New High Performance Monofoilers

Discussion in 'Sailboats' started by Doug Lord, Dec 19, 2008.

  1. Chris Ostlind

    Chris Ostlind Previous Member


    That last photo you have included in the vast collection as submitted; Could you tell us as to why the two foils are not functioning with the same parallel orientation to hull?

    Is there a differential side loading process going one there from the forward foil to the aft? If there is, perhaps you could explain the process, the calculations necessary in order to understand the loading and the source of the loading that causes the deflection?
  2. Doug Lord

    Doug Lord Guest

    Thanks, Doug. I'm going to do a thread summary like this for multifoilers as well.
  3. Doug Lord

    Doug Lord Guest

    If you're referring to the bottom photo on the 18 post: the forward foil on AET is angled forward about 5-7 degrees and may cause the appearance of not being parallel. The reasoning behind it is to help prevent ventilation.
  4. Chris Ostlind

    Chris Ostlind Previous Member

    The 7 degree angle "might" be correct with some additional fudge factors added. You can see the overlay of a properly angled hull with drawn-in foils at seven degrees. The difference in the photo and the CAD overlay is two degrees additional angle, which may, or may not be allowable in the scheme of things.

    What you are saying, in reality, is that the foil strut (vertical component) does not deflect at all from sailing loads.

    So, where is the additional deflection coming from if it is not side loading? This is very much like what happens to any daggerboard when sailed.

    Attached Files:

    Last edited: Jan 4, 2009
  5. Doug Lord

    Doug Lord Guest

    Not true-there are several possible explanations.
  6. Chris Ostlind

    Chris Ostlind Previous Member

    Then list them, please. Please be sure to include deflection.

    All materials deflect, Doug. They deflect from even the tiniest of loads, if you can measure the movement. The side loads on the foils of that boat shown are potentially huge and the foil verticals just aren't big enough to resist the potential.

    You went through this before with SimonN regarding torsional loads when gybing and the effect it has on vertical foil components. He even produced a photo of the characteristic. I'm sure if you think back a bit, you'll remember the conversation.
  7. Doug Lord

    Doug Lord Guest

    Not interested, thanks. If you want to start another thread on the engineering issues of T-foils I'll be glad to contribute what I can. I remember that discussion and I think I stand by what I said there.
  8. Doug Lord

    Doug Lord Guest

    Mirabaud LX

    This boat is so unique it has it own thread(s). But a summary here: The boat is the largest monofoiler on the planet to fly-26' hull 30' overall but with an amazing all up weight of 350kg INCL CREW! The boat was developed by Thomas Jundt- an inspired sailor/inventor engineer.

    Technical data:
    LOA: 10m
    Width (structure, without the ladders): 1,8m
    Weight: 150 kg (25 kg for the foils)
    Surface of sails: (upwind) : 32m2(344 sq.ft.)
    Surface of sails: (downwind) : 62m2(667 sq.ft)

    This boat was developed from work Thomas did on the foiling 18 AET. He has incorporated many innovative features including dual wands, moving the daggerboard forward of the mast and more.

    I've found W/SA an interesting way to take a first look at small foilers but amazingly this 26' super foiler has a result SMALLER than that of the foiler Moth! Nothing short of an engineering marvel.
    W/SA Moth=2.558(lbs per sq.ft.SA)
    W/SA (upwind)Mirabaud=2.23
    Click on image:

    Attached Files:

    Last edited by a moderator: Jan 2, 2009
  9. Doug Lord

    Doug Lord Guest

    R Class Foiler: Leading Edge of Skiff Development

    Here is a short article(from the r-class site) about testing-note the foiler is faster than the non-foiler BEFORE it fully flies:
    "In the first phase of testing, our goal was simply to achieve liftoff. We experimented with a manual flap control in varying wind strengths. Sean had some trouble joining together the first set of main foil halves due to issues with the moulds, and the first version of foils had a couple of failures when the halves parted under high load. Another fault was the T joint's robustness, or lack thereof.

    The join was modified and the foil repaired, but not surprisingly it failed again. Sean built a second main foil which also failed. The laminate schedule has since been revised.

    Once we had the basics of foiling sorted, the next challenge was controlling the foiling height whilst maintaining sailability. A rudimentary system with an adjustable-height wand was fitted. It was routed along the gunwale and around onto the rear of the centrecase platform. This set-up was chosen mainly to avoid moving the kicker, which was connected to the base of the mast post. Although there was a fair bit of friction in the system, it worked well enough to show that the boat could foil under control, and that it was worth putting in a proper system.

    With the base of the kicker moved up, the cable could be routed directly from the modified holder and clamp to the centreboard. Friction is now very low and the mechanism works well.

    We've been testing the wand setting at a low height to minimise the danger of loosing control by foiling too high. We'll try varying the ride height when we've got more confidence in the mechanism and the boat's characteristics at different points of sail, wave states, and wind strength.

    Some of the first test with the new wand is shown in the charteris bay clip

    It's apparent both from two-boat sailing between a foil-equipped L3 and a standard L3, and watching the videos, that even when the foiling hull is still in contact with the surface of the water, it is quicker than the standard boat. We've not been able to test in light enough conditions to determine at what stage the foils become a disadvantage.

    In the last couple of tests the rudder stock popped off the bottom of its pivot tube. This was due to the stock distorting under load and the pin being slightly too short. This has all been rectified, and so far, nothing else has required strengthening. The rationale is still to build as light as seems reasonable and beef it up if it breaks. Fortunately, there's not been a lot of that!

    When foiling, the boat is much more stable and easier to sail than a conventional R. Until now Sean and Dan have been testing without a spinnaker, mostly to keep additional clutter out of the boat. In the next test they'll likely try a small flat spinnaker as they feel that, although the boat is easy to sail upwind, they haven't yet seen the foiling R's downwind potential.

    There has been plenty of outside speculation that "the boats will be harder to sail" on foils. It turns out that the R on foils is actually more stable and much easier to control. It didn't take long to acclimate to the decrease in lateral resistance from the much smaller vertical main foil, and stop falling into windward when wiring.

    Now that Sean and Dan have done the hard initial work, and shown that the foils are clearly quicker, it's time to get the next keen boats up on foils. We've decided to use pre-preg for the next sets, so we have to finish setting up the vacuum table and oven before we can start. Once we have a few more foiling boats we can work on optimising set-ups.

    Thanks to Sutter Schumacher for the photos and help on this article."
    There is a lot of misinformation around about foiling. This is a short summary of what is known about the R class foiler:
    1) The boat is more stable on foils than the standard boat.
    2) The foiler is EASIER to control than the normal boat.
    3) The foiler is faster than the normal boat before it lifts off-and is faster and points higher after liftoff. This is very interesting since it is a good indication that a dinghy could be designed using "foil assist"(not fully flying).
    4) The R class foiler uses a wand that is adjustable so that altitude can be adjusted.

    Attached Files:

    1 person likes this.
  10. Chris Ostlind

    Chris Ostlind Previous Member

    Interesting that you have, almost immediately, post a quoted letter from R-Class experimentation that deals with foil structural integrity after refusing to discuss that reality; dismissing the topic with, "Not interested, thanks. If you want to start another thread on the engineering issues of T-foils I'll be glad to contribute what I can."

    It looks as if you wish to discuss germane issues only when they suit your projected argument.

    You can't solve obvious engineering and physics issues by pretending that they do not exist.
  11. Doug Lord

    Doug Lord Guest

    The failure of the structure of a foil assembly happens on many foiler developments. The fact that such a failure is mentioned is interesting but doesn't change the subject of this thread. This thread is not necessarily about solving design and/or engineering issues of the various development projects but is more about relating the experiences and results achieved-according to those involved(as much as possible).
  12. Chris Ostlind

    Chris Ostlind Previous Member

    Oh, I get it now....

    This is just another gloss piece of yours that is not meant to go anywhere constructive save for the end result you desire; That being: All foilers are the coolest things on the planet. Virtually this entire thread has been about the technical aspects of foiling as it might apply to the new boats mentioned, as well as existing boats like l'Hydroptere, that are out there being used.

    Go, look again at the different posts and you'll see that the nice folks who have dropped in here have had strong and wonderfully insightful observations about all things technical as they apply to foiling in general, much less the boats you described at the outset.

    You even posted a quote from the guys doing the R-Class discovery process with their struggles to come to grips with the physics of a good foil design, as well as the structural aspects of build failure education as they moved through their development process.

    Please stop pretending that the physical aspects of vertical foil member bend-off at high lateral loads is not an issue with which to contend. It's an issue for every other sailing craft out there, Doug. To pretend otherwise regarding foiliers is so out of the loop that I shudder to think of how you classify the topic.

    Doug... This is a public Forum. The discussion is well within the topic and perhaps you should stop suggesting otherwise.
    Last edited: Jan 5, 2009
  13. Doug Lord

    Doug Lord Guest

    RS600FF Beats Moth

    In Grafham Grand Prix held in freezing temperatures " in the Medium event the foilers were to the fore with the RS600FF of Sam Pascoe beating the Moth of Alex Adams." As best I can tell, while this is not the first time an RS600FF has beaten a Moth it is the first time it has happened with the RS in first place overall(first in the Medium Handicap fleet). And the UK Moth site speculates this and the upcoming Bloody Mary may become "flyer" races with numerous emerging foilers vs the Moth. Cool! Congratulations to the RS guys!

    Attached Files:

  14. ancient kayaker
    Joined: Aug 2006
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    ancient kayaker aka Terry Haines

    Doug, to my uninformed eye those boats look somewhat alike with merely detail differences. Is this a case of the devil's in the details or is there a significant technical difference?

  15. Doug Lord

    Doug Lord Guest

    AK, there are significant differences as well as some similarity:
    SA: 86 sq.ft
    Sailing Weight(includes crew): 220lb.
    All up weight minus crew=66lb.
    main foil area: 1.076 sq. ft.
    Foil Loading(Lbs per sq. ft. at 80% max boat weight with crew):163.56
    W/SA: 2.558lb. per sq.ft.(sail loading)
    SA per sq.ft. of main foil area(a SA/ws ratio shortened to cover planform area of main foil only): 79.92
    For ease of comparison foil area for the RS was arrived at by using the same FOIL LOADING as a Moth. This is a guess and may not be accurate so W/SA is the only accurate comparison possible with known data.
    Only upwind SA is considered. Moth crew=154lb.RS crew=160lb.
    SA: 131 sq. ft.
    Sailing Weight(includes crew): 327lb.
    All up weight minus crew=167lb.
    main foil area: 1.6 sq.ft.
    Foil Loading: 163.5 lb. per sq.ft.
    W/SA: 2.5 lb. per sq.ft.
    SA per sq. ft. main foil area: 81.88
    So the sailing weight of the RS is 1.49 times a Moth; SA is 1.52 times a Moth; and the RS all up weight minus the crew is a whopping 2.57 times that of a Moth.
    Interestingly, the W(all up weight in lb.s) divided by SA(in sq.ft.) is nearly identical for both boats.(As it is for the 26' Mirabaud!)
    The Moth has an L/B ratio of over 10/1 where as the RS is much lower than that with a much wider hull. This can affect take off in that the Moth may be able to reach take off speed quicker than the RS in marginal conditions. One other major difference is that the RS600FF is the first trapeze equipped singlehanded foiler.
    Hope this helps a bit....
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