Quant 17 Foiler

Discussion in 'Sailboats' started by Doug Lord, Sep 28, 2017.

  1. OzFred
    Joined: Nov 2015
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    OzFred Senior Member

    The RS600 FF was a beast that should never have been turned into a foiler. An overpowered singled handed trapeze boat is not a good candidate for conversion.

    Foilers like Moth and A Class can be setup to skim, however it's not a preferred mode as it doesn't take full advantage of the benefits of foiling. In light winds, you want to be fully foiling. If skimming in chop, the boat is slowed by every wave it encounters then accelerates as it lifts off again, producing a stop–start motion that can be just as uncomfortable as floating mode. In practice, it's likely no easier (and certainly no faster) than full foiling. The Quant 23 and 17 get their stability from widely offset foils that generate very large righting moment (very similar to what johnelliot24 has done with his mutant FD), not by dragging their transom through the water.

    The issues of full foiling in small boats in sheltered waters are greatly overstated. The most highlighted issue is crashing while going downwind in choppy conditions. Nearly all the crashing Moth videos come from downwind sailing in conditions of 20 or 25 kn plus in fairly open water. Below 15 kn (or 20 kn on lakes), Moth crashing is not an issue. Anyone in a modern boat with a solid season of racing under their belt can sail in breeze up to 20 kn without crashing. The biggest issue is the 30cm wide hull that most find challenging to balance in floating mode. Once that is overcome, the rest is easy, which is why the GlideFree foils can be attached to a Laser, Aero, whatever and they are foiling in minutes with no modifications to the standard boat.

    Here is Dave Lister doing foiling tacks and gybes way back in early 2009. Way too boring for those who think crashing at 25 kn is more spectacular though.
  2. johnelliott24
    Joined: Dec 2006
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    johnelliott24 Junior Member

    When the FD makes more progress I'd like to post results and get help. Can you tell me how I can open a new thread and get the attention of the foiling/high performance sailing people? i.e. how to get people from this thread to read the new one?

    Back to the Quant post, these foils have a lot of appeal because they are very "sleeper" and cleanly mounted. Does anyone have any ideas how well these foils work VS deeper J foils or T foils? It seems like the Quant foils are planing to a degree where they exit the water, and they generate a lot of ventilation. How does this compare with foils that are deeper? I'd like to make a set like the Quant's in black so that from a distance no one can see them but because of there 3 dimensional curves they will not be quick to build, so it would be nice to know how efficient they are first.
  3. OzFred
    Joined: Nov 2015
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    OzFred Senior Member

    For a new thread, click the "New Thread" button in the upper right corner (see image below).

    There are many lurkers, the best way to get attention is to post useful information regularly. What you have is a good start. :)

    As with all things, there are pros and cons for various setups. Moths use a wand controlled Ts because they suit the class rules (which where amended to specifically to favour them), A Class use insert from above foils and do not allow wands (again through class rules that favour them and exclude insert from below) so they've developed Z foils (which can be very J like). Nacra use Z foils, and so on. It's really a matter of setting your parameters and goals, then working within that. If you're happy with a T foil version of the Quant/AC75 setup, that's perfectly OK but you're in new territory so when it comes to the detail of what works, you're the expert courtesy of having actually done the work!

    Attached Files:

  4. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    The Quant foils rarely if ever ventilate according to the designer and builder. They are quite efficient allowing the boats to foil in very light air-according to the designer and builder they'll fly in 4-5 knots of breeze and fly upwind in 7-8 knots of breeze. So far as I know the top speed is just over 26 knots.
    I'd say the Quant type foil (Q foil) would be your best bet but you can learn a lot by experimenting with different types of foil.
    There are two main types of foil:
    1-surface piecing foils-- where altitude is controlled by boat speed and whose area reduces as the boat goes faster. These include "Q" foils(Quant foils), Z foils and others like ladder foils.
    2- fully submerged foils---where altitude is controlled manually, electrically or mechanically (Wand surface sensor). T-foils are a good example-an altitude control system is required.
    a- a subcategory of fully submerged foils are "uptip" foils invented by TNZ before AC 34. These foils control altitude by leeway coupling which can regulate ride height pretty closely depending on their design. They require no moving parts and generally maintain the same altitude regardless of speed.
    They are sometimes called by a bunch of different names including "J", "L/V","L" and others. Mainly because many people just don't know that they were named uptip foils by their designers.
    I think you'd do well to start your own thread-- maybe something like "Flying Dutchman Foil Experiments". You could also research the history of foiling to get some ideas-if I remember correctly a guy named Hanno Smits in the Netherlands put ladder foils on an FD many years ago.
    Good Luck!
    UPDATE: 1) Hanno Smits FD on ladder foils: FD H40 on hydrofoils. http://www.wind-water.nl/contents/fd.php

    2) check out this thread: "Simple" hydrofoil addition to a laser II https://www.boatdesign.net/threads/simple-hydrofoil-addition-to-a-laser-ii.56378/
    Last edited: Jan 4, 2018

  5. Dolfiman
    Joined: Aug 2017
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    Dolfiman Senior Member

    Doug Lord likes this.
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