View Poll Results: If you are reading this thread are you an IOM owner
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May 12, 2013, 04:34 PM
Registered User
Quote:
Originally Posted by john m taylor
The picture below shows in the background the latest Shiraz being constructed. (Coloured Orange). However, in the fore ground is the first wooden Chardonnay (IOM) being constructed ready for test. The Chardonnay (IOM) has the same features but is a larger, flatter hull than the Shiraz. Its planned to make the Chardonnay available in the new year as a set of plans for building enthusiasts to construct.

www.taylormadeyachts.com

John, your alcoholic twins look very good indeed.
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May 12, 2013, 05:25 PM
Registered User
hiljoball's Avatar
Putting pre-bend in the Sail Etc 11.1 mm groovey and 11.1 round masts is quite easy. They take bend readily. I found that a radius of about 1.75 meters was good for a bending jig. ( a piece of fiberboard cut to the curve with a metal loop at one end to secure the top of the mast). With care, you can bend them with your chest.

But the French 11 mm high tensile masts are much harder to prebend. Not knowing the correct radius for a jig, I started by scribing an arc of 1.25 meters, and drilled a series of holes, on two inch centers, for a set of wood screws, used as pegs. The length of the arc is about 1 meter. I bent the mast around the pegs, but it jumped back straight.

So I drew an arc of 1m, then .9, then .8 and finally 0.7m - drilling the peg holes and bending the mast. Finally at 0.7m radius, the mast took the prebend. And it takes a lot of force on the free end to bend it down to the pegs - no way I could do it over my chest.

To protect the mast from the pegs, I trapped a thin spline of scrap wood between the pegs and the mast tube

Having the jig is nice as it gives good control and most important - repeatability.

I have read that the three wheel jig works well, but have not made one.

John
May 12, 2013, 06:33 PM
Registered User
ndeverell's Avatar
Quote:
Originally Posted by hiljoball
Putting pre-bend in the Sail Etc 11.1 mm groovey and 11.1 round masts is quite easy. They take bend readily. I found that a radius of about 1.75 meters was good for a bending jig. ( a piece of fiberboard cut to the curve with a metal loop at one end to secure the top of the mast). With care, you can bend them with your chest.

But the French 11 mm high tensile masts are much harder to prebend. Not knowing the correct radius for a jig, I started by scribing an arc of 1.25 meters, and drilled a series of holes, on two inch centers, for a set of wood screws, used as pegs. The length of the arc is about 1 meter. I bent the mast around the pegs, but it jumped back straight.

So I drew an arc of 1m, then .9, then .8 and finally 0.7m - drilling the peg holes and bending the mast. Finally at 0.7m radius, the mast took the prebend. And it takes a lot of force on the free end to bend it down to the pegs - no way I could do it over my chest.

To protect the mast from the pegs, I trapped a thin spline of scrap wood between the pegs and the mast tube

Having the jig is nice as it gives good control and most important - repeatability.

I have read that the three wheel jig works well, but have not made one.

John
I bent the black mast in a tree !
just choose the right branches
worked ok but a little dangerous
These masts take a lot of pressure before they will stay permanently bent!
May 12, 2013, 07:14 PM
Registered User
I really believe that the few minutes it takes to make a three wheel bender is well worth it.
May 12, 2013, 07:24 PM
Registered User
ndeverell's Avatar
Quote:
Originally Posted by TedFlack
I really believe that the few minutes it takes to make a three wheel bender is well worth it.
True
May 12, 2013, 09:22 PM
Registered User
Yea i have made a 3 wheel bender for the club,but i have perfected prebend over my belly, and don't drill holes first unless you want to make No3 rigs with your intended no1 spars,how do i know i've broken 2 so far.I have a feeling the drilled spar won't break with the 3 pulley bender though.
May 13, 2013, 02:33 AM
OlivierFRA100
FRA3700's Avatar
Quote:
Originally Posted by TedFlack
Congratulations to Olivier Cohen on winning the French Nationals.

http://www.championnatsvrc2013.com/w...P_IOM_2013.pdf
Quote:
Originally Posted by The Tug
Also big congrats to Olivier think thats two years in a row,no stopping that Blue uh!!.Bigpat i dunno i'm using the french spars and would say they are stiffer than a groovy one boat still uses them here and has to have the prebend put back in from time to time as it will walk out because the mast is soft,so i dunno bro i'm no metalurgist.
Thanks guys ! It was a very windy event, mainly top of rig 1, and rig 2 middle and top for one day.
1st BP, 2nd Obsession, 3rd V8, 4th BP, 5th Ace, 6th Fusion, 7th Obsession, 8th Obsession, 9th BP, 10th BP
May 13, 2013, 02:51 AM
Love RC Yachts!!!
I agree that if you repeatedly set a 3 wheel roller to bend the masts, it is the way to go.

I too use a small radius to bend the French masts, at 900mm, though I will make a 750mm radius jig. Most others i know use this radius too, though one person i know bends them by hand around a padded door jamb after drilling them!

Metallurgically, high stiffness means an ability to bend a long way, and not permanently deforming, hence why the black masts require such a small radius jig and a lot of bending!!!. I know there is noticeable variation in the temper of these masts, which results in some bending easier than others in a single batch. I have never lost prebend in a groovy or 10.8mm masts, but know a few that have had this with the black masts. I understand the original masts were 0.5mm wall, but newer ones are 0.6mm wall, which should help this issue.

I have also found that the bend sould be concentrated in the top third only, any lower and the mast can form an S bend, or a straight section when rigged, thus not following the sails luff curve evenly.

As said before they are high stiffness, but low rigidity. In my opinion, whatever mast you use, in an IOM they aren't subjected to big loads in normal use......
Last edited by bigpat; May 13, 2013 at 04:28 AM.
May 13, 2013, 04:06 AM
OlivierFRA100
FRA3700's Avatar
Some great videos of FRA Nats on this youtube channel (especially A fleets) Some still to be uploaded

http://www.youtube.com/channel/UC0ff...0vvRIpw/videos
May 13, 2013, 06:55 AM
Registered User
Ahhhhhhhhh!! Olivier you're always a winner,even with the video!! still photos are great but nothing beats when they move. On these mast i bought a few blue ones in West Kirby and then had Brad send us a bunch of black ones prob from a different batch and i had the gut feeling the blue ones were slighty stiffer using the belly bender.
May 13, 2013, 08:46 AM
Registered User
Olivier,

Congratulations.

Having watched most of the video's, I'm sure glad my old eyes didn't have to judge the weather mark. I understand it needed to be where it was to get the proper leg length but what a challenge.

Interesting mix of boat designs that all did very well.



BigPat-

Metallurgically, high "stiffness" means an ability to bend a long way, and not permanently deforming, hence why the black masts require such a small radius jig and a lot of bending!!!. I know there is noticeable variation in the temper of these masts, which results in some bending easier than others in a single batch. I have never lost prebend in a groovy or 10.8mm masts, but know a few that have had this with the black masts"

I think you mean high "hardness" in your first sentence. Once a 7075 T9 mast (which is hard) is bent it usually stays that way where as a 6061 T6 mast (which is soft) may straighten.
Last edited by TedFlack; May 14, 2013 at 08:24 AM.
May 13, 2013, 10:22 AM
Registered User
Quote:
Originally Posted by TedFlack
I can dig it out and measure it if you need the dimensions. Having Mothers Day stuff going on right now so it will be a while before I can get to it.
Hi Ted
I would like to see the dimensions. I made one but I think I put the outside wheels to close together. I had to put a ton of pressure on the center wheel and partially crushed the mast.
Don
May 13, 2013, 04:27 PM
Registered User
Quote:
Originally Posted by Don Case
Hi Ted
I would like to see the dimensions. I made one but I think I put the outside wheels to close together. I had to put a ton of pressure on the center wheel and partially crushed the mast.
Don

The pulleys are 300mm apart on center. They are 55mm in diameter. It is kind of crude but all I do is screw the pulley down but leave it loose enough to rotate, they pulleys are mounted to a piece of wood that I clamp to the work bench. The center pulley, which is the one that does all the work is screwed done as well, it is offset from the outer pulleys.

It takes a few tries (start small or you will have too much bend) to get the middle one to have the proper offset. Mine is about a straight line between top of lower pulley, bottom of outer pulleys. Kind of like this

O---------------O
--------O--------

Ignore the dashed line, it was the only way I could show the spacing where the pulleys are.
Last edited by TedFlack; May 13, 2013 at 04:35 PM.
May 14, 2013, 04:23 AM
Love RC Yachts!!!
Quote:
Originally Posted by TedFlack
Olivier,

Congratulations.

Having watched most of the video's, I'm sure glad my old eyes didn't have to judge the weather mark. I understand it needed to be where it was to get the proper leg length but what a challenge.

Interesting mix of boat designs that all did very well.



BigPat-

Metallurgically, high "stiffness" means an ability to bend a long way, and not permanently deforming, hence why the black masts require such a small radius jig and a lot of bending!!!. I know there is noticeable variation in the temper of these masts, which results in some bending easier than others in a single batch. I have never lost prebend in a groovy or 10.8mm masts, but know a few that have had this with the black masts"

I think you mean high "hardness" in your first sentence. Once a 7065 T9 mast (which is hard) is bent it usually stays that way where as a 6061 T6 mast (which is soft) may straighten.
No, stiffness is what I meant, relating to a structure (ie: mast). Hardness is more in relation to the surface characteristics of an object (resistance to scratching) Toughness is related to this ( resistance to deformation from impact/ shock).

The higher temper of the French masts, means that thy take a lot of force to bend permanently, and hence they should be hard to bend back also.....

Generally the French sticks only require 6mm or so of prebend, as opposed to 10-12mm for other mast sections.
May 14, 2013, 08:36 AM
Registered User
bigpat,

I was using the wrong word, should have used "Yield strength" rather than "Hardness". From a metallurgy article:


"Stiffness is measured by Young's modulus, or modulus of elasticity. Between 6061-T6 and 7075-T9 these values are nearly identical. Modulus predicts how much metal deflects under load, as long as the load does not exceed the yield strength of the metal. Modulus of elasticity for 6061 is 10,000 ksi and for 7075 is 10,400 ksi, or about 4% higher. The modulus for an alloy is not affected by temper, which is designated by the T6 and T9 after the alloy numbers

Yield strength measures how much load the metal can withstand without taking a permanent set (deformation). The 7075 will withstand much more load before becoming permanently deformed than 6061.
If the stresses applied are not enough to permanently deform 6061, then the deflection, or bend, of the metal will be approximately the same whether you are using 6061 or 7075."


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