nose diving riveira

Discussion in 'Powerboats' started by aussiebrian, Feb 25, 2010.

  1. tunnels

    tunnels Previous Member

    Its good to hear from you and along with everyone else we'll all be waiting for the happy ending to this story .
    Good luck and hope all ends well !!
    Thank you for the reply !:D
  2. monrosm@shrewsb
    Joined: Apr 2006
    Posts: 50
    Likes: 1, Points: 0, Legacy Rep: 20
    Location: England

    monrosm@shrewsb Junior Member

    Possible Cause

    Just a thought as to why the boat is nose diving....It could be that your propeller starts to cavitate at a certain speed (25-30MPH) in essence the propeller can no longer grip in the water (if you can understand that) and creates a void along the blades, this in turn will dramatically reduce the power produced by the propeller and cause the boat to nose dive. This is a bit like a materials natural frequency.

    If this was the cause it could be that your engine/prop configuration are off and you will need to rethink engine power/propeller size, pitch and number of blades....
  3. tunnels

    tunnels Previous Member

  4. tunnels

    tunnels Previous Member

    iTS BACK !!

    Waiting for the good news!!:D
  5. aussiebrian
    Joined: Feb 2010
    Posts: 11
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: australia

    aussiebrian Junior Member

    Hello everyone,
    As I informed tunnels earlier this week, I have returned my Riviera project to the water after moving the motor.


    Everything works as a boat should. The hull jumps out of the hole almost in its own length, and steers perfect through all speed ranges. We managed to get nearly 50mph (5000rpm) out of it. So it's wind in the hair (whats left of it), bugs in the teeth ready for summer.

    I still have a couple of things to do. The engine cover doesn't fit 'cause of the motors new location, and I may have to fit a small cavitation plate over the rudder where it protrudes past the transom. In some instances, when turning, air syphons back under the hull and causes the prop to loose traction, but its not a real concern.

    All in all, the "nose diving" has disappeared completly. I've taken some video but I am having trouble attaching it, so i will get one of my teenage daughters to figure it out and send it through.

    Thanks for all the assitance everyone supplied, it made the task less daunting knowing what to change and expect.

  6. Oyster
    Joined: Feb 2006
    Posts: 269
    Likes: 9, Points: 0, Legacy Rep: 104
    Location: eastern United States

    Oyster Senior Member

    Great to read that you are on the mends! Maybe a photo or two of the boat just sitting on the water and some numbers from the transom to the stiffing box, gear and all of that stuff too? Maybe the overall number to the front of the engine too? TIA
  7. Ike
    Joined: Apr 2006
    Posts: 2,542
    Likes: 377, Points: 83, Legacy Rep: 1669
    Location: Washington

    Ike Senior Member

    Good to hear it. WIth planing boats the CG of the boat for and aft is all important. I hope you enjoy your boat now.
  8. mark775

    mark775 Guest

    "there is a dimension on where to drill the shaft hole, 48" from the transom. Apparently, I have since found out, that's wrong, and everybody who has built this boat successfully, and there is quite a few, ignored this dimension and determined there own. It seems to be common cyberspace knowledge, but it never made it to a glen-l webletter, forum post, and worst of all an ammendment to the 40 year old drawings" - Am I missing something or isn't this a rather severe oversight? Was there a reply to this?
    Yes, props had been tried but I doubt the rake was messed with and this is the main thing that could have pulled the bow up.
    Glad the thing works now. A question about the engine bay photo of the sister vessel;


    I've seen this before, it must be tradition or something, but why the leftover RedHand look in the engine bay? What a beautiful boat to have an engine space that makes one recoil...
  9. Oyster
    Joined: Feb 2006
    Posts: 269
    Likes: 9, Points: 0, Legacy Rep: 104
    Location: eastern United States

    Oyster Senior Member

    I don't have the plans in hand. But there has been imput and comments from seasoned builders and conversation back and forth directly with Glen L. I bet that without further context and content your assertion and broadbrush may not hold water . Keep in mind there have been numerous built with diverse engines too over the years. Please elaborate a bit more.
  10. J3
    Joined: Jun 2010
    Posts: 60
    Likes: 1, Points: 0, Legacy Rep: 16
    Location: MI

    J3 Junior Member

    Not familiar with RedHand? Are you offended by the color? Or cutouts? Or what?
    Most real-world light colored engine compartment bilges I've seen are filthy and greasy in a few years. Clear coated wood would look great here as well, but would it be harder to maintain or touchup if dinged while doing mechanical work?
  11. tunnels

    tunnels Previous Member

    Over the years of messing with boat of many differant kinds Its been my habit to draw mechanical stuff out full size on a nice clear patch of the floor or a sheet of ply depending on size of the project .
    Lots can be gained from doing this ! What the designer has drawn and what you actually have could be two differant things be it slight or major.
    The angle of the propshaft could be less by shifting the rudder back a fraction and reducing the prop diameter a little. Props over the years have become better in design and understanding so diameter is looked at differantly than it used to be .
    During my early days as a green horn and a gofa i crawled into many bilges and sat and looked and took note of what i was seeing and what was going on round me . I also took particular notice of quiet Engineers that just got on with the job and made boats go fast and were reliable and hardly ever did anything go wrong .
    My dad was a self taught engineer, welder , and mechanic all rolled into one and i guess a little of his know how rubbed off during the growing years . Its never to late to learn and you should never stop learning . ;)
  12. mark775

    mark775 Guest

    "Not familiar with RedHand? Are you offended by the color?"

    "leftover RedHand look in the engine bay" -Does it sound to you like I'm not familiar with RedHand? Yes, I am mildly offended by the color - My personal taste doesn't lean towards National Park Service "Decades of Stain" color match. I am curious, because I have seen this before, why it is apparently an accepted color. Engine rooms ideally should be glistening white, IMO, but I understand the desire to downplay that on these boats. Some careful color combining between engine and bay, in concert with polished aluminum or stainless, even mylar film on sound insulation or bilgecoat grey on a work-a-day boat - dang near ANYTHING other than that red. Personally, I would probably match the upholstery and tone it down a bit with some matt bright finish or polished aluminum. To each their own - perhaps it is just me. Anybody - does that red have a meaning - like matching some kind of early paint formulation?
  13. tunnels

    tunnels Previous Member

    Just think theres a high percentage of males that are naturally color blind , red is one of the colors that males have trouble with !!. to me its a nice shade of purple goes well with the pink motor and the yellow distibutor cap !!!:p
  14. mark775

    mark775 Guest

    Funny, I use Baltoplate bottom paint on my powerboat and if one doesn't sand smooth and burnish - it is pastel purple (if sanded, it looks like polished metal) . Hard to look at but has a purpose.

  15. Jango
    Joined: Aug 2005
    Posts: 519
    Likes: 7, Points: 0, Legacy Rep: 63
    Location: Mid Atlantic

    Jango Senior Enthusiast

    Since many Builders look at this Design, as a "copy of the 40,s - 50,s Chris Crafts, where the Interior colors are a Dark Red.The natural thing to do was try to copy that.
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.