Interesting product. Who is going to be the guinea pig?
The new advertiser on OSO with Roca Speed Rails is selling one of the important innovations on the BatBoat. Ocke Mannerfelt who invented the BatBoat also invented speed rails. They make a huge difference for a small investment.
It would be great to hear what difference it makes on a boat without the other innovations on my boat.
Check out the Baja section, we have been talking about them. It seems the main downfall is how to keep them on.
Last week I put in an inquiry, but they are/were closed for turkey day. I expect to hear back next week. Did notice that they are not for heavy boats, so I don't know if I will get any option to try them.
I see London, I see France...
I have tried them....
I have a Phantom 25 Offshore hull with a Promax 300 outboard. Its bow heavy and need lots of positive trim. It runs fairly quick - 76-78 mph at 6100-6200 rpms spinning a blueprinted Tempest 26. Gearratio 1:1.75. The boat weights approx. 2.500 pounds incl driver and 10 gallons of fuel.
I mounted four speedrails according to the book. Two in front and two 75% towards the stern. This should create bowlift. We used Sikaflex and the speedrails turned to be almost impossible to take off.
It proved to be a great miss. The boat ran higher, but flatter. The top speed decreased approx. 3 mph. Cruise speed increased 1 mph. The boat runs 53 mph at 4.000 rpms. Now it ran 54 mph at 4.000 rpms. It did turn fairly well, but it turned much more precise without.
I pulled off the two speedrails towards the stern keeping the two in front. Top speed increased somewhat, but still 2 mph lower than without. The boat started to porpoise as well at 55 mph - 60 mph.
The speedrails may work on heavier hulls at lower speeds. For me they were a pain in the ****.
I rather advise the following: a) get rid of extra weight; b) rebalance the boat; c) blueprint the bottom; d) play with propheight / x dimension; e) play with props; or buy a Skater...
I installed them on my Donzi Z-25. You use screws and 5200 sealant and they are not going anywhere. I picked up about 3 MPH. You have to read the directions carefully, so you get them in the right spot. I have since sold the boat. It was a cheap speed increase.
I don't know about Ocke Mannerfelt inventing them...Maybe he got a patent but they have been in use in some form or another for many years. Drag boats have used them PROP tour boats have used them for years and years. They can get a boat very loose very quickly. I'm sure there are others who know alot more about them.
Ocke says he invented them on his website and holds the patent.
By: Thomas Berglund
The design motivation for us have been to design a craft that could combine outstanding performance with enviromental care and marine safety.
To accomplish this we had to design a boat with extremely low drag compared to other crafts. This means reducing friction, both below and above the waterline.
"The proportion of air beneath the boat is extremely critical. You must be friends with air, you do not want to struggle together. A dolphin has a muscle engine of about 4 hp and can go 50 mph. But if we built a dolphin, we would have to give it approximately a 70 hp engine to go the same speed. So there is a lot we can learn from nature about reducing friction."
This is the craft of the future, which will be less powerful, use less fuel, produce lower emissions and be safer, all while operating at the same speed.
Here we will briefly explain how this type of boat works.
Probably the most outstanding and obvious feature on the boat are the wings. They work by the phenomenon of ground effect, air forced downward by the wing rebounds back against it, after it hits the water. What happens when "flying" close to the surface is a reduction in the downwash of the wing. Downwash is caused by the turbulence at the tips of the wings.
This produces transverse stability at speed, thereby conteract any inclination to chine walk. The wings help stabilise the boat when running in rough water and maintain the angle of attack even when the boat is airborn. The boat does not land on its side and when returning to the water the wings compress the air underneath, softening the landing. If the angle of attack increases to much, the wings will stall. This forces the bow down, preventing a blowover.
Do not the wings create drag? Yes they do, however at this relatively low speed is it of little importance.
The bottom features two transverse steps. The first step set the angle of attack and guides the hull. The second step sets up the waterflow for the last part of the hull which carries the load.
The goal is to minimise wetted area and planing resistance by causing the water not to touch the forward portion of the surface behind the step.
The steps suck in air and add it to the water under the boat, produce air bubbles like ball bearings that will provide a faster surface for the boat to run on. Planing over a bed of foaming water means that friction is reduced.
Speed Rail TM
Speed Rail is another product invented by us. It is a 3 foot long aluminium profil that fits the running strakes of the boat (of any boat actually).
Whereas normal spray rails deflects water horizontally away from the boat, creating friction and drag, the Speed Rail deflects water downward to further enchance lift, speed and fuel economy.
It also helps stability in both tracking and turning. The device is used on many European offshore raceboats.
Speed Rail have won two awards, in Sweden the "Golden Wheel" and in USA "Best accessories" at IMTEC, Chicago boatshow.
Speed Rail is patented.
As I said he may have received a patent or TM (trade mark) on the use of "Speed Rails" but they have been used for years. Well before November of 1996 racers were putting aluminum flat bar on their hulls to deflect water 1/4" ,1/8" lip made for more lift. If someone takes the time and has the inclination to apply for a patent or a trade mark on something that has not been patented or TM before they are often granted one. I would not be surprized to find the old Switzer wings had screw holes along the strakes.
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