One for Mathemeticians

[tillergirl]

I am convinced that my boat gets more sun on the starboard side than the port. Am I deluding myself (easily done)

The boat is on a swinging mooring in a creek that runs north-west to south-east. The tide ebbs to the south-east and has a symetrical ebb-flood period.

The evidence - brightwork has faded more on the starboard side; weed on the waterline grows more on the starboard side and one of the windows on the starbaord side is showing signs of UV damage.

Shouldn't the exposure to the sun equal itself out over the season?

<hr width=100% size=1>

 

[Birdseye]

Interesting question. Cant think of any astro reason why this should be the case, but the surrounding topograhy might make a difference.. Or it could just be the way you did the antifoul and varnish - the starboard side facing the north when you fitted out (ie cold and miserable so you didnt hang round putting a thick coat on).

Hopefully, someone will now post and tell us the obvious reason we have missed.

<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[CharlesM]

perhaps there is a prevailing wind direction that sometimes (at weak tides) points the boat in the opposite direction to what you would expect if only taking the tide into account?

Charles

<hr width=100% size=1>

 

[alec]

I have heard of this before on the East Coast.

If I remember rightly, it has something to do with Spring Tides occuring during the middle of the night and day. Somehow presenting the starboard side more to the sun .

Perhaps a yachting Druid could help.



<hr width=100% size=1>

 

[Ovni]

There are three possible solutions;
One is mentioned already, the effects of the wind. If the wind is in your area more east, specialy in the morning, it's a solution

The second possibility, when the tide goes over from eb to vloed, how turns your boat? Because it is a creek the flow of the water will push the boat from 11 hours over 10, 9 ..to.. 6,5 and back from 5,6,7 to 11. In that case the sb side will be more often towards the south. This will give the highest sun / uv light.

Third, are you sure that the eb and flow are perfect symetrical? In that case (I asume it's in the UK with semi diurnal tides) from eb to flood should last (360/28.981404) *3600 seconds. I don't know a place any where in europe where this equalty happens.

If number 2 and three are combinated, the boat will float with the sun and go fast back to the old position: the sb side runs with the sun.



<hr width=100% size=1>http://groups.yahoo.com/group/Ovnisailors/

 

[Evadne]

The sunlight won't be equal if she grounds at all, either in the middle or on one bank as she swings. You will get a full blast on the ebb, then a bit more on the same side until she can swing around on the flood.

Given SW prevailing winds and the sun being in the south, I reckon it ought to be the starboard side that gets more sun if this explanation is correct, with this orientation of the creek. For me it would be the port side, and I know this situation applies. I'll check on the weed growth next week.

<hr width=100% size=1>

 

[bedouin]

Three possible factors:

Firstly in a creek you would not expect the ebb and flood to be symmetric. Local factors have a great influence but you may be getting 7 hrs ebb and 5 hrs flood.

Secondly current patterns will be slightly different on the ebbs and the floods.

Thirdly unless your boat has parallel sides you will find that the orientation of the sides to the sun is not symmetrical. E.g. you may find that the port bow "faces" West on the ebb and East on the flood whereas the startboard bow "faces" North on the ebb and South on the flood

<hr width=100% size=1>

 

[Trevor_swfyc]

Tiller Girl,

You said the boat is moored in a creek, so can we take it that the boat dries out. If this is the case the boat would spend x hrs dried out stern facing SE and y hrs afloat, y/2 stern facing NW and y/2 stern facing SE. It therefore spends x hrs longer facing stern SE. Which would result in the port side facing the sun longest, the weed tends to grown on the damp shaded side rather than the hot sunny side, ie starboard.



<hr width=100% size=1>

 

[SteveGorst]

Firstly in a creek you would not expect the ebb and flood to be symmetric. Local factors have a great influence but you may be getting 7 hrs ebb and 5 hrs flood.

I agree with this but unless I'm mistaken the ebb presents the port side of the boat to the sun not the starboard!!

The plot thickens....

<hr width=100% size=1><A target="_blank" HREF=http://"www.nwcc.info">North Wales Cruising Club</A>

 

[tillergirl]

I don't ground at low water so that does not come into the equation. Springs peak at 2pm/3pm and the flood presents the starboard side to the midday sun when UV, heat etc are highest. I was under the impression that the ebb and flood were largely the same but perhaps I need to while away some time making some local observations. Today high water was 05.16 and it was around 11.45 when the tide turned (it was a little difficult to tell exactly because of the artic wind today).

I was initially attracted to the idea that the spring tides contributed because the flood presented the starboard side but isn't there a counter argument that says the neaps present the port side on the ebb at the hottest time of the day.

Prevailing winds are South Westerly but what about sea breezes. Perhaps this is the answer or one of them. When the sea breeze sets in it is firstly on a hot sunny day, seconds sets in from the east. This would hold the boat against any ebb putting her into a north/south attitude presenting her starboard to the sun.

What do we think to that? If there is anything in that the weed growth this year ought to be more even given the lousy weather and lack of sea breezes.

<hr width=100% size=1>