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Rave V - Designer Notes

Larry Knauer, Lead Designer of the RAVE V has provided these detail comments regarding the design which is moving into production.  If you care to comment, please do so and Larry can respond.

Rave V Sketch

“Designed for 400 lbs payload (people and equipment) basically 2-200 pound passengers.  Forward passenger/sailor is on the center of gravity and therefore does not impact sailing capability except for the weight.  Aft passenger/ sailor is designed at 200 lbs and the plan is to ballast the boat for 200 lbs in the aft seat as a minimum weight.  For passengers in the aft cockpit under 200 lbs ballast will be added to the aft cockpit to reach the 200 lbs design plan.  For passengers over 200 lbs forward weight ahead of the center of gravity must be added to keep the leverage point the same as a 200 lbs aft passenger.  The added weight of the aft passenger and the forward ballast will reduce the weight available for the forward passenger.  Ideally this will be done with forward and aft calibrated ballast water tanks to make ballasting easy for the captain to accomplish while in the water.  This is currently done for many high performance sailplane (Glider) designs.  This approach significantly simplifies the need for trimming the foils for pitch changes caused by weight distribution.

Design foiling speed to start about or below 7 knots at the design boat and passenger weights.  Design V foils to unload as the boat accelerates and lifts out of the water.  This is accomplished by the decrease in the lifting area as well as a change in foils design along the length of the foil to be optimized based on speed (Reynolds number) and lifting force out of the water.  The lowest point of the v foil is a connecting sonic tube lifting cylinder that has a diameter between 1 and 1.5 time the cord of the foil legs.  The sonic tube should have a length about 1.5 to 2 times the diameter of the tube.  The center of lift of the tube and the foil legs should be aligned but we may consider the sail forces in trading the center of lift of the tube with the foil legs to optimize the center of foiling lift with sail forces and speed variability.

The foil legs should be connected AKA arms with one leg being the same length as the AKA arm.  The foil legs should connect on the inside of the AMA on the outside legs and at the port and starboard cockpit sides.  For ease of raising and lowering the foils the out board legs should be hinged at the AMA and AKA interface and can be either forward or aft of the AKA depending on where they are needed to balance the forces.  The leg attached at the cockpit sides should have a raising and lowering slide similar to the approach used by Corsair to raise and lower the center board on the F28 R.  If the out board leg is the same length as the AKA then the slide can pivot allowing the inboard leg to be pulled up at the cockpit and no in water hinge will be required.  The connection of the sonic tube to foiling legs would not need to be a hinge (this could be traded as an option if foil depth desired for foiling is not sufficient to lift the boat clear of the water for the desired foiling speeds and force management and provide enough depth control of the foil.    The sonic tube can be the hinge point between the foils by having a tube within a tube sliding cylinder hinge.  The hinged non- sliding tube is the current baseline.  The foil legs form a triangle between the inboard and outboard legs of the foil and the AKA arm.  This allows for a much stronger and lighter total structure for the AKA as well as each leg and eliminates many of the bending loads in the AKA and the foil legs.  The location of the center of the foil lift will be driven by the location of the center of pressure on the sails. 

A third foil will be located aft of the aft cockpit  at the connection point to the cockpit and the center of the  sonic lifting tube to be as far aft as practical under the primary cockpit.  This foil and tube will also serve as the rudder and will have a swivel to allow for the foils to swing side to side similar to a rudder but because of the high force of the sonic tube much less motion is required to provide the same force to turn the boat as a typical rudder.  The location of this aft foil should be such that the loads on the foil are shared with the two primary foils to balance the forces needed to keep the boat level at the various speeds and sail forces with the trim point being a lifting force on the aft foil equal to each of the forward foils thus simplifying the foil design and manufacturing.  By maintaining a predictable center of gravity and sail force as a function of wind and boat speed this will significantly reduce the need for rudder pitch trim on the aft foil.  There will likely have to be some amount of trim adjustment in the aft foil and this can be designed into the swivel for the rudder foil attachments at each AKA.  The swivel will be designed to be a three access swivel verses instead of a two access rudder swivel.

The design object for ability to point into the wind will be a desired off wind angle of 35 degrees and a total tack angle of less than 90 degrees to be comparable to most modern mono-hull sail boats and about 5 to 10 degrees better than most modern multi-hull boats.  The design desire is to be able to foil at these closer beat angles as well.  This can only be accomplished by aligning the sail forces to the water side forces to be similar to a mono-hull boat design.  To do this the center of pressure for the sail must be outboard and leeward to the center of water pressure for the hulls and foils.  The design solution to do this is to have an A frame mast arrangement with there being two primary masts connected at the base near the forward AKA and on the AMA and the top of the Masts joined together in an A frame shape.  This design significantly reduce the bending loads on the mast and moves the center of sail force outboard pat the center of pressure of the foil water side forces.   This allows for a significantly lower weight for the mast and rigging.  Because the center of force is moved outboard and the force acting on the sail has a lifting component the sail force area can be much larger.  It is estimated that each sail can be 1.25 time larger and have the same heeling forces on the foils and AMAs.  This larger sail area and the moving to the outboard position will help the boat to foil at much lower speeds in addition to the benefits of better pointing angles.  The exact location of the mast attachment to the AMA will depend on optimizing the sail forces to the foiling forces.  There will also need to be an assessment of the rake angle forward or aft to optimize the sail forces.

It has been well known since the 1930s that an elliptical wing plan form is the highest lift o drag ratio and the half ellipse is next best.  The use of the Spitfire trailing edge half ellipse combined with the semicircle “winglet” joining the tops of the masts which eliminates the “Wing” sail tip vortices or the need to have the top of the sail wash out with twist is considerably more efficient.  The losses at the tip of a wing or top of a sail represent about 30% of the induced drag caused by the lift of the wing or sail.  The combination of the half ellipse and the “winglet” results in a substantial increase in sail area efficiency.  This should result in a 5 to 10% net sail area efficiency.  So the 320 square foot sail on the Rave V will have the effective area of 352 square feet on a conventional sail plan form.

 The masts are to be airfoil shaped design and the sail will be raised and lowered similar to any other sailboat.  A rotating bearing for each mast at the base will be used and it is desired to allow the top of the masts to twist slightly to assist in optimum sail to apparent wind angles.  The top of the mast will also have a blind pin connection similar to putting winglets or wing extensions on a modern sailplane (glider) to simplify rigging and a hinge point at the top of the semicircle mast winglets as well for storing with the mast up and AMAs folded inboard for movement on the trailer in dry storage bot yards.  This twin mast twin Main sail design eliminates the need for a Jib and results in needing only two main stays for raising and lowering the masts as well as stabilizing the masts when up in place.  These forward and aft mainstays will be adjustable to allow for changing the rake angle of the main sails.

A Simplified version that eliminates the need for a foresail is being considered and the option to sail under the twin mainsails simultaneously is being evaluated.  This approach will eliminate the need to furl the Main sails and eliminates the furling Jib.  The mast moves slightly forward to maintain the common center of pressure as the baseline design with the four sails.  This approach would be simpler to sail and reduce costs.  The trade on sail area and force distribution will determine if this simpler approach can foil at as low a speed as the baseline design.”

32 thoughts on “Rave V - Designer Notes”

  • Bill Wiselogle

    This is tremendously exciting. My family and I attended the America's Cup in San Francisco last year, and the sight of those 72-footers foiling past at 55 mph was absolutely breathtaking. To be able to foil in a small boat in comfort would be a dream come true. What's your goal price point? Thanks, and best of luck on this project!.

    Reply
  • steven mclaughlin
    steven mclaughlin December 9, 2014 at 8:09 am

    as a former rave owner: It will be very good to be able to foil upwind as this was a major disadvantage of the old rave design. I would like to see it when it is completed and on the water.

    Reply
  • Claus Dettelbacher

    Wow, flabbergasted that this project is now taking shape.

    Applaud the V foil solution and the A-rigg makes sense too.

    One question that needs to be addressed is how easy is it to launch and store the foils ON the water - which will decide how easy it will be to single handedly launch and beach the boat.
    Will there be a small second alternative rudder for sailing in shallow waters or low wind conditions with retracted foils? This would be of high importance to me to be really able to switch between an ordinary shallow-draft tri and a high speed machine for the open waters.

    I assume the foils will be molded (carbon?) and not aluminum anymore.

    Are you using the same casts for the hulls as with the old Rave? Would keep cost down I presume.

    Good Luck!

    Reply
    • Larry Knauer

      Bill, Steven and Claus
      we appreciate the early response and support plus questions and recommendations. the A frame rig and the V foil alignment allow the boat to point higher as the center of force for the sail moves slightly leeward of the V foil water center of force much like a leaning mono hull boat and unlike a typical multi hull where the opposite happens as you add force. This will make a tremendous difference in ability to point. Hobie demonstrated this benefit with the Trifoiler design that pointed pretty well but the foils were still leeward of the sail pressure but much less.
      the V foils will be hinged at the AMA and can be lowered into position either at the dock or on the water and pinned to the AKA. at this time we are looking for this to be a two position condition, either up or down. this can be accomplished easily from the front cockpit position at low speeds. we are considering an option to have variable depth adjustments but this adds complexity and cost for what appears a small benefit. sailing with foils retracted and rudder up is likely only going to happen at low speeds and light winds so the AMAs and AKA should provide sufficient lateral forces to allow the boat to sail well with foils retracted. the rudder in the raised position will provide considerable steering as it will be nearly 4 feet behind the aft bulkhead and the sides of the v foil sides at that speed and distance should provide more than enough steerage. we are looking forward to putting this to practice and demonstrating the easy ability to beach the boat and deploy and retract the foils. The rudder V foil will have a single locking pin that can be released or locked from the aft cockpit that will allow the V foil to swing up to the shallow water position.
      The V foils will be made of advanced composit materials and we are currently working with Lockheed Martin on a promising Nano carbon thermal plastic that can be molded to the desire shapes. the baseline is to use carbon fiber lay up for the V foils but if we can get the Nano carbon Thermal plastic to work as projected we can reduce the production cost and time significantly.
      keep the recommendations and questions coming.

      Reply
  • Larry Knauer

    Bill, Steven and Claus
    we appreciate the early response and support plus questions and recommendations. the A frame rig and the V foil alignment allow the boat to point higher as the center of force for the sail moves slightly leeward of the V foil water center of force much like a leaning mono hull boat and unlike a typical multi hull where the opposite happens as you add force. This will make a tremendous difference in ability to point. Hobie demonstrated this benefit with the Trifoiler design that pointed pretty well but the foils were still leeward of the sail pressure but much less.
    the V foils will be hinged at the AMA and can be lowered into position either at the dock or on the water and pinned to the WAKA. at this time we are looking for this to be a two position condition, either up or down. this can be accomplished easily from the front cockpit position at low speeds. we are considering an option to have variable depth adjustments but this adds complexity and cost for what appears a small benefit. sailing with foils retracted and rudder up is likely only going to happen at low speeds and light winds so the AMAs and WAKA should provide sufficient lateral forces to allow the boat to sail well with foils retracted. the rudder in the raised position will provide considerable steering as it will be nearly 4 feet behind the aft bulkhead and the sides of the v foil sides at that speed and distance should provide more than enough steerage. we are looking forward to putting this to practice and demonstrating the easy ability to beach the boat and deploy and retract the foils. The rudder V foil will have a single locking pin that can be released or locked from the aft cockpit that will allow the V foil to swing up to the shallow water position.
    The V foils will be made of advanced composit materials and we are currently working with Lockheed Martin on a promising Nano carbon thermal plastic that can be molded to the desire shapes. the baseline is to use carbon fiber lay up for the V foils but if we can get the Nano carbon Thermal plastic to work as projected we can reduce the production cost and time significantly.
    keep the recommendations and questions coming.

    Reply
  • Doran Oster

    I loved my old Rave. What fun! I will certainly buy a Rave V if it meets the design criterion. But, frankly, there are a few elements that I don't understand.

    1. The original Rave had a width of about 20 feet from tip to tip of the T-Foils. Even with the broad base and flaps that boat never foiled much higher than a broad reach. The centers of the V-foils on the Rave V look to be much narrower (about 8 to 10 feet apart) and windward foils have no flaps to overcome lift . It seems to me that the Rave V will not foil as high as the original Rave. What am I missing?

    2. The foils seem to retract by rotating.. It seems this can only be done when the boat is stopped or almost stopped. If you are coming into the beach, do you stop and retract the foils in deep water? If so, how do you sail in with your rudder out of the water?

    3. Is there a working prototype? If so, can I come to Ohio and try it?

    Reply
  • Larry Knauer

    Doran
    great to hear you were happy with your original Windrider Rave and we expect the Rave V to be even better.
    we are working on the detailed designs and math models with some testing of key components and expect to have the prototype ready for testing and demonstration in May of 2015.
    the width of the original Rave was a problem with pointing when you look at the force angle between the sail area and the hydrofoils the significant leeward center of pressure on the foils makes getting to a good pointing angle difficult. if you look at the Moth and Hobie Trifoiler you see they got better pointing for a foiling boat by getting the sail center of pressure closer to the hydrofoil center of pressure. in a mono hull the center of force on the sail actually is leeward of the center of hydro force on the hull and keel which allows the mono hull to point much higher. The Rave V uses the V foils and twin sail A frame to achieve this same condition and should allow much higher pointing than most non foiling multi hull boats. work done in the 1950's showed this would greatly improve pointing.
    we are designing the foils to be retracted at low speed when coming to the beach. there will be a pin on each forward foil at the Waka that will be design for release along with a lock pin on the rudder. if the speed is too high there will likely be too much force on this release pin so slowing down to beach will be the standard mode of operation. it will be a simple captured pull pin arrangement. and allow the foils to be retraced in a few seconds. we are looking to be able to pull the pins nominally at under 5 knots and a pin force under 5 pounds. we are also assessing if we want to add the complexity and weight to pull them at higher speeds in an emergency. The rudder will stay in the water but extends aft. think of how the Hobie rudder rotates to lifts out as you come to the beach. it is still pretty effective at low speed.
    Keep in mind the number one objective is "Sailing Simplified"
    keep the ideas and questions coming as they help us refine the details of the design to better suit you needs.
    Larry

    Reply
  • Doran Oster

    1. Excuse me for being dense, but is seems to me that having one sail lee of center and one sail weather of center results in an average heeling moment about the same as the original Rave.

    In any case, when you are sitting in the middle of the boat, the lee foil lift is the only thing counteracting the heeling moment of the sail, Bringing the lever arm of the foil closer to the center hull means you have to add proportionally more lifting force to the lee foil. More lift means the foil has to be deeper in the water and that means more drag.

    Something has to counteract the sail's heeling moment or the boat capsizes. It seems to me, the only way this boat will sail above a broad reach is if you have a crew sitting on the windward ama (like typical foilers) or some way of giving the windward foil negative lift.

    I'd like to be wrong. Please send a reference to the work in the '50s.

    2. Rudder: It is one thing to have a Hobie blade rudder kick up the last few feet as you come into shore, but a V-Foil kicked up is a most effective sea anchor. It seems to me that it will be almost impossible to beach this boat if the wind is blowing off shore.

    It is not my intention to rain on anybody's creativity. These comments are only intended to offer a fresh perspective and to improve the final version of the boat.

    -d

    Reply
  • Larry Knauer

    Let it rain as we all learn from being open to discussing pros and cons of various design concepts.
    I would encourage you to draw a force diagram of all the forces including the sails as well as the foils. the advantages of the A frame as well as the V foils combine to reduce the pitching moments of the boat and moves the center of forces such that allows for higher pointing. if you do the force diagram you find the Aframe sail is providing a downward force on the windward side and a lifting force on the leeward side in addition to the forces offered by the V foils that as you attempt to raise windward foil there is a reduced lift and the leeward foil increases in lift. all of these forces act as part of the self righting and leveling design. the use of the sonic lifting tube at the bottom of the foils eliminate the short coming of a pure V foil form a cavitation and lower lift to drag ratio as the foil lifts out of the water. this design is derived from scramjet missile designs for high Reynolds number lifting bodies.
    The easiest reference to find on the 1951 work by H. Barkla can be found in the book by CA Marchaj titled "Aero-Hydrodynamics of Sailing" copy right 1979. more recent work on Land Yacht testing and development including some wind tunnel data provides additional insight into the A fame design forces. By them selves you can easily show that the A frame or V foil are not optimum but when combined and used with the sonic lifting tube the forces work to the advantage of the complete system of forces.
    The only time you are going to lift the rudder is when you are beaching or in an emergency and in both cases a lower efficiency (higher drag) rudder will act in favor of what the captain needs to do to either beach the boat or avoid an emergency. The added drag with the rudder retracted is a benefit not a hindrance.
    I look forward to getting you out on the Rave V and demonstrating what this combination of designs can do to simplify sailing and improve foiling at lower speed as well as allowing for higher foiling speeds.
    I encourage dialog and looking at what has worked for other foiling boats, ice boats and land yachts. Keep in mind that wind powered vehicles design to operate at multiples greater than wind speed need different design considerations than historic mono hull or multi hull boats.
    it is exciting to be part of the revolution happening in the foiling boat industry. With the number of boats in development and internet access to the data available there could not be a more exciting time to be bringing the Rave V to the market.
    Larry

    Reply
    • Doran Oster

      Hi Larry,

      Thanks for the reference and the opportunity to expand the discussion. Let me be sure I understand your explanation: Looking at the front view diagram above, the heeling moment force could be represented by the mast height, and the distance from the mast step to the ama could represent the force that counter-acts heeling. Do I have the geometry right? If so, my experience with the original Rave makes me worry your design will still blow over before it foils much above a broad reach.

      You can test this a simple land-based test bed . First build the fully developed prototype mast and sails, but before you spend money on the hulls and foils, mount the rig a rough frame that represents the boat. (I know a guy with some PT 2 x 8s that can do it in an afternoon. Hollis, you got your ears on?) You can use saw horses to represent the foils. Now see what happens when you point the test jig above a reach and trim the sails in a stiff breeze. If the test-jig resists capsizing, I'm ready to contribute. If it capsizes, consider the following:

      1. Why not let the skipper control the rudder with a tiller so he can get out of the cockpit and adjust his weight? . This eliminates your water ballast too.

      2. Make an alternate design that uses T-foils placed outboard of the amas. The skipper sits in the cockpit to control the rudder with foot controls and the flaps with a joystick. I have already demonstrated with my original RAVE that hand-controls are easy to use, they beat wands around the course, and there is an easy way to add automatic incidence control to the T-foils.

      Best regards,
      Doran

      Reply
      • Sebastian Gara
        Sebastian Gara August 6, 2015 at 8:16 am

        Like the idea of skipper controling outside cockpit and be involved with adjusting ballast since Ballast requirement would change as change points of sail. Love this discussion

        Reply
  • luc de keyser

    please explain more in detail the structure and physics of the sonic lifting tube. Thank you.

    Reply
    • Larry Knauer

      Luc de Keyser
      I apologize for the late reply, it seems we lost your and a couple other emails in the spam filter.
      the structure of the tube is similar to some circular tube lifting bodies tested by NASA and others for supersonic and hypersonic lifting bodies and engine inlet configurations. data from those test indicate that a tube shape with an length to diameter of less than 2 has a better lift to drag ratio 50% greater than an equivalent rectangular tapered airfoil shape. For large aircraft this would be very interesting except that the size of the tube would be so large that the structure to build such a tube would be very difficult. For operating in the water the tube generates better lift per wetted area than a fixed wing shape. The objective of the sonic tube is to provide a certain percentage of the lift and act as a better interface at the apex of the V foil acting as a winglet. Several airfoils with tube type winglets have been tested by NASA and others that show this is a viable approach. the higher lift per unit area in water makes this even better to use the sonic tube as a lifting and winglet system combined with the V Foils.

      Reply
  • Thom Davis

    It is certainly an interesting design. Hope it works. Personally, something like this would not interest me. I want to sail, not spend a couple hours getting ready to sail and another couple of hours putting the toy away. Plus, I sail in 15-25 kts wind. Don't see much ability to depower when needed.

    Reply
    • Larry Knauer

      Thom
      I apologize for the slow response to your input. It seems we lost several emails in the spam filter.
      The design we are working on is specifically addressing the difficulty in assembling the original Rave V. we are using the design requirement to be able to get from your driveway to being sailing nearly as easy as the Windrider W17. This design solves the issues with the original Rave as well as those that other foiling boats had in getting from the driveway to the water. As the owner of a Corsair F28R I expect this Rave V to be easier to go from the trailer to the water than my Corsair.
      We have been looking at work by people like Tom Speer and his A frame Land yacht work to understand the benefits of variable control for both main sails to control the power levels as speeds increase. these techniques and capabilities should allow for better power control and boat stability. the boat will be foiling out of the water about 2feet at the higher speeds and wind velocities and should allow the boat to handle the chop better than prior foiling boats. we are using a boom design with the ability to reef one eye down for extremely high wind conditions but the 15 to 25 knots should not be an issue unless the chop has a wave length the couples poorly with the foil separation. No boat can do it all and we are focused on a boat that foils easy and is safe to operate in foiling conditions by sailors of all levels.

      Reply
  • Hollis Caffee

    I find your concepts both fascinating and confusing. I write as a former Rave owner and a former Moth Bladerider owner. The Rave was a fun boat on a beam reach with 15 knots of wind and a real dog in anything else. It was too heavy and a pain to assemble from trailer to beach. The other problem with the Rave which looks like you may repeat is that there was no way to take advantage of crew weight to work against heeling moment. If it could have been steered from the ama rather than depending on foil lift (both positive and negative) there would have much less drag and it might have been able to keep up with the Optis on the upwind leg. The Moth was and is a major balancing act and learning to ride a unicycle was easier than learning to sail the Moth. Also, I was really tired of wading up to my armpits to start off and we have very cold water and rocky beaches in Maine. I found myself dreaming of putting two Moths together with a big cross beam but that still would not have solved to problem of the non retracting foils. You might want to get input from Mike McGarry and Tom Hamen. They were very involved in the design of the original Rave and now that Sam Bradfield is gone, probably the most experienced in the field. Also, you should really listen carefully to Doran as I have known him for years and he is one REALLY smart dude. Like Doran, I would be willing to go to Ohio to see how this thing works. Maybe then I would understand it. Besides, your water probably melts before ours does.

    Reply
    • Larry Knauer

      Hollis
      I apologize for the slow reply to your note. For some reason your email got trapped in the spam filter.
      I hope you got most of your questions answered in my prior responses to Doran and yes we are very interested in his as well as others critical comments to the basic design features. sailing Corsairs and Windrider 17s in Denver and on Lake Erie I fully understand the desire to not have to wade out in frigid water to launch. We are working to make this as easy to launch as a Windrider 17 and be able to load and unload at the beach staying as dray as you can with that boat. we do have to have foils and rudders that raise up and are easily locked down after leaving the beach.
      the reason we want the boat stability is to allow sailors of all physical abilities to foil the boat even if they are not able to hike out. the combination of the A frame sail and he V foils allows us to be more creative with the sail and foil forces that will give the ability to sail closer to the wind but not give up too much speed. there will still be a better speed point further off the wind and depending on course and winds you will have to pick the best tack headings just like any other multi hull boat. we are looking to lower the initial foiling speed and will likely loss a little high end speed do to the slightly higher drag configuration but we still believe we will exceed 30 knots. this combination should open up the "fun" factor at about 8 knots.
      we appreciate all the great feedback and comments we are getting from the foiling community and we tweaking the designs to accommodate those lessons learned. My 30 plus years in Aerospace thought me long ago that I can not possibly know it all and there is a wealth of data from others available to guide us on this path.
      Larry

      Reply
  • Doug Lord

    Larry, what is your projected weight for the boat plus rig minus crew?
    Did you look at using a rudder T-foil in a cassette to allow retraction-seems it would be much lighter and it is a well proven solution on multihull and monohull foilers.
    I am concerned that you don't have enough RM-if I were you I would look at that very very carefully-which I'm sure you have but it just doesn't seem right. I hope I'm wrong..... Doug Lord

    Reply
    • Larry Knauer

      Doug
      I apologize for the slow reply, it seems we lost some emails in the spam filter.
      We have a design weight target o 300 pounds for the boat and all it rigging. we used the A frame mast and V foil design to help significantly stiffen the boat and get rid of the high bending loads that is allowing the structural weight to be reduces. we are current looking at about 308 pounds and working to get under the 300 target. we are looking to have a payload and crew weight of 400 pound for a total sailing weight of 700 pounds.
      we are keeping the option of an inverted T foil rudder open as an option as it does have some benefits for raising and lowering. the key is the forward pitch stability in that you want the rear foil putting a significant nose down force if the forward foils pitch to high. always want the more nose down moment.
      yes getting the right forces aligned for the proper RM is a key design feature and needs to consider potential gust loads in addition the basic static loads. those detailed analysis are being looked at and final v foil angles and percent of lifting for from the foil legs verse the sonic tube are being traded for the final design solution. Analysis and testing are being done at The University of New Orleans Marine Arch and Eng school. the use of the A fame and V foils does significantly change the load paths and moment arms and it is not a simple combination of loads but does show to be much more stable in a narrower foot print that a single center mounted mast.
      all these are good questions and all help us to be sure we are not missing important design consideration.
      keeping in mind we are not looking for the fastest foiling boat but are looking for a boat with great performance that is safe to sail/foil by all levels and abilities of sailors. we are sticking with the Windrider mission of "Sailing Simplified" with the Rave V to be Foiling Simplified.
      Larry

      Reply
  • irv mandelberg

    Ballpark price ?

    Reply
    • Larry Knauer

      Irv
      I apologize for being so slow to reply. for some reason several emails got lost in the spam filter.
      the best place to see what the pricing and fund raising data are is to go to:
      http://www.fundable.com/windrider
      or to contact dean@windrider.com
      look forward to hearing back from you.
      Larry

      Reply
  • Larry Knauer

    Doran
    thank you for you time and consideration. We are completing the models and closing the equations to demonstrate the design. Students and the Marine Architecture and Engineering school at the University of New Orleans will be working to provide the final analysis. The static demonstration you suggest might provide some insight but without the dynamic representation of the A frame sails and V Foils automatically adjusting for lift depending on sped and depth of the foils could lead to the wrong conclusion. Representing the distributed sail forces normal to the mast can not be represented as you suggest nor can the variable lift of the foils depending on speed and depth be represented by saw horses.
    The basic idea of the Rave V is to have a "sailing simplified" foiling boat which is what lead to the idea of a ballast tan similar to the ballasting done in modern gliders to minimize the trim requirements. I own and fly an ASH 25 Mi and use both front seat ballast as well as tail ballast to optimize the CG for best performance and to stay within the required center of gravity. the Rave V is a Glider on Water so it is very logical to use that technology for this application as well. We want to be able to have captians with physical disabilities that are not able to hick-out and counter balance the boat while foiling. The Rave V will easily accomidat the more adventurious that want to hick-out and use a tiller. the rudder design can easily be adapted to add a tiller for those. there will likely be a pitch problem though if you get too much weight out of the rear of the boat as the rear foils/rudder are designed to lift the 200 pout captain in the aft cockpit. if that weight is not there the rear foils will likely lift the stern of the boat too high and cause the forward foils to dig in. to accommodate changes in center of gravity to that extent would require adding trim adjustment to at least the rudder an possibly the forward foils. all this can be done but goes against the basic principles of "sailing simplified"
    we are building math models and physical models to validate the design principles.
    We look forward to your order when we prove to you that the boat is not going to "flop on its side".
    Larry

    Reply
  • Doran Oster

    Good luck, Larry. I look forward to sailing the prototype. If it works as advertised, I'll buy one.
    -d

    Reply
  • Larry Knauer

    Doran
    Look forward to getting you out on the prototype and demonstrating what this remarkable boat will do.
    thank you for your questions and feedback as it helps us discuss key points with everyone. As well as helps in refining our design to be the best it can be.
    Larry

    Reply
  • Doug Lord

    Thanks, Larry and best of luck!
    Doug
    PS-Merry Christmas and Happy New Year!

    Reply
  • Erwin

    Great that a new Rave is in development. The use of the sonic tube sounds promising. However I do share Doran's concern regarding heeling momentum. With the original Rave one has to adjust the windward foil flap fully upwards in high speed runs to create lots of negative lift, thus preventing the boat to heel too much which cannot be overcome by the lift of the leeward foil. In this new design the pivoting points of the foils are pretty close to one another. There is a reason why all small foiling multihulls using v shaped foils thus far require the crew to hike or trapeze out to keep the boat flat.
    One other question; is the main hull like a sit on top design and self bailing and so it will not fill with water? That was a problem in the original Rave when sailing in choppy conditions when one would spend quite some time pumping the water our. With the new design weight balance is even more important so having 100 or 200 pounds of water sloshing around in the main hull would be a problem.
    Good luck with further development and I look forward to the test runs this summer.

    Reply
  • Larry Knauer

    Erwin
    thank you for your interest and recommendations. some recent work by Tom Speer and the foiling A Cat wok he presented at TFW conference last July shows some interesting results discovered by the New Zealand team. showing that the J or in the A cat cast the C foils produce a negative lift on the windward side when the leeway is taken into account. the V foil offers this same benefit and combined with the A frame sailing rig there is a nature anti heeling moment. Unlike T foils and conventional single mast configurations that do not benefit from these down forces as I indicated to Doran one needs to lay out the full force diagram to see the full impacts. this is a 10 equation calculation that the students at UNO are working on. One item we have noticed is we may not have sufficient loads on the aft foil and we are looking to increase the aft down force as well as likely reducing the lifting force of the aft Rudder and foils. it is possible we might go with a Rudder and sonic tube combination and eliminate the V foil aft as the loads are just to small. these trades and calculations are in work to finalize the location of the CG and the position of the forward foil as well as the shape of the aft foil.
    as we listened to comments Like Doran's on the ruder and beaching conditions there would be added benefits to the rudder sonic tube combination but would likely cause some aft trim to be added. all this is part of the ongoing analysis. plan to get foils and sonic tubes into the UNO water table early spring.
    the trade of a sit on top style deck may come into play or a better means to reduce/ get ride of water employed. the desire for this boat to be great for sailors with physical disabilities as well as wanting to sail in colder climates tend to take us away from the sit on top and get wet other foiling boats are using. all are thing to consider. we appreciate the comments and recommendations, some form of self bailing would be advantageous.
    Larry

    Reply
  • Gordon Moore

    Great and inspirational design !
    Anxious to see the first up and running and take the lead back from the Weta Trimaran !

    Reply
  • todd bogatay

    This is a truly fascinating project! I'd love to try one and if it works buy one. Will it be tested in New Orleans? I live in SE Arizona and dream of sailing in the Sea of Cortez.

    Reply
  • Tony Watermann

    Very impressive if it goes as well as hoped.

    I have designed similar foils that fit my small beach cat and work very well.

    Lots of comments on sail forces etc etc.

    Not as big an issue as many imagine, my foils are closer together and I simply power the sail up accordingly.

    You will soon know if you are overpowering and simply correct. One thing different to the theory and sailing models is the actuality of sailing this and feeling what it does.

    Mine is very forgiving due to the foil design and dampening effect on forces.

    Please email me testing video, very interested in this as it almost mirrors what I have designed and fitted to my small 4.4m beach cat.

    Reply
  • Doran Oster

    So? When do I get a ride?

    Reply
  • Larry Knauer

    so far so good on the testing. still making little tweaks to get fully foiling but it is going well. the A frame rig is working slightly better than thought in the original analysis and the boat points incredibly well in light winds. at least 15 degrees higher than the W17 when we were sailing side by side. I am looking forward t getting out with a few mono hulls and seeing the comparison in light wind. I thing we will be as good as most mono hulls in pointing up wind. going to be fun to see how close we can point once we are fully foil borne. as we clean up the mast head and go from the "heavy weight" prototype mast head to production mast head and clean up the aerodynamics should get even better. We made a few compromises in the prototype foil build to speed up the build that when we go to production will improve the light off speed and reduce drag considerably. it is amazing how forgiving the design is and ability to perform with less than optimal foil and sonic tube construction. show we will be significantly damage tolerant the rudder tube had to be increased back to the original analysis size and it is performing well. the lifting tubes at the foil apex are showing good results at the smaller design size. we were able to swap the rudder tube in 12 hours with and over night cure. amazing simple effort. the narrow rudder is working very well and the sliding ability to raise and lower it allows for easy trailing and beaching. we are meeting or exceeding all the design objectives so far in the test completed and look forward to getting last final tweaks done so the boat becomes fully foiling. more to come after we get the sails back from being re-cut to reduce the sail area and improve the ability to rake the mast a bit further.
    Roberts testing in Sarasota is showing great results.

    Reply
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