Excessive Rake

[ausaviator]

Hello, I noticed this whilst browsing second hand cats.

Am I dreaming or is this a ridiculous amount of rake? Surely it would have some major affects on performance?



From:

Catamarans for sale

[David M]

With their higher speeds than monohulls the longitudinal hydrodynamic resistance on the hull is greater causing the sail to want to rake forward. Raked aft they are less prone to have the sails center of effort shift forward of the hulls center of lateral resistance causing lee helm.

At high speeds, imagine the wind pushing the top of the mast forward and the hulls resistance pushing the base of the mast aft causing the bow to pitch down, shifting the sails center of effort further forward.

You especially see a good amount of rake on lightweight racing catamarans whose hydrodynamic resistance on the hull compared to its sail area to displacement ratio is much higher. On larger cats not as much rake is needed because of the reduced sail area to displacement ratio and reduced righting moment for the amount of displacement.

[Cheechako]

Looks pretty excessive to me. Maybe he has a lee helm problem! Or maybe he thinks he's a pirate!

[David M]

Ok, I just saw the picture. That is excessive even if it were a racing catamaran

[Overlord]

It's a dean cat. I find them unsightly with that ridiculous racked mast.

[Cavalier]

Originally Posted by Cheechako

Looks pretty excessive to me. Maybe he has a lee helm problem! Or maybe he thinks he's a pirate!

... maybe it's not a mast at all, just a very manly VHF antenna!

[ausaviator]

Ok, so it's not an isolated instance! This one looks worse!

[belizesailor]

Not sure why Dean's are built with such an extreme rake. It's not like it is a one-off build issue.

Any Dean owners out there who know the rationale?

[ausaviator]

Even their 44 model has a similar set-up.

[Factor]

Yep - way too much. Moving Finger, a very very fast racing tri with canting and variable rake mast doesnt have that much.

As I understand the Dean Company design reasoning - the mast is proportionally further forward than most and the rake moves the centre of effort to a balanced position, but that is just what I was told when inquiring, I haven't done any analysis myself.

[Roy M]

These bring to mind the old Delta rigs. I haven't seen one in San Diego for at least 25 years.

[thinwater]

If the rake helped, performance classes would have gone there. They do some, but not so much and for reasons not relevant here (lift and loading up the rudders on cats without boards).

Could it have been to get the mast base out of the salon? Not a good enough reason.

Hmm....

[eliems]

I think I read somewhere it is to compensate for not having a backstay. It does look odd but the Deans have a good reputaion as a tough sturdy but comfortable Blue Water cat that makes pretty good speed for it's class.

I have been thinking about a Dean 400 currently for sale.

[cwyckham]

Looks like it hit a bridge! I guess they wanted to have more unobstructed area in the Salon, so they pushed the base of the mast forward. Just silly, IMHO

[cal40john]

Originally Posted by David M

With their higher speeds than monohulls the longitudinal hydrodynamic resistance on the hull is greater causing the sail to want to rake forward. Raked aft they are less prone to have the sails center of effort shift forward of the hulls center of lateral resistance causing lee helm.

At high speeds, imagine the wind pushing the top of the mast forward and the hulls resistance pushing the base of the mast aft causing the bow to pitch down, shifting the sails center of effort further forward.

You especially see a good amount of rake on lightweight racing catamarans whose hydrodynamic resistance on the hull compared to its sail area to displacement ratio is much higher. On larger cats not as much rake is needed because of the reduced sail area to displacement ratio and reduced righting moment for the amount of displacement.

I would argue that it is a lack of buoyancy in the bows that allow a cat to pitch bow down more than a keelboat. More an issue on beach cats than cruising cats. And while the CE is moving forward as you pitch bow down, at least on all the beach cats I have sailed the CLR moves forward much faster and farther due to more bow in the water and less stern in resulting in weather helm, not lee helm.

Top racing beach cat sailors change rake for the conditions. Hobie 16s with no daggerboard have a different reason. Boats with daggerboards will sail with a more upright mast in lighter conditions and will rake back for stronger winds. I haven't seen an explanation that I like yet but talk to any racing sailor and they will tell you that raking the mast aft will depower the rig and allow you to point higher, this is for cats, planing dinghies and keelboats. The beach cat sailors also like to point out that the weight of mast is further aft, but that seems a minor point to me.

The first cat I chartered, a Privilege 39 had a lot of rake, it did not look like other Privilege 39s. On one day we had a nice wind and on a broad reach we had to reef the main because the weather helm was so bad the steering system was binding and locking up. At first I thought we had the rudder hard over, but a lull unloaded the gear and then I could turn it farther.

I like the other explanation better that it was designed with the mast base forward and the mast raked to balance the boat.

JOhn