Racks cook book - layup suggestions welcome

[Phil Alderson]

You need to include carrot within the layup for your racks cook book!

http://news.bbc.co.uk/1/hi/scotland/edinburgh_and_east/6342381.stm

[roland_trim]

I've added some tea lights to the mix now.

Last night I melted 20 tealights into a pan and then applied the wax to the mast tip mandrel with a roller. This worked a trick - no lumps bumps or need to smooth out after.

For future reference
-  dip the whole roller in the wax
-  very hot (I left pan on the heat). 
-  Roll out some of the excess on a pad/floor/filing cabinet then roller onto the mandrel.
-  If any dripes exist (from not rolling out the excess) roll over them again. The hotness of the roller appears to melt the wax and smooth out the lumps!
-  Cover the floor, you get wax spittles everywhere.

[daryl_wilkinson]

-  very hot (I left pan on the heat).

The wax is likely to ignite if you do that, be careful.

[roland_trim]

Very good point. Was using a paint stove (i.e. burner and pot in one that you carry around).

[Banshee Ambulance]

Would there be any problem in making the longitudinal rack tubes out of Ali? I have seen at least one 14 built this way. You would have to insulate it pretty well from the rack supports but the extra weight should not be too much of a problem as most of it is behind the center board.

[Phil Alderson]

Using Ali racks should not be much of a problem, possibly a bit more flexi than carbon, then the problems with corrosion.

the rack tubes on Aqua were glass and they worked OK, I just made them slightly larger diameter than is common for the carbon ones.

[Will_Lee]

Both Subtle Knife and Badgers Nadgers had just that - cheap and demountable.

[ross_burkin]

Handy if you need to get them into 200 double stackers!

[Tim Noyce]

As Will says, ally racks are just fine. Subtle is down to weight and has ally racks, you can feel them flex a bit when you are out on the wire but there's nothing wrong with them. Don't have to worry as much when you roll the boat over as well.

[ross_burkin]

Off topic and stupid, but if you made a hull out of aluminium do you think it would be down to weight?

[JimC]

Off topic and stupid, but if you made a hull out of aluminium do you think it would be down to weight?

I imagine it would be possible if it used a honeycomb core, but insanely expensive, extraordinarily delicate and a ******** for picking up weight with water collecting between the skins...

[peter_barton]

When I changed my 18' Skiff racks from ali to carbon in 2005 it saved a staggering 14kg as both sides of the ali ones had had to be sleeved. As well as noticing the overall weight change (especially when carrying it!) I am sure I noticed that it was easier and more responsive to steer due to 'wide' weight being removed.

So is the flexibility of detachability worth that? Surerely it is not that much cheaper? It doesnt sound progressive to me, or am I missing something?

[Banshee Ambulance]

Its only the longditudinal tubes I would make in alloy so would not be as big a weight gain as on your 18. The point of doing this is to save money in the build of the hull. I think that money saved here could be used in a better performance/cost ratio somewhere else. I don't think performance would suffer much.

Interesting point about the rotational inertia though. Feel free to correct me but I would have though inertia in pitch = bad, inertia in yaw = bad and inertia in roll = not so bad.

 

[Will_Lee]

That is interesting and has implications for the positioning of correctors. I have certainly thought that roll inertia is perhaps desirable - hence Antidotes correctors on the back wing supports, but I have never tried moving them about.

Alu racks and carbon racks: I am not too sure there is a difference in weight (in the Cherub setting) as the I don't think you get to reap all the benefits of carbons superior strength over alu because the tubes limiting factor is toughness and ergonomics. Don't know the g/m for racks on Subtle vs carbon racks on other boats though. Rich will know the former. Looking at the ctech website, the 50mm od tube with 1.2mm wall is 280g/m.

[JimC]

inertia in roll = not so bad.

There's a bit in Bethwaite 2 about this... I couldn't say I've studied it deeply enough to be aware of all the implications though. Obviously its a much bigger deal, even proportionally, in an 18...