MERLIN ROCKET FORUM

Topic : That Ram Fing in front of the Mast bit!!!

So ive got an nsm4 and it has a ram on front of the mast that cause the jib sheets to get caught on, but apart from that what elsa does it do?


Posted: 03/09/2008 18:45:11
By: James 3403
That'll be the strut.

It prevents excessive mast bend caused by the kicker. Wisdon is to set you mast up with the jib and rig tension on then apply the strut until it "firmly adds support".

If overpowered upwind ease it off a little bit, probably about an inch on the control line.

Insufficiant strut/lowers is a good recipe for bad pointing, unfortunatly excessive strut also causes much the same!


Posted: 03/09/2008 19:10:54
By: chris M
Too much strut force will make your mast into an S shape! 

Can't really stop the jib sheets catching on it, thats just what you have to live with. Try different knots on the jib clew, or tapered sheets?


Posted: 03/09/2008 19:41:11
By: Mags
Agree Chris's comments about the use of the strut. I have found the least catchy way to rig jib sheets is cut them from a single length, make a loop in the centre, push the loop through the clew eye (it is usually a tight fit and needs a pair of clean pliers to squeeze the loop small enough to get through it), then lead the two ends back through the loop and pull tight. Very neat, no knots to get caught and, if the sheet is thick enough not to cut your fingers off, it definitely won't slip. It may help to tape over the strut's pin retaining circlips as well but I haven't found it necessary.
Peter


Posted: 04/09/2008 09:00:18
By: Peter 3112
Not sure if your NSM 4 is the same rig as our NSM2 -  but the NSM2 (and our Smokers) didn't have forestays.....

Without the strut the mast will fall down when you remove the jib hallyard tension...
(the gate isn't stong enough to hold it up.

Colin


Posted: 04/09/2008 09:45:56
By: Colin
Couldn't you just make the mast gate a wee bitty stronger?


Posted: 04/09/2008 10:24:00
By: .
Think of the extra weight!!


Posted: 04/09/2008 11:46:09
By: Dave F
What about the weight, windage and aformentioned inconvenience  of the strut.


Posted: 04/09/2008 12:04:36
By: .
The strut is an essential part of the tuning apparatus on the boat. You cannot remove it without seriously effecting the performance. On more modern merlins this was replaced with lowers. Several of the NSM 2s & 4s of that era had a strut & fixed lowers which were led at 90 deg to the mast and tied to steel loops bolted through the gunnel.


Posted: 04/09/2008 12:15:50
By: RH
WHen the boat was new I rigged a system that allowed the strut to be used in reverse - ie I used it to pre bend the mast in light conditions to make the sail flatter (pre deck stepping technology) - might be handy.
Rig the boat on shore and have a play with the strut and the kicker - you will see that very small strut movements will have a significant impact on the rig. Letting the strut off will make life easier in a breeze but if you let too much go you will lose speed and pointing.


Posted: 04/09/2008 12:56:33
By: Peter Scott
Thank you - 3434 has a strut and fixed lowers at 90 degrees and we were wondering whether someone had just plonked them on anyhow when converting from hog stepped. Now I know it's meant but what's the theory of them??


Posted: 04/09/2008 14:13:53
By: Pat2121
Many of these lowers were retro fitted when some of the newer boats started coming out with them as standard. They were meant to limit sideways bend on the lower section on the mast and the strut was used for fore/aft control. Never quite sure how effective they were.
Of course when the lowers were angled back they could do both operations.
Not induce bend though.......aka Scotty


Posted: 04/09/2008 15:51:11
By: RH
thanks peps for your help. will try some of that at shustoke at the weekend
if i wanna get really technical then wat sort of rig tension should i put on the boat for different conditions and how important is it to get it right?


Posted: 05/09/2008 12:31:23
By: 3403
Funny the things Merlin sailors don't obsess about.  You seldom see people fiddling with their spreaders or measuring rig tension but lots dangling things off main halyards to measure rake.

Answer somewhat depends on what system you have for adjusting it. Usually enough rig tension to keep the leeward shroud just tight when hiking out to windward - this will increase as the mast bends more as the wind and kicker tension increases - but if it is light you can try using extra rig tension to prebend the mast along with pulling slightly forward on your strut. You can adjust quadrant levers out on the water to take up the slack but it is a bit of a fiddle and never adjust the loaded shroud for obvious reasons


Posted: 05/09/2008 13:22:42
By: Andrew M
James no doubt scotty will be there on sunday,(he might even be race officer) you cant miss him, ask the man himself ,he'll be happy to give you a few pointers!


Posted: 05/09/2008 23:32:36
By: D. H
When i briefly sailed a hog stepped Rowsell NSM II we put on as much as we dared in all conditions. Don't know how much good it did the boat but it was very fast and the owner did the same too! This i think was because the sails were quite full (Alverbank) and they needed this prebend in order to work.

What you need is a figure from Bosnia for how much bend you want at spreader height. You find out what you have by tieing the main halyard to the gooseneck and tensioning it. What i used to do was then fiddle with the spreaders until i'd acheived this figure at a "reasonable" rig tension ie not floppy like a mirror but not really tight like an enterprise either, a happy medium. I've never seen a merlin sailor use a tension guage!

Once you have that you won't be far away, and you use your strut to complememnt it. You hold the prebend in light/meduim condtions and allow it to bend more in stronger winds when overpowered by letting the strut off a little.

The strut will have more influence over your power levels than rake will on your rig. I used to find that rake was death to boatspeed on the one I sailed, and if really desperate we used the cunningham (lots of it the bolt rope was elastic!!) to further depower. Another good trick is to move the jib cars back, probably all or most the way if it's howling.


Posted: 06/09/2008 10:03:27
By: chris M
To expand on the comment above about "bad for the boat", high rig tension in an older hull will probably cause it to close up slightly, as the shrouds are pulling the sides of the hull inwards.

On my NMS1 there is little point heaving on lots of tension - the boat closes up and the rig goes floppy again. I've never got my leeward shroud tight when the wind is up enough to hike hard. (I even measured the width of the boat once, and it decreased by a good few centimetres when the tenion was wound on hard.)


Posted: 07/09/2008 12:50:38
By: Mags
I think the one i sailed was just a very good and stiff boat. Certainly the leeward shroud never went slack!


Posted: 07/09/2008 18:08:27
By: chris M

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