nose diving riveira

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

  1. tunnels

    tunnels Previous Member

    wow is this a hot boat !!:p
     
  2. Oyster
    Joined: Feb 2006
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    Oyster Senior Member

    This is the plan's profile for the Rivera, Tunnels ,et. al..

    [​IMG]

    FWIW, another builder states his setup is From transom to front of shaft log 59" exactly Front of shaft log to face of shaft flange on rear of transmission is 7" exactly.

    Brian stated
    If you convert this to inches this relates to 65.9 inches and Dave says his setup is is 66 inches.

    [​IMG]

    [​IMG]

    His strut is shorter by one inch if I am correct and reading his post correctly. This makes his shaft angle less than drawn plans if his strut is mounted flush without a shim. His problem on running angle according to another builder's setup is not weight too far foward unless the other builder also has his setup wrong.

    The position of the bottom frame to the stuffing box on Brian's hull is further aft since the numbers on the location of the output flange of the transmision is darn near the same. We still do not know the true measurement of the boat beam on the bottom if all of his chines faired out right. But if the frames are correct in their drawn sizes, then all the frames and measurments fairs out further back than speced. But if that frame deminision is correct, then all the numbers along the way is further back than the plans for the locations on the bottom with the bottom frames fairing out further aft to the plans.

    If not and the frames are correct and set at their proper location along the centerline, and just the hole is foward, I stick to my opinion and the main problem with bow down being that he has less bottom foward even with the issues of propeller size and cavitation problems. His boat is steering by the bow for sure.
     
  3. Jango
    Joined: Aug 2005
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    Jango Senior Enthusiast

    I completed GlenL,s Monaco, 19ft version of the Riviera in 2004. Being an ex Inboard racer in the 50,s, I am fully aware of balance implications in planing Hulls. Since my Boat is powered by a 450 HP Sm.blk. I was concerned about balance and porposing.

    I located my Strut 13" from back of strut shaft centerline to outside of Transom. With a 15 deg angle, stuffing box is Fully behind #2 rib. My Total weight is only 2250# w. Driver, I use a 12 x 15, Equipoise Prop at up to 6500 RPM. I can get bounce, but only above 75 mph. With careful throttle control [NO abrupt increases], in smooth water, ride is smooth with zero bounce.

    These Hulls need the CG as far Aft as posible. Mine is 87" from the Transom [without driver]
     
  4. Jango
    Joined: Aug 2005
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    Jango Senior Enthusiast

    Forgot to Add - I used the 6 3/4 Drop Strut from GlenL, not the 7 1/2 drop. Even with a 13" Prop, because of the angle, you will have ample clearance.
    This alone accounts for about 4" of motor placement.
     
  5. tunnels

    tunnels Previous Member

    After a couple on almost sleepless night dwelling on this problem the Vee drive sure looks like a good alternative to get away from the steep shaft and weight to far foward .
    It would Drop the shaft angle way down and with the motor round the other way moves the weight back and mounts the motor a little flatter .

    I have been searching for a story about some one that redesigned the hull shape of one of these boats that had a sightly deeper dead rise and a little beamer in the bottom to carry the weight better plus som othe minor changes . Have to keep looking !

    maxcarter@marine-design.co.nz Max Carter has designed and built a few of these types of boats and would be the best person to run all this by he's one of the best and most mathodical designers still alive .
     
  6. Jango
    Joined: Aug 2005
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    Jango Senior Enthusiast

    If I were to build this Boat again, I would do the Vee Drive WITHOUT any unnecessary changes to the bottom shape or size. My engine/trans only weighs 660 lbs or about the same as 3 men. CG of power plant would be about 48" from transom - no problem at all with present bottom design. Other big advantage would be seating arrangement - Dual cockpit in center of Boat which used to be called a "Riviera" by Chris Craft.
     
  7. Oyster
    Joined: Feb 2006
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    Oyster Senior Member

    There are only a few conclusions that fits this problem. We now know that the engine is within tolerances in regards to its location along the centerline of the boat. We also can conclude that the stuffing box is foward of the aft most frame because of the different measurement of what appears to be where the two projects enter the bottom in the drilling process, but quite possibly plays nothing into the role of bow down scenerio .

    While there maybe some serious issues with the wheel and its clearances, if anything the actual running angle of the mechanical parts are pretty close to the plans. So with the nose of the boat down and handling is a problem and the boat is actually built to plans, either the bow is built heavy weighting the bow down which can also help to trim the boat out in the initial power up. Or after on plane and increases its speeds, the lack of bottom trims the boat out further than designed.

    Several questions still go unanswered and can further help isolate the problem and quite possibly create a workable compromise dealing with the finished boat now.

    But since we also have the advantage of other hulls running fine for the large percentage of hours and conditions due to customer feedback, its not how the boat would be modified from a person's point of view in another custom build as much as prior presidence being set using simular engines and the builds that gives us something to go on. for this particular boat thats now finished. Boat building is likened to what happens to a balloon. For every action there is a reaction somewhere else.
     
  8. Yellowjacket
    Joined: May 2009
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    Yellowjacket Senior Member

    This appears to be a carefully built boat and the original poster has crafted a fine version of this design. While there could be some differences between the boat and the plans they don't seem to be large enough to cause the problems that he is seeing.

    While the OP has tried different props, could the problem be lift that is being created by the prop? Or, just as importantly could a prop with less stern lift, be a potential answer? Perhaps a more detailed description of the prop in terms of cup and rake might be worth looking into before he goes hacking at something that he had put a lot of effort and time into.
     
  9. Typhoon
    Joined: Mar 2009
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    Typhoon Senior Member

    Given what we know now about the boat with regards measurements etc, I think we can start also looking for hook on the bottom of the hull.
    I don't think you could change the build of the boat and alter buoyancy enough forward to really affect planing, and planing is dynamic lift anyway, so even if it is say 6" narrower across the chines at a set point, there'll still be considerable lift.
    I also don't think you could add substantial weight to a boat built the way it is in the bow only, and not increase weight everywhere, so unless there is 50m of chain and a 30kg Danforth tucked under the bow, I don't think that's it.
    I think if I was Brian, I'd find CG like I suggested and put a LONG straight edge on teh bottom of the hull from the transom.
    He needs to find out exactly where he is with the boat and eliminate every variable.
    I wonder if the boat has been set up on the jig wrongly and there is too much warp in the rear of the hull? What we see on the video is a pretty extreme dive at quite low speeds.....
    SO, Brian, could you PLEASE:
    1. lift boat and determine CG.
    2. Put a long (1.8 to 2.4m) straight edge on the bottom of your hull near the keel and tell us if you see daylight.
    3. Take a couple of measurements across the hull underneath the boat, from chine to chine, at set measurements forward from the transom.
    There is another solution...reinforce transom and hang a lovely 125 Mercury redband on it.

    That is one of my suspicions too, the prop I've seen on the boat is pretty big, lots of blade area and cupping. I suspect the props aren't designed for the boat but are off the shelf for much newer, heavier fibreglass boats with much shallower shaft angles and a desire to create huge wakes for wakeboarding.

    Regards, Andrew.
     
  10. Oyster
    Joined: Feb 2006
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    Oyster Senior Member

    I know that I change the running end of this with some minor details and a few hours of work without destroying the boat, maybe not perfect but enough to find out which area to dig deeper. He can add and I too have added minimum five inches total with rails of lifting strakes to the chines on all of the small hulls that allowed me to use smaller hp engines, generating lift and removing water from the hullsides allowing the boat to break free and run on top of the water. This was also the fix for many Hatteras hulls in lieu of repowering. They also did this for the 53' in particular because they did have a tendancy to wet you. Many of the older non turbo engines got this update way back in the 1980s.

    In regards to the bow, its quite possible if the planks are solid hardwoods of some durable species in lieu of solid veneers glued on plywood, and depends on the framing types and sizes, you can surely add some serious weight foward.

    We just do not know this and cannot get enough feedback making this issue and boat nothing more than a mental excersize for me down the road. I have the plans for the Biscayne 22 and boated with a fellow that had the Monaco with a diesel. Many of these types of hulls have come a long ways with the engines and hp. So I attempt to learn each day with these specialty hulls, never knowing the next day that I may also take the leap once again. But its also nice to figure out these types of problems when they also pop up.
     
  11. TollyWally
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    TollyWally Senior Member

    see post 7
     
  12. Typhoon
    Joined: Mar 2009
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    Typhoon Senior Member

    I was trying to re engage Brian to do something to help up. I'm aware of what's previously been said.
    Anyway, he seems to have sulked off for a while, probably what most would do (I know I would, I'd go away and have a good think).
    Hopefully we don't see the boat listed on Ebay or similar any time soon, I don't think it'd take TOO much work to make it serviceable.

    Regards, Andrew.
     
  13. tunnels

    tunnels Previous Member

    I think he's got a lot going on on the Glen L forum site ! check it out!! had a look last night but was in a hurry :p
     
  14. Oyster
    Joined: Feb 2006
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    Oyster Senior Member

    Yea a lot of chatter,:D and a lot of chatter, and, and, and, accomplished nothing. At this point I doubt that we will actually know the answers that reflects the facts on the ground. But its been an excersize to maybe help other ones coming along the way. Most of these types of boats have evolved into areas of speeds that most never were designed for, including building materials that makes the boat stronger and weigh less in some cases. This really changes thngs in the home settings unlike the numerous controlled factory production setups too for the wooden runabouts where they were consistant in the steps and rigging. Been fun though excersizing and cleaning the few remaining cells between the open ports in the skull.:p
     

  15. tunnels

    tunnels Previous Member

    yeah i know what you mean , brain gymnastic are hard to come by these days and i thought and hoped we had a volting horse here, as i say the Glen L site has some teasers in there so joining to have a look see , same old questions but .
    Keep up the good work !!:D
     
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