How important are shiny-smooth foils?

Back in the Dawn of Time, c.1961, we polished the bottom of the family GP14 and quite soon afterwards we were informed, father having read another article, that that was quite wrong and we spent another weekend with very fine wet and dry sandpaper. Cannot remember the results but I do remember the work involved.
 
Gentlemen, thank you for your points of view. The shiny-versus-deliberately-not-shiny issue, is certainly new to me; fortunately it's not terribly relevant to my rudder yet!

On the general point of spending many hours of care improving something which mayn't make a vast amount of difference, I'm easily persuaded that the sailing (in particular, improving my ability) is much more significant than any subtle tweaking of basically-sound elements...which is what I began the thread to find out...

...BlowingOldBoots, I slightly suspect you of taking the mickey...it appears to have been established here that my level of sailing is unlikely to benefit from hours or days of additional care, but you advise further work till it's right...

...apologies if you were sincere...may I atone, by adding some requested photos of just how agricultural my standards are?

They really are, but that's why I started by asking if it mattered: (click pics for a better look)

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The pictures aren't great because the phone isn't a camera. They may actually give a worse impression than is deserved. I know a little extra sanding & filler wouldn't be a total waste of a wintry afternoon, but I'm listening to whether jaws are dropping in collective horror. ProMariner, I apologise...these pics must be like an autopsy for you.




...
 
dancrane said:
...BlowingOldBoots, I slightly suspect you of taking the mickey......
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;)

I enjoy these threads of angst: entertaining, humorous, educational, aggression free. I am really looking forward to the sailing questions post sailing. Onwards and upwards, as someone once said about something.
 
BlowingOldBoots said:
I am really looking forward to the sailing questions post sailing.
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Suits me! No angst here, I hope. ;)

Let's begin with something so basic it ought to be obvious...and yet, even after a mile or two of beating and reaching, I didn't work it out...

...should the genoa sheets pass inside or outside the shrouds? SWMBO asked and I simply didn't know. The Osprey has a secondary, smaller jib fairlead & cam cleat further forward for using a smaller headsail...

...but with the relative overlap of the 4m sq genoa, I couldn't tell whether the sheet was better fed to the main block & jammer outside the shrouds for freedom when slackened, or inside for tight beating angles. And trying it didn't clarify the answer. Does it matter?
 
I don't know about your boat specifics. It is likely top be set up for inside the shrouds though as this is quite common. The reason is that it gives you better close hauled adjustment of the sheet tension for various wind speeds while maintaining the sail sheeted in close. Off the wind when the jib sheet touches the shroud is less important because the spinnaker is the sail of choice when it can be flown. Certainly on the Wayfarer when I am fine reaching (inside shroud sheeting position) I still don't rub the shrouds, but on a reach I do. By that time the spinnaker is out, if not I live with it. Fit shroud covers over the chain plates to help the passage of the sheet without snagging anything.
 
Just to add to BlowingOldBoots's very good advice, on the same class of boat the setup may be different. I have used both inside and outside sheeting on different Wayfarers. Go for inside if at all possible. It should be fairly obvious when you have the sail up. Look at the angle of entry to the fairlead/cleat and also check if the sail fouls on the spreaders.
 
Thanks for that, good sense. Here's a pic of the boat on her side, which ought to show the relative positions of blocks/shrouds etc.

In fact, the starboard genoa block is missing here, which doesn't make it clearer...but judging by the port side, I'm sure inside is best.

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dancrane said:
Thanks for that, good sense. Here's a pic of the boat on her side, which ought to show the relative positions of blocks/shrouds etc.

In fact, the starboard genoa block is missing here, which doesn't make it clearer...but judging by the port side, I'm sure inside is best.

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Not sure that I can see anything through the sunglasses that are needed with decks that colour.

FWIW I have just done the whole rub down and fill job on a merlin rudder and centreboard, but mainly because they are both here at home, and it connects me with the boat which I cannot get to at the moment.
 
Weirdly, having spent the spring convulsing with dislike every time I saw that green paint, I've begun to rather like it!

Sadly its condition isn't as good now as when that pic was taken - not that it was perfect - but I've covered my GRP repairs with duct tape, so it looks a lot less tidy. Ironic that the sidedecks had some serious cracks under the green, which I hope are fixed now, albeit not neatly.

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All being well, I'll spend the winter prettifying her, with a nice quiet tan or cream...or teak veneer. Having first established what really needs doing.

PS, can anyone see (from this photo) how best I might elasticate the hiking straps so they're always ready to get my feet under? There's nothing to tie them to.
 
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dancrane said:
...should the genoa sheets pass inside or outside the shrouds? SWMBO asked and I simply didn't know. The Osprey has a secondary, smaller jib fairlead & cam cleat further forward for using a smaller headsail...
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Yes, it matters quite a lot. Jibs should be sheeted at the correct angle of attack. As to what the correct angle of attack is, well that depends on the lift/drag ratios of the foils/hull and rig. Modern racing boats keelboats can sail with incredibally closely sheeted jibs. Do you get better VMG by pointing high, or by footing off and planeing?
 
Keen_Ed said:
Yes, it matters quite a lot. Jibs should be sheeted at the correct angle of attack. As to what the correct angle of attack is, well that depends on the lift/drag ratios of the foils/hull and rig. Modern racing boats keelboats can sail with incredibally closely sheeted jibs. Do you get better VMG by pointing high, or by footing off and planeing?
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Can a Wayfarer plane upwind...!?
 
flaming said:
Can a Wayfarer plane upwind...!?
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Begging your pardon Flaming, my boat isn't a Wayfarer - not that I imply any disrepect to that breed. But I reckon an Osprey in good condition certainly will plane upwind - whether mine makes that grade, I'd be less sure.

Thanks for the thoughts Ed - I haven't yet tested to see whether hard on the wind makes better VMG than a close reach. I've read that the design isn't at all extreme - not inclined to skim riotously downwind whilst being a total bitch to windward - so I expect a close beat is possible without losing much speed.
 
+1 except don't sails with stuff that is likely to break.

When you are in the top 2 or 3 in your racing fleet, and want to gain a few yards each lap, polish hull and foils. Till you get to the point where those few yards will gain you places polishing stuff is not necessary unless you find the work preferable to sailing.
 
dancrane said:
I was sanding excess gelcoat off my repaired rudder blade and trying to detect improvement, when it occurred to me that the fine-grit sandpaper is probably smoother than the rudder.

It still works, steers satisfactorily (although I don't know how much better this boat might have steered), but how important a factor is the enviable glossiness of new foils/hulls, in getting the best performance possible?
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In case you eventually decide to start racing -or simply want properly polished hull/appendages, "the shinier the better" is often not the best choice


this graph shows the behaviour of friction coefficients (vertical axis) depending on Reynolds numbers, horizontal axis (a number related to the length of a body and its speed through a fluid).
The various curves represent relative granularity, ie the relative size of surface grain against length. As an example, a 2mm sewing thread on a 4m sail has the same relative granularity as a 0.25mm sand grain on a 50cm chord fin/rudder.

Depending on your Reynolds number :D the faster you go or the wider fin/rudder you have, there may well be an advantage to have a coarser granularity, which of course may be an elegant excuse to leave things as they are :)

image1091.gif
 
Roberto said:
In case you eventually decide to start racing -or simply want properly polished hull/appendages, "the shinier the better" is often not the best choice


this graph shows the behaviour of friction coefficients (vertical axis) depending on Reynolds numbers, horizontal axis (a number related to the length of a body and its speed through a fluid).
The various curves represent relative granularity, ie the relative size of surface grain against length. As an example, a 2mm sewing thread on a 4m sail has the same relative granularity as a 0.25mm sand grain on a 50cm chord fin/rudder.

Depending on your Reynolds number :D the faster you go or the wider fin/rudder you have, there may well be an advantage to have a coarser granularity, which of course may be an elegant excuse to leave things as they are :)

image1091.gif
Click to expand...

The missing science from my post #9!!! :)
 
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