I have one way of building masts for the Multihull I build but am wondering if anyone has a better way to build the.
Currently I:
shape a blank out of Laminated Blasa, eg 25mm long foil x 2.2m long with a 4mm flat edge on the training edge
I glue a aluminium tube - 5/32 dia onto the trailing edge.
Vacuum BAG Uni Carbon (200gsm) onto the Balsa and 135gsm Glass Cloth around the outside insuring a wrap around the trainling edge.
Sand smooth
Using a hacksaw blade I cut the slot up the training edge in the alumnium tube and file smooth to form the sail track.
For a 2.2m mast the weight comes in at about 250gms which is still quite heavy - not so bad on a Multi but any weight saved is a bonus.
I am also considering gluing a 5mm drill to some 1/8 piano wire to make a extended drill bit and have a go at drilling out some of the Balsa to get rid of some weight…
I had some thaughts similar to your desription. But I was thinking if it is possible to cast some kind of wax copy of the balsa, maybe re-inforce it some how, when finished it could maybe be melted out in some way… As you can see this has only reached the thaught stage, so have no idea if it could work.
Alternatively, shaping a solid aluminium rod should work. If you wax it before applying carbonfibre and epoxy, it should be possible to release it by putting it in the freezer. (If you have a long freezer). Aluminium will shrink more than the carbon/epoxy, which shoud give enough room to remove the aluminium piece. Again i’m not speaking of experience, i have only heard about it.
Hi Dave and Anders
this is what I did some time ago when I was intending to improve the mast profile. I did not continued but it may come back the idea !
Cheers
ClaudioD
This is all carbon, built of uni and sock over a mandrel. It measures +/- 28mm x 10mm and we’ve built it so for to about 2150 mm length. The luff groove is 4mm. Top 500 mm is tapered. Bare tube (@2155mm) weighs 175 g. We’re looking forward to getting one to Antigua by April to race in the Ministry of Tourism sponsored RC sail series. Current mast on the “BOX” is aluminum, carbon skinned and weighs about 280 g. in the same length.
As the box was originally inspired by my son’s participation the AC32, Valencia 2007, I’ve posted in the America’s Cup forum with a bit more about the boat.
Mast has been an exciting and at times frustrating project. But the several hanging from the shop ceiling make the effort worthwhile.
That’s some great looking mast material.
More thoughts for you… I wonder if a lot of rigidity could come from the outer shell on section that size. If the shell took up that function, then using lighter tubes (are they available with thinner walls?). The sail track tube especially looks like its walls are heavier than they might need to be. And maybe semicircle cross section instead of the full tubes might save some weight on the leading edge part…
Like Anders, I’m kinda thinking out loud here – I have no solid data on component weights or rigidity, but your work looks beautiful and I’m sure that it could be tweaked into a lighter version that would be even better.
Hi Guys, just tripped over this thread and wanted to ask if anyone has tried wrapping two carbon tubes togther with wetted out C.F cloth and then inserting inside heat shrink sleeve, I see you can get it in various sizes up to 100 mm dia http://www.thesitebox.com/cable-accessories/heat-shrink-sleeve.aspx
Just use hot air gun to shrink sleeve tight over the mast, let it cure, cut off the sleeve and cut the slot with Dremel and one KISS arse mast …mind you I have not tried it yet, just a wild thought :rolleyes:
Yup, I did the heat shrink sleeve thing, but with fibre glass, not CF.
I had 2 CF tubes, 10 and 6 mm, a wee bit of balsa, and wrapped in 2 layers of light glass.
All put inside heat shrink.
The heat shrink worked as expected. I was worried as different epoxy suppliers say theirs is the only one that won’t stick to epoxy. bah!
I went to my local electronics supplier and used what they had.
the resulting surface is not super smooth, but close. Like a peel ply surface I think. Mine also had imperfections, but that was my fault, as I was getting frustrated at the wrapping of the glass.
I wanted to use a CF sleve, but at $20 a foot, and I needed 6 feet, I had to pass.
Hi All, Here’s what I think I’ll try for my next attemp… Basicall what Claudio has shown but by using smaller Tubes and spacing them with small “frames” of Balsa about every 200mm.
My calcs suggest that the mast of 2.2m should come in under 200 grm - assuming I’m careful with the build… Basically I’m going to use a 6mm Carbon Tube at the front and a 5mm tube at the back with a space between the tubes of 9mm, then glue a 3 x 20mm strip of balsa each side of the tubes and shape to a foil. Then Vacuum Carbon Uni to form the outer shell, and finall use the cutter idea of Claudio’s to cut the sail track,
The Hollowing out the balsa Idea was too tricky (no suprise) but had to try it…
