I have just started to build a new mast for my Mini 650, and after that I will attack the one for the Blade.
So for those interested: http://www.gust.ax/gallery/mast/
Exchanged some words with Phill and there is a good possibility to end up around 13,5 kgs for an 8.5 m spar with the same stiffness as a Superwing.
I am happy if I arrive to 15kg
Document, document, document, please document. All very interesting!
Looks like you used quite a heavy cloth on the inside?
Well, I had been plannig some iceboat sailing, but no ice so I started to build the mast and 300g glass was the only thing at home.
But that is not a problem, the glass is at 45 deg to the woodfibres and there will just be a little bit less on the outside. I also used Spruce instead of WRC for this one for the front part, the reinforcements on the inside will be WRC, and for the F16 spar all wood will be WRC.
the halves together are about 12kg so I am only about half way to target so far (25kg)
First spar in the bag, hopfully pics tomorrow
Looking forward to see the pics! Any better weight estimate?
The spar for the Pixie 14 is out of the bag! Profile 124 x 58 length 6.2 m weight 8,8 kgs.
I used no carbon on this one as it was the first try, only BX and UD glass. Material cost less than 100 Euros, about 20 hours of work so far.
If I get it my way, all the fittings on the mast as the spreaders will be done in carbon
and laminated on to the spar.
Phills suggestion for the profile for the Blade mast is 130 x 64 and if I am using the same profile as for this one it would give 135 x 63,5, other ideas?
What about s slight tapering?
The bagging: http:/
The result: http:/
Gato,
When you start on the Blade mast you should really post that on the F16 forum; I'm sure you 'll get alot of response there and it is of course an excellent read for all of us !
Wouter
Thanks Wouter but I think I remain here, there will not be as much discussion, but at least it will stay on topic I hope...
So no opinions about the profile or the tapering??
I would not have gone for a pure wingmast but a more rounded profile. With a wingmast it is critical to get the AoA (angle of attack) adjustment 100% while a rounded profile is more forgiving. But getting the bending properties right would be more important to me than the profile of the mast.
Tapering.. If you want to do it, do it. Just make sure you get the bending properties right up there. Kind of a black art I think as there is so little documented on the topic, but fast if done right. Unless you are pretty certain you get it right, it is probably more work than it is worth.
The wing profile suits this method of building well, a rounder profile would require more solid wood in the front part or a lot narrower strips.
I am not at all sure to get the things right, but normally there will be a lot of good advises once the thing is done...
Isn't that the way things usually work out <img src=
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You are stepping into largely uncharted terretories with this project so I think most are waiting eagerly to se what you come up with.
So, maybe it’s better to remain quietly in the workshop and then to go out testing in secret... <img src=
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Oh, that would be really nasty of you. First wetting our appetite saying what you are doing and then nothing more. <img src=
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I think as long as you are doing just the hulls everybody are happy, but as soon as it is a question of other parts for the cats there are too many who are involved in selling them one way or another. <img src=
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I will publish pics on my blog, and if anybody wants to discuss it will hopefully be here.
Gato,
The mast homebuilding project is very interesting considering the price of a new mast, and shipping options for it.
I am curious about how are you going to make the mainsail track. I assume you already have that sorted, but how ?
Gato and Florian,
J.R. Watson at Gougeon have been building boats with epoxy for a generation soon. I asked him about beams (sorry for going off topic, but it is kind of related and very interesting for homebuilders). Here is his reply:
We are considering it for our boats.. List of to-do's are constantly growing..
Having access to guys like J.R. Phill, Marcus and others and sharing information between us is what forums should be about. Not squabbling and personal agendas.
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=
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