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Discussion in 'Boat Design' started by Guest625101138, Jul 14, 2008.

  1. Guest625101138

    Guest625101138 Previous Member

    There are quite a few but it is not something I keep references for. After a few years of testing the engine and some tuning I have a reasonable understanding of it. I find heart rate monitoring to be very effective feedback. One of my most treasured possessions is the little Garmin edge GPS. I use it every time I train.

    I have actually seen a fellow in the Murray Marathon who had to keep his heart rate below the limit set by his doctor. The doctor agreed that the exercise would improve his quality of life but he had to be careful not to overdo it.

    It is surprising how easier things are mentally in competition than just exercising. However you have to be careful not to overdo it when it is not mentally tough. The hardest part in competition is holding below the sustainable level.

    Some of the words in your previous post will provide good hooks for a Google search. There are some good papers that are only available if you buy them. I usually move around until I find the next best that is immediately available. I have paid for things that did not live up to my expectation. Sometimes you can find the same paper free on another site.

    As well as cadence you can also play with crank length. I know a fellow who spins 120mm cranks at 140rpm in normal operation. He gets over 200rpm in a sprint. He has a really smooth action.

    There is a lot of data on set up of pedals. Some experienced recumbent riders tend to have legs fully extended at the end of the stroke. I find this uncomfortable.

    Rick
     
  2. I57
    Joined: Feb 2008
    Posts: 172
    Likes: 6, Points: 0, Legacy Rep: 62
    Location: Melbourne, Australia

    I57 Senior Member

    Windy day and training

    Got to the lake at 2pm on Saturday and blowing a gale. Boat went ok despite
    the conditions and nothing broke. Slow going directly into the wind but at
    least I could make headway, turning was a bit hairy as the big slab sided
    outrigger was catching the wind. Going back downwind the boat started to
    nose dive and I had to ease up to bring the bow above water. A good test in
    the conditions, boat still needs some minor changes.
    In reply to Tiny Turpins comments about fitness the only way to get fit is to
    get out there and just peddle. Building up fitness takes a long time and steady
    even training over a few months is needed before you want to try any anerobic type training. Getting out in the boat as often as we like isn’t always possible so what I’ve done is made a trainer out of old bike parts, a recumbent version of an exercise bike. Riding a bike and other forms of exercise are good but to peddle your boat you need to train those muscles used in the recumbent position. As Zatopek said “if you want to race the mile train for the mile, if you want to run a marathon, train for the marathon”. He won three Olympic gold medals so he probably knows what he is talking about.
     

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  3. Guest625101138

    Guest625101138 Previous Member

    Ian
    I did not leave long before you arrived. I pedalled with one of the Hobie flappers for a while. How many were there when you arrived?

    Actually there was a sailing dinghy out in it around midday. I think it was their first time out. They had the sail mostly luffed and could not make way into the wind. They capsized it about 200m from the wall and dragged it to shore. Then drove the car down to retrieve it.

    Only a couple of the sailboarders were prepared to venture out.

    The Hobies flappers are short enough to surf on those waves doing maybe 8 or 9kph. The guy I was with said it gets hairy though as they broach easily.

    V14 has quite a lot of buoyancy in the bow with some lift so is much harder to bury than V11. The waves were not quite big enough or far enough apart for me to drive the bow in. However it did not take much effort to hold 11kph down the bottom end of the lake once the wind got up. I have to lean into turns when it is so windy to avoid the wind flipping me on the crest of wave.

    It was quite wild so if you can make headway into that sort of wind you should be always able to make shore. Barring a component failure of course.

    I always try to get out early to beat the worst of the wind. Also a little cooler.

    Rick
     
  4. I57
    Joined: Feb 2008
    Posts: 172
    Likes: 6, Points: 0, Legacy Rep: 62
    Location: Melbourne, Australia

    I57 Senior Member

    Windy day

    Rick
    When I got on the water the Hobbie flappers had the boats onshore and the only other boat out was a windsurfer who was breaking all speed records. When I was out the wind kept having short harder gusts to the point I went as far north on the lake as I could before turning around. I am wondering about trimming down the depth of the outrigger to get less windage. Its a question of how much reserve bouyancy is needed, the outrigger displaces about 17kg and total volume of outrigger is 65 kg.

    Ian
     
  5. Guest625101138

    Guest625101138 Previous Member

    Ian
    It is not nice if you do not have sufficient reserve in the small hull. Once it disappears under the surface you will roll. It is an interesting experience and hard to do much about unless you are prepared for it.

    I think what you are experiencing is the sort of roll that catamarans experience. However one of your hulls is so light that when it is upwind it does not have enough load to hold it down. It is quite light so does not provide much moment when being lifted.

    Were you trying to turn with the outboard hull upwind or downwind? I think you might actually find it easy with the small hull down wind because it has ample buoyancy and it will be safer to load it up than trying to use it as a counterweight. It is unlikely you will bury it with the current reserve.

    I am warning against reducing the reserve. However if you want to cut it down then a test is to lean as far out as you can to load the outboard hull. Notice where it sits and then allow at least a 50% margin over this.

    With V14 I can turn either way but I do it with care. I lean into the wind and try to keep the windward hull loaded. My amas do not have enough buoyancy to support the roll from turning combined with the roll on a wave plus the wind load on my body. If I did not lean in I would roll leeward.

    It is a matter of thinking about what is going on and working out the best method. It is also good to know the limits, which usually involves getting wet at some stage - better planned than unplanned.

    Rick
     
  6. portacruise
    Joined: Jun 2009
    Posts: 1,120
    Likes: 32, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Rick, did you have your folding prop mounted for this run? Maybe the high winds blew away weeds and you didn't need it. I take it the waves were not up high enough so the prop was not gulping air at some points. Severe conditions like that often compromise my steering and control at certain locations on a lake. Vic.

    Porta

     
  7. Guest625101138

    Guest625101138 Previous Member

    Yes I am using the folding prop. I want to compare it with the fixed blade one after the other on a calm day.

    There was not a lot of weed early but it started to get pushed out from the northern end as the day wore on. It did not bother me. I lifted the prop a few times to check the strut but this can be done when I slow to turn. The strut collected a few strands but the prop sheds anything as soon as I stop rotating.

    I did manage to suck air but it was only when trying some sprinting after I stopped timing. Once I got to around 15kph the boat was lifting enough that the prop was getting air in the troughs so that limited my speed downwind. Going upwind the waves come too quick for it to get air.

    It was windy but the fetch is only 1500m so the waves get no bigger than about 0.6m high. However once they are over 0.4m I start to plough through them and it gets very wet. This is good in summer but can be too cooling in spring. Our northerly wind is hot air so it was quite warm on Saturday - not freezing cold.

    Rick W
     
  8. portacruise
    Joined: Jun 2009
    Posts: 1,120
    Likes: 32, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    I see there is an additional advantage of having your prop positioned near the center of your boat when there is chop. It would appear to reduce loss of thrust due to gulping air. Do you get any rocking with your great looking and well streamlined hull or just plough straight through the 60 cm waves on the level? Does chop have any effect on the outriggers?

    With my longtail configuration and shorter hull length, there is a lot of rocking in chop. The rocking is lever amplified at the longtail prop end so the angle has to be constantly adjusted to maintain maximum thrust. V.

    Porta



     
  9. Guest625101138

    Guest625101138 Previous Member

    Vic
    If I drive into waves it holds almost level and the water just comes over the deck and seat. It gets very wet. I tend to slow down so it lifts more meaning I stay drier. At normal speed into small waves the V14 hull will slap a little because it has a flat bottom and this tends to dampen pitching.

    If I was regularly operating in 2ft waves I would use longer amas. The short ones hang in the air when the hull is suspended between waves. If I do not balance carefully it will flop roll onto one ama and they have limited buoyancy so it is possible to lose it. Once the waves get to this size I tend to sit on one and ride it rather than driving over it and having the amas completely suspended. Longer amas would be better for these conditions. Also the support beam for the amas is bluff and creates a lot of resistance when buried. These would need to be set higher or streamlined for working in waves.

    Rick
     
  10. MLampi
    Joined: Aug 2008
    Posts: 74
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Bellevue, WA

    MLampi Junior Member

    Sometimes extra flotation is a good thing. ;)

    Some boats employ a highly peaked deck to divert the water to the sides. While this would create unwanted windage if done at the bow, it could still work if positioned directly in front of the pedal drive.

    Some of the outrigger canoes use bent tubing that arches up from the deck and over the gap and down to the ama in an effort to reduce that sort of drag.

    You might also consider making the amas with more of a trapezoidal cross section for extra flotation. Otherwise, you might have to use a second support beam to reduce torque problems.

    Michael Lampi
     
  11. Guest625101138

    Guest625101138 Previous Member

    Mike
    My Pahoa has the neatest set up for iakos I have seen. Refer photo:
    http://www.boatdesign.net/forums/at...edal-powered-boat-baltic-sea-coastline-v7.jpg

    However I do not like the single outrigger. The preferred set up for this boat uses the conical amas made for V10. You can see them mounted on V7 in this video:
    http://www.youtube.com/group/HPB

    V7 has the high foredeck but I left the undrained footwell for storage and it will fill with water in decent waves. That is more of a pain than having water just flow over.

    For moderately rough water I would go for a faired cockpit and amas about 3m long with twin faired beams. See this image:
    http://www.boatdesign.net/forums/at...al-powered-boat-baltic-sea-coastline-ka77.jpg

    For really heavy weather I would go for ballast keel and fully self righting.

    Rick W
     
  12. portacruise
    Joined: Jun 2009
    Posts: 1,120
    Likes: 32, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    Hmmm. Sounds much like Greg's machine! Probably no cavitation whatsoever in heavy seas with the prop configured at midsection.

    Wonder about getting as low as possible in a semi enclosed craft to avoid the pounding waves and minimize some of these issues. Maybe a quasi submarine with a separate sealed compartment to intake water into a ballast keel. Include some large one way snorkels to keep splashing water out and the rider dry and riding smooth and level. That's something like the South American craft used by drug smugglers to avoid detection by patrolling aircraft.... V.


    Porta
     
  13. Guest625101138

    Guest625101138 Previous Member

    Vic
    Once inside the hull you have already reduced performance. The minimum width to operate is about 400mm. The lowest drag hulls are usually around 220mm maximum BWL.

    Once enclosed cooling becomes a big problem. This is what Greg found in the first boat hence the reason for all the ports and hatches. It is also desirable that the cabin is high enough that you can bend forward. We did look at a sliding hatch but it creates need for a more complex structure. Also I think something sliding is more likely to get broken off.

    The EARTHRACE boat is semi-submersible. It ploughs through the big waves. It is large enough that the risk of a complete roll is very low so no need for self-righting.

    Rick
     
  14. portacruise
    Joined: Jun 2009
    Posts: 1,120
    Likes: 32, Points: 48, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    weed resistant shaft

    Rick, I got an idea for a weed resistant live flex shaft which I will be trying out in a week or so. In normal operation the flex shaft tends to feed a few twisted weed clumps which it manages to entangle toward the prop end as they are pushed back by the water flowing past. What I am thinking is that having a small bulging, smooth surface, very coarse counterscrew to rotation on the shaft surface would tend to give a counter thrust water flow upward along the immediate vicinity of the rotating shaft. Maybe with the right pitch this will tend to push weeds away from the shaft entirely? What do you think? Vic

    Porta

     

  15. Guest625101138

    Guest625101138 Previous Member

    Vic
    I doubt that you will be able to pitch a small diameter screw to create a reverse flow. Determine the pitch angle at a small radius and you will see what I mean. It will sap quite a lot of power as well.

    One thing I tested that was effective in calm conditions was a thin foil angled down into the water ahead of the shaft so flow forced weed up the blade. I could reach it to remove the collected weed. In waves some of the weed would wash off in the troughs. So to be fully effective the blade needs to plunge deeper than wave troughs you will operate in. This also adds drag but I think much less than reversing flow.


    Rick
     
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