bending masts

[Guest wwbaginski]

hi , here is Doppio coming last Sunday to the shore with almost no wind, but it can be observed that masts do bend nicely. What do you think about their shape - I'm a bit surpised that they bend in the lower part more than the higher one. Masts are glued of two paralel pine sticks - they are very lightweight regadless they are solid. I had Doppio in winds of Force 5 unreefed and everything was fine.

[tom151]

it can be observed that masts do bend nicely. What do you think about their shape - I'm a bit surpised that they bend in the lower part more than the higher one. Masts are glued of two paralel pine sticks - they are very lightweight regadless they are solid.

Looks good to me, and the bend is what I would expect - considering the triangular shape of the sails.

With the sail having less area as it goes up the mast there's less force trying to bend the mast from that point onward.

She does look nice in the water!

Cheers,

TomH

[JeffM]

Looks to me like the force of snotter and sprit are bending the mast.  Not necessarily a bad thing, since that flattens the sails.  In light winds, you might want to ease the snotters for more draft (deeper curve) in the sails.  In strong gusts, my masts bend at the tops.  BUT my masts are 3 inch diameter aluminum tubing at the base, 2.5 inch in the middle, and 2 inch at the top.

[Guest wwbaginski]

makeing preprations to glue on plastic tracks, I 'm cleaning my masts. I measured them and it came out that they are 1 cm thinner than should be due to the design. 6.5cm instead of 7.5 cm. it makes half an inch od difference. they are solid fire masts, laminated of two layers. I hope it's not a danger yet, as they were working ok so far.

I think one (but I hope not the only one) way to go  is laminating lower 1/3 part with a fiberglass cloth, to 7.0 cm as this is the diameter of the aluminium tube which holds the foremast. Other ideas will be appreciated.

[Peter HK]

Hi Wojtek

As an aside your friend Peter came to visit and look at my CS 17 last weekend. It must be close to a record that an expat Australian living in Sweden, with a Polish friend who has built a B&B boat, came to Brisbane, Australia to check out a similar boat. We had a nice time discussing boats/sailing.

Re the mast.

My Cs17 plans show 3 inch (76 mm ) diameter for solid wooden masts. I think the only alternatives are:

1 As you suggest glass (not carbon) the wood to the 70mm diameter- probably strong enough- or

2 Change to aluminium base sections (recommended diameter 63.5mm) that will be able fit in your mast tube and use the top of the existing wooden masts in the aluminium bases.

Hope this helps

Peter HK

[Guest wwbaginski]

thanks. can't find that kind of aluminium around so glassing is more likely. As for Peter, he personally built Tom Dunderdale designed Apple but likes my cat-ketch a lot. He rigged (elaborated, collected all the "jewels" and finally mounted them)my boat and I'm very satisfied with his rig. Allows for  solo sailing, what has never been tried by me yet. Take a look to www.duckworksmagazine.com to see our boats sailing in Finland.

[Guest wwbaginski]

Peter, why did you say "no carbon"?

I'm asking, because today I've visited my little chemistry store  to buy a glass tape - not a marine store at all but they sell all chemical stuff for boatbuilders too.  I faced  products completely new for me: carbon tape, carbon cloth, basalt cloth.... Half a year since my last summer visit. Not much more expensive that glass products, just 1/4 or so. The seller said carbon is much more lightweight than glass, basalt is much stronger. Both to be used with epoxy.

[Rune Forsberg]

Hello Wojtek!

I'm in the mast part of my project now...(finally) And I have found a place in Sweden that has a tube which is 60x3 the quality is 6082 (supposed to be around 15% stronger than 6061). It's not the intended 63x2,1or3,175 but hope it's near enough. I haven't got a price for it yet but it's in their standard supply so it shouldn't be too pricey (I hope).  They don't have a suitable upper tube so I'll go for wood, as many others here have done. Standard length is 6m so split in two that would be 3m alu and 3m wood. Should work fine don't you think?

All the best

Rune

[Peter HK]

Peter, why did you say "no carbon"?

Wojtek

My understanding is that wood and carbon are difficult to use together- the carbon is so stiff that the more flexible wood component doesn't provide strength. If the carbon layer is not strong enough by itself and the masts flexes enough for the wood to provide strength, then the carbon will have failed/cracked. A solid core with a thick layer of carbon would be very heavy. Better to use more flexible fibreglass. Or go with the aluminium option as noted by Rune

Cheers

Peter HK

[sscoville]

Wojtek:

I cut the diameter of my wooden masts too narrow as well.  I decided to do the following - I went ahead and finished my first attempt with all their imperfections.  This will get me sailing.  Later (although i may get lazy or more likely start a new project) I plan to build a second set of masts, hopefully bird's mouth fashion.  Then I will have a back up set of spars.

[Guest wwbaginski]

Hi Rune, congratulations on the progress. I was looking forward to get a news from you. How about this year Raid Finland? BRS-CS side by side comparision

Your alu concept sounds interesting. So the upper wooden part diameter would be 5,4 tapered to 4,0 cm? Solid wood version calls for 7,5 tapered to 4,0, so I would like to hear Graham's opinion. Please let me know prices once you get them.