More pictures CS 20

[Rob Blackburn]

A week later and things are starting to flesh out.

Very happy with the lines. We are a bit puzzled by how much flotation to allow for in case of swamping. There is no real advice in the drawings. What are others thinking/doing on this one?

Mast aluminium is not available to same US specs. Shall have to wing it. A friend suggested getting the cuffs/collars milled from teflon?

Sounds dearer but should never get locked together.

Rob Blackburn
Oz

http://homepage.mac.com/b..._PHOTOS/PhotoAlbum26.html

[Richard Whitney]

Rob

Looking good.  I see you have white epoxy filler over that side of the Tasman too.  I also enjoyed looking at your collection of SeaPearl and other photos of tents etc.  I am trying to think ahead to that bit.

[Joel Page]

Are carbon fiber masts feasible for the home-builder?  If so, it seems they would be perfect for these boats.

[Anonymous]

Rob,  

Lookin' Good!

You have accomplished in a week what took me more than a month.  

I set aside the enclosed volume under the seats forward of the midships bulkhead for flotation.  I did not use any styrofoam filler, just enclosed the space with wood and a good epoxy seal at the joints.  There should be enough volume here to keep the boat from sinking.

[Brent]

Oops, I forgot to logon for that last reply.

Something I learned along the way...the white epoxy filler is probably cabosil or some similiar silica product.  These are great for making those hidden fillets.   There are blends of cobosil, microspheres, and wood flour that make fillets that are much easier to sand.  I get 5 litre pails for about $10 versus $6 for cabosil. I used this stuff on the fillets that end up visible from the cockpit.  The microspheres are a little more prone to absorb moisture, so I made sure they got a good couple of coats of epoxy over them.

[BradW]

Mast aluminium is not available to same US specs. Shall have to wing it. A friend suggested getting the cuffs/collars milled from teflon?

Hmm, I thought Australia used the same Aluminum Association International Alloy Designation as the US.  Euro designations are/were different.  I don't know what Graham specified for the CS, but I would think any of several 6XXX series alloys in an appropriate size tube would be good.  The 6XXX series use magnesium and silicon as the main alloying elements and are heat treatable to good strength with good corrosion resistance.  6061 is the most common one around here.  You do want a tube that is tempered, usually to T4 or T6, not annealed ("O temper") because it will then be very soft.   A lot of tubes will be 3XXX alloys, usually 3003, because they are very formable, but don't have as good strength because they are not heat-treatable.  That said, a hefty cross section can make up for lower strength.

In any case, good luck, and great pictures!

[Rob Blackburn]

Thanks for the bit on the different aluminiums. I am inclined to go along with the theory that a little more wall thickness down low should help.

I had one of those phone calls.... you all know the one. I am a pharmacist and the guy at "Aluminium Specialities" is an authority on aluminium.. Well around and around we went with me not having the right question and him only wanting to answer in monosylable grunts. But in the end I went down to a mate's shed who is a welder and he showed me different diam/wall tube and in big lengths to give a feel for what the tube will do. I came away thinking that if I got a stiffer mast, then what is wrong with that?

Carbon fibre did cross my mind as a friends brother has made a racing cat with his own designed/built carbon mast/beams but have not made any serious enquiry on this.

It was  Scotty the welders suggestion to do the teflon rings/cuffs. It made me wonder whether you could put an aluminium mast tube in the bow instead of glass and use the teflon cuffs on the bottom of the main mast. But then not sure how you could fix the alum to the wood and keep it fixed. I read alumin does not bond with epoxy. Could build in and use sikaflex around the top but then would prob look messy.

Shall have to keep thinking on that one.

With the flotation we are going with the 1litre equals 1kg of flotation theory and waiting until we get the seats in roughly to see how much to allow for air space. Shall put some in aft corners and some abeam the centreboard. Think we will go with air only with bigger 10" inspection ports.

Went to the Byron Blues and Roots festival last night till midnight and saw a heap of US acts, Marva Wrigtht, Eric Sardinas etc... Fantastic.

Cheers for now.

Rob

[Joel Page]

I just visited the Hall Spars web site.  They have an interesting discussion of carbon fiber masts, construction techniques, etc.  Pretty hi-tech, to put it mildly, and way overkill for these boats. Another site has some prices for custom carbon fiber spars; small (but fully rigged) masts can be yours for less than $2000 apiece!  Also, they are evidently rather brittle, and can shatter if subjected to high point load impact (like dropping a few feet onto the boom gallows?), according to the JBoat website.  Aluminum costs a fraction as much, is much more forgiving of amature technique as far as mounting hardware is concerned, can be dropped within reason, and probably functions nearly as well.

[Greg Luckett]

Rob Blackburn,
Thanks again for the link to your boat pictures.  I enjoy looking at each of them in detail.  Please be encouraged to share more when you can.
Greg Luckett

[Greg Luckett]

Rob,
It just clicked up stairs as to who I was chatting with last night....LOL.  I look forward to chatting with you some more.
Greg Luckett