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Old Feb 27, 2012, 05:47 PM
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hiljoball's Avatar
Canada, BC, Lake Cowichan
Joined Jul 2011
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Quote:
Originally Posted by FWAL View Post
Hi John

Can I ask how far out you let your main?
On the run, I let out the main as far as I can, all the way to the shrouds. I don't worry about the shroud crease on the main on a dead run.

John
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Old Feb 29, 2012, 03:12 AM
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Cape Town South Africa
Joined Jan 2010
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Quote:
Originally Posted by hiljoball View Post
Hi Craig,

It took me a couple of moments to figure that you are talking about 'lead' - the distance that the mast is ahead of the fin.

It is normal to experience weather helm at top of rig conditions - that's natures way of telling you to switch down.

But there are things you can do to reduce the weather helm/broaching at top of rig conditions, mainly to depower the main.

I assume that you have done the normal tuning for the stronger wind: - mast vertical, plenty of backstay to flatten the main, flatten the foot to about 20mm draft,

1. put slightly more twist in the main by easing the vang half a turn or more
2. Move the main sheet adjustment out a couple of notches at close hauled

John
Hi John,

Thanks for advice.

The three rigs (ABC) are typically set up at 1,2 and 4 degrees of aft rake respectively. On the boat with the wider transom the hull shape seems to cause added weather helm, such that in strong A rig conditions the mast needs to be vertical or even pushing towards forward rake. This is after all the normal trimming, such as backstay and less vang to fllatten and twist the top of the sail off.

On the boat with the narrower transom even though the mast is closer to the fin, sail trimming is enough to negate the weather helm. On this boat the limiting factor for the A rig is downwind behaviour. I.e. once the bow becomes an uncontrollable submarine downwind its time to change

Regards
Craig
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Old Feb 29, 2012, 01:23 PM
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KoneWone's Avatar
Germany
Joined Mar 2009
513 Posts
Quote:
Originally Posted by hiljoball View Post
It took me a couple of moments to figure that you are talking about 'lead' - the distance that the mast is ahead of the fin.
Hi John, Just point of clarification, the lead is the % of LWL between the hulls CLR & sail plan CE which brings me to a question about IOM's:

Is sail plan always cut to have the CE at the mast and the coupling (the lead) to have the CLR always set to front edge of the Keel fin ?

Cheers Alan
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Old Feb 29, 2012, 03:40 PM
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Joined Dec 2010
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It looks as if the aliphatic glue has reacted with the foam shadows causing a staining which has leached through some of the pin holes This is a shame but wont deter me from NOT painting her.
Being off the shadows also gives a better idea of rocker
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Old Mar 01, 2012, 08:03 AM
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Cape Town South Africa
Joined Jan 2010
89 Posts
There is a discussion on a boat design forum about chines. I have quoted an iteresting take below:

I mentioned earlier that I thought the Britpop had a "light" bow .. this explanation would suggest that it allows it to point better upwind.

http://www.boatdesign.net/forums/hyd...m-41874-2.html.

I read through the newsletter section about chined hullforms, and a few things are apparent to me from the discussion and the photographs. The picture of the IOM chined boat on page 14, compared to the pictures of other boats on later pages, shows the hull with comparatively full sections forward, a lot of rocker, and very slight sections aft. The other boats, such as the SKAs, have finer sections forward, less rocker, and fuller sections aft.

The new IOM chined hull seems to have better pointing ability because as the boat heels, the volume distribution and particularly the waterplane shape at heel promote lifting the bow. As the French designer in the article indicates, the chine is just a consequence of how he wanted to shape the heeled waterplane--he wanted slack sections aft, not full sections, so that as the boat heeled, the narrower waterplane aft allows the stern to sink a touch more and, correspondingly, the bow to rise, pointing a little more to weather, which is the direction you want to go anyway. And as the boat heels this way, it also increases the angle of attack on the keel and rudder, which increases lift, and with more lift, there is more power pulling the boat to windward. the boat balances better with less increase in weather helm.

This effect has been known for well over a hundred years, and as I have stated before elsewhere in this forum, most latter-twentieth-century designer types, collectively, seemed to have unlearned this lesson. This has more to do with heeled waterplane shape and controlling the center of that shape, the longitudinal center of flotation (LCF) than it does with the chine. Therefore, I agree with the French designer.

Capt. Nat Herreshoff, the winningest designer of the latter 19th and early 20th centuries, promoted this feature in his hull shapes--slack stern sections compared to fuller bow sections to control the LCF. As the boat heels, LCF should either stay in the same fore/aft position, or move forward slightly. As the boat heels, the bow lifts, the stern sinks, angle of attack is increased, the boat sails to weather better.

In modern times, over the last few decades particularly, we have seen hulls getting wider and wider and with fuller sections aft. Of course, you can get more stuff into such hulls, but at the same time, the builders and designers of such craft have been touting "powerful stern sections" as an indicator of superior performance. Nothing can be further from the truth, and in my opinion, "power stern sections" is a hoax. Such boats do not sail well, they balance poorly to more bow-down attitudes and pick up weather helm as a result. They're cranky. You'd see this in their heeled waterlines, they are fuller aft; the LCF moves aft as the boat heelsl. So, heeling over, they pick up more buoyancy aft, which raises the stern, depresses the bow casting it to leeward, and reducing the angle of attack on the keel and rudder--all just the opposite of what you are seeing on your new chined IOM models.

So, the better performance does not come strictly from the chine--rather, it is all about area distribution of the waterplane which is shaped by consequence from the chine to produce the desired bow-lifting effect. You can do the same thing without a chine, but the chine, in this case, seems to accentuate the effect.
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Old Mar 01, 2012, 10:23 PM
k4s
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Joined Aug 2009
391 Posts
Don't like the odds of our usual saturday sailing.We have a bit of a weather bomb about to hit.Even C rigs could be to much
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Old Mar 02, 2012, 12:00 PM
k4s
Registered User
Joined Aug 2009
391 Posts
Think staying home today was the right call...

Tauranga
19C 10C
Rotorua
17C 8C
Whakatane
19C 8C

Actual

15.6C

Feels like 16c
Tauranga

3 clothing layers & 1 windproof layer

Data updated 6:55am Saturday 3 Mar 2012

WindStrong
W48 km/h
Gust 67 km/h

(in last 10 minutes)

Rainfall0.0mm
Humidity77%
Pressure991hPa

(latest hourly observation)

Here in Taupo it's blowing dogs off chains...even postponed the NZ Ironman event due to conditions
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Old Mar 02, 2012, 12:15 PM
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United Kingdom, London
Joined Jun 2005
857 Posts
This weekend is the first of the IOM ranking races in the UK Saturday has 56 entries and Sunday 54 entries the weather forecast is good all the top UK skippers will be there and there should be some new boats sailing, I'm entered and sailing an Isis2 I'll take some pictures and post them on here asap.
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Old Mar 02, 2012, 05:30 PM
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Perth Western Australia
Joined Jul 2009
1,109 Posts
Good luck Tony can you post results as well
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Old Mar 03, 2012, 04:30 PM
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United States, MI, Bloomfield Hills
Joined Feb 2010
577 Posts
1 Brad Gibson 42 Birkenhead MY&PBC Britpop 2.4G 6.0
2 Martin Roberts 22 Birkenhead MY&PBC MMX 2.4G 8.0
3 Robert Walsh 25 Fleetwood MY&PBC Lintel 2 2.4G 11.0
4 Graham Elliott 09 Birkenhead MY&PBC Britpop 2.4G 1 12.0
5 Darin Ballington 98 Manor Park RYC Britpop 2.4G 2 12.0
6 Graham Bantock 95 Chelmsford RYC 875 15.0
7 Peter Stollery 39 Guildford MYC Britpop 2.4G 23.0
8 Derek Priestley 67 Fleetwood MY&PBC Lintel 2.4G 1 26.0
9 John Tushingham 51 Keithley & Dist MES Robot 2.4G 2 26.0
10 Tony Edwards 75 Leicester RYC Robot 795 28.0
11 Simon Clarke 94 Woodspring MSC 2.4G 34.0
12 Victoria McNaulty 62 Birkenhead MY&PBC Britpop 2.4G 36.0
13 Mark Dennis 19 Chelmsford RYC Picanto 685 37.0
14 Trevor Binks 72 Eastbourne MYC Obsession 2.4G 44.0
15 Ken Binks 83 Eastbourne MYC Psycho 2.4G 45.0
16 Josh King 26 Windrush RYC Lintel 2.4G 52.0
17 Vernon Appleton 36 Coal House Fort MYC Picanto 2.4G 53.0
18 Richard Stenhouse 43 Market Bosworth RYC Lintel 2.4G 59.0
19 Phil Playle 77 Chelmsford RYC Arrival 40syth 63.0
20 Terry King 181 Windrush RYC Lintel 2.4G 66.0
21 Martin Crysell 52 Guildford MYC Picanto 2.4G 69.0
22 Peter Moore 24 Bournville MY&PBC Widget 885 69.0
23 John Cleeve 144 Ryde MYC Obsession 2.4G 75.0
24 Roy Stevens 54 Tri Services Topico 675 76.0
25 Bob Connor 14 Woodspring MSC Lintel 2.4G 83.0
26 Paul Stubbs 91 Manor Park RYC Widget 2.4G 84.0
27 Richard Aucott 78 Woodspring MSC 2.4G 85.0
28 Mike Clifton 02 Two Islands RYC Madmax 2.4G 86.0
29 Lester Gilbert 105 Buchanness MYC Picanto 2.4G 88.0
30 David Potter 20 Birkenhead MY&PBC Lintel 905 91.0
31 William Culshaw 21 Birkenhead MY&PBC Lintel 2.4G 94.0
32 Liz Tushingham 108 Keithley & Dist MES Arrival 2.4G 96.0
33 David Burke 30 Birkenhead MY&PBC Lintel 945 98.0
34 Greg King 47 Windrush RYC Britpop 2.4G 100.0
35 Tony Guerrier 50 Three Rivers RYC 2.4G 109.0
36 David Alston 11 Leicester RYC Isis 2.4G 109.0
37 Dave Staniforth 198 Manor Park RYC Widget 2.4G 110.0
38 Peter Cropper 68 West Cornwall RSC 975 113.0
39 Joe Binks 175 Eastbourne MYC Isis mk2 2.4G 113.0
40 Mick Chamberlain 277 Lincoln RYC Gadget 2.4G 119.0
41 Chris Harris 66 Bournville MY&PBC Viper 2.4G 123.0
42 Graham Whalley 16 Manor Park RYC Widget 2.4G 128.0
43 Nick Cowern 35 Levenhall RYC 2.4G 128.0
44 Doug Penman 142 Bideford & District MYC 2.4G 133.0
45 Chaz Jordan 99 Hampton Court MYC Lintel 955 136.0
46 Jon Harris 70 Bournville MY&PBC Widget 2.4G 140.0
47 Dennis Payne 07 Windrush RYC Widget 2.4G 143.0
48 Graham Allen 88 Huntingdon RYC Stealth 2.4G 144.0
49 Sarah Conner 114 Woodspring MSC Stealth 2.4G 151.0
50 Richard Cole 172 Bournville MY&PBC Gadget 2.4G 153.0
51 Terry Rensch 60 Guildford MYC 2.4G 160.0
52 Mike Thompson 38 Bournville MY&PBC VTX2 2.4G 164.0
53 Ian Cooke 195 Birmingham RYC Bubbles 2 925 164.0
54 Don Charlesworth 177 Leicester RYC Isis 825 180.0
54 John Smith 81 Manor Park RYC 2.4G 180.0
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Old Mar 03, 2012, 04:31 PM
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FWAL's Avatar
United Kingdom, Wales, The Mumbles
Joined Dec 2010
578 Posts
Cut out some servo apertures and pot recesses.
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Old Mar 04, 2012, 02:33 PM
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ToniGe23's Avatar
United Kingdom, London
Joined Jun 2005
857 Posts
Day 2

The race team worked hard in testing conditions to keep things moving along and managed to squeeze 7 races out in very difficult conditions, driving rain on arrival turning to sleet/snow and then sunshine with very gusty conditions.


Results for Sunday 4th March 2012.

1 Brad Gibson 42 7.0 1
2 John Tushingham 51 23.0 2
3 Martin Roberts 22 31.0 3
4 Robert Walsh 25 33.0 4
5 Tony Edwards 75 34.0 5
6 Peter Stollery 39 36.0 6
7 Ken Binks 83 36.0 7
8 Mark Dennis 19 37.0 8
9 Darin Ballington 98 42.0 9
10 Derek Priestley 67 48.0 10
11 Graham Elliott 09 57.0 11
12 Trevor Binks 72 61.0 12
13 Graham Bantock 95 68.0 13
14 Richard Stenhouse 43 68.0 14
15 Josh King 26 69.0 15
16 Greg King 47 71.0 16
17 David Potter 20 80.0 17
18 Victoria McNaulty 62 102.0 18
19 David Burke 30 104.0 19
20 Mick Chamberlain 277 107.0 20
21 Tony Guerrier 50 110.0 21
22 John Cleeve 144 113.0 22
23 Terry King 181 113.0 23
24 Simon Clarke 94 114.0 24
25 Peter Moore 24 126.0 25
26 Dennis Payne 07 135.0 26
27 Vernon Appleton 36 135.0 27
28 Roy Stevens 54 135.0 28
29 Martin Crysell 52 145.0 29
30 Graham Whalley 16 146.0 30
31 Liz Tushingham 108 153.0 31
32 Bob Connor 14 156.0 32
33 Doug Penman 142 159.0 33
34 Peter Cropper 68 172.0 34
35 William Culshaw 21 182.0 35
36 Richard Aucott 78 189.0 36
37 Chris Cooke 96 200.0 37
38 Mike Clifton 02 202.0 38
39 Terry Rensch 60 205.0 39
40 Jon Harris 70 210.0 40
41 Dave Staniforth 58 236.0 41
42 Graham Allen 88 250.0 42
= 43 David Alston 11 261.0 43
= 43 Sarah Conner 114 261.0 43
= 43 Don Charlesworth 177 261.0 43
= 43 Nick Cowern 35 261.0 43
= 43 John Smith 81 261.0 43
= 43 Chaz Jordan 99 261.0 43
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Old Mar 04, 2012, 10:32 PM
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USA, LA, Mandeville
Joined Feb 2005
886 Posts
What hull was Graham Bantock sailing? His new design?
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Old Mar 05, 2012, 03:50 AM
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United Kingdom, London
Joined Jun 2005
857 Posts
Hi Hew,
Yes, Graham was sailing his new boat unfortunately he had radio problems on the Sunday.
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