Catamaran rigging - 60 deg mast rake???

[Sailing Ohm]

Hello y’all! So this question is simply for my own edification and I admittedly know little about catamaran rigging.
What is the benefit of the extreme rake on some catamaran masts?
I got a new neighbor and I swear his mast is at a 60degree angle. (I’m using the building window line to estimate 90 deg. So that’s where I got 60 from).
At first I thought it was damaged but it looks like it is supposed to be that way.
This seems like it would put a lot of pressure on the rigging, especially the forestay and at the base of the mast and its attachment and also greatly reduce sail area.
Obviously some naval engineer thought there was a benefit but what is it?
Thanks in advance for the info!

[Spot]

Raked indeed...
I get 76 degrees +/-

[Matt Johnson]

That's a Dean catamaran. You can google their reasoning, but it boils down to wanting more windward ability.

Matt

[Sailing Ohm]

Originally Posted by Spot

Raked indeed...
I get 76 degrees +/-

Awesome. Thanks for the exact calculation!
What did you use to find that value?

Now hopefully someone will be able to tell me why.

[smj]

I pity the rigger that has to go to the top of that mast.

[Spot]

Originally Posted by Sailing Ohm

Awesome. Thanks for the exact calculation!
What did you use to find that value?

Now hopefully someone will be able to tell me why.

I took an image file and put it into QCAD which has a free entry-level version. I drew the line for the rake, then one parallel to the waterline, and used a standard angular dimension to read the angle. If the object is flat to the plane of the photographer or if the image is a scaled line drawing it works pretty well. If you know the size of the object, the image can be scaled 1:1 with the real world and rough dimensions can be taken.

[StuM]

Interestingly, everything I've seen says that Deans have a 7° rake, that one is twice that!

[chrisr]

i'm on the same angle as stum...i've always called mast rake as the angle between the mast and vertical ie a mast raked aft 5 deg or 10 deg etc

so personally i'd be saying this boat has a rake of 14 deg

maybe others disagree ?

as regards the reason for mast rake : the aim is to improve upwind performance by moving the CoE for the rig further aft and thereby force the boat to turn up towards the wind more. it'd used when for some reason or other it's not possible to move the mast further aft

often a feature on mainly downwind boats that need all the help they can get to go upwind

not a great fan of extreme rake myself as it's a half arsed solution...

cheers,

[Sailing Ohm]

Thanks for the info y’all and clarification about mast rake.
I do agree that the degree should be called the offset between the rake degree and 90deg. That makes sense.
Always trying to learn new things and luckily sail boats always have new things to teach.

[MV Caroline]

Originally Posted by Matt Johnson

That's a Dean catamaran. You can google their reasoning, but it boils down to wanting more windward ability.

Matt

And, obviously, increased weather helm.

[Wallaby]

Originally Posted by Matt Johnson

That's a Dean catamaran. You can google their reasoning, but it boils down to wanting more windward ability.

Matt

Lay the mast down on the deck and it will go to windward even better.

[clakiep]

Reasons for : correcting weather helm, easier to come about - longer 'chord' or lower aspect ratio of mainsail. Reasons against : more stress on forestay (but less on mainsheet), horizontal stress on mastfoot, more longitutenal compression on mast, and, looks terrible ugly if over 10 degrees.

Capt. Claus - ocean tramp of the eighties

[mikereed100]

There are a lot of reasons for mast rake on a cat:

1. To balance the rig when the mast is stepped far forward.
2. Cats can flex a lot and don't have backstays. A pronounced rake can make it easier to achieve forestay tension for windward ability.
3. The rake allows gravity to take some of the compression forces from the full battens off the sail track making it easier to raise and lower the main.
4. It looks cool.

Most cats measure rake from the vertical, so in the case of the Dean above, the rake would be 14.4 degrees.

[Don Lobo]

Is there a reason why the mast would be raked to 76° or so, rather than extending the boom longer and moving the coefficient towards aft that way?

Seems that would also work, but I guess there could be complications to that. It seems that raking the mass just illuminates a triangle of the luff of the main sail

Maybe they are already doing a combo approach to this Challenge, going up wind as much as possible

Cheers!

DL

[sailingchiro]

My rigger told me to hang a bucketful of water from the halyard and move it aft till the halyard (center of bucket) was 4' from the mast base. Then put a 9" bend in the mast. So I did. Seems to work.
14 degrees seems excessive.

Loved the comment, I would hate to climb that mast.