Full keel vs fin keel for offshore?

[kmacdonald]

My opinion is they will only work in moderate conditions and better. A rubber dinghy will do the same. In survival conditions neither will work.

[RedHerring]

Originally Posted by robert sailor

Sea of Cortez is coastal sailing and thats how 95% of those boats got there certainly not enroute around the world.

I'm pretty sure I'm going to see quite a few early 90s Benes in French Polynesia, once I make it there. We'll see.

[dcstrng]

Originally Posted by Tidjian

So all debating aside I think the overall answer to the thread topic was, the keel doesn't matter as much as other factors....


More important factors than the style of keel is the design of the boat. Structural stability, age, condition, storage, cockpit size, displacement, etc...

I think you've pretty much nailed it... Notwithstanding transient acrimony here and there, there is an astonishing amount of experience contributed to this thread. From a pure theoretician's standpoint, see Marchaj who bridges the aero-hydrodynamics gap on the full v. fin topic and accounts for the widely varying Reynolds numbers, or better still the NACA research papers (readily available for free online) and look to the effect of aspect ratio on the eventual stall behavior of a foil.

Very low aspect foils (full keels generally) are by and large less efficient for their surface area than high aspect (fin keel) -- as many here have explained -- but tend to keep working through noticeably wider angles. However, very low aspects foils, hang on to much greater angles than do high-aspect foil (visually; note the angle of attack difference at landing between pure delta wings, XB70-- high angle -- semi deltas like the SST and the long wing airliners). High aspect foils tend to be more demanding structurally, but these challenges has generally been overcome in the marine architecture world by the better builders.

[Paul Elliott]

Originally Posted by kmacdonald

My opinion is they will only work in moderate conditions and better. A rubber dinghy will do the same. In survival conditions neither will work.

Please define "work". I think the life raft will "work" better than the dinghy in tough conditions. Nothing will guarantee that you survive, but some will do a better job of improving your odds.

In the olden days, a sailing dinghy gave you a chance to rescue yourself. After the mutiny on the Bounty, had Capt'n Bligh been put to sea in a modern liferaft he and his crew would most likely have died of thirst. Now that we have EPIRBs and PLBs and VHFs the survival equation has changed somewhat.

[kmacdonald]

Paul, I used "work" meaning "save your life". Given that the dinghy will "work" as a life raft in most of the conditions a life raft will, and the additional cost and weight of a life raft, I chose not to carry one. Sinking isn't something I worry about at all.

Note: check the weather before leaving, sail in the appropriate seasons, etc.

[RedHerring]

Originally Posted by Paul Elliott

but some will do a better job of improving your odds.

Question is, by how much? And can you not do something else with $2k that would improve your overall chances to survive an ocean passage better than a life raft?

Per my napkin estimates, the probability of a situation where a life raft works, but an inflatable dinghy doesn't is close enough to zero to make the real value of that investment not so obvious.

[Paul Elliott]

I'm not going to engage in the "How much is your life worth?" debate. According to my napkin estimates I will *never* need to use the life raft. But the ocean racing rules require the raft (and I enjoy ocean racing), and in extremis I probably wouldn't be able to inflate the dinghy anyway, and I can afford the raft without having to skimp on anything else I might want (I know, lucky me!).

So I carry the raft. Others make their own choices, usually for perfectly good reasons.

[kmacdonald]

Originally Posted by RedHerring

Question is, by how much? And can you not do something else with $2k that would improve your overall chances to survive an ocean passage better than a life raft?

Per my napkin estimates, the probability of a situation where a life raft works, but an inflatable dinghy doesn't is close enough to zero to make the real value of that investment not so obvious.

That's my opinion also. Well put.
Paul, I too could afford one but chose not to have one. I do like to spend my money wisely though.

[RedHerring]

@Paul Elliott: completely agree.

One way or another, everyone makes those "how much risk is acceptable" judgements all the time, e.g. whenever you get into a car and go on the highway.

Originally Posted by Paul Elliott

But the ocean racing rules require the raft (and I enjoy ocean racing)... So I carry the raft. Others make their own choices, usually for perfectly good reasons.

Having to appease some sort of authority (race committee, wife etc) is a very good reason to carry a raft, for sure.

[newhaul]

Originally Posted by RedHerring

Question is, by how much? And can you not do something else with $2k that would improve your overall chances to survive an ocean passage better than a life raft?

Per my napkin estimates, the probability of a situation where a life raft works, but an inflatable dinghy doesn't is close enough to zero to make the real value of that investment not so obvious.

I agree. Also fwiw my rib has the ability of filling my floor with water as a ballast to improve heavy sea comfort.
A couple pieces of of pvc pipe and a poly tarp ( orange if you can find it or white ) make a good cover and sun shade.

[dano098]

I fly a lot by myself. I'm thinking of the raft for one available at Sporty's. Link to follow.

https://www.avweb.com/news/reviews/1...1.html?type=pf

This is summary of aviation raft resources. Dated.

[dano098]

Here is single raft; throw it and pull, don't let go.

http://m.astoverwater.com/switlik-on...Life-Raft.html

[dano098]

Better link: http://www.switlik.com/aviation/isplr/features

[thomm225]

Originally Posted by Paul Elliott

If you are truly going solo, then don't get the six-man raft.

The above may be a true statement but Steven Callahan looked at both a four man life raft and a six man before deciding to go with an Avon Six Man Life Raft.

He then mounted it to his 21.3' Sailboat Napoleon Solo and headed across the Atlantic for the start of the Mini Transat 6.50 single-handed sailing race which was to start a month or so later

Long story short he believes hit something in the middle of the night about 400 mile west of the Canary Islands on his return trip across the Atlantic during the race and his boat began to sink.

This began his amazing ordeal of 76 days at sea on a 6 man life raft. He drifted and was pushed by the trade winds the remain 3/4 of the way across the Atlantic to one of the Windward Islands in the Caribbean before he was rescued.

All this he describes in his book called Adrift. 76 days Lost At Sea

https://www.amazon.com/Adrift-Sevent...ys+lost+at+sea

[james247]

Originally Posted by dwedeking2

Here's one I found

A very good diagram
As I get older 45' is the minimum comfortable boat at sea. Trade winds range from 20to 35 kn. give me some draft 6 to 9' get the centre of gravity low. A Skegness rudder and a deeper keel bolted or integrated but a fin. There are some good benefit s in old full keels but a stiff modern boat will be a better home 9 times out of 10