This is a very good rule of thumb that I was first introduced to as a student by some very experianced Aeronautical Engineers. Typically it leads to an approx 25% weight saving over ali and a significantly stiffer part. I would usually specify a double bias instead of the biax in order to provide some off access strength.

Thanks guys, now we are getting somewhere! For the mainsail track I will make a tube in glass or carbon (lerned the method from Phill) glue it on and then laminate it to the spar and cut it open before fairing and finishing.
Well you are not off topic if it comes too beams, after the mast I will probably give them a try.
I had been thinking of using UD carbon for the stiffness and BX 45deg. glass or carbon (the BX carbon is hard to obtain were I live)for the rest.
All fittings will be done in carbon and laminated r done directly on too the spar

One thing that is important to me is to keep the things simple at least in the beginning,
simple methods and tools.
I will use normal hand lamination and bagging but no infusion or pre preg. or autoclave.
For the more irregular parts I’m thinking about bagging them in sawdust.

Because the BX (Double bias) carbon is hard to get, the other alternative is to wrap unis around on a 45 degree angle.

Laminate schedule would be some thing like:
Outside
Carbon unis at 45 degrees (clockwise)
Carbon unis along mast
Carbon unis along mast
Carbon unis at 45 degrees (anti clockwise)
Core
Carbon unis along mast
Carbon unis along mast
Carbon cloth (0/90)
Inside.

Disclaimer:
This is not an engineered solution just a starting point.

What about using BX 45 deg. glass instead of carbon?
As they are not working in the same direction as the UD carbon it should work?

yeah thats fine, you'll just need a little more.

I understand nobody give much about what I say or about my maths but here goes anyway :

The aluminium masts and beams used on the F16 (Halve of which I designed) use 1.6 mm to 2 mm thick walls. Only Bimare has used 3 mm thick walls on the beams at one time; John Pierce used 4 mm on his Dolphinstrikerless Stealth which was a predecessor to the F16 (but not full F16 compliant) at the time.

My point, 3 mm thick (aluminium walls) is NOT a good rule of thumb for F16's; it overestimates the parts used in real life by 50 to 85 %; overestimating the associated weights accordingly.

I have yet to see a 1.6 mm thick wall on a carbon mainbeam. In my experience with stunt kites I found that carbon beams are relative easy to break when point loaded, especially when the loading is perpendicular to the carbon fibres. This happens at several points along the mainbeam (bolts, transition from hull to overspan, mast step). Basically the glue matrix cracks up allowing movement of the fibres which then break one by one to finally break to whole element there locally. The thinner the walls the easier it was to break carbon tubes that way. We used to reinforce the tips of the carbon tubes for this reason. I strongly suspect that the underlaying layer of timber layer will go some way of improving this.



Density of extruded aluminium is 2710 kg/m^3 (for 6061-T6)
Density of carbon laminate is what ? 1850 kg/m^3 (from top of my head)
Density of Gaboon ply is what ? 650 kg/m^3 (from top of my head)

This means you may not have a carbon wall thicker then 145% of the alu wallthickness if the criterium is to arrive at equal weight of less. Going from 2 mm alu wall to 3 mm carbon wall is an increase of 150% for example.

With respect to ply : 417% increase in wallthickness will do the trick. Therefor a 6mm thick middle layer of this ply (as adviced by J.R. Watson) will weight the same a 1.45 mm thick aluminium wall already (= 90% of 1.6 mm thick walled alu mast section). So here to you need to cut down if any significant weight savings are to be achieved.




Only if the mainbeam is dolphinstriker less; otherwise it would seriously consider making both beams the same. 450 kg of mainsheet pull in the middle of the rearbeam is alot of loading as well.

It seems from the experience I have that the rule of thumbs supplied here by J.R. Watson are too crude to be of much use to an F16. Although they may well be accurate for larger vessels like yachts and Tornado's (don't they use 3 mm thick alu beams Rolf ?). Mind you F18 masts use 1.6 mm wallthickness on the masts as well. Tornado alu masts use 2 mm wallthickness and the A-cat carbon mast I have a cut-off from, uses 1.2 to 2.0 mm thick walls (pure carbon) depending on where you measure it. This is an Australian composites mast and was used by Gary on Altered when that boat was still a mk5 Boyer A-cat.

I hope this info helps.

Wouter

Wouter do you read what you write?

"F18 masts use 1.6mm wall thickness"
"Tornado use 2mm..."
"A class... 1.2-2mm"

Sounds like carbon thickness is similar to aluminium to me. I'm pretty sure the 3mm was pulled out of the air for the sake of an example and that Gato was always intending on confirming numbers etc.

One thing is sure. nobody is going to get me to put 3mm of carbon...
Even the alu mast for the mini has a wall thickness of 1,6mm
It's just the profile that is larger and makes it 2.5ks/lm
Btw. the same profile in carbon is about 1,6kg/lm

Maybe we better stick to the mast here and open a new tread for the beams, as the mast will be the more important and the rest is depending a lot on the outcome of that.
The reason why I am thinking of going into the beams afterwards is that I can not find 80mm alu tube with less than 2,5mm walls, I would have to make a special order for it = expensive.
I also got plans for a new cat today so I will not run out of “hobbywork”. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

I am in much the same situation with the beams, hence my interest. A new thread sounds like a good idea.

Phills suggestion for the profile for the Blade mast is 130 x 64 and if I am using the same profile as for the Mini it would give 135 x 63,5, other ideas?
I have that one in my computer so it's easy to scale.
If everybody is happy with that I start cutting.

Humm, lets see if anyone can spot the differences ?


"F18 masts use 1.6mm wall"

F18, total crew weight 140-170 kg, double trapeze, total righting moment 774 kgm, spinnaker, forestay with jib, total 21.15 sq. mtr upwind sailarea and typically 9:1 or 10:1 mainsheet with crew using both arms to work it. 12:1 and 16:1 cascaded downhaul. Mast survives severe impacts with watersurface


"Tornado use 2mm..." (I repeat that this is the ALUMINIUM Tornado mast)

Tornado, total crew weight 140-170 kg, double trapeze, total righting moment 900 kgm, forestay with jib, spinnaker, total 22.82 sq. mtr. upwind sailarea, typically 9:1 or 10:1 mainsheet with crew using both arms to work it. 12:1 and 16:1 cascaded downhaul. Mast survives severe impacts with watersurface


"A class... 1.2-2mm" (I repeat that is dependent on where you measure; sides are 2 mm, front/web are 1.2 mm)

A-class, total crew weight 60-90 kg, total righting moment 334 kgm, single trapeze, double forestay and no need to have a tight forestay, total sail area 13.94 sq. mtr. , typically 6:1 mainsheet with skipper using only 1 arm to work it. 8:1 downhaul. Mast breaks during severe impacts with the watersurface.


So yes, the wallthickness are similar where the masts in the way of strength, loading and durability are not.


Wouter

Well Wouter, I was asking about the profile, and as those spars dosent’t have the same profile it is not so straight forward to compare the wall thickness. You of all should know that it makes a difference just if one puts the carbon on the inside or the outside on a 4 mm thick wall of a wooden spar with the same profile. Let’s keep this kind of discussion on the F16 forum in the future, it seems to belong there. That was my reason not to shift it over there, even if somebody did the mistake to do it.

Gato, you've probably seen thats I've just asked for some data on the existing ali masts assuming someone comes fwd with it I'll try and put a laminate spec together for you. When are you hoping to start?

I would also be very interested in the laminate schedule. We are not doing anything about it this year, but there are other projects looming on the horizon. Suitable masts costs an arm and a leg up here, so doing a wood/carbon/glass sections would be perfect.

No worries, I don't have time at present to do it from scratch but if someone gives me a leg up with the ali data then I'm happy to put something together (all care no responsibilty)

Gato,

Actually the cross section of the carbon mast I quoted in my post is as good as identical to the superwing F16 mast crossection. Of course all comments about higher loadings, smaller wall thickness and such also hold for the F16 superwing.

I'm amazed at the shear stupidity of some people here. Did you guys honestly think that I hadn't checked for that ?

And Gato your comments on putting carbon on inside or outside of the mast is just misplaced. Failure of the mast is not because of the crossection failing but because the wall is buckling locally under compression loads and thus initiating a larger failure mode. Increasing local buckling resistance (double sandwhich construction) is therefor more important then the downsides of placing some carbon on the inside of the mast. If you are using 4 mm thick ply then you can just as well forget about the whole project altogether as the ply will already weight 8.5 kg on its own and won't do much in the way of strength and stiffness.

But I get the hint. I will scram off now and leave you guys to discovering these things yourself.

Who needs a qualified engineer anyway right ? I only went to "school" and learned nothing !


Bloody ignorants !

Wouter

Scarecrow, Yes I have seen and it would be rely nice if you could do that, it’s a little bit beyond my abilities; I would have to use the crystal ball. But there is no real hurry for my part to start with the laminate; I think we will go into April before that. Btw. I will try to get my hands on BX carbon you managed in a very soft way to convince me!! Seeing myself winding UD at 45 deg. clockwise and anticlockwise on a 8,5 m spar using my favourite epoxy whit the best hardener to gain low viscosity but with a pot life of max 45 min... Prefer to destroy the material on the water.
If we could decide on the profile I could start to cut stations and line everything up and do the timberwork.

If somebody is interested in “guessing” the final weight the wood weight glue included will be something around 6,5 kg. The mast I already made had a wood weight of just under 5 kg, and I used spruce instead of WRC on that one.The calculations are adjusted by a sharp plane.
There is another thing that is troubling me a little. If we shift to all carbon my method of joining the strips by glassing them together will result in some completely useless extra weight in glass, but I don’t see myself doing it with carbon. In that case I would portably have to put all the carbon going on the inside and bag it.