LDL hull vs 70kts rib

Discussion in 'Boat Design' started by veradotrips, Apr 15, 2015.

  1. veradotrips
    Joined: Apr 2015
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Sweden

    veradotrips New Member

    Hello this is my first post here. I am a big fan of the whole ldl concept both for smaller boats eg Nigel Erens and larger boats like the Steves FPB series.

    But i looked at Nigel evens site where he specifies the fuel consumption of the Range Boat 39 which according to him would be 1,2 L/NM at 14 knots.

    Range Boat 39 fuel consumption:

    Does this not seem kind of high? 1,2 L/NM is very close to the fuel consumption of the Goldfish 38 Supersport, which is a 38 ft rib with twin 370 hp Mercury diesels which pretty much breaks the sound barrier compared to the range boat, with a top speed of 68 knots. At 40 knots this boat consumes just 1,4 L/NM. and with the smaller 300 hp Mercury diesels it comes down to 1,2 L/NM.

    Goldfish 38 supersport fuel consumption:

    Goldfish 38 supersport:

    The Goldfish is a notorious treehugger high speed powerboat but it should not be this close, right? Have i misunderstood something here?
  2. Rurudyne
    Joined: Mar 2014
    Posts: 1,170
    Likes: 40, Points: 48, Legacy Rep: 155
    Location: North Texas

    Rurudyne Senior Member

    I'm guessing the 3000 lb displacement difference has a lot to do with it. One thing I'm sure about, as you'll be aware, with the LDL boat backing off the throttle a couple kts will really drop the power, maybe half or maybe less. So that may be something like 70% better economy at 12 kt? Does that sound about right?

    The Rangeboat isn't an unusually narrow boat, not even 4:1 LBR, not like a Bolger Wyoming that displaces about the same but is 50' x 8', so while it is benefitting from the low displacement/length aspect it is not picking up economy, or giving up elbow room, from/to a high length to beam ratio that might enable it to sip less fuel still.

    ... and it's a whole lot prettier.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.