|30th January 2008 05:10 PM|
Hope you havent got it ?? (Hysterisis)
Anyway ; it was me that mentioned it and I agree I dont think it has any real effects in this case.Inernal damping differences between C and glass will be tiny. ( I would imagine)
I cant see how it woul be possible to build two masts of equal stiffness; equal weight ; one of 100%C and other 50% C (yet same reflex ???)
Lighter masts of equal stiffnes must have quicker reflex.
The equal weight lower carbon would be softer.
I just think for sails under around 8 metre 100% masts are too stiff (Unless they are RDM)
|30th January 2008 01:33 PM|
The SDM/RDM thing was just to indicate that it _could_ be possible to build masts with different materials but similar weigh properties, not meant to be a real basis for comparison.
In practice it is of course impossible o build on glass mast and one carbon mast and have both weight, stiffness and geometry identical (since carbon is stiffer in the same weight).
The argument from the start is that it is the is is the weight difference that is responsible for the reflex difference, not the the material choice per se. In theory this is a clear distinction, but in practice the two effects get kind of hard to isolate (and keeping everything except geometry the same is probably the closest you gonna get towards isolating material choice).
|30th January 2008 07:08 AM|
It's my thought that comparing SDM masts with RDMs might be taking certain liberties on the scheme of things, regardless of differing carbon contents. As I'm sure that you're aware, different sail designers taylor their designs around different diameter mast types, and that doesn't even begin to address preferred bend curves.
To be fair in a broad sense, I'm inclined to think that comparing SDMs to SDMs and RDMs to RDMs makes for more sound comparative data. I still have an interest in SDMs (with different masts of carbon fiber contents), and I know without a doubt, that much thought considered right is truly subjective in nature, especially considering varying sailing interests and respective design formats.
If one starts contrasting apples with oranges, its my thought that things ultimately have to get much more complex when considering different disciplines and preferences out there.
|30th January 2008 05:54 AM|
Poster #20, I'm not sure you got the distinction. One claim is that faster "reflex speed" is due to lower weight primarily. Another claim is that is is properties of the carbon fiber itself that causes the faster reflex.
Under the first clam (which is what I believe in): if you build one mast in 100% carbon fiber and another one with identical weight and stiffness using less carbon and more glass, they will have virtually the same reflex speed (and if you compare say a 55% standard diameter freeride mast with a 100% rdm wave mast you in could in practice come out with rather similar stiffness and weight data).
People that believe in the second claim will think that the 100% carbon mast will have a faster flex response in this case.
|30th January 2008 12:17 AM|
But surely if reduced mass of bow can increase its reflex speed the same will happen with a mast.
Whole point of high carbon masts is to increase reflex response.
(ie otherwise a heavier fibreglass would offer same performance but just heavier.Which it does not .)
|29th January 2008 09:06 PM|
On carbon "flex response": Just as Sailquick, I SERIOUSLY doubt damping properties of carbon vs that of fibreglass has any noticeable effect here. Weight (mass) is what matter the most and then we have to quite common effect of the high end carbon mast simply being stiffer.
I believe that the bow example depends on the same thing, carbon bow being lighter in this case. Its not hard to imagine that there is actually more matter that has to be accelerated in the bow itself than in the arrow. So light weight will matter a lot.
If the actual damping has anything to do with it, I would bet that the type of layup, how fibers and matrix are packed, matter more than the choice of fiber (weight/stiffness effects aside). It may be the case that high end high carbon masts, also sports a "tighter" laminate.
|29th January 2008 07:27 PM|
- A little essay about masts
- A selection of results of mast measuring
- The IMCS anything better ?
|29th January 2008 04:13 PM|
I have to admit that I had a 100% carbon Gulftech 490 SDM (originally made at their Texas facility) in the late 90s that ultimately failed due to cam wear. It broke above the boom on the outside at Coyote Point, but I was able to sail back on the remaining 2/3rd left with a folded over section banging on the boom. Admittedly, I was quite lucky to be able to sail it in.
Despite my misfortune, it was an absolutely awesome mast until it died. In fact, I still have the unbroken section, to include the 7.7 sail that was damaged by the break in the mast.
Although there appears to be some dissatisfaction with high carbon content masts, I have to say that all mine have been great. Not all of them have lasted forever, but I always got at least 3-4 years before failure. Even though I'm a bit of a lightweight (70 kgs), I must admit that I have been able to leverage well off these masts.
Overall, I had to say that my experience with 100% carbon masts has been very positive. However, I have to be frank that I wouldn't invest in a 100% carbon NP mast. No reason to gamble on a historically questionable product. I think 2006 was undoubtedly a black year for NP. It's hard to recover from such a poor show.
|29th January 2008 10:13 AM|
Yes Floyd, that pretty much sums it up I recon.
I too have done a bit of IMCS mast testing and have noticed the same as you. Quite a few time the SDM 100% masts from the same factory were actually stiffer than the lower % ones and usually over what the specified IMCS claimed. For a lighter weight sailor like myself this was a problem. The 100% masts were noticeably thinner walled (as one would expect) and seemed much more susceptible to damage from mishandling and accidents. I was particularly concerned at the effects on durability concerning wear from cam rubbing and the boom clamp on an already very thin section.
|29th January 2008 02:00 AM|
When a mast is deflected it stores energy. When deflection force is removed force will be used to return mast back to its original (and beyond if poss) position.
Two forces are resisting the motion to return.
A) The weight (mass) of sail and mast
b) The dampening effect of sail
If you reduce the weight the thing will fly back quicker.(ie the force stored is acting on less weight) since Force = Mass x Acceleration: if you half the weight you will double the acceleration (back to norm) On top of this 100% masts are not only lighter I suspect they are also stiffer;(regardles of IMCS) compare a 490 100% and 490 75%. I have hung weights from them.The 100%C is always stiffer(and lighter))) so they store even more enegy (IMO) compounding the effect.
In archery a carbon bow will match (in speed of arrow terms/length of flight) a fibreglass one with only 70% of its draw weight.Because it has a faster reflex.It is not just a sail /mast term its physics/materials concept.
I also think (not sure of this one though;cant quite remember it from uni days) that carbon fibre has very low hysterisis.(ie very low internal daming;some materials show resilience to returning (polymers in MTB suspenion) some show very little (Spring steel/carbon fibre)
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