Carbon Vs. Aluminum mast pros and cons

Overbored

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So. Cal
High performance racing aluminum mast vs. a high performance Carbon racing mast on the same boat. Given a light 30' racer/cruiser, modern rig, swept back spreaders, what are the performance differences? will you feel the difference or will you need the instruments to see the .001 % difference. what are some of the pros and cons of a carbon rig. one con I have heard of is that the UV coating needs to be redone every couple of years.

 
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Rodfavela

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All other elements being equal, a boat carrying an aluminum rig will be in some disadvantages when compared with a sistership using a carbon rig. The first element that will be noticeable is the heeling moment as the aluminum rig is much heavier than the carbon which also creates heavier pitch fore and aft on choppy water . Followed by potential corrosion for those based in the ocean. Carbon rigs are tuned slightly different than aluminum due to the flexing properties and how the pre-bend and bend are applied. This changes from boat to boat and probably is not the same level of difference across the board.

Clear coating is a small price to pay. Consider that there are several boats, such as the Viper 640 that started with aluminum rigs and switched to carbon with successful results.

What boat is it?

 

Overbored

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So. Cal
All other elements being equal, a boat carrying an aluminum rig will be in some disadvantages when compared with a sistership using a carbon rig. The first element that will be noticeable is the heeling moment as the aluminum rig is much heavier than the carbon which also creates heavier pitch fore and aft on choppy water . Followed by potential corrosion for those based in the ocean. Carbon rigs are tuned slightly different than aluminum due to the flexing properties and how the pre-bend and bend are applied. This changes from boat to boat and probably is not the same level of difference across the board.

Clear coating is a small price to pay. Consider that there are several boats, such as the Viper 640 that started with aluminum rigs and switched to carbon with successful results.

What boat is it?

I can see it making a difference on a 650 but how about

boats like the 10r, the new first 30 , the pogo 30 the Elan 320
 
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allene222

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Other than the humor of my post there is a serious side. A sister ship replaced their spruce rig with an aluminum one and said it was a mistake, that the spruce was lighter. I know his boom weighed 50% more than mine and I assume his mast was similarly stout so I was wondering if he was correct that the spruce was lighter than the aluminum. If so, then mine must be much lighter, although there is an awful lot of paint on it after 60 years. OK, some numbers. My boom is 17 feet 6 inches and weighs 50 pounds. His was 75 pounds.

 

Joakim

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The first element that will be noticeable is the heeling moment as the aluminum rig is much heavier than the carbon which also creates heavier pitch fore and aft on choppy water .
I would rather say that carbon rig can be much lighter. In many cases it is just slightly lighter, since there is a huge variety of carbon rigs (and also aluminum rigs). I know many cases where the difference is only 10-20% (including standing rigging), which I wouldn't call much. About 20% seems to be the standard case for production boats, but it is possible to go much lighter with higher grade and more expensive carbon and maybe even PBO rigging.

 
One downside of the carbon masts is that you need to follow-up with the relevant sail material.

No more sails made of anything else than a high-tech carbon, technora, etc. suit...

 

Tucky

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You absolutely need to compare the weight of the mast and rigging with any material- on my 42.5 rotating mast where the aluminum extrusion is perfectly sized and the carbon extrusion is generally undersized with extra carbon and rigging, the weight difference is minimal. Sometimes the difference is enormous.

 

Overbored

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So. Cal
Thanks for the replies

I have been looking at some of the new 30 ish foot racer / cruiser designs and most are offering a standard boat with aluminum / wire rig and a Carbon mast / Rod rigging setup. Bene first 30, elan 320 / elan S3, pogo 30 etc. The boats are in 8000# displacement and really not planning boats except maybe the Pogo. it seems that the boats have not changed and they add the carbon for a very large $ number. Will there be a performance gain that you will see or will the PHRF guys here Carbon mast and hit you for every thing the mast is worth and then some.

What about maintenance will the carbon require more? is it easier to damage?how log does the clear coat last before you need to spend 5K to redo it.

 

solosailor

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one con I have heard of is that the UV coating needs to be redone every couple of years.
Most carbon masts are no longer clear coated as it does wear out in 4-7 years. Look at every modern carbon rig such as Melges 32, etc. and they are painted, not clear coated. Clear coating is for Honda Civic hoods.....

 

Bruno

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I am looking at this myself, if weight and CG ht is similar then cost and robustness are most relevant factors, bend can be accounted for in luff curve,, fraction rig tip dump dampening is also relevant, if using a cap runner then maybe not.

 

DDW

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Marconi rigs are loaded in compression, the failure mode is Euler buckling, and in that mode is it stiffness, not strength that governs. Carbon laminate can be a lot stronger than aluminum, but it isn't much stiffer, so your section is going to be about the same. But density is 60% approx so you will save about 40% of the weight of the extrusion. All the other rigging (which is a substantial percentage of the weight) will be the same (unless it is not - replaced by something high tech which could be done for either aluminum or carbon rig and so an independent consideration).

Heeling moment differences also depend on how the boat sails: if sailed more upright, heeling moment of the rig really isn't that much. If sailed at 40 deg heel upwind all the time, then more of a consideration. Pitching inertial depends on where the boat is sailed.

 

Schnick

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Few years back I was sailing in a fleet that had about 3 or 4 J/120s in it. We were the only carbon rig 120, so we owed 3 sec under PHRF to the other sisterships. We were not any quicker except upwind in chop in my opinion (pitching moment). For that scenario, the carbon was not worth it.

For a given stiffness, the carbon rig will be lighter than aluminum. For a given weight, the carbon rig will be stiffer than the aluminum. That is the gain tradeoff. I think there are many carbon rigs out there that are not much lighter than aluminum would have been, but they are able to carry bigger kites off the masthead without extra stays, and they are able to power up the sails more due to the stiff rig. Nearly every OD class that allows different rig options, eventually evolves toward stiffer and stiffer rigs as the sail materials get better.

 

Joakim

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aluminum / wire rig and a Carbon mast / Rod rigging setup. Bene first 30, elan 320 / elan S3, pogo 30 etc.
I don't know the details for these boats, but for First 34.7/10R it is ~130 kg vs. ~110 kg both having the same CG. I would except similar difference for First 30 and Elan.

Heeling moment differences also depend on how the boat sails: if sailed more upright, heeling moment of the rig really isn't that much. If sailed at 40 deg heel upwind all the time, then more of a consideration. Pitching inertial depends on where the boat is sailed.
No, it doesn't depend on that. The weight reduction high above CG moves the CG down. A keel stepped mast in a 30' boat has CG about 7 m above CG of the boat. A 30' C/R weighs about 4000 kg. The CG moves down 7*20 kgm/4000 kg = 0.035 m = 3.5 cm increasing the righting moment at any heel from 0 to 40 degrees something like 3-4%. Similar change could be made by adding 70 kg to the bulb or a 35 kg child to the rail. Thus it is not a big difference in RM.

It's a different story for a lighter boat with a better quality carbon mast. E.g. a J/111 mast is about as heavy as 34.7 carbon mast and a aluminium replacement would be something like 170 kg. That is 60 kg difference, and it has higher CG and still the boat has about the same displacement. So the difference is already something like 7% in RM and equals to adding 100 kg to rail.

So for a 4000 kg 30' boat I wouldn't pay much extra for a carbon rig. For a sub 2500 kg boat it would make much more sense.

 

DDW

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Heeling moment differences also depend on how the boat sails: if sailed more upright, heeling moment of the rig really isn't that much. If sailed at 40 deg heel upwind all the time, then more of a consideration. Pitching inertial depends on where the boat is sailed.
No, it doesn't depend on that. The weight reduction high above CG moves the CG down. A keel stepped mast in a 30' boat has CG about 7 m above CG of the boat. A 30' C/R weighs about 4000 kg. The CG moves down 7*20 kgm/4000 kg = 0.035 m = 3.5 cm increasing the righting moment at any heel from 0 to 40 degrees something like 3-4%. Similar change could be made by adding 70 kg to the bulb or a 35 kg child to the rail. Thus it is not a big difference in RM.

It's a different story for a lighter boat with a better quality carbon mast. E.g. a J/111 mast is about as heavy as 34.7 carbon mast and a aluminium replacement would be something like 170 kg. That is 60 kg difference, and it has higher CG and still the boat has about the same displacement. So the difference is already something like 7% in RM and equals to adding 100 kg to rail.
Yes, it does depend on that. Actually if the rig CG never gets outboard of the center of buoyancy (a cruising cat is an example) then a heavier rig actually improves stability. Heeling moment isn't a distance - it's a moment. Yes a lighter rig will lower the CG of the boat. It also decreases the displacement which reduces initial stability. If the boat doesn't heel much, it won't matter much.

Using your example of a 30' boat with a rig CG of 23' (that is horrible by the way, good reason to have an unstayed rig). Rig loses 44 lbs (trying not to mix units here). At 20 degrees heel that extra weight is 7.8 ft out from CL or 346 ft-lbs. But at 40 degrees heel it s 14.8 ft out from the CL and you need twice as much rail meat (651 ft-lbs) to compensate. The actual moment are less and the difference is greater, because the center of buoyancy shifts outboard some amount - and a greater amount in a boat designed to be sailed more upright. At 5 degrees heel the boat will probably be stiffer with the heavier rig. On a 1 deg inclining test it will probably look stiffer.

 

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