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Thread: FSR mono with twin surface drive...Would it work ?

  1. #1
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    Default FSR mono with twin surface drive...Would it work ?

    Saw this FSR mono.
    https://www.hydromarine.de/NEUHEITEN...oot::1903.html
    It says it can be build as a FSR, (prop and rudder under the hull ?), and as a ordinairy surface drive mono..But would it work well with surface drives ?..Or just have to much drag ?

  2. #2
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    The hull in link is set up as surface drive . just remember these hull types are mainly designed for [ naviga ] handling / sharp turns not all out top speed like a typical deep v mono hull.

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    Thanks. If the goal in naviga is handling /sharp turns. Then I wonder why it was created with such an enormous flat spot ? I would imagine it just adds to straigt out stability, (and drag).

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    might need to ask the Naviga Race guys that question.

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    I am a Naviga racer, and that boat doesn't fit any of the Naviga electric racing classes, FSR-E hulls are much smaller, not that much bigger than Eco Experts despite carrying triple the battery weight, in the region of 650mm/26", that H&M boat is more like a FSR-V 3.5cc in size.

    While I am not experienced with IC boats the deck looks made for FE, while it does have a flat back you could cut out for a pipe, it is very different from the FSR-V race boats I see around, which are all of a 2 or 3 hatch design and much less boat looking and with an exposed engine bay and easy access to the fuel tank like this for fast restarts and in race refueling.


    As it doesn't really fit any FE or IC FSR classes that explains them trying to expand the market for it into surface drive.

    While I haven't seen this particular one converted, I have seen a couple of Ecos and a FSR-V 3.5 hull fitted with surface drive hardware, none of them impressed me much. You lose the acceleration and steering benefits you get with the submerged drive, and while you do lose some hardware drag you also lose the lift from the prop under the hull so have more wetted area. While the flatter V or in this case completely flat bottom of a submerged drive boat does allow better turning than a stepped surface drive mono, stepped surface drive monos handle the 5 m radius Naviga oval turns fine, so there is nothing to be gained there for racing, and while a shallow deadise is more efficient than a steeper one, it pales into insignificance when compared to the steeper angle of attack you get with a stepped hull, so they lose out in speed.

    FSR are endurance classes, 15mins for FSR-E, and 30min heats with 45min finals for FSR-V around a rectangular 60m X 10M rectangle with a dogleg on the back straight like an american offshore course, these runtimes with limited battery weight/energy or fuel load puts an emphasis on efficiency hence the "flat spot" (a very shallow V is more usual like this, but the principal is the same)

    the lower the deadrise angle the more efficiently planing surface will make lift, so you make the boat very flat and it will be fast, but on the other side of the same coin it will be thrown around more by waves. To make it handle the waves better you make it narrower so you don't get more lift despite getting more efficient lift, but on the other side of that coin being narrow it will roll over in the corners, so you add outriggers and mount small planing surfaces, lifting strakes and turning vanes to them. The outriggers add weight and drag slowing you down so you build them into the hull raising a tunnel up above the planing surface so there is no water drag, and as they are on and behind the CoG the tunnels can add aero lift that is more efficient than any hydro lift... I am not a submerged guy myself, I have only ever had 1 and haven't designed any, so I could be wrong, but I have seen them evolve over the years and I believe that was the process in getting to where they are now.
    Paul Upton-Taylor, Greased Weasel Racing.

  6. #6
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    Thanks. Another "strange" mono with a bit of aero lift in the "V", (have not seen it before, and do not know how far the tunnel in the V goes) image 5 of 8.

    http://shop.miniracingteknik.se/inde...product_id=885

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  8. #8
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    Hi. Now I know. Thanks.

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    But it could be kind of fun to experiment with a tunnel 2/3 ? of the lenght. Maybe 2-3 inch wide.... A cat-(step?)mono.

  10. #10
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    I got the hull. It looks great with 2 MTC drives. But as said earlier it may not run very well, (do not have a great feel about it). Maybe I will make it as in pic. 2. A "thing" I do not think exists. A MTC surface-driven "under the boat. midship"
    https://www.rcgalleri.dk/fotoalbum/t...317-project_19

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