Firefly centreboard pivot

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highburyal
Posts: 43
Joined: Tue Nov 20, 2007 12:12 pm
Location: Forest of Dean

Firefly centreboard pivot

Post by highburyal » Mon Aug 31, 2009 9:54 pm

Ok, so its been a while since I contributed to the forum; in the mean time I've trailed a firefly to the Alentejo in Portugal (does anyone know of any other other firefly sailors in Portugal?), been arrested by the Guardia in Villa Nueva de Millefuentes for sailing an Wayfairer without the correct documentation and done very little boat restoration. Back on the case now however! Rebuilding the centreboard case for F2451, but can't work out where the centreboard pivot should be, the plans in the rules don't seem to show height from either the hog or datum. Any ideas anyone?

Feeling somewhat despondant about J17, may have bitten off more than I can fix on this one, but haven't given up yet. Will strip out the rotten wood and see if there is anything left.

Rupert
Posts: 6254
Joined: Thu Sep 16, 2004 8:40 pm
Location: Cotswold Water Park

Re: Firefly centreboard pivot

Post by Rupert » Tue Sep 01, 2009 2:15 pm

If you look on the Firefly site, there is a list of measurements of the leading boats at last year's Nationals. I think the pivot location varies alot, but is on the list, possibly in the tuning section. When I sort Saskia out, I will measure her.
Rupert

highburyal
Posts: 43
Joined: Tue Nov 20, 2007 12:12 pm
Location: Forest of Dean

Re: Firefly centreboard pivot

Post by highburyal » Tue Sep 01, 2009 6:46 pm

Thanks Rupert, but the list I found on the firefly site only shows distances of the pivot from the transom and mast step, not vertical height.

Michael Brigg
Posts: 1663
Joined: Fri Jul 06, 2007 7:11 pm
Location: Gosport, UK

Re: Firefly centreboard pivot

Post by Michael Brigg » Tue Sep 01, 2009 8:34 pm

Hi Al,

Nice to see that J17 is still alive,(ish)
I recall we had some discussion on the old firefly forum before it went down but I cant quite recall the detail. Was it something to do with a Firefly called "Spadger?" I thought it might have been Roddy Bridge's boat, but actually that one was "Toledo" so that was a bit of a false errand.

Back to the Centreplate Bolt. Diagram 1 (Centreplate case) as I read it gives a bolt hieght based on the "Datum Plane" (I assume this is a line from the bottom of the Transom to the Bow stem. This is difficult to determine as their is no other diagram showing where the Datum plane is taken from.

However it looks to me as though the bolt lies at the point where the "Station3" measurement is bisected by a line drawn between the upper surface of the internal keel band at station 5 and Station 1 (Or from the outer skin between Station6 and Station 1)

Then in section "Part D Dimensions":-
Item 7 "Position of centerplate bolt from Aft side of Transom" is 2117-2142mm (ie 2130+/- 12mm)
Item 21 "Hieght of Centreplate Bolt from Outside of Skin" is 73-93mm (ie 83mm+/-10mm)

I think that is pretty unambiguous?

Here is a link to the Firefly Rules pdf in case you cant find it.

http://www.rya.org.uk/SiteCollectionDoc ... irefly.pdf
PART D - DIMENSIONS
Item
No
Rule No. Dimensions Minimum Maximum
*1 B9 Height of sail letter and number carved or
stamped in aft hog for wood boats or thwart
for GRP boats
30
2 Aft side of mast to aft side of transom with
mast in its foremost position in the gate
2500
3 Aft side of mast to aft side of transom with
mast in its aft most position in the gate
2470
*4 B11(a)
(iii)
Horizontal movement of mast in any direction
at deck level
8
5 B7(i) Height of mast heel when stepped to inside of
skin, measured at a point 25mm athwartships
from the centre line of hull
85 95
6 Aft side of centre thwart to aft side of transom 1400 1500
7 B3(j) Position of centre of centreplate pivot from aft
side of transom
2098-2118mm

8 B3(l) Centreline of shroud or its projection at deck
level from aft side of transom
2117 2142
9 B4(a) Length overall 3644 3660
*10 Plan width of deck overhang including rubbing
strake from sheerline
50
11 Width of thwart 130 150
12 B4(b) Beam measured to sheerline at:
a) 760mm from aft side of transom 1228 1253
13 B4(b) b) Maximum beam 1426
14 B4(b) c) 2580mm from aft side of transom 1115 1143
15 B4(b) d) 3090mm from aft side of transom 736 756
16 B4(b) Foredeck camber. Vertical distance from top
of deck at centre to sheerline at 2580mm from
aft side of transom
95
17 B3(h) Depth of keel band on wooden boats 3 7
18 Protrusion of keel excluding keel band from
skin at any point
11 15
19 Width of keel at any distance between 300mm
and 2580mm from aft side of transom
49 63
*20 Width of centreplate slot 13 19
21 Height of centre of centreplate pivot from
outside of skin
73-93mm
Michael Brigg

highburyal
Posts: 43
Joined: Tue Nov 20, 2007 12:12 pm
Location: Forest of Dean

Re: Firefly centreboard pivot

Post by highburyal » Wed Sep 02, 2009 10:49 pm

Michael,

Thanks for that, I had been working from a printed copy of diagram 1 in the workshop and didn't check the whole rules.

Still working on F2451 Spadger, I think the name deserves to stick, found floating down the River Usk at Newport Uskmouth SC. Getting on with it now so hopefully on the water for next spring.

J17 is in a sorry state, but as I sailed in her from Itchenor in late 70's or early 80's with Tim's dad I would love to get her back on the water, but at some point will have to have a reality check over emotional connection.

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