Trimarans and the BladeRunner...

Hi Catmando,

OSO'ers are always welcome! DJD (CTDave) and Packinaire are members here as well.... so welcome aboard.

The description of your Carlson "Reverse Three-point Air-entrapment Monohull" made me do a double-take. I thought you just posted the ultimate oxymoron! Then I remembered the "Veloci-Slot", built by Steve Stepp. I think this is the hull configuration you're describing. In laymen's terms... a Tri-Maran.

I vaguely remember one being built by Glastron or Carlson. It's been a long time since I've seen one. If you have a picture, post it. I'd like to see it.

No cash required to hang here. If you love big-boats, you're in good company.

Yes, I remember the Triton! Thank you for reminding me. That was the hull I've been thinking of all along. And I remember it had a sharp V entry, graduating back to a very shallow deadrise. (was it completely flat?)

I recall some feedback from a guy that owned a Triton... claiming the hull was "squirrely" in rough water. The principles of the design were fairly sound for smooth water operation. No surprise it worked well in these conditions. I always thought... if the sponsons were raised slightly, it might have exhibited better rough water capability. However, this may have sacrificed lateral stability.

Hard to say... no seat time. Speaking of seats... there are manufacturers of gas/shock suspension seats. Can't say the brand name, I don't remember. But I can tell you... they are effective. We used them on a couple of test platforms.

Fix that digi-cam and I'll learn to spell helmet.

One of the 51' Bladerunners is powered by twin Cat C-18's. It is waiting for the right weather conditions to try to circle England in less than 30 hours to break the current world record. Here is their website for those interested.
http://www.roundbritainrecord.com/

Jorge Lang

I got an update that they will attempt to break the record starting at 9:30 in the morning British time on 7-9-05. They will be posting live updates on their website. Should be pretty interesting.

Even with the technology it's still one heck of a challenge just to complete it in one piece.

Time to ruffle some feathers around here. (it's the only way to draw in lurkers!)

I'm on the fence with this one guys. I've been keeping quiet on this thread for some time, but I've got some very definitive thoughts on this subject. Aspects of this hull design have merit and stand on sound principles. I KNOW this hull works in smooth water. But I have reservations about it's rough water capability. I'm basing this partly on the feedback I got from an owner of Steve Stepp's "Veloci-Slot" in the mid-80's. The other part is... my instincts tell me differently.

This hull has an extremely shallow deadrise aft with a very narrow cross section forward. BladeRunner's theory is to "slice" through the water with a narrow bow and then induce air within the tunnels to soften the ride. In concept, the tunnels should create equal pressure to increase stability... but this is not realistic in varying water conditions. It would appear this hull runs very wet under and through the tunnels, so pressure differentials WILL exist. This is where the outriggers are suppose to compensate, but on this design they appear to have a cross section so narrow, they would provide limited buoyancy to counter lateral oscillation.

Their website claims superior rough water performance over catamarans and Deep-V's, going on to say this design is not susceptible to "hooking". I understand the basis for their claim... the outriggers should effectively help maintain direction (if a lateral oscillation is induced that could result in a hook). BUT... this design also creates 3-point surface contact toward the rear of the hull and a 1-point contact at the bow. If you don’t follow me here… think tricycle, or better yet… 3-wheel ATV’s. (inherently unstable)

The fact that the majority of lift, both static and dynamic is being generated in the aft-half of this hull, coupled with an extremely narrow girth forward that provides little dynamic lift… is a “hook” waiting to happen. It’s simple hydrodynamics… once the nose gets buried in a wave, the rear of the hull will seek an alternate path during wave impact and the deceleration forces that are generated. Essentially, the nose will have better “grip” at this point, whereas the aft section of the hull (remember: shallow deadrise, coupled with aerodynamic lift) will be loose.

This was the scenario that plagued previous versions of these hulls and they were abandoned for offshore racing. Sooo… my point is, I’m sure a lot time, money and testing went into this hull. I have nothing but praise for anyone that puts forward an effort like this, but I wonder if a deep-v or a cat may be a better choice for an attempt of this nature.

Just random thoughts from a warped mind. I hope I’m wrong…

Right now, ten minutes after the start, the boat is running almost 75 mph which is pretty fast to be in the beginning of this race.

From the drawings on their website I think this hull isn´t too bad Carl? It does not have a fine entry, but is rather the same deadrise all the way which will give a pretty good ride even in rough seas since the centre hull is long and narrow. I have been racing narrow boats with 26 degrees all the way and this has less deadrise.

I wish them luck and more thoughts on the boat design are of course welcome!

Looks like they'll be seeing some waves in the 6 ft range.
http://www.ndbc.noaa.gov/station_page.php?station=64045

Yes, it seems they met some swell down at Lands End when the speed dropped to 46mph but since then it has been closer to 70 again, when they now have been out for seven hours. On the link http://www.roundbritainrecord.com/default-flash.htm you can see the speed at each 15 min interval by moving your cursor over the marks.

I'm surprised that there isn't more coverage of this. BBC has dropped the ball. I checked Ladbrokes and the odds aren't even posted.

I think that 24 hours after the worst ever terror attack to London, this event has a very low priority. Without that disaster and with England just nominated for the Summer Olympics it could have had the top priority, but I can fully understand that this will not gain much media attention for a while. Still it is exciting for us to follow on the net!

AMG
I suppose that you are correct. Perhaps I've spent too much time in areas where bombs are not noticed that much anymore.
I've been checking the buoys and weather stations to see what kind of seas the boat will be confronted with. It is quite exciting.

The site doesn't say who is on the throttles. He's going to be a busy man.

Lars,

You’re absolutely right about the deadrise remaining constant from the bow to the stern on the BladeRunner. If the hull progressed to a sharper deadrise toward the bow, this would further aggravate the scenario I described earlier. But here in lies the problem… in order to obtain a design that slices through a wave, a sharp entry must be used or a narrow forward cross-section. Fabio Buzzi did this with outstanding results, but this was with an inflatable RIB that had tremendous “inflated” buoyancy at the bow and also laterally.

If the hull doesn’t have sufficient girth forward (buoyancy), it will not displace a wave, but rather… penetrate it. Clearly, the design is trying to balance wave dispersement AND buoyancy by using a relatively shallow deadrise at the bow. But I really question if this is sufficient, because the primary hull represents less than 50% of the overall width of this boat at midship and aft. In contrast, the forward section of the hull is only half as wide as the rest of the boat.

Getting back to the deadrise… the BladeRunner is using a fairly shallow deadrise for an offshore boat. I couldn’t find any specs, but it appears to be in the 20-degree range or less. (see photo below) Anyone who’s run a 22-degree hull in offshore water will be the first to give you their chiropractor’s name. 24-degrees at the transom is often the standard, with RIB’s like Fabio’s running 26 degrees or more. Of course, as deadrise angle increases, stability decreases, therefore an inflatable RIB can get away with this.

Again, like I said earlier, the BladeRunner design stands on sound principles. This is why other manufacturers have attempted this before. But the real world sometimes differs from the conceptual world. It’s an absolutely beautiful boat and I’m the first one to embrace new technology. I’m not trying to discredit these guys… I’m only trying to understand why this hull design would be a better choice than a catamaran or a deep-v mono-hull for this record attempt.

The following posts and pictures are for reference…

Bow Close-Up & BladeRunner 51 Bow Rendering…

These picture illustrates how the bow might lack sufficient girth forward to compensate for a stuff. Again, they are trying to strike a balance of silhouetting a wave, while reducing wave impact that would cause bow rise. The rendering shows the deadrise is constant at the bow. Certainly a shallow deadrise in the forward section will offer more buoyancy and dispersement, but it would also result in a less favorable ride through rough water.

Hull Stern & Stern Quarter profile...

These pictures show the wide signature created by this hull’s configuration at the stern. The deadrise appears to be quite shallow. If it were not for the air cushion created by the tunnels, this would be a very unfavorable ride in rough conditions