First sail out - bent the mast!

[Dave Newell]

Gday All - well we named our second hand un-named CS 17 #36 "Wyvern" and re-launced it amid much pomp and ceremony, wise words and cheap champagne.

What a great day on Wallaga Lake - took a bit to get used to the "big" and stable feel after sailing racing dingeys - never felt out of control even with 15-20 knot gusts. took the two kids out and three-four adults at a time - heaps of room! and comfortable for the pregnant and more elderly amoungst the group - just sat there and enjoyed the ride! beating upwind produced just enough spray to let us know we were really sailing (reminiscent of hanging off a trapeze as a teenager - without the exersion!)

need to work a bit on motoring and mooring up to the jetty - nearly had a spectacular collision - thank goodness for the tyres! went a bit slower next time.

the cat ketch rig is so easy and safe to sail and we got the hang of it pretty quickly - but on returning to the boat ramp at the end of the day, noticed that we'd managed to bend the main mast at deck level! bugger! rang the previous owner to get his thoughts and he thought we were sailing too hard on windward beats and had the mainsheet cranked on too hard. could be as im used to sailing racing skiffs pretty hard. also found out that he had used a softer aluminium alloy tube than recommended in the plans - 6060 instead of 6061 - about half the strength of the recommended. so it was probably a combination of my sailing style and the weaker tubing. any thoughts on how hard you can/should sail into the wind? - the boat does seem to point quite high when pushed.

i cant seem to find 6061 tube (or its equivalent) with a 2-3mm wall anywhere in Australia. i can get the right strength but only in a 6mm wall. my question is will having a thicker wall in the bottom section affect the mast bend and therefore the set of the sail, wind spilling effect, etc?

also, the centreboard got quite a vibration up at speed and wondered if anyone had experienced the same and what they did about it.

will post some photos when i have a bit more time.

thanks

Dave

[Joe Nelson CS#35]

Have you read this thread?

http://www.messing-about.com/forum/viewtopic.php?t=2717

You might contract Rob and see how he likes his latest solution to the mast.

The centerboard probably has too much slop between the board and case. You should be able to add some thinkness to the case at the bottom edge with epoxy and glass.

Has the board been wet very long? It might swell a bit and quit rattling. There is a fine line between too loose and too tight. Since that part of the boat doesnt need much protection from the sun..you could add coats of epoxy until you reach the right tollerance. If memory serves me the plans call for a 3/16" target tollerance.

[Dave Newell]

thanks joe - will check it out

dn

[Designer]

Glad that you had a great time with the boat. It was intended to be sailed hard so that once you get the mast right you can have a blast. I can't believe that you can't find the right size aluminium in 6061 T6. I used to use it for booms, catamaran beams and spinnaker poles. Call Alcan or Comalco, you are not going to find it at the corner store. I am a bit rusty about Aus. suppliers as I haven't lived there since 1970. If you don't get any joy there call some sparmakers and find out where they are getting their tubing from.

Because you like to sail a bit heavy handed, go with 3mm wall thickness.

The vibration in the centerboard is probably coming from a bad foil. Check for symmetry, especially the trailing edge, make sure that the trailing edge comes back fairly flat to a square trailing edge with nice sharp corners.

[Dave Newell]

thanks graham - have pretty much scoured the countryside for a single length of 6061 t5 2or 3mm wall tube. have checked out all the major manufacturers and they say that 6082 (slightly harder) has pretty much replaced 6061 in australia. 6082 seems to be only available in 6mm and up wall thickness. 6060 is the most widely available alloy and i would guess has been used by most cs builders in australia - looks like rob blackburn used the same alloy in his masts that broke/bent. will try mast manufacturers but didnt find much joy in my initial research.

thanks for the tips will keep you posted.

dn

[Dave Newell]

well here is a pic of the bent main mast - it bent right at deck level. im pretty sure it was a result of changes to the designers specs not sailing conditions and style. the mast alloy used was 6060 instead of 6061 (lower tensile strength) and smaller in outside diameter than recommended (60mm instead of 63.5mm). also the main sheet system is different from specified and pulls the sprit end down at a bad angle when sheeting on hard into the wind. heres my recommendation to current and future builders - DONT MUCK AROUND WITH THE DESIGN! :evil:

unfortunatly as far as the mast alloy goes the smaller and weaker section is what is readliy available in Australia and I have so far been unable to find the right one, even after countless calls and hours on the web - got a bit closer but not spot on. in the end close enough might have to be good enough and see what happens - will keep on searching for a while but i want to get back on the water! anyone who knows where i can get a 3m length of 63.5mm 6061 T6 tube with 2-3mm wall please let me know!

(by the way check out the gallery for pics from our first outing with the Wyvern)

Cheers

DN

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[Andrew]

Dave

Glad to see you had a blast out on the lake. And good to see someone else from this side of the pond!

I worked in Bega for a few years not sooo long ago. Beautiful country/lakes/beaches etc.

Maybe I'll get back there one day when the weekender is finished

Andrew

[Andrew]

PS.

Should have said earlier - If you need anything checking in Canberra (tubing wise) I'll be more than glad to do that for you

Andrew

[Dave Newell]

Thanks Andrew! good to know of another wooden boat person "down the road" - make sure you come for a sail down this way when you get your boat finished. i learnt to sail on lake burley griffin, racing cherubs and ns14's from the YMCA club - lots of thrills and spills with that fluky wind.

i have just managed to track down a solution for my mast section which others on the east coast of OZ may be interested in - Goldspar masts (02 9997 1211) in sydney have some 6082 (the good stuff!) 60mm x 2mm wall which they are going to sleeve for me with a 1.5 mm collar (to come up above deck level) - if i bend that ill eat my life jacket. bit more expensive but worth the peace of mind i reackon.

as graham said to me in an email - the important measurements in the mast sections are outside diameter (which really needs to be the 2.5" (63.5mm) he specifies in the plans and the alloy type which needs to be 6061 T6 as a minimum).

happy building/sailing

DN