am I missing?

Thanks for your thoughts. I think that righting moment may be key to this analysis. I have been looking for designs with a minimum ballast to displacement ratio of 35%. I recently saw the new Tartan 245 design and it looks like the ideal trailer-sailer for me, but the ballast-displacement ratio is just 30% (bummer). But if you look closely at the keel profile, it is easy to see how additional ballast (weight) could be built into the foot of the keel, thereby offsetting the lower ratio in terms of righting moment. So the question is, how much righting moment is lost when comparing comparable designs of a swing versus fixed keel? And performance-wise, would it be more significant in lighter or heavier winds? I would not want to have an under-ballasted design that requires early reefing, but beyond that, would I notice a difference in light winds when I might be sitting on the low side anyway?

And yes, I understand that modern lifting keel designs with a bulb are faster, but that is not the question.

For the S2 designs, are the lifting keels ballasted, or is most of the ballast internal?

You are going to have to look at it on a case by case basis. There are swing keels that have lead bulbs and there are those that have little more than a steel plate.

All other things being equal the length of the lever arm is going to be shorter with a steel plate than with lead down low. The centre of mass of a steel plate will be near the middle of plate. The centre of mass for a swing keel with low down lead ballast will be closer to the bottom of the keel. I am sure you could calculate it....

But don't over look form stability. Some boats can resist more heeling than others just due to their shape.