IOM General Discussion - Page 722 - RC Groups
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Jul 16, 2017, 02:16 AM
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coolmobility's Avatar
Age since manufacture and storage temperatures from tempering, can also affect temper through normalisation and age embrittlement. Alloy tube manufacture is amazingly complex.

So, in theory, the old mast you've had for years, in your shed may be stiffer than a new one, or vica-versa.
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Jul 16, 2017, 05:41 AM
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SailingJunkie's Avatar
Bet the range of stiffness we are siting here pontificating on between brands and within brands is so narrow that it is not worth the effort. Just build the freekin rigs and go sailing! What ever minimal advantage, you spend so many hours formulating, you toss down the loo in one bad shift.

SJ
Jul 16, 2017, 09:13 AM
Registered User
Ditto SJ. But it is interesting.
Phil
Jul 16, 2017, 09:32 AM
Registered User
Completely agree with SJ (SailingJunkie) ...

Just build the rig with whatever mast is available ... JUST ENJOY THE FUN OF SAILING & FRIENDS ... and ... a cold beer after
Jul 16, 2017, 09:55 AM
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RCphotoguy's Avatar
Quote:
Originally Posted by slo.ca6
Completely agree with SJ (SailingJunkie) ...

Just build the rig with whatever mast is available ... JUST ENJOY THE FUN OF SAILING & FRIENDS ... and ... a cold beer after
I hear where you and SJ are coming from, but what you don't seem to understand is that for a lot of us the techy side of the sport is part of the enjoyment for us as well. I for one am happy to see the detailed posts here and the knowledge shared in this forum.

Sharing info in this thread is a good thing, sharing attitude, not so much.

For you all to imply that being into the techy side of the sport somehow lessens the fun of sailing with friends is just plain silly.
Last edited by RCphotoguy; Jul 16, 2017 at 10:06 AM.
Jul 16, 2017, 10:17 AM
Registered User
Quote:
Originally Posted by RCphotoguy
I hear where you and SJ are coming from, but what you don't seem to understand is that for a lot of us the techy side of the sport is part of the enjoyment for us as well. I for one am happy to see the detailed posts here and the knowledge shared in this forum.

Sharing info in this thread is a good thing, sharing attitude, not so much.
If the Italian mast is 7075-T9 and is 11mm with .6 wall it is the same as the French mast which is 7075-T9 and also 11mm and .6 wall. However someone earlier said the Italian mast drilled easier than the French mast which leads me to believe it is not T9.

Some basic information is that 7075 alloy is stiffer than 6061, the hardness of 6061 was usually T6. The hardness doesn't change the stiffness but it does change the ability to put pre-bend in the mast. T6 will take a bend easier than T9 but will also unbend easier. I had T6 mast that would go back straight after applying a lot of backstay but a gentle bend over my knee would put the bend back in....that will not happen with T9. A real tubing bender is required to bend 7075-T9, also the T9 can actually break while bending if the holes are drilled in it before bending....or so I have been told.

All this information is available on line, try this for some basic information 6061 versus 7075. But keep in mind that T6 and T9 are way different.
http://blog.onlinemetals.com/6061-vs...luminum-alloy/
Last edited by TedFlack; Jul 16, 2017 at 10:57 AM.
Jul 16, 2017, 10:38 AM
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SailingJunkie's Avatar
Quote:
Originally Posted by RCphotoguy
I hear where you and SJ are coming from, but what you don't seem to understand is that for a lot of us the techy side of the sport is part of the enjoyment for us as well. I for one am happy to see the detailed posts here and the knowledge shared in this forum.

Sharing info in this thread is a good thing, sharing attitude, not so much.

For you all to imply that being into the techy side of the sport somehow lessens the fun of sailing with friends is just plain silly.
Not in the slightest. I'm about as techy as one might get but I did not want anyone to loose sight of the margins we are discussing here and how narrow they actually are. Development and sharing are what advance the hobby and keep the conversation alive.

SJ
Jul 16, 2017, 11:01 AM
Registered User
Agree with SJ last post as well ...

Not intended to take-away from tech side in the least ... SJ's post above is just pointing out the minor differences at time of discussion are minor - with the original information given ...

To address the differences of French vs Italian mast stiffness question ... I earlier pointed out what was needed to answer the stiffness question (i.e. all the techy engineer variables needed)

Given the assumptions and or limited earlier information ... vs ... recent updates ... seems there are still several unanswered questions / confirmation as to mast material ... the two main questions I see are actual tube wall thickness (i.e. 0.5mm vs 0.6mm) AND material with heat treat (i.e. 6061 or 7075).

Even if assumptions are made that cross-section is simple round tube (not complex aerodynamic tear-drop with internal web and open slot on trailing edge) and material is same (i.e. Aluminum 7075) ... then the real difference in stiffness lies in HEAT TREAT (i.e. T6 or T9 ... whatever?)
Jul 16, 2017, 11:08 AM
Registered User
I guess I need to repeat the T6 versus T9 discussion. So to make it easy I Googled it again and found this:

Dont confuse stiffness with strength. Stiffness is how much it deflects for a given force. Strength is how much force it takes to break it. Annealing or heat treating has no effect on stiffness but a massive effect on strength. Architectural grade 6063 and aircraft grade 7075 have the same stiffness (for practical puposes)But heat treated 7075 may be many times stronger than 6063. Common boom grades might be 6061t6 or 7075t6 or proprietary variations of them that could be given any old name or number. Higher t numbers dont mean higher strengths, the just mean different kinds of heat treatment which can include heating, aging, quenching and even cryogenic cold treatment. H numbers generally mean cold work. Changes in alloy composition mostly affect stiffness by only a few percent but do have massive effects on strength and the way it is heat treated. All generalisations that engineers will argue over, but for the real world, thats the low down.
Jul 16, 2017, 01:17 PM
Registered User
It is also important to remember that in certain situations controlled mast side to side deflection can prevent the sails from being overpowered as wind speed increases.
Jul 16, 2017, 02:36 PM
Will fly for food
davidjensen's Avatar
Either way we are dealing with noodles for masts!
Jul 16, 2017, 07:32 PM
Registered User
To those curious for the answer to
"Mast Stiffness" ... the techy (geek) answer can be found doing a Google search using search phrase "Tube Beam Stiffness"

https://en.m.wikipedia.org/wiki/Bending_stiffness

You will find Wikipedia answer as follows ...
"The bending stiffness (K) is the resistance of a member against bending deformation. It is a function of elastic modulus (E) , the area moment of inertia (I) of the beam cross-section about the axis of interest, length of the beam and beam boundary condition. ... Bending stiffness in beams is also known as Flexural rigidity."

Boiled down / extracting what the above means ... WHEN MATERIALS & HEAT TREAT "All the Same" ... only tube wall thickness are different ... a calculation for "Area Moment of Inertia (I)" is needed

Within the above Wikipedia link is link that define Area Moment of Inertia (I) ... or ...

Another Google search for equations for Area Moment of Inertia is this link (see following link) ... for Annular Tube as well as Oval Annular Tube cross-sections

http://www.engineersedge.com/materia...gyration-3.htm

"Area Moment of Inertia (I) equation for annular tube OD= D and ID= d is the following I = Pi (D^4 - d^4) / 64 "
NOTE : D^4 means OD raised to Power 4

As noted above ... the stiffness (K) does NOT NEED TO BE CALCULATED when only difference is tube wall thickness ... assumpng Material PROPERTIES are SAME (E - Modulus of Elasticity) and Heat Treat (T).

For more techy reading ...
"Stiffness vs Strength "
Aluminum vs Carbon Fiber vs Steel

http://www.dexcraft.com/articles/car...-of-materials/
Last edited by slo.ca6; Jul 16, 2017 at 08:44 PM.
Jul 17, 2017, 04:22 AM
OlivierFRA100
FRA3700's Avatar
Quote:
Originally Posted by TedFlack
If the Italian mast is 7075-T9 and is 11mm with .6 wall it is the same as the French mast which is 7075-T9 and also 11mm and .6 wall. However someone earlier said the Italian mast drilled easier than the French mast which leads me to believe it is not T9.

[/url]
Hi Ted, PG masts are 0.5 mm wall, not 0.6 mm.


For those who asked, my rig 1 with PG mast and booms weigh 240 g.
Jul 17, 2017, 08:20 AM
Registered User
glendaw's Avatar

Masts - and sails


One thingabout this conversation about masts is that our sailmakers take a lot of care to cut a specific luff curve into their mainsails. They work in millimeters (that's pretty small for our American friends! )They also give us fairly specific information about how much pre-bend to build into the mast, as well as how far down the mast to go when bending. The amount of bend in the mast will be quite important in getting the sail to operate most effectively.

As I mentioned earlier, we tested a bunch of masts. Our method of testing might be pretty basic after hearing slo.ca6's explanation, as well as other info (thanks for contributing those details everyone), but the difference in the deflection was fairly noticable. All we did was to support the mast at two points and hang a weight from the same point in the middle of the two support points, then measure the deflection.

The Italian masts deflected less than the French. Measuring it as carefully as we could, the difference in deflection was in the vicinity of 9% to 13%. So that will be significant for some, but not others - that's fine - each to his or her own.

However, it may be worth noting that Zvonko was using the Italian masts at the recent worlds - a bit different to "everyone is using French masts". What is more important to performance?....weight minimization or less deflection. Interesting.
Jul 17, 2017, 02:57 PM
Registered User
KoneWone's Avatar
Are there sailmakers out there that give specific information about mast pre-bend ?


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