Re Mast Rake on a Ross930

[RedLine 0]

Just Wondering if anyone has any advice on this. Just had my mast re-rigged, and noticed that my particular set-up seems to have more Rake than most 930's. I only have one other local 930 to compare this with and his is set-up a lot different than mine. Is there a reccomended standard mast rake measurement for a 930?

 

I have also just had a set of masthead jumpers added which will alter the amount of bend in the top section. But doesnt change the rake. The boat seems to go well enough with this heavy rake, but I guess in stronger airs may make it prone to more weather helm?

 

Stu

[Guest]

The boat seems to go well enough with this heavy rake, but I guess in stronger airs may make it prone to more weather helm?

 

Stu

 

The answer is yes but only you can say whether it's excessive. I'd be more worried about her performance downhill relative to a more upright mast. It's a bit of a try it and see thing.

[Murky 1]

As BM says. The other variable that will be individual to your boat is the way the mast works with the cut (especially luff curve) of your main. You probably need to get a good idea of how the jumpers might have changed the way those things are working together, but in the first instance, I would be led by that, more than what other boats might be doing.

[Guest]

I've got probably 500mm of rake in the marina, maybe 600.

Everything cranked on hard (very hard) brings the masthead back nearly over the companionway hatch.

Some have more than me, some less.

 

I don't have jumpers and do have a fully battened main.

 

We don't have any heavy or lee helm issues 99% of the time, usually it's very light and only a one finger job. Actually if anything the helm can occasionally be 'too light' especially downhill or real light stuff, just nothing there even though it steers when you want it to with no drama. No worries at all in a big blow. The dude on the main sheet can change the helm load incredibly fast though. 100mm of main sheet in or out can make a hell difference.

 

If Grant Jenkins did the rig he has a magic number he knows for the rake or average rake or something like that. From memory I'm reasonably close to that number.

[MrWolf 0]

For what its worth the Matrix Masts starting rake is 420mm or 2.5 to 3 degrees

[Guest]

Oh a number. Off to the boat with a tape measure now

 

I did measure mine with the number Grant uses and I was bloody close.

 

Be interest to see how close I am to Matrix's. The 500-600 is a guess from the office desk.

[Atom Ant 0]

I'd say if your boom catches on the lifelines when you tack, you've got too much rake

[RedLine 0]

Hi Guys

 

Thanks for all the replies. I'll take some measurements, and see how close it is to the reccomended Matrix settings. But it seems to go well uphill as well as downhill. So not too bad. Pic showing the rake attached.

 

Cheers

 

Stuart

[Guest]

Photos do make it a tad tricky but I'd say it looks like you have a lot more than me. I'd almost go as far as saying it looks like more than 'average' but again it just maybe the photo/angle thing again.

 

I'll show you my measurement if you show me yours

 

Nice clean colour scheme by the way. Looks good, he says signing off due to excessive paint envy

[Guest]

Don't worry KM, even Atom Ant will be that colour soon!

[Farrari 4]

KM, you should post a picture of the Reptile for comparison. For mast rake of course, not paint job cause we know how will win that hands down

[MrWolf 0]

Hi Guys

 

Thanks for all the replies. I'll take some measurements, and see how close it is to the reccomended Matrix settings. But it seems to go well uphill as well as downhill. So not too bad. Pic showing the rake attached.

 

Cheers

 

Stuart

 

 

You weren't kidding !

 

That is a lot of rake !

 

way more than was "originally intended" by Murray Ross.

 

I would have thought you would get weather helm upwind in medium conditions and be slow downhill.

But if as you say you aren't either on that front it would be a bit of a mystery as to why that might be.

Can't say I can recall seeing another 930 with that much rake ???

 

Who set it up for you ?

[wheels 543]

As KM said, it's hard to see from a

Pic, but it also looks like a hell of a lot of Bend. It looks like the entire thing could hurl a Mini 100m

[Atom Ant 0]

I agree, that's a sh*t load of rake. Possibly double what you've been talking about. You may well find if you stand it up somewhat you will notice no change in upwind speed and pointing but an increase downwind. If your helm goes too light then you can always adjust the rudder rake to compensate.

[Guest]

KM, you should post a picture of the Reptile for comparison. For mast rake of course, not paint job cause we know how will win that hands down

No contest for sure, me by a mile.

 

Just measured my beast. No load on the mast, which does mean the smallish amount of pre-bend stops at the hounds and the top mast is then straight, which it never is out of the marina. My heavyweight full battened main is the winner in the mast verse sail stakes.

 

From the aft face of the mast at the base I have 550mm if rake to the aft face of the main halyard sheeve. +/-20mm, it was raining. If the pre-bend curve continued I'd say it would be pushing 650mm. Again with the straight top mast it's measuring close as 13.23mts from the sheave to the centre top of the transom.

 

I'm pretty sure I'm reasonably average maybe a hint towards the 'more' but bugger all from what I've seen in the fleet. I'm also pretty sure it is very close to or on Grunta Jenkins target measurement, which is probably one of those 'good spot to start when work off' ones.

 

When equally crewed we can play with the other fast lads on a equal footing. Hotdogger excluded as she is configured quite different than the rest of the class fleet. Last few times the Akl class boats all played together there was only a coat of paint in it between the top 4 or 5 boats. So I think our rig isn't in a bad place but I have been thinking about straightening her up just a tad, just a small tad.

 

Knot too sure you can compare the fleet rakes to helm load. I have noticed many have varying rudder rake. Mine is pretty much plumb but a couple do rake forward and a couple a hint backward. That will have some baring on helm loads. So I think you'll probably have to play around a bit to see how an mast rake plays with the helm.

 

So what rake numbers do you have now? I'm intrigued to know if it's the photo that makes it look a lot or knot.

[MrWolf 0]

Ross 930's with a loy of rake like the photo have been tried years ago, and in fact was quite common in the mid 80's.

As expected it was not too flash downwind. It was also in the days of pin head mains with short battens.

 

Once you go to more roach/full battens you should expect if anything, the Centre of effort is going to move aft.

all other things being equal that would generally lead you to less rake than with the old style rigs.

[RedLine 0]

Got down to the boat for a sail today, and used the tape measure. I have approx 1100mm of rake! From plumb from the mainhalyard sheeve to the aft face of the mast. So pretty much double the normal settings. I saw another 930 in Wellington (Airship) recently that seems to have a similar amount of rake.

 

Its just been re-rigged by duffy rigging in Wellington, and they just matched the length of the existing stays. I could shorten the forestay a bit and maybe put a toggle on each of the cap shrouds. to take out some of the rake, But till I'm certain that there is an issue, I'll leave it alone. As I was tacking upwind today in about 15Kts true, with no real weather helm. And downwind on a delivery trip I had the boat planning @ upto 14kts without much effort in 15-20kts.

 

As I've only owned the boat a couple of weeks, I'll just see how it goes!

[Guest]

1100mm = shite that is huge. Far more than any of the Akl boats and by quite a bit I'd say.

So it's knot a trick photo then.

 

Let us know how you go. I find that quite intriguing.