When it comes to "going out" most of us have our rules of thumbs, 15kts and 1.5m swell, wind or tide direction or what have you.

For me I don't choose to go out in >15-20kts and/or 2m swell. I'm starting to think that that might be a bit restrictive as it doesn't take into account the swell period. A large swell might well be comfortable (I'm talking comfort here and not tolerated or safe if caught out) with a longer period between peaks.

Is there a good rule of thumb when determining a comfortable wave height versus period.

Yeh what Ramona said. Wind is your best guide.

"Swell" consists of 2 parts - Swell - Which is the underlying wave action, generated from far away - Typically a longer priod. Then sea, the localised wave action generated by wind (typically shorter period than swell). This is perceived as chop in more modest breeze. And of course the overriding factor here is height of sea + swell.

Theres an old sailing truism - The best time to put in a reef is when you first think about doing it. Similarly, if you have to think about whether to go out or not, probably best not to go out.

There is a mathematical response to this question (I'm a water engineer specializing in flooding and know something about ocean waves), but you are, presumably, talking about how waves affect comfort and other perceptions.

Technically, our term "wave" covers a multitude of phenomena, from surface ripples to tsunamis, from waves that transfer mass (e.g. tides) to waves that transfer energy (e.g. ocean swells) and every combination in between.

Something of interest, however, is how waves slow down and "pile up" as they approach the shore and the water gets shallower. They also diffract. I've seen some cool (and scary) simulations of what happens when a 10m tsunami hits Moreton Bay. So, a wave offshore would be much more comfortable than the same wave inshore.

I'm a bit conservative by nature and I have 2 family members who I need to be a bit careful with if I want them to keep enjoying sailing.
We have experienced some crappy weather and big sharp seas. We are not novices to sailing but I can't help think we sometimes miss out based on 2m swell mindset. And I'm talking about choosing to go out in and not what you'll be confident in being in..

I was going to sail from Fremantle to Busselton tonight with my family and a mate who has some small sailing experience but no long passage and no overnight experience. I was put off by the 2.5 to 2.8 metre forecast swell even though the winds were 5-15kts. The swell period was 13 seconds..

See here a good summary;

www.bom.gov.au/marine/knowledge-centre/reference/waves.shtml

Swell can be a contributor to seasickness. Anytime your eyes can't grasp what your ears are feeling, you have the potential to get sick. Plenty of people get sick riding over swell in calm conditions.

Good call Toph, you might have ended up pulling a very long watch.

The surf starts getting good when the period gets to about 12. So I would think you would start having fun if 12 second waves were hitting tide or intersecting from different directions. It also amazes me how quickly large period waves travel.

So nobody will be putting this into practice next Tuesday!

44 knot winds and 8m plus seas off Newcastle.
Even up at the Camden Haven it will be 42 knot winds and 7m seas.

FreeRadical said..
Good call Toph, you might have ended up pulling a very long watch.

Spoken like someone who's experienced it