I am not certain what you mean by that Gato? The alu is not made for the domestic market but largely shipped abroad. Shipping rates are good compared to other transport methods so it has been quite good business. With the new transfer lines and increased prices abroad we are loosing both jobs and business at home. The only ones who makes money on this change are the people owning the power plants (which use our community resources like water and mountains to produce their electricity [socialist indoctrination shining through]). Was this what you commented on?

I was commenting on producing aluminium, that is in many cases a quite unnecessary thing.
On top aluminium is not a very good material when it comes to some things that has to do with boats.
The main reason why it’s used is the fact that it is a lot cheaper to fabricate things from than many other raw materials but can be sold at the same price or sometimes even higher.
Just as an example, masts, a wooden mast is out ruled by the fact that it is involving too much manual work to produce it, and you can not make a lot of profit selling it. Still I have the feeling that it can mach an alu spar in performance.

Ah, but so heavy, Gato is planning to lose few kg's with his ply/epoxy mast when comparing to wing aluminium section <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />.

I was wondering how long you could resist Valtteri, I know you are really happy about having 5-6 kgs of corrector weight on top of the main beam, even if it’s recycled sodacans...

Not to spoil the "corrector weight" party here, but the measurements supplied to me are in direct conflict with eachother. As a result I'm not convinced that the weight measurement is correct itself.


Now I like wood/timber but their ratios of "strength to density" and "stiffness to density" are lower then those of aluminium ; as such I don't see how a pure wooden mast can be superior in weight when having the same specs regarding strength and stiffness as an aluminium version.

Glass fibres share the same stiffness and density values with aluminium, but have a much higher yield stress limit. So by using that you can make a lighter and more flexible mast that won't break but I'm not sure that that is advantagious. I personally found glass masts to quickly resort to pumping on my landyachts. A combination of glass and wood will not be much differ in this respect unless significant amount of wood is used making the mast heavier.

The only real attractive option is mating timber with carbon fibre and I do expect some good results from any projects in that direction. Especially when thinwalled ply is used here.

Wouter

Did you take the sandwich construction of the wood mast into account in that comparison?

I am a bad guy, there will be carbon involved... <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />

Rolf,

Yes

Wouter

Gato,

I'm thrilled to learn you go down that route.

I'm very interested in the results that you obtain that way and I have very high regards for the spirit to just try it.

You there are no other objections then I suspect that putting carbon on both sides (inside and outside) is best when compared to putting the same amount of carbon on only the inside or outside. I say suspect as I haven't done a more thorough analysis in that aspect yet. My expectation is that you can then get away with a significantly thinner ply wall. You be stressing the carbon fibres maximally but it is said that you can do that with carbon without much ill effects.

Best of luck !

Wouter

It wasn't measured with professional scales but even if it would be few percent off it still weights a lot and it doesn't change by using professional scales. I trust my scales more than your math based on these two and another mast that had smaller wall thickness, so there is too much unknown in it to draw any exact conclusions.

IMHO alu is only good to save some money (not even that much) when comparing to a carbon and building your own wooden one does that even better.

But the carbon will not be used for cosmetic purpose, the last time I putted it on the inside...

Phill has made one using 2 mm ply, UB and BX carbon, that the all I got from him no more <img src="http://www.catsailor.com/forums/images/graemlins/frown.gif" alt="" />

Come on !

I also gave you a series of actual aluminium tip weight measurements taken at the time our F16's overhere were all officially measured by a ISAF certified measurer. I also gave you several weights of bare sections we weighted.

If our identically shaped and fully fitted alu masts, incl. halyards, have tipsweights in the range of 7.8 to 8.2 kg then how on earth can your bare alu mast section weight 19 kg and have a tipweight of at least 9.5 kg without any fittings or halyards included at all ?

That is not math, that is common sense saying that something very weird happened somewhere. Now I for one don't believe that the aluminium alloy suddenly increased over 30% in density for your mast alone. We checked compliance in crossectional shape, so that isn't the cause either.

Now I still want to find out what really caused this weight measurement that you are upset about. If anything we can make you happy again and address the situation techically (new mast die ? lay claim at producer ?) if that is required.

The most logical culprit at this time are your scales or your method of weighting.

<img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />Either that or some 8 people in 3 different continents measuring about 10 different masts over a time frame of several years did all make the exact same measuring mistakes to arrive at very similar values. Not to mention the guys in the official engineering literature all making similar typos with respect to aluminium density and the way to calculate the total weight of thinwalled extruded sections. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Nahhh !

Wouter

No cosmetics, but increased resistance of the wall under buckling failure. Very important in masts.

Wouter

The plan for the spar for the mini is to make a “box” with ply on both sides of foam that will go from one side to the other of the mast and some UD carbon on the inside where the box meet the sides.
On the outside UD carbon and BX glass or carbon. There should be no problem as the fibres are not in the same direction.
With the rather small cross section of the F16 spar I don’t think I need to make transversal walls.

Wouter,

You assume that the only difference is 15 % of wall thickness, I guess that with that difference you can have also lot more alloy in some parts of the section. As I said before I didn't do weighting with professional scales but I trust them more than your calculations where there is too many unknown variables. I'm planning to weight it better though when our season starts in few months, so let's continue with carbon alu differences then.

For now I'm disappointed about not getting a carbon mast because clearly there is big performance difference i.e. lot more in weight difference than 4 kg's when comparing carbon to masts that we have here. As a engineer you should understand that dragging those extra kilos high up in the air is not that wise and percentage in weight difference is more than in price <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />.

Come on Wouter,

There is over 15 % difference in mast wall thickness and you assume that the masts are otherwise identical? It's easy to slip 1 kg more alloy for example to reinforcements and sail track if you already slipped 15 % more to the wall <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />.

Let's continue this when I have properly measured the mast when I have access to better scales in few months.

What’s the min tip weight? Just to know if it's of any use to taper. Want to keep the center of gravity as low as possible. <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

We have discussed alu vs. carbon masts under the F16 rule a lot earlier. There is not more to say about that.
It will be interesting to see what you find out about your alu masts. Extrusion or a bad weight.. Myself, I am very interested in finding out how thick the "core" in Gats F16 mast is going to be.

If I recall.. Bethwaite had wing emulating wooden mast on his 1970s world title cherubs. Werent wings but a D shape... Construction methodology may be found in his book or online perhaps in the Cherub webpages.. Suggest the UK one before the Au ones.. I do recall them being stripped so perhaps western red cedar and a white pine?

The issue was they were so stiff for and aft they had to have slots cut into the front to allow them to bend. Worked well but eventually the slotted areas just popped out..

ps one can get aero-grade ply in 1mm!!