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2nd September 2010, 05:40 PM #1996
The following snap is the sum total of my work on the boat today, the elbow being quite snarky. Added to which, the dire warnings from The Boss of the consequences of needing physio on said joint (she didn't mince her words ;).
I didn't practice either, since that elbow always suffered when I used to play, ending in the lock-up of the whole limb including fingers. It's a habit that I learnt very early on and have never been able to shake - and which appears to have transferred itself to sanding as well. So instead of doing both today I only did a quarter of the sanding intended and none of the extra stress on the joint. Added to which, I have also felt a bit squiffy.
1 (and only). Grey primer, ROS scars and roller stipple dealt with on aft half of starboard side panel
Follow this link to my Flickr account if you can be bothered (Flickr wants you to of course, that's the way they make their money)
Hopefully there will be more done tomorrow, after I've gone and got some more sandpaper (I have only the one sheet of 80-grit left).
A note on my take on the finishing of the hierarchy of the various hull surfaces that I meant to put in earlier: the most important is the hull bottom, followed by the side panel chine and bow/chine corners; then the side panel wetted areas (flat sailing); then the side panels and immersed bow transom (leaning), followed by the bow transom and finally the stern transom, although the edges between the stern transom and hull bottom and sides needs to be clean. That is to say, I can probably get away (in my own head at least ;) with the upper sides, the stern and upper bow transom being rougher that the rest of the hull. I am probably over-egging things as usual, but would be interested to hear what MIK and any others who chose to voice an opinion have to say :).
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2nd September 2010, 07:32 PM #1997
Ha - the humidity is much higher than I would like it to be - my tools keep rusting no matter what I coat them with, short of paraffin wax or marine grease ;). Actually, with all the wet-sanding over recent times, the RH is probably close to 100 %, even with the dehumidifier running flat out...
Cheers,
Alex.
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2nd September 2010, 10:57 PM #1998
The elbow having what amounted to a day off seems to have done it some good, as has a small amount of aspirin. Hopefully I can get cranked up again tomorrow, as I'm almost in sight of getting past this little hurdle.
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3rd September 2010, 11:47 PM #1999
The elbow had another day off today - from sanding at least - although I did get some more 80- and 120-grit white AlOx sheets so that I can continue tomorrow.
No-one feel inclined to comment on my musings about the hull at the end of my post-before-last?
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4th September 2010, 01:23 AM #2000
Hi Alex,
While I agree that it is more important for the surfaces that contact the water ( in the order given in your quote ) to be closer to mirror finish ( as a maximum standard ), all other surfaces need to at least look smooth and shiny from 3 feet away ( just using your eyes - no magnification ! ).
This is probably a much lower standard than you have been using but I would consider it at least a minimum realistic standard, and the parts that contact the water should at minimum, be smooth enough to have a well defined shiny, but not necessarily anywhere near a perfect, x10 magnification at 3 feet, mirror smooth finish !.
The performance difference between the minimum and maximum standards would be less than 2% ( this is conservative estimate ! ), last time I checked the PDRacer competition rules, this is so much smaller than needed, to make any difference on winning or loosing a race !.
If on the other hand you were building a boat for high end competition where a 0.25 ounce difference made even a slight chance of winning or loosing a race ( these are only situations where the hull finish are going to have at least some effect on competitiveness ), then all crew going on a serious diet would make a huge difference !!!.
If it looks good to most people who see it then it is going to be just fine ( most people wouldn't notice any imperfections smaller than 5 mm across anyway, so relax, and enjoy building your boat, you may find the standard of construction then just takes care of itself !.
I hope your elbow, and any other parts, recover quickly from all that hand sanding !!!.
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4th September 2010, 10:04 AM #2001
Hi David,
Congratulations, your's is the 2000th post in this thread :))))). That's as much of a prize as I can offer, I'm afraid, so I hope it's sufficient ;).
Thanks for the input on the hull smoothness. I'm not really fretting about it, just pondering about it from a sort-of slightly theoretical-ish point of view, the hull being more-or-less a box with a curved bottom and therefore with slightly more distinct surfaces than many other boats. It won't matter to the actual finish, as I'm being as inordinately fussy on all surfaces anyway - as usual.
The elbow is feeling much better, thank you - I am looking forward to another day's sanding and making it worse again ;).
Good to hear that your own boat is moving ahead again :).
Cheers,
Alex.
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4th September 2010, 12:45 PM #2002Member
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In an interview with Greg Fisher, who's won multiple national championships in the US, he said if sanding, fairing, and polishing the bottom of your boat makes you feel better go ahead and do it but that time would probably be better spent in the boat practicing.
I varnished everything on my PDR except the bottom thinking it would be easier to repair the scuffs and scratches if I left it bare epoxy. Just sanded it with 320 grit sandpaper.
Brad
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4th September 2010, 01:04 PM #2003
Hi Brad,
Welcome to this thread and thanks for the comments . As my sailing is very rusty and not that good to begin with, your and David's comments are most relevant.
Cheers,
Alex.
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4th September 2010, 06:04 PM #2004
For racing the rule of thumb is something like 2/3 the effort on the front 1/3 of any of the sailing surfaces.
Generally I apply this to the centreboard and rudder and the bottom and sides just get a nice paint job.
The optimum finish seems to be around a 400 grit.
Frank Bethwaite's brilliant book says surfaces have to be polished, but his supporting data is highly dodgy .. or was in the magazine version of the article that made it into the book later
If you drew a line at a particular amount of drag on his graphs and looked at the boat speed the drag was achieved at the polished hull was a full knot faster than the non polished one. You never see those sorts of differences on the racecourse.
So looked like a calibration problem and not questioning the result closely enough. For something around 14ft long it is about a 25% speed difference upwind. If it was that much there would be no ongoing argument about whether gloss or whether 400grit sanded.
But I don't think a gloss paint finish is a problem either. Foils I would normally sand with 400 grit and spend a lot of time getting the leading edge right. Hulls a nice paint job.
Shooting for the states or nationals the hull might get a going over too.
MIK
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4th September 2010, 07:02 PM #2005Senior Member
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It is not always intuitive as to what will create the least drag and even with the best of testing, the dynamics of real world conditions make it pretty much impossible to really pin down. It really gets clouded when you are dealing with the upper limits in any field of competition and it somewhat reverts to superstition. There are just too many variables and the differences are so minute. Toss in a liberal mix of adrenaline and let the hallucinations commence. The placebo effect is just too strong and the differences are too minute to really quantify. Probably the only way we could get a real grip on what would give the real best performance under real conditions is to do a double blind study. Everybody has the same design and then the tested design parameters slipped in without anyone's knowledge and then constantly swapped and raced multiple times with the performance tracked over entire racing seasons.
But the one true and tested performance enhancement we are leaving out: Painted flames and pinstripes.
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4th September 2010, 07:29 PM #2006
Well done David!
I know one guy, he had been national champ at least once, I think twice, who used to sail in the Heron class that used to say that his painting never reached its true potential until the boat was about three years old.
How did he know.
For my real take on it ... Q&A How to Race a Dinghy Successfully - Michael Storer Boat Design
If pinstripes and flames calm the sailor so they can concentrate on the race ... Well and Good.
There has been some evidence that highly polished surfaces or water repellant surfaces are poorer because bubbles stick to the hull.
Also that too rough will be draggy. So I take 400 grit to be a reasonable balance point without the amount of labour getting out of control. A fresh painted surface, even sprayed is not particularly smooth usually either. So some sanding is warranted.
Triffic point you make though ... and it needed be said.
MIK
MIK
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4th September 2010, 11:39 PM #2007
MIK and David,
Wood Duck represents one lone and unconstrained data point ;). But I knew I'd forgotten something - the flames! Where's that hated airbrush - I should be able to delay finishing the boat by up to a year using that ;) <snigger>.
I have a couple of snaps of today's progress: one and a half sides sanded back:
1. Starboard side panel 80-grit sanding complete: except where it isn't, of course ;). Dark spots are the resin-coated Pacific maple plywood showing through where I've sanded the high-build off the high spots (buoyancy tank bulkhead and F1 in this instance). It's a bit of a pity I've gone through to the resin, since it probably means three coats of undercoat. Oh well. Note the water on the floor: at least it's not dust in the air
2. Port side panel half-finished using the 80-grit paper. Again, buoyancy tank bulkhead and F1 lumps have had their high-build sanded off 'em in patches. I could disguise them with the flames! And my daughter wants me to paint duck wings, feet, eyes and beak, etc. on the hull. I dunno about that, though...
Follow this link toFlickr Landmy Flickr account, where you can see the dark spots even larger - and maybe even see the the wood grain ;)
Tomorrow should see the end of the 80-grit - and hopefully the 120-grit as well - but I keep on saying that, don't I? ;). Hmm. Believe it when you see it, folks.
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5th September 2010, 12:43 AM #2008Member
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I don't know about pin stripes and flames but it's a well known fact that boats with neon red foils have a performance edge.
Alex,
For your next boat you may want to consider using Gaboon and finishing with clear. It seems that the wood grain creates enough distraction that you have to get down to eye level to see all those nasty brush strokes and dust particles
Brad
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5th September 2010, 01:57 AM #2009
Hi Brad,
The next boat will in fact be the Eureka canoe, and in gaboon, and bright-finished ;). I'm also going to have a go at a kayak in gaboon after the Eureka. I was going to do the Goat in gaboon as well, but finances are getting away from us, and as I already have six 6 mm sheets of Pacific maple on hand for it, I might as well just use that, and use paulownia for the framing (as in the 'Duck). And various blemishes will be even harder to see if I finish it bright ;).
Cheers,
Alex.
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5th September 2010, 08:52 AM #2010Senior Member
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- I should be able to delay finishing the boat by up to a year using that <snigger>.
Um, Alex....
You do realize my boat is not closer to the water than yours. You are hull #303.
I am #292
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