White Rabbit and Trimaran Yachts

I received some images on White Rabbit, although this is a tri-maran. I haven't seen the hull under the waterline, but I'm pretty sure this isn't a wave-piercer. We were thinking about doing a review on White Rabbit...

Well, according to Boat International June 05 edition, it is called E-Motion, and there is a great rear photo of it in the magazine, but i'm not sure if i'm allowed to scan it in. Could you answer that question Carl?

Hi Jon,

On this website you´ll find all about her; http://www.yachts.nwbs.com.au/

Probably a design we will see more of in the future, eventhough it will have the same problems as catamarans to be widely accepted..?

Dunno Lars. To me that wave-piercer tri is much more attractive than any cat I have seen.

Kelly Cook

As I have seen trimarans of this kind since I was a kid and they have still not made it, I dunno either...

Btw, it is not a wave-piercer but has four active foils between the hulls.

What will help the development of trimarans might be the rocketing fuel prices. And combined with sails they might be the best option in the future?

I read the article in Yachts too, but it really didn't answer many questions. For example...

1. There's no doubt that White Rabbit (and the trimaran concept) is inherently stabile, both at speed and at rest. This configuration is further enhanced with an active foil system. According to the Y.I. article, it's a VT Maritime Dynamics system and there are four foils, each with 50 sq. ft. of surface area. It's pretty safe to assume they're using horizontal foils that span the distance between the center hull section and the sponsons (two on each side, fore & aft). Between this stabilization and the narrow cross section of the center hull and sponsons, I'd have to expect a dramatic decrease in pitch and roll momentum.

2. Before I looked at the article, I kept wondering about its engine room config. Obviously the propulsion systems aren't located in the outriggers! BUT... the center section is SO narrow, it had me wondering. According to the specs, the engines are staggered, front to rear. Clearly, there isn't enough space for the engines to placed side-by-side. Although this is rather unconventional for a yacht, it's actually a GOOD thing, because it further enhances stability. Quite simply, it keeps the engine weight closer to the longitudinal centerline of the hull.

3. The article tends to emphasize the above deck space. Probably with good reason... White Rabbit has a 50 foot beam! But of course, they didn't say much about below deck space. I think it's reasonable to assume, given this hull configuration... the below deck space won't match a comparable a mono-hull.

4. This hull has many benefits, BUT... I have to wonder how maneuverable it is? I understand it has a fixed bow thruster and a deployable stern thruster. I would imagine this was mandatory, because there is very little space between the props to create any leverage against the hull for maneuvering/pivoting AND you've got two rather large outriggers that are effectively acting like long rudders. This would create an opposing force against turning.

5. The article also indicated that wave slap was considerable reduced. I can understand this, due to the sharp bow entry and the narrow cross section of the center hull and outriggers, BUT... in my experience, wave slap can become more pronounced when water CAN'T be displaced and is forced to travel under exposed sections of an inner hull. In studying the pics of White Wabbit ( ) it's clear the tunnels have sufficient vertical height to allow most wave-chop to pass uneventfully. But when the seas get big... I dunno!

Wisdom is welcome!

I think your comments are right on target Carl. I've never run a tri (except a dottering deckboat). But guys with "tunnel hull" performance boats report essentially the same limitations. At least with regard to wave slap. These little tunnel hull speeders are of course, in a different realm from the big wave-piercers. But, they report that all is well as long as they are able to run fast enough to lift the hull high enough for the tunnel roof to clear wave tops. However, when wave height does reach the top of the tunnel, the slap is a killer. They are then forced to slow wwaaayyyyy down and limp on in displacement mode. Also, could "piercing" equal "broaching" in extreme swell?

Kelly

You've raised a good question. White Rabbit is not a wave-piercer, but the narrow cross section of the forward center hull raises some questions. You could say White Rabbit is a "wave-piercer" by the definition of the word, not the actual hull design.

Lady Lola (seen in the picture below) is a conventional mono-hull. Here she is seen encountering large swells. White Rabbit will not have the same forward bouyancy of a traditional mono-hull. It will have a tendency to "pierce" the wave, as opposed to going over it.

This is only conjecture, because I haven't been onboard anything like White Rabbit, especially in big seas, but theoretically... this would be my concern.

Ocean Swell, Bow Down

That is an interesting photo. I can't seem to pick out that large of a swell??

Here you go Brian. I thought that picture on the other website was not particularly clear either, so here is my version.... hope this helps.

Looking at the two photos together, it seems to look like a pot hole in the water!

But if you follow the direction of the swell it does make a little more sense!

And that was my 100th post

[the sad individual then cowers back in the corner, awaiting its next feed]

That New Zealand WavePiercer is something beyond beautiful. This boat was truly deserving of last year's SuperYacht Society award.

Another thread (forgot about it) on wave-piercer's and trimarans is here...

http://www.yachtforums.com/forums/showthread.php?t=1047&highlight=wavepiercer

Congrats Jon!

Quite the optical illusion on that Lady Lola swell, heh? The pitching of a hull in rolling swells will only magnify the problem we're discussing, as we can see in the down angle of Lady Lola's hull in these pics. With White Rabbit, this pitching should be reduced over a conventional monohull, BUT... if a trimaran was to encounter a specific set of wave frequencies, it could have a different outcome. Hard to say, but interesting to discuss.

Yeah, I recon the photo is taken at an angle of the port side of the boat which is facing bow end into the swells. Therefore as the photo is not straight, the swell appears incorrect as we do not see the position the photo is taken.

Would that be an appropriate assumption?

I've been offshore in big swells, running along the side of other yachts in the 100'+ range and I've seen the dips firsthand, both on our boat and theirs. In the Lady Lola picture above, the swell in the foreground is basically hiding the bow, BUT... she IS at a bow negative angle in relation to the horizon. Also notice the release of displaced water to her stern.

It appears to me she was coming off the back side of a swell and the following swell was about to give lift to the bow... just before this picture was taken. The spray off the bow in this picture shows she was beginning to displace the oncoming wave.

This picture is not unusual in offshore conditions, but the angle taken (from the backside of the swell in the foreground)... IS unusual. You can't believe how BIG it gets offshore. Sometimes a superyacht doesn't feel big enough! Because rogue waves happen... you will sometimes see the forward and/or bridge windows "boarded" up. Usually it's with custom fabricated aluminum plates, but I've actually seen plywood used for this.

If I get a chance, I'll snap a picture of a "boarded-up" yacht for you when they arrive in Ft. Lauderdale after a trans-atlantic crossing. It's not pretty, but their windows aren't broken!