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Building a mast

Posted By: Gato

Building a mast - 02/24/08 04:23 PM

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/
Posted By: Gato

Re: Building a mast - 02/24/08 04:48 PM

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
Posted By: Rolf_Nilsen

Re: Building a mast - 02/24/08 05:44 PM

Document, document, document, please document. All very interesting!

Looks like you used quite a heavy cloth on the inside?
Posted By: Gato

Re: Building a mast - 02/25/08 08:54 AM

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)
Posted By: Gato

Re: Building a mast - 02/27/08 05:50 PM

First spar in the bag, hopfully pics tomorrow
Posted By: Rolf_Nilsen

Re: Building a mast - 02/27/08 07:44 PM

Looking forward to see the pics! Any better weight estimate?
Posted By: Gato

Re: Building a mast - 02/28/08 07:25 AM

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?
Posted By: Gato

Re: Building a mast - 02/28/08 09:25 AM

The bagging: http://www.gust.ax/gallery/sydvast_2/08-02-28/
Posted By: Gato

Re: Building a mast - 02/28/08 10:32 AM

The result: http://www.gust.ax/gallery/sydvast_2/08-02-29/
Posted By: Wouter

Re: Building a mast - 03/01/08 07:36 PM


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
Posted By: Gato

Re: Building a mast - 03/03/08 06:59 AM

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...
Posted By: Gato

Re: Building a mast - 03/04/08 06:28 AM

So no opinions about the profile or the tapering??
Posted By: Rolf_Nilsen

Re: Building a mast - 03/04/08 07:23 AM

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.
Posted By: Gato

Re: Building a mast - 03/04/08 08:31 AM

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...
Posted By: Rolf_Nilsen

Re: Building a mast - 03/04/08 08:49 AM

Isn't that the way things usually work out <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
You are stepping into largely uncharted terretories with this project so I think most are waiting eagerly to se what you come up with.
Posted By: Gato

Re: Building a mast - 03/04/08 10:10 AM

So, maybe it’s better to remain quietly in the workshop and then to go out testing in secret... <img src="http://www.catsailor.com/forums/images/graemlins/crazy.gif" alt="" />
Posted By: Rolf_Nilsen

Re: Building a mast - 03/04/08 11:35 AM

Oh, that would be really nasty of you. First wetting our appetite saying what you are doing and then nothing more. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
Posted By: Gato

Re: Building a mast - 03/04/08 01:11 PM

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="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" />
I will publish pics on my blog, and if anybody wants to discuss it will hopefully be here.
Posted By: isvflorin

Re: Building a mast - 03/04/08 08:44 PM

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 ?
Posted By: Rolf_Nilsen

Re: Building a mast - 03/04/08 08:55 PM

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:

Quote
The rule generally regarding carbon vs aluminum is that the wall thickness that works for aluminum (say 3mm) will work for carbon – all geometry the same. The Marstrom and Lindahl A-class have carbon beams that are just under 3mm thick. If strip planked you could subtract from that a little. I would especially like to see the beam striped in halves with carbon put on inside, halves then joined then outside carbon applied. I think you could get away with 1mm inside and 1 mm outside with 6mm thick spruce strips. 75% unidirection 25% braid or biaxial or woven for hoop strength. Striped up you could increase geometry toward the center, tapering as you get to the hull (can’t do that with extrusions or pultrusion) but you could with a strip version – especially applicable to the forward beam. In addition to function, it would look cool too. (This was actually done in some of the early C-class by Hubbard and A-class boats like the Loca. The aft beam should be lighter than the forward beam. You could also add to the outside if under built – the way to do it if you’re pushing the envelope.


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.
Posted By: Anonymous

Re: Building a mast - 03/05/08 02:14 AM

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.
Posted By: Gato

Re: Building a mast - 03/05/08 06:58 AM

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
Posted By: Gato

Re: Building a mast - 03/05/08 07:17 AM

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.
Posted By: Anonymous

Re: Building a mast - 03/05/08 07:28 AM

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.
Posted By: Gato

Re: Building a mast - 03/05/08 08:58 AM

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?
Posted By: Anonymous

Re: Building a mast - 03/05/08 09:12 AM

yeah thats fine, you'll just need a little more.
Posted By: Wouter

Re: Building a mast - 03/05/08 09:28 AM

Quote

The rule generally regarding carbon vs aluminum is that the wall thickness that works for aluminum (say 3mm) will work for carbon



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.


Quote

The aft beam should be lighter than the forward beam


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
Posted By: Anonymous

Re: Building a mast - 03/05/08 09:58 AM

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.
Posted By: Gato

Re: Building a mast - 03/05/08 11:30 AM

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
Posted By: Gato

Re: Building a mast - 03/05/08 03:54 PM

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="" />
Posted By: Rolf_Nilsen

Re: Building a mast - 03/05/08 04:04 PM

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

Re: Building a mast - 03/05/08 04:51 PM

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.
Posted By: Wouter

Re: Building a mast - 03/05/08 07:17 PM

Quote

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.



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
Posted By: Gato

Re: Building a mast - 03/05/08 08:31 PM

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.
Posted By: Anonymous

Re: Building a mast - 03/05/08 10:14 PM

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?
Posted By: Rolf_Nilsen

Re: Building a mast - 03/05/08 10:37 PM

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.
Posted By: Anonymous

Re: Building a mast - 03/05/08 10:50 PM

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)
Posted By: Wouter

Re: Building a mast - 03/05/08 11:06 PM

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
Posted By: Gato

Re: Building a mast - 03/06/08 05:25 AM

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.
Posted By: Gato

Re: Building a mast - 03/06/08 06:26 AM

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.
Posted By: Anonymous

Re: Building a mast - 03/06/08 06:52 AM

Gato, lets assume you're going to use your existing profile. Can you please email it to me and I'll use its geometry when defining laminates. Do you have access to a tube for the track? do you definately want to strip plank or is ply an option? Whats the minimum practical thickness for your stripping system?
Posted By: Gato

Re: Building a mast - 03/06/08 09:58 AM

I will get you the profile, and I can put you in contact with the French arcitect who has the original alu spar or profile. (comming from a Mattia cat 20 feet+)
I deffenetly want to try one in stip. For the ply there is no option 4mm the thinnest you can find in a wood producing country like Finland (this one made in France...)
Posted By: Rolf_Nilsen

Re: Building a mast - 03/06/08 10:17 AM

Scarecrow,

"(all care no responsibilty)", I dont think anybody expects more than that from advice/work given freely. I for sure sure dont. <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />

Gato,

I looked at getting some WRC, and it was very expensive. I dont know what prices you get, but for me it is either spruce (we can select our planks ourself) or all carbon. Would be interesting to know what you pay for carbon and WRC in Finland. Spruce is cheap here, and we have tracked down a local source for carbon fibers at EUR29 a Kg.
Posted By: Gato

Re: Building a mast - 03/06/08 10:58 AM

WRC 2500 Euros/m3 Carbon BX 310g 35 Euros/m2 Custom made epoxy around 7 euros/kg.
Posted By: Gato

Re: Building a mast - 03/06/08 11:01 AM

So Rolf, Shall I take some epoxy and come over to Norway to buy my carbon, I think it will pay the trip.
Posted By: Gato

Re: Building a mast - 03/06/08 11:24 AM

I will make the strips from 4mm ply, and the tube for the track (sail) I will make myself in glass or carbon
Posted By: Rolf_Nilsen

Re: Building a mast - 03/06/08 01:45 PM

It is a very special deal we have got with a manufacturer who thinks our project is cool. Basically we get to buy leftovers from their production of uni, bi and triaxial cloth for our own use in this spesific project. Cloth weight and length is limited. From 4 to 20 meters and heavy weaves, but as we pay for the kilo we can live with that.
Posted By: Gato

Re: Building a mast - 03/06/08 01:58 PM

Sh...t, I was alredy trying to find a big lorry <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
Posted By: Gato

Re: Building a mast - 03/06/08 02:06 PM

Just wondering if somebody did supply the data.
Posted By: Anonymous

Re: Building a mast - 03/06/08 09:38 PM

Of course not. I'll do it from scratch it will just take a bit longer.

Rolf, you could always strip plank a female mould and then make a straight carbon mast.
Posted By: Rolf_Nilsen

Re: Building a mast - 03/06/08 09:47 PM

Scarecrow,

I'll try checking with some of the other guys to see if they know the numbers on the current masts. As the superwings are extruded by AHPC, it is possible that they have not run the numbers on it but gone by experience when doing the die.

Female mould and laying up a 'classic' carbon mast is a possibility. Doing it in wood would be a more fun project on the other hand. <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" /> But I am always willing to listen common sense.. Anyway, it is not for this year. We are using old Tornado masts for now.
Posted By: Anonymous

Re: Building a mast - 03/06/08 10:41 PM

My bad I thought the superwing was the default mast extrusion that wouter refers too any generally successful F16 mast will do.
Posted By: Gato

Re: Building a mast - 03/07/08 07:36 AM

Feamale or male, think you end up with the same amount of sanding, it's just a question if you want to do it on the mould or on the spar.
The thing with this metod of using stip planking is that it's easy, cheep and a fast way to get a staight or even a tapered mast.
when I started my first one I had been expecting a lot more work.
I would be more than happy if enyone takes the advise and use it to make a mould
Posted By: phill

Re: Building a mast - 03/07/08 10:35 AM

Folks,
I do not want to interrupt the flow here so I will make this short.
The fact is I keep all my emails both sent and rxd. I went looking back through them to find some mast deflection data and stumbled across emails about work I was doing on a composite mast.
Back in 2003 I made a carbon composite section 6m long and did some deflection tests without and then with cardon on the outside of the section. It's kind of nostalgic reading through the old emails. From the emails it seems this was just before building the Blade prototype.

How time flies.

I also did comparative deflection tests with a superwing and Aussie wing of the same length so I could see how this project compared. (The Aussie wing 50x125mm extruded in Australia in the 80s to combt the importation of Sori sections for the A cat fleet. But in reality it was too heavy.)
I have rough sketches that include all components and layups I used.
Anyone interested in doing a bit of experimenting I'd be happy to send these emails to you so you can either improve on what I had tried or just say oh well it is better done some other way.

It seems from the emails I had worked out a way of modifying the technique to produce an F16 mast that would weigh around 9.91kg without fittings. How is not detailed in the emails. But If pushed I could probably work it out again.
I never actually sailed with this mast just did static deflection tests. So no guarantees.

Anyhow just thought I'd mention it.

Regards,
Phill
Posted By: Anonymous

Re: Building a mast - 03/08/08 05:25 AM

I now have all the data I need (thanks Phill). I should have a mast for you by next weekend.

Gato, what sort of timber will you be using?
Posted By: Anonymous

Re: Building a mast - 03/09/08 05:32 AM

F16 mast design is done. Will let Gato work out the bugs before giving it to anyone else though.

Theoretical tube weight with 4mm gaboon ply (stripped) core approx 11.5kg. Real world this will go up due to bog etc. Timber makes up about 45% of the weight.
Posted By: Gato

Re: Building a mast - 03/09/08 06:17 PM

So friends, what do you think, I started to build the F12 cat that Scarecrow designed. Personally I think it would be fare to him to build the mast for the F12 first using the same method. My intention is to have this one in the water before end of may, and to be able to present it to the clubs at the opening of the season.
Posted By: isvflorin

Re: Building a mast - 03/09/08 07:06 PM

Gato,
do you ever get out of the shop ? <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
Just joking but you seem to have a lot going on. Good luck with the new project and please post pics.
Posted By: Rolf_Nilsen

Re: Building a mast - 03/09/08 07:09 PM

What do I think? I wonder how you are getting all this stuff done! Otherwise, I think it is great to get some F12s in the water. It is also really inspirational to see what is done, the results, and the spirit of cooperation. Fantastic.
We are busy stripping hull halves and building bulkheads. But next year, I have a hunch a strip/ply mast will be a project.
Posted By: Gato

Re: Building a mast - 03/10/08 05:01 AM

There are no secrets, I sold my television about ten years ago <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
Posted By: Gato

Re: Building a mast - 04/25/08 05:44 AM

So here you are a simple way to build a mast...
http://www.gust.ax/gallery/mast/08-04-23/
http://www.gust.ax/gallery/mast/08-04-24/
Posted By: Rolf_Nilsen

Re: Building a mast - 04/25/08 08:56 AM

Excellent work Gato, thank you for sharing!

Where did you get the "double carbon tube" shown here: http://www.gust.ax/gallery/mast/08-04-24/p4200033-640.jpg

Where do you buy stuff like peel ply and what is the approx. price?

Any opportunity to weight the mast and look at the bending properties yet? As I said, it is very exciting to see home built masts take shape! I want to try my hand at this..


You have one sharp plane! http://www.gust.ax/gallery/mast/08-04-24/p4210001-640.jpg
Posted By: Anonymous

Re: Building a mast - 04/25/08 09:54 AM

Rolf,

I believe thats the F12 mast. Gato also has the drawings for an F16 one. The F16 mast has similiar static bend characteristics to the "standard" aluminium one but is much lighter and ironically probably cheaper. I believe he makes the carbon tube himself.

You can buy "peel ply" at any dress making shop.
Posted By: Gato

Re: Building a mast - 04/25/08 10:19 AM

Thanks Rolf, sharing is the only way to progress. Yes, It's the F 12 mast. I made the double barrel tube myself, but in the heat of the action I forgot to take pictures, but I will make another one for the Pixie of a “nice lady”, so if not to much distract by her I will try to correct my mistake... This spar is in weight about half way between alu and carbon, 5,3 kg. Bending characteristics as Scarecrow stated.
Posted By: Rolf_Nilsen

Re: Building a mast - 04/25/08 01:44 PM

I dont have eyes only for F16s. If this technology is feasible for the F12, and perhaps the F16, it will probably scale well up to 20 footers as well? Beyond that I suppose pure carbon is better? What makes this attractive is the relatively easy homebuilding option! Shipping masts is an expensive undertaking.

Would it be possible to buy a set of F16 mast plans, if you have them done already?


I think you both are awesome. Gato for actually doing what everybody are talking about, and Scarecrow for doing this kind of design work!
Posted By: Anonymous

Re: Building a mast - 04/25/08 07:17 PM

Rolf,

send me an email to chris (at) ctmd.com.au and I'll send you the F16 mast drawing.
Posted By: Gato

Re: Building a mast - 04/28/08 02:05 PM

Guess it will work fore bigger mast, my next try will be for my Mini 650 and that one is carrying some 80m2 of sail downwind and 40m2 close hauled. My Blade is a little bit on the shelf for the moment
Posted By: Rolf_Nilsen

Re: Building a mast - 04/28/08 08:52 PM

Quote
You can buy "peel ply" at any dress making shop.


Really? Any kind of nylon cloth? I was worried that the cloth treatment would leave residues in the surface of the epoxy. I have used some ripstop nylon from an inner tent and that worked very well..


I got the plans from Scarecrow. Think I can do this! Would be a really fun project, but not until the next winter I think.
Engineering wise, is the carbon taking all the loads or do the wood contribute as well? Perhaps especially in the "horizontal" level?
Posted By: Anonymous

Re: Building a mast - 04/28/08 10:03 PM

Rolf,

the ply is definitely a contributing component in the structure, primarily in the longitudinal structure. It is not considered to provide any "hoop" strength because it is stripped.

Buy a couple of samples of nylon and have an experiment. A lot of commercially available "peel plys" are [censored] and aren't easily removed in one piece.
Posted By: ncik

Re: Building a mast - 04/28/08 11:41 PM

Quote
I was worried that the cloth treatment would leave residues in the surface of the epoxy.


You should still give peel ply finish a light to medium sand before secondary bonding.
Posted By: PTP

Re: Building a mast - 04/29/08 12:10 PM

pardon the lame question, but when do you take the peel ply off? before it is completely set, after (seems like nylon would permanently adhere to it)
Posted By: Rolf_Nilsen

Re: Building a mast - 04/29/08 12:22 PM

That is the beuty of it, epoxy dont adhere to nylon, so you can remove the nylon and any aborbent layers on top of it in one go. You remove it when the epoxy have set fully.


Scarecrow. If the ply strips dont add "hoop" strength, using WRC strips would be even better?
I dont have the math to understand why, but I though the carbon fibers would take all loads longitudionally until they eventually broke. Then the wood would begin to carry loads? Is that a matter of oversimplification?

Nick, I think they left the peel ply on in the beginning, and pulled it off when they were to glue something to the surface. It was thought to be state of the art and the solution to the eternal sanding. As you say, they found out differently, to their cost.
Posted By: PTP

Re: Building a mast - 04/29/08 01:08 PM

Quote
Scarecrow. If the ply strips dont add "hoop" strength, using WRC strips would be even better?
I dont have the math to understand why, but I though the carbon fibers would take all loads longitudionally until they eventually broke. Then the wood would begin to carry loads? Is that a matter of oversimplification?


I have wondered about this- are the strength characteristics of wood and carbon different? I would figure they obviously are, so how does that work then in terms of using two difference substrates in an application that will be bending all the time? Does the wood break before the carbon or vice versa? If the properties of each are very different then one breaks before even getting near the break point of the other
Posted By: Anonymous

Re: Building a mast - 04/29/08 09:49 PM

Rolf, any stripped material is going to provide limited hoop strength, simply due to the fact that you are relying on the tensile strength of the resin between strips.

PTP, yes the material properties of timber and carbon are different, as are carbon/foam etc. The trick is to engineer the structure to make sure each component is not asked to contribute any more strength than it is capable of. I did quite a bit of work many moons ago with a company who were building carbon masts for offshore racing boats in a very similar fashion to what we are doing here. I know they built a mast for at least one 66' pocket maxi.

Peel ply definately reduces the need to sand but doesn't eliminate it. Leave it on for as long as possible, ie take it off when the job is done or when and if required to access an area for secondary bonding.
Posted By: ncik

Re: Building a mast - 04/30/08 01:16 AM

It is not necessarily the strength of the materials in a laminate that determines which will break first, it is the stiffness of each material. Deflection/bending is the key.

Imagine two simple laminates; stiff carbon and flexible fibreglass. Under the same load the carbon will deflect less than the glass. Keep increasing the load and you will find as expected that the fibreglass laminate will break first, but at a much greater deflection than the carbon.

Now join the two laminates together. The carbon is so much stiffer than the glass that the deflection allowed by the carbon won't be very large, and certainly nowhere near the deflection required to stress the glass fibres greatly. Increasing the load and the carbon will continue to restrict deflection below that required for the glass to fracture, until the carbon breaks a little below what it would've alone (because the glass is providing a little bit of support).

This is a highly simplified scenario, it gets a bit trickier when considering hoop stresses and laminate shear forces, buckling, etc.
Posted By: Anonymous

Re: Building a mast - 04/30/08 04:48 AM

Well put Ncik, I might have been a bit simplistic in my answer.

I don't like writing the over the top highly technical and condescending answers that some others use, but sometimes go to far in the other direction.
Posted By: ncik

Re: Building a mast - 04/30/08 10:26 AM

Thanks, was hoping someone would put me straight or back me up. I haven't done much composite engineering as a professional and some of the stuff has gone missing from my mind through lack of use.
Posted By: Anonymous

Re: Building a mast - 04/30/08 10:34 AM

Are you going to be around during Sanctuary Cove? Come and find me. Stand 377 (superyacht tent)
Posted By: ncik

Re: Building a mast - 04/30/08 11:57 PM

Haven't decided yet. Will certainly drop by if I get down there.
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