Windshield Reverse Rake

Discussion in 'Powerboats' started by robrohdeszudy, Jul 7, 2005.

  1. robrohdeszudy
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    robrohdeszudy Junior Member

    I see a lot of hype about the rake direction of pilothouse window glass. But it seems mostly to center around aesthetics. I only have open boats at the moment, so can someone help me out with the ACTUAL functional advantages, particularly of reverse rake?
    Thanks,
    --Rob
     
  2. stevel
    Joined: Aug 2004
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    stevel Lost at sea

    Water will run off of a windshield that is raked forward quickly so that you can see where you are going.
     
  3. RThompson
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    RThompson Senior Member

    Fwd rake in the screen's also avoids reflection of instruments at night and cuts glare during the day (especially for salt covered glass).
    Rob
     
  4. robrohdeszudy
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    robrohdeszudy Junior Member

    Thanks. Figured it was something simple like that. And I would also assume the gaskets tend to leak less because no water pools on them. Conversely, raked glass sheds wind better and vertical glass is a compromise.
    --Rob
     
  5. MarkC
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    MarkC Senior Member

    Allows you to mount radios etc. above your head, without endangering your noggin.

    Looks nautical!

    Streamlining is really only a fashion - no real effect...?
     
  6. robrohdeszudy
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    robrohdeszudy Junior Member

    >Allows you to mount radios etc. above your head, without endangering your noggin.

    Makes sense

    >Looks nautical!

    Didn't before they started doing it. That's only been since the 1940s or so, I think. Until rather recently it was seen as looking "industrial". The popularity of trawler yachts has increased interest in the reverse raked glass aesthetic.

    But they started doing it for REAL reasons. Glare and drainage, I'm told. Another one that hasn't been mentioned is much less solar gain in hot weather.

    >Streamlining is really only a fashion - no real effect...?

    Not true. On a deep-keeled trawler with lots of power it probably makes little difference. But on a smaller, lighter boat with less power, the ability to shed wind might let you get home. Not because you're going to go that fast. Because the wind might be BLOWING that fast! Even in heavy boats the wind pressure in a real storm can blow your glass in. This is why pilothouses with vertical and reverse raked glass are generally rounded - to help shed some wind pressure.
     
  7. ClarkT
    Joined: Jun 2003
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    ClarkT Senior Member

    In addition to the additional outfitting space, I'd say the best reason for reverse rake is to minimize solar heating in the tropics.

    Conversely, if you are in northern lattitudes (there goes my Northern Hemisphere bigotry), the swept rake will help you capture some solar heat.
     
  8. yipster
    Joined: Oct 2002
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    yipster designer

    i can still imagine another reason: on bigger ships its easyer looking down? sounds ok?
    but all together i'm not convinced, dont like the windage nor look, on a high tug, maybe...
     
  9. kmorin
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    kmorin Senior Member

    forward leaning cabin glass

    When the Alaskan King Crab road race and rodeo started paying millions per season per boat there weren't enough new metal crabbers to go around but there were lots of older halibut long liners in Seattle. Most of those pressed into this service had plumb or aft leaning cabin windsreens and the cabins were well aft -schooner style. But that reduced the crew's ability to "turn pots".

    In the Alaskan fishery of the 60 and 70's some of these boats had their cabins' glass stove in by boarding seas. Other's had their cabins moved forward to accomodate the deck crew's desire for a shelter deck and to give better view of the next bouy in the string. Turning pots with 5 to 10k$ in them tends to focus the skipper on the bouy not the seas. But many of these boats had the cabins crushed and the windscreens pushed in by breaking seas.

    More and more the boats came in (early in the season at a loss of $) with stove-in houses, so the when the new Marco boats with forward houses came out they used the leaned forward glass to keep the breaking sea's impact off the glass. In Alaska this fashion is still referred to as a 'crabber cabin' design in many ports, when discussing any boat.

    Small, boats and skiffs with free standing dog-house type sheltered helms now use the line for all the reasons mentioned here, volume in the cabin is increased, radios above, glare reduced and dry windscreen. But the real influence as far as I'm concerned was the Marco (Seattle yard) crabbers need to work into head seas that broke over 80 and 90' boats in the gulf of AK. The sea comes down almost parallel to the cabin's windscreen and breaks on the overhanging house top and the deck, without damaging the "windows".

    It took a while to catch on elsewhere as it is homely as can be in regards boat lines.

    Cheers,
    kmorin
     
  10. yipster
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    yipster designer

    thanks, interesting history and that makes a lot of sence.
    on the other hand ive also been hearing story's about real rough stuff taking off reverse raked deckhouses :eek:
     
  11. kmorin
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    kmorin Senior Member

    rough stuff

    One fall, years ago, I was in Seward, Alaska and saw an ocean going barge that was moored there. The barge was about 150' x 400' x 40' or 50' deck to water. The tug was around 150', one of the Foss Fleet tugs and the reason for stopping in Seward wasn't to discharge cargo.

    The forward port 'corner' of the barge was torn off. I don't mean stove-in, I'm not implying some 'water damage' or that a wrinkle had been hammered into the hull. There was a corner of the barge gone.

    The tear was about 60' along the deck, as a diagonal bow to port side, and the 'teeth' of the ragged edge made the entire show look like the barge had a mean-mouthed grin.

    A friend worked on the temporary patch- bulkheaded off that corner of the bow and filled it with cement until they could get to a shipyard that could haul something that large.

    Yep, that "rough stuff" in the Gulf of Alaska can get a might "lumpy" to use one of the terms of the local fishermen. I doubt anything but a submarine can avoid it all, even if the windows leaned forward.

    Cheers,
    kmorin
     
  12. yipster
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    yipster designer

    on tv i've seen a documentairy about that alaska fishing, crew had to jump for shelter between huge waves coming over houling crab boxes in. rough stuff!
     
  13. Bendigonian
    Joined: Nov 2011
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    Bendigonian Junior Member

    This thread is antique but it's still worth noting that forward rake gives some aerodynamic and hydraulic benefits, and Shuttleworth concluded that aerodynamic smoothness gave measurable benefits, even at the 5-10 knots that a normal cruiser would do. Still, Lagoon seem quite happy with vertical windows, albeit with quite an overhang, or verandah, and quite small window size.
    Forward rake also protects the interior from sunlight at the cost of a bit of extra deck, and reduces reflections both interior and exterior. Long nose trucks in Oz routinely have anti-reflection strips on bonnet and roo bar top, otherwise you wouldn't be able to see a thing on a sunny day. And try leaving a bit of paper on the dash in your normal aft raking car windscreen, again on a sunny day...
    It's no co-incidence that air traffic control towers and all manner of pilot boats and cargo ships have forward raked glass. If you have an inside helm it would be mandatory; with just an aft helm, maybe not so much.
    Various investigations by Oz Civil Aviation and US Mil put the optimum outward rake at 20 degrees. If you don't have to get closer to the glass than arm-length, then 15 degrees is a good compromise. So looking down from on high to the deck or sea would demand 20 degrees. Just looking into the distance for obstacles close to sea level, would allow 15 degrees.
     
  14. DCockey
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    DCockey Senior Member

    What aerodynamic benefit?
     

  15. Bendigonian
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    Bendigonian Junior Member

    Aerodynamic benefit?

    I did mean benefit over plumb windows, not benefit over extremely aft raked windows, which I don't think could be accomplished with forward rake, without looking damned silly. I can't see that encouraging air, or water, to go down and around is any less efficient than up and over:)
    I know what I was thinking, I just didn't express it well.
     
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