AJ wrote:
you loose up to 50% of your body heat through neck and head
This is not true. This myth has been debunked long time ago.
https://www.theguardian.com/science/2008/dec/17/medicalresearch-humanbehaviour
So keep your hood for diving and bring a raft or immersion suit if you feel that you need something that really can help.
@Emir
There are too problems with your response.
1) the Guardian article is about heads, air, and hats, my mythical evidence is about heads and necks, cold water, and a cap which covers all your head and neck, and is insulating. The compared situations are very different indeed.
2) your response is borderline impolite. I am not aware of having said anything (ever ? to you ?) that would justify this “stop the nonsense” response.
I suggest this approach : read > understand > write and be polite.
Depends if you are planning to swim that day? and for how long? and best chance for passengers?
I flew twice +3h over open sea without a raft but I did swim about 4h a day in both cases (once in Mediterranean and once in Bahamas, I was flying back with wet underwear, so technically ready to go again to the beach if the engine quits)
I do skip the raft when flying 20nm between CapGrisNez and Dover, but I would I take one for long English channel crossings, it would be stupid to fly without, could not swim more than 30min in the Channel, can’t imagine between Germany & Sweden
I rarely care about passengers (my wife can swim far, longer in colder waters than me) but also something one need to keep in mind
The risk from a takeoff failure (EFATO?) has nothing to do with risks of flying over open waters unless you fly from aircraft carriers, I would rather take an EFATO on departure in water than on the pylons in front of my home inland airfield
I doubt highly that while in the water, you’re going to lose 50% of your body heat through your neck and head – there just isn’t enough surface area (especially considering that part of you, with a lifejacket, will be well out of the water, while the rest of you will be submerged in a medium that’s far better at taking heat away). It just doesn’t pass the reasonableness test that perhaps 10% of your surface area (out in the air) can lose as much heat as the 90% of your surface area that’s immersed in a huge heat sink.
The Wadden Sea between the Frisian Islands and the German/Dutch coast is quite shallow and often not even covered by water during low tide. If the engine quits right after takeoff from Norderney (to take your example), you will (crash)-land quite near to the shore. If it quits while you are at 1000 ft or higher, you can glide close to the land and still have a high chance of making it ashore
I learned flying in East Frisia and nobody there ever carried a raft…
AJ wrote:
1) the Guardian article is about heads, air, and hats, my mythical evidence is about heads and necks, cold water, and a cap which covers all your head and neck, and is insulating. The compared situations are very different indeed.
2) your response is borderline impolite. I am not aware of having said anything (ever ? to you ?) that would justify this “stop the nonsense” response.I suggest this approach : read > understand > write and be polite.
I don’t understand how you found my answer to be impolite. It’s just stating the fact and I’m pretty sure I’m right and you’re wrong. And I gave you the advice based on safe practice rather than on myth.
Yes, you lose a bit more through head and neck but not as near as 50%. I can quote few researches done on this subject.
https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/heat-loss
https://www.researchgate.net/publication/14054663_A_dynamic_model_of_the_humanclothingenvironment-system
https://www.researchgate.net/figure/Simplified-model-of-heat-transfer-between-the-divers-body-and-the-water-The-internal_fig1_233951484
And some popular articles on this:
https://www.badgeraustralia.com.au/blog/myth-or-truth-do-you-really-lose-40-percent-of-your-body-heat-through-your-head/
https://www.bbc.com/future/article/20130708-is-most-heat-lost-from-your-head/
https://www.drmyths.com/most-of-your-body-heat-is-lost-through-the-head/
https://www.undercurrent.org/UCnow/dive_magazine/2015/DiveHood201505.html
So your advice applies to you as well 
Ibra wrote:
can’t imagine between Germany & Sweden
I don’t bother with a raft on a typical crossing, e.g. on M736 at FL100. Even in a spamcan such as the C172 you’re actually at gliding distance from the shore for all except 10 NM which only takes a few minutes to fly. The marginal risk is negligible.
OTOH between the Swedish mainland and Gotland, I do carry a raft.
@alioth
[[there just isn’t enough surface area (especially considering that part of you, with a lifejacket, will be well out of the water, while the rest of you will be submerged in a medium that’s far better at taking heat away).]]
here too, it’s worth a 2nd thought. For once, there is a tiny little “extremity at the top of our shoulders which consumes 30-40% of your bodily energy, and where is it produced? next, which parts will your autonomous system shut down, to save your life temporarily, and which one’s cannot be shut down? last, how and where is this thermal circulation routed, deep inside or under thin skin? Once you have analyzed these questions in depth, you cannot help realizing that the surface area of one part alone is a very bad measure for thermal losses per inch squared.
thank you for your new answer. Different opinions are just fine – always – i.p. when expressed in such a way. Next step must be check and verify. Excuse my laziness, I only followed the first of your links (mentions the word water 29 times, but doesn’t apply to your figure in the Northern Sea), and I skipped “popular” links. I do not insist the number is 50%, it could be 42.6%. If it was under 35% I’d be extremely surprised. If you couldn’t bring a dinghy, and you agree one can’t put on a Neopren suit after ditching … these 40…sth % can be worth your attention at preflight.
If you disagree with what I said to alioth above, and if you have some serious data which help all of us understand why the numbers are significantly different, please let me know. I consider the subject interesting and relevant.
