Vintage - Steel to Ally centre plate swap

[Interested Party]

Had out first sail of Planet last night - between rain squals.  Unfortunatly the heavy rain stole most of the wind...Ho-hum!  However we are starting a list the list of mods.  Some of which are just make and mend.  The wooden mast was fine though.
but I have to say that the heavy galvanized steel plate was a bit of a pig to raise.  It certainly is heavy.  It dropped well enough!
I am thinking of swapping to an alluminium plate.  I understand that later classic boats went to an Ally plate.  Or is that Fireflies?
The slot in the case is quite thin, so I do not think I would get in a wooden one in, that would be thick enough.
Cheers
Steve

[andymck]

Some have made carbon plates that seem to work well, Speak to Nigel Waller, otherwise most changed to Ali

Andy

[johnk]

Aluminium alloy was permitted for centreboards in 1964 (as was wood). However most earlier boats did not have a centreboard case that was wide enough internally to permit a wooden centreboard that was strong enough. Consequently the only option for these boats to lose weight was to move to aluminium alloy centreboards. The aluminium has to be thicker than steel to retain the same stiffness. Firefly centreboards are just thick enough. I remember a Firefly (now a N12) sailor (and not a heavyweight) righting his Firefly only to find that he could not hoist the centreboard into its case. It had bent!
If you do fit an aluminium plate, consider having a hole for the centreboard bolt rather than the slot that was traditionally used. I can remember as crew inverting a Procter Mk 8 in Plymouth Sound. The steel centreboard droped out of the boat. Fortunately my stopper knots on the control line held so we did not lose the centreboard. We righted the boat, put the centreboard back in and finished the race.

[Interested Party]

Will a firefly centre plate fit a National 12?
It would be too much good luck as I have just been offered one .....
 

[Interested Party]

Here is a comparison of the Firefly Centre Plate and the steel Plate out of my National 12 (Planet 672 -1948 ). 
The overall length is the same.
The slot has the same angle and depth.
The width at the widest point is the same.
The Alloy plate is less that 2/3s the weight of the steel plate.
However my steel plate is very much more tapered down its length. 
Also the top edge of the board is also at a different angle
Is this the correct shape?
The centreboard case looks, at first glance, to be able to accomodate the Firefly plate.  But I have not tried it yet.
Either way I would be reluctant to chop too much off the Firefly plate, as it would be more likely to bend...... 
 

[johnk]

The peak bending load on a centreboard is where it goes throgh the keel. It should be safe to taper the Firefly board to match the old steel one. Do try and fit the Firefly board (unmodified) into Planet and check that the board will retract fully. Depending on Planet's centreboard case shape - together with the keel rocker - you may need to trim the Firefly board anyway to ensure complete retraction. Good Luck.

[Interested Party]

All,
I have not forgotton about this.  It is just that currently the firefly centre plate will not fully retract into the centreboard box.
The Firefly centre plate is aproximately 8.5mm thick and the N12 slot is about 12mm thick at the back of the case.  So it was always going to be a tight fit.
Add in blobs of paint and sealant and you will very quickly jam the thicker plate.  Which is what has happened to me.
What I need to do is to remove my slot gasket and carefully clean the slot before I try again. 
On the plus side I have just ordered a poly-cotton Firefly cover for my vintage National 12, saving me £40 or £50, having tried a Firefly cover first of course.
Cheers