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      Abbreviated rules   07/28/2017

      Underdawg did an excellent job of explaining the rules.  Here's the simplified version: Don't insinuate Pedo.  Warning and or timeout for a first offense.  PermaFlick for any subsequent offenses Don't out members.  See above for penalties.  Caveat:  if you have ever used your own real name or personal information here on the forums since, like, ever - it doesn't count and you are fair game. If you see spam posts, report it to the mods.  We do not hang out in every thread 24/7 If you see any of the above, report it to the mods by hitting the Report button in the offending post.   We do not take action for foul language, off-subject content, or abusive behavior unless it escalates to persistent stalking.  There may be times that we might warn someone or flick someone for something particularly egregious.  There is no standard, we will know it when we see it.  If you continually report things that do not fall into rules #1 or 2 above, you may very well get a timeout yourself for annoying the Mods with repeated whining.  Use your best judgement. Warnings, timeouts, suspensions and flicks are arbitrary and capricious.  Deal with it.  Welcome to anarchy.   If you are a newbie, there are unwritten rules to adhere to.  They will be explained to you soon enough.  


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About RickW

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    High performance boats
  1. R2AK 2018

    The prop strut is faired below the waterline. After I took this video I faired the strut above the waterline. It now maintains attached flow. In its original form it did not ventilate until 17kph; about 9kts and that was due to the flow separation trench reaching the blade tip. The curved shaft becomes less attractive as the boat gets bigger. It is possible to just stick a shaft out the back set at the right angle to stay submerged as the prop self-aligns to flow so is self-supporting; not cantilevered unless at rest. The idea of the curved shaft is to get the prop operating in a plane perpendicular to water flow. It is possible to operate without a strut but that puts compressive load into the shaft, which increases the cyclic stress because it takes up an elliptical arc rather than a circular arc. The forces on the prop to align are relatively high. If it is forced out of alignment like on a rigid inclined shaft, the blade loading is unbalanced and vibration gets bad at speed. The shaft works in its elastic range so there are no losses in maintaining the curve. This video shows a strutless prop. You need to look closely to see the blades flashing as they turn: https://1drv.ms/v/s!Aq1iAj8Yo7jNgnLsvkqvBKgUiFVk Prop is most visible in the port turn where it hangs out about 400mm from the side of the hull. After considering various options for curved shafts, I and others have convinced Russell Brown that a two belt drive with a lifting leg is the best option for him. That makes sense for heavy pedal boats. He will retain the sideways facing.
  2. R2AK 2018

    I have doubts that you can make a flapping system more reliable than a prop. The only parts my drive has in common with a bike is the crank arms and pedals. The T10 belts are made for high efficiency industrial drives. The gearboxes I use are purpose made for sprint loads (I am unable to supply these separately right now but there are Mitrpak boxes available that are OK). The shafts are very high strength stainless steel. A 2.4m length can almost be forced into a circle within its elastic range. The prop blades fold. I have run over 100mm deep gravel beds at 12kph without damaging a prop. The prop blade hits, that forces blades to fold and forces the strut outward and upward. The prop drag causes the boat to yaw sideways and the prop gets dragged over the shallows. With a log it just bounces over. The folding prop was developed for the Murray Marathon. That is a 404km river race. The river is full of shallows, weeds, leaf litter and logs. In a typical race the prop will hit hard maybe 4 times. There has never been damage to the folding prop. It is all mounted compliantly so just bounces over things. This clip shows how the prop can be inspected by curving the shaft upward: A typical outboard with survive a ground and I have even seen minimal damage from hitting a floating log at high speed. So I believe a compliant system that gives when struck works quire well. There are many rudder systems designed to give under a collision or grounding.
  3. R2AK 2018

    The short chord of the my best blade increased the effective working arc. That was another reason the high aspect blade was more efficient. Generally material strength limits the aspect of a foil. That is why carbon is so popular for foils. Draft is sometimes a limiting factor but on high performance boats there are usually ways to lift the foils to reduce draft. Also on high performance boats cavitation can be an issue. That becomes a limiting factor for the foil thickness and allowable range for AoA.
  4. R2AK 2018

    In my view a robust design criteria for sailing boat rudders is to consider the peak force at design maximum speed and allow a 3X safety factor. Once you design to that you realise it is a serious structure on any size boat. Hence setting up rudders on a proa is challenging enough without trying to make them also produce thrust. With that word of warning I will give you an idea of what I got to work best. It is best explained with reference to the attached photo. The blade shown was not the best I made but the AoA control was the same as shown here. In principle the aim is to have the unloaded bladed always stay in line with flow. If the crank stops the blade will self-align and the boat just coasts. So there is a parallelogram linkage arm that keeps the blade essentially flat at all angles of sweep if there is no load on the blade. The crank rod joined the main swing arm midpoint and provided a stroke of 1ft on the middle so the blade swept through 2ft. This blade is 800 wide and was sweeping through 600 so quite a large area. It was operated around 60rpm for 8kph. Much above that caused my lightweight boat to bounce. There is a torque rod that acts as the blade pivot running through the back end of the vertical control arm. The control arm is pivoted off the very back of the swing arm. The torque rod is connected to the blade at the extremity of the width. When the blade is swept, the torque rod limits the amount of rotation of the blade relative to the control arm so that creates the angle of attack. If the boat is moving slow but the crank is moving fast then the blade ends up almost vertical through the middle of the stroke. The most efficient arrangement was this drive geometry with a blade 1.2m wide and 130mm chord. The high aspect blade just reduces the induced drag so the blade efficiency is higher. The blades had foam inside so they were close to neutral buoyancy and the crank was balanced as best I could achieve. I also had an adjustable spring to balance the weight of the swing arm and tie bar. The cyclic pedal motion was a little jerky but better than a Hobie drive. As you can see this was basic engineering with nothing more complex than welding. The pictured blade gave good acceleration and the wide blade gave tremendous acceleration. I could get the boat to speed in one rev of the crank. It is likely that you could produce reasonably efficient thrust from a turning rudder blade that has a torque controlled flap on its trailing edge. The torque could be controlled by rubber blocks. That would be simpler than the system I have for use on an existing blade such as a rudder. For example, I know a rubber flap in a yoke that pivots at the front being swept up and down generates reasonable thrust. Hobbies do not have a particularly sophisticated control on the AoA; essentially just rubber flexing. My goal was to get as efficient as I could. Ultimately it was the whole boat dynamics that limited my efficiency. High aspect blades with significant swept area can get up near 90% efficiency. High aspect foils provide high efficiency. The aqua skipper gives you an idea of what an efficient foil looks like: If you do a few half squats as fast as you can with feet lifting off the ground you get a good idea of how much power it takes to drive these things. This size blade can produce required lift at around 12-14kph to keep an average person foilborne. It equates to around 250W. That is well above what is sustainable by most adult males. If you stop pumping you sink and it cannot be started from deep water. Most people use them about three times before they are over them; meaning they get fed up with swimming back to shore dragging the thing when mostly submerged.
  5. R2AK 2018

    Fairing that prevents flow separation ahead of the prop is the important consideration. The thinner it is the easier it is fair. Although at the typical low speeds that human power achieves on a heavy boat the drag of any fairing will be small compared with the hull.
  6. R2AK 2018

    A well set up belt will cost 1 to 2W at cadence of 75rpm. A gearbox with seals 2 to 3W. Two belts up to 4W. Two gearboxes up to 6W. The gearboxes will be higher losses when new due to higher seal drag. These values are for things in good condition. A feature of belt drives is that they are indeed maintenance free. Chains rapidly deteriorate unless operated in an oil bath and churning oil robs power. A bike chain will lose 1 to 2W to start with and gets worse as the load goes up because the links drag on the chainring and sprocket when the crankshaft and chainring flexes. The mechanical transmission losses on a properly set up belt drive are trivial compared with the prop losses. In these slow speed applications about 25% of the power to the prop is wasted. Even with an ideal prop on a very easily driven hull it is not easy to get better than 85% efficiency from the prop. The most efficient prop I have designed is 370 diameter with 400 pitch made in carbon. Blades have 20mm chord and are 2mm thick over most of their length. This prop will absorb around 1kW within its allowable thrust on a boat that moves easily. It was purpose designed for a big boy using a sprint boat that is being built now. Only three of these props have been made.
  7. R2AK 2018

    The small electric thrusters have low electrical efficiency; in range 60 to 70% has they are high resistance motors. I figure they do this to enable them to handle bollard pull conditions without burning out. A generator is not going to have efficiency much above 80%. So with an electrical transmission like this you are burning up 50% of your input power. If you selected you own motor/generator with care you might get as high as 85% each or 72% overall. If you are concerned about the size of mechanical pedal systems then an alternative to belts is a pull wire. The attached photo shows the Loomis clutch drive system in rowing mode. The pull wire is only 1/16" thick and there is a rubber band to enable the return stroke. Care has to be taken in running the pull wire over rollers that keep the wire captive so it stays in place when not in use. This link shows the same boat in pedal mode. That drive requires two capstans but the thrust is more even. This system only requires a short tensioner to avoid slack wire. https://1drv.ms/v/s!Aq1iAj8Yo7jNgnEkIdADHaeRrjVR The attached photo shows the same boat in rowing mode. That drive only requires a single capstan and a return band that rewinds the wire. Rowing with a sliding seat is not quite as biomechanically efficient as cycling but it engages the big leg muscles as well as arm and back so has higher power potential. Rowing without a sliding seat is not much different to paddling from a power perspective but with this pull wire there is no blade skill required; just brute force. For a larger boat it is much more efficient than rowing or paddling providing the prop is selected to suit the boat. Earlier in the thread there is a close up photo of the dual capstans on the swing arm prop drive.
  8. R2AK 2018

    In the context of the original question, the boat is a given. So weight is given. Also the weight of a pedal drive system is not really a concern for R2AK boats as it is a small proportion of the overall weight. Drive weight is likely a greater concern for ease of stowing if that is a requirement. The point is that POWER matters and is the key measure of human capacity. The drive train should be chosen in combination with the selected prop to maximise the boat speed for a given human capacity. With a set gear ratio there could be times when the human becomes torque constrained in the circumstances of pushing a head wind. That requires reduced power input to avoid muscle fatigue. In the circumstances of motor-sailing it is possible to become rev limited. I cannot keep up with the pedals on my standard drive system above 11kts when motor-sailing.
  9. R2AK 2018

    The moulded carbon seats with some padding are light and quite comfortable. I can make a carbon-foam sandwich seat that weighs 300g without padding. The Greenspeed nylon mesh seats are comfortable but heavy by comparison. It is not uncommon to include a head rest in the seat. The shoulder angle is usually around 80 degrees and the neck/head rest vertical. This link shows the Trisled seat with headrest: http://trisled.com.au/hpv/gizmo/ This shows Trisled seat items with prices: http://trisled.com.au/product-category/seats-seat-pads/ A few pedal boats in the USA have seats from Oceancycle in the UK: http://oceancycle.co.uk/products,seatsAndAccessories The OC fibreglass seat is good value in the UK but mail cost makes it less attractive. It is possible to make a form fitting seat starting with some wet glass between plastic sheets moulded into a bean bag that you sit in till the epoxy sets. Body heat gets the curing going in 30 minutes or so. The body mould can be reinforced and faired to be used as a mould for a foam sandwich seat. 3mm thick marine foam can have darts cut to enable moulding to the shape then heat applied to get it to follow the dish shape. The layup needs to be sand bagged or vacuum based to get it to conform well to the mould. The backside will be as neat as the finish on the mould and the topside will have some covering so finish is not of concern. The Trisled developable panel shape works quite well. The right general shape for your body size with a little padding is as good as a perfectly moulded shell. Sitting low on a boat that has high initial stability but low ultimate stability is not particularly good. If a stabiliser gets fully immersed the boat will roll so there is merit in being able to influence the list from wind for example with elevated weight moving side-to-side. I feel prone in a highly reclined position; more or less at the mercy of the waves and wind. My seat back is around 30 degrees. I know from experience that a seat back angle of 60 degrees is terrible for the knees. Of course there is some relationship between the height of the seat and height of the crank
  10. R2AK 2018

    The key performance factor is POWER. With a prop and pedal drive there are primarily two factors affecting the relationship between torque and power; the prop pitch and the gear ratio between crank and prop shaft. The prop diameter also has a slight bearing on the relationship but is typically very small influence as any slip translates directly to reduced efficiency. On my boats the prop slip is around 2% in calm conditions and could be 3% in heavy going. For endurance racing the key factor for knee load is the closing angle between thigh and torso. That is affected by crank length, seat back angle and distance from seat to crank. Ideally the angle does not get below 100 degrees. The linked photo shows one of the best endurance riders in the world on his round Australia record bike: He did the 15,000km unassisted in under 50 days - best day 417km. You can see his full leg stretch is almost straight. The back angle is around 20 degrees and his closing angle is a little under 100 degrees. It is then a matter of using the gears to avoid working muscles anaerobically. Indeed, the speed up a long steep hill might be slower than walking. For example, pushing 100kg up a 10% grade at 10kph translates to 980N at 0.28m/s or 280W without accounting for losses. That requires some level of training as well as reasonable fitness. A trained rider needs to spin around 100rpm to achieve that output within muscle aerobic output. Matt Johnson can hold around 330W for 1 hour spinning around 85rpm but I think that is hard on muscles unless he is in top condition. For high power sprints the thigh-torso closing angle might be set below 80 degrees. That is much harder on the knees but is only short duration. When I sprint I slide forward on the seat and use my arms to lock me in place. The attached photo shows the difference in back angle between Greg K and his wife. Helen is not an experienced recumbent rider and preferred a more upright position. A low back angle also increases the weight carried on the back rather than the rump so the rump muscles get better blood flow and obviously lowers windage for forward facing pedaler. The gearing should be such that the pedals feel almost awkwardly light at the sustainable power for the first 20 minutes. For power output determination I recommend spending no less than 1 hour on a recumbent exercise machine to find the preferred cadence and power output at sustainable heart rate. If there is any muscle fatigue after that time then the cadence is too low. If there is breathlessness then power output and heart rate are above sustainable. I always use a heart rate monitor with a $100 cycling GPS to monitor speed relative to HR. This is a good measure of overall performance - per attached chart. In calm conditions I can detect a single strand of weed by the difference between my expected speed and actual. I can see the effect of wind/waves using speed difference upwind and downwind. The unit also provides cadence and I can use that to determine the impact of current. That is important in rivers and tidal areas. With regard to knee issues, most novice recumbent riders have the back angle far steeper than ideal for endurance pedalling. I prefer around 30 degrees so I can use my torso to control roll. There are other factors with knee in-line alignment that can cause knee pain. I have to pay attention to my left knee wandering outward from the in-line position.
  11. R2AK 2018

    The blades on my folding prop are 25mm wide, 145mm exposed length (wetted area 0.007sq.m) and fold back to 45 degrees when not providing propulsion. The blades have less drag than in-line Hobie flappers when coasting, similar static thrust and more efficient once moving. Plus I can alter the pitch to match the disc loading to the boat.
  12. R2AK 2018

    Not sure what you are referring to with "his" rudder foils. Warren is spinning a prop as I am in my boat using roller clutches - see photo of Warren's propulsion leg. I used a curved shaft to avoid submerging my capstan and roller clutches. I have seen a wide range of flapping systems. One example: I have set up opposing vertical foils to avoid harmonics but the pedal mechanism was horrible. There have been scale ship propulsion using vertical oscillating foils. There was a pedal drive for a single foil but you get some idea of the issues here: https://www.youtube.com/watch?v=3N3wrZN8mRQ Chains drives in a horizontal plane are a tough ask on a small boat in the marine environment. Also I doubt you can get much thrust from a rigid blade. To get some drive from the area you really need to have lateral motion as well. Things may appear simple until you have to engineer them to operate in a confined space on a platform that rolls about. A well designed paddlewheel can be as efficient as a prop but put it on a platform that is rolling and pitching and they are a long way behind a prop. I have actually seen a flapping system that had a steel frame similar in shape to a dolphin back and tail with heavy rubber stretched across the frame. The trailing edge of the rubber was free to flex. It was driven in vertical oscillation by a motorcycle engine with its gearbox and mounted like an outboard on the transom of a 14ft tinny. It could do about 15kts and would even move the boat along a beach, albeit by accident. A horizontal version of that would work. I also think a flap on the back of a pair of high aspect rudders would work but would always favour a prop. The flapping outboard inspired my dabble into flapping pedal drives. Once I started doing the calculations to refine the flapping system it became obvious that rotating foils make the most sense for propulsion. The Hobie flappers are an elegant design but I know they will not make the distance in the MR340 without repairs when pushed hard. It takes considerable development to ensure a particular system will have adequate durability. Likewise the capstan drive is an elegant and even efficient drive but it is reasonably easy to have wire work off the capstans and turn pulleys. The reasons I gave up on the capstans was lack of reverse thrust as well as complete inability to remove fouling from the prop. At the same time I realised I did not need much wetted surface area or added weight with widely spaced stabilisers to achieve static stability on a low drag, slender hull.
  13. R2AK 2018

    Kenny A flapping foil can be made as efficient as a propeller. Although larger in area than a prop, the flow over it is not much faster than boat speed. Flow over the tip of prop blades can be a number of times faster than boat speed. The problem I had with the large single sweeping foil was setting off vertical bouncing of the boat above 9kph that added drag. The opposed sweep of the Hobie flappers overcome that. The Hobie flappers are not as efficient as a single high aspect sweeping blade providing the latter is not bouncing the boat. I used a torque arm to control the blade AoA so the angle of attack did not alter much; meaning the leg load was almost constant. Also the AoA was constant over the entire blade. The Hobie flappers rely on rubber flexing to provide the angle of attack. Setting up any flapping system requires matching its load to human biomechanics. That would be the challenge for flapping rudders. I consider the Hobie flappers awkward compared with spinning a crank. My most biomechanically efficient pedal system used hanging swing arms to pull wires driving capstans on roller clutches turning a prop shaft. The aim was to get my CoG as low as possible so I could pedal a narrow hull without using stabilisers: https://1drv.ms/v/s!Aq1iAj8Yo7jNgm1SJ7euuXess2iX The attached video shows the inventor of the roller clutch drive in his boat. His is set up like a small outboard whereas I drove a curved shaft. His turning is very good. The videos are a decade old now so resolution is not that good but file sizes are smaller. Warren_HC.wmv
  14. R2AK 2018

    I took the sissies comment in the spirit it was intended; with a smile. Also most of the design work I do for pedal boats is for guys and gals in North America. The fellow I am working with on commercialisation of a boat lives in Texas. The fellow that supplies the 17-7 shafts in another Texan. A fellow in Missouri has made moulds for building the Twin-8 and V16-62 hulls. The 6.2m hull he made for Greg K weighs just 5.2kg: I am also privileged to do design work for Matt Johnson who has the biggest engine of anyone I have worked with. He can still sustain 300W for a couple of hours. He is planning to just pedal to Alaska this year. He is reducing the weight of Rouleur right now by eliminating any sailing gear and using lighter materials in some areas. Pedalling a boat that moves easily is good fun. I just took your sissies comment as an opening to explain why I started playing with pedal boats 15 years ago and promote what I feel are benefits. I gather by Brandon that you are referring to Brandon Davis of Turn Point Design. I had some input on the pedal drive that Brandon Davis set up. He started out with the idea of a curved shaft but steered away from it after I pointed out the challenges. He also had one of my folding props but decided to go for a bigger diameter prop after playing with JavaProp. My prop is really suited to easily driven boats although it has been used on a couple of reasonably heavy R2AK boats; both much heavier than Matt's Rouleur. Brandon has commented on the ease he can move his little cat under pedal power. I will await some layouts.
  15. R2AK 2018

    OK - it is probably time to do some layouts. An inclined shaft with a universal joint is possibly a workable option. If you are starting out only 250 above the waterline then you may get away with a single curved shaft. I have used my folding prop with submergence less than 250. There is benefit in having the prop closer to the middle of the boat than right aft or even behind the transoms. Generally a pedal drive is used in calmer conditions so pitching is not too bad but the closer it is to the longitudinal CoB the better from a ventilation perspective. With a small cat, that lists with the weight of the pilot, there can even be benefit in having the prop off centre as a prop nearer a hull is less likely to ventilate in a beam sea. Also the centre of resistance is offset from the centreline so the thrust line for neutral helm is offset as well. I do not know at what angle a single universal joint feels jerky but I have never used one with an angle as low as 12 degrees. I would usually opt for a double to smooth the torque but a single might feel OK at lower angles. I have not looked through the entire thread to see if you mentioned the size of the prop you are using. My folding prop is only 330 diameter so it requires a submergence of about 260 at the hub centre where I locate it to avoid ventilating in waves; typically only 1m aft of the CoB. With regard to sissies, one of my inspirations for pedalling on water was a great uncle, a WW1 veteran, who never got a drivers licence. He cycled everywhere until he was 92 when his diminishing eyesight limited his ability to cycle in traffic. With that as a reference, I figure cycling is good for my health and longevity. There are not many forms of exercise more enjoyable than being in a reclined seat pedalling a boat at a nice pace over water - weather provides variation. People I know who have built pedal boats inevitably lose weight. Being able to hit 10kts under my own power at my age is quite satisfying.