Atkin "Ripalong"

Discussion in 'Powerboats' started by frank smith, Dec 1, 2010.

  1. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    I understand what Par is saying , but Billy Atkin may have had other things in mind with this design , He says it is # 2 of the series, and improved.
    I suspect that he was more concerned with operating in a certain sea state at below 20 mph for the most part , and that might be the point of bow sections .
     
  2. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    It would be nice to find it or one like it today, I would like to see it run at speed.
    I have been on a lot of high speed deep vee hulls but not on that type of hull .
     
  3. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,173
    Likes: 398, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    The absence of any appreciable rake or hollow flare at the bow suggests she might be a bit wet, and I believe the weak link with boats operating in this speed range is they are moving at much the same speeds as wave trains commonly do, and consequently find themselves climbing wave backs too much of the time, when running with the sea.
     
  4. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 114, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    The hook...hollow...pushes the bow down. Very much energy is required to launch a boat out of its displacment hole , onto a plane and onto its desgned lines for seakeeping. other apendages like planning boards can be used to overcome this squat .

    The draketails, The simmons sea skiff..many atkins boats, the verity skiffs, the boston whaler and on and on.... are all designed to use hull form to go from displacment to plane rapidly without mechanically forcing the bow down with adjustable trim tabs .

    Chuck paine drew it on his Gulf stream patrol craft.

    You must simply decide which appraoch you wish to follow...PARS caveman, knuckle dragging, just put a V8 in that baby and who cares what kind of damage my big wake leaves or Simmons or Atkins simple design appraoch with hull form.


    With the Atkins approach you will live within the design power restrictions.

    With the PAR appraoch you will live with the inefficient monster that you have created everytime you go to the fuel pump. Children will line the fuel dock, point their fingers and laugh as they watch you struggle for a wad of cash to pay the big number. Your hearing will rapidly fail from the racket given off by the V8. Whole families will have to pick up beach towels and flee the beach when your wake appraoches.
     

    Attached Files:

  5. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 114, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    the famous "Bartender " profile didnt load...sorry
     

    Attached Files:

  6. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Frank and Mr. Efficiency, the whole point of this is to force Michael to answer some basic questions, which have been asked before. The answers will prove, one way or the other if he has more then an arm chair understanding of the concepts, principles and dynamics involved in his broad paintings of various designs, designers or hydrodynamics in general. Again, he's failed.

    I very familiar with the Ripalong style of hull and Billy wasn't attempting address anything thing other then the target speed with this hull form, for which he specifically shaped the hook or in this case attempted to, as he had much more success when he revised his hull shapes after what was learned just after WW II. Of course Michael would know this, particularly with my repeated references to the Navy's series 50 model tests.

    My point is this hull is part of a general evolution in powerboat hull forms. This one is old folks, really old and full of issues. Is it a valid design? Of course. Is it efficient? Not even close, no matter how you measure it. Any true student of design can see the issues, as they're staring right back at you. This is the point of contention I have with Michael who attempts to present himself as one with considerably more understanding then he actually has. I've asked repeatedly for Michael's description of why this hull is a good one. Why is it efficient, why is it whatever, but he just babbles along as if not replying is an effective means to prove he has a clue about what he suggests.

    The bottom line, just after WW II huge changes to powerboat shapes and power plant weights, immediately presented themselves to the industry. The Higgings and Elco PT models, the 50 series tests and several other era approaches brought research into high speed planning hulls, were being preformed. These studies are classic and well known, if confusing in presentation. Anyone that's studied, as Michael overly claims he has, would be aware of these tests and subsequent tests, all of which can be clearly seen displayed in the lines of power craft from that particular era. Any reasonably skill "student" of design can look at a set of hull lines and tell you, fairly accurately what era it was developed in. Michael can not and presents himself as someone that can. He can't see the power robbing, suction making shapes on Ripalong. He has no idea what Billy did to the the hook height, width or length, let along curvature to make it (this hull form) hit the target speed.

    In other words, Michael speak what you know, which is clearly what you haven't been doing. I can dissect every post you make for they're filled with contradictions and fallacy.

    Lets just look at your second Paragraph shall we;
    Well here come the contradictions (surprised?). The draketails, the Simmons and darn near all of the Atkins powerboats use a hook, which is in direct contradiction to the last portion of this paragraph. Either you know what you're talking about or just blabbing. I don't even think you can recognize the difference between Billy's work or John's, even though there's a half a century between them.
     
  7. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    Par , All of this points out one thing in favor of the outboard of stern drive , "thrust vectoring" .
     
  8. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 114, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Well Frank..." Thrust vectoring "...to trim a boat wastes energy.

    A problem with outdrives in general is that they place the engine weight aft...the vessel will be stern heavy and will have more volume, displacement aft , more drag, more weight to move and consequently need more power.. It will struggle to climb out of its displacement HOLE to break onto a plane. Always best if a vessels weight is near the center of the vessel with its aft planning surface is pure. The center of a vessel is what pounds thru the sea so this is were you put the weight..the VEE of displacement.

    Im looking at a whole row of modern IO drive boats out of the water who also need trim tabs to compensate for this imbalance. . Once on a plane the IO will be efficient because its thrust is near parallel to the waterline of the vessel.

    When you load weight in the ends of a boat she will suffer. The new outdrives such as the Volvo penta IPS system allow you to move the engine forward, keep the stern lighter and the planning surface profile flatter, while enjoying the directional thrust of an outdrive. Well worth investigating.

    A vessel with this drive system would be designed for the system and unfortunately would not be able to "ground out " and rest on its own bottom like the old " simple" Atkins design and pod drives are expensive. .
     
  9. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    I dont think the idea of using a shaft to connect an out drive to a motor is new , and I agree I would like the weight where it is best . What do you think of an angle 0f 40degrees with a convex section forward reducing to say 10 degrees aft .
     
  10. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    What a complete sack of ****. So, outboards, jet drives and I/O assemblies are all wrong, What a clueless ***. Why don't you log onto a site where accuracy and realty coincide in the same sentence, because you really haven't a clue as to what you are talking about Michael.

    You're are quite correct Frank, separating the drive assembly from the engine isn't a new idea and though not commonly seen in smaller craft, it's not an uncommon thing in larger.

    Frank, asking Michael anything about design, is like asking a chimp if he can recount the first sentence of the Gettysburg address. It's just not possible with his level of understanding. He's literally is talking out of his butt.

    Again he's not answered a single question (he can't). Let's try some more of his statements:
    So, tell us Mr. knows what he's talking about (Michael), how does the Volvo drive system permit a flatter planning profile. In other words, why would an outboard equipped boat require a "less flat profile" in comparison? Why would a jet or I/O require a different profile, you clueless dung heap. You spout off about what you think you know, but can't back it up with logical, rational debate, let alone any factual account of the hydrodynamics involved. Go back to the bath tub and play with your rubber toys little boy.
     
  11. tom28571
    Joined: Dec 2001
    Posts: 2,472
    Likes: 114, Points: 63, Legacy Rep: 1728
    Location: Oriental, NC

    tom28571 Senior Member

    Depends on where you measure the 40 degrees. If at the forward waterline (station 0), it is too flat and not ideal. Between station 1 and 2 it is getting better. 30 degrees at station 2.5 is a very good all round deadrise to balance the many competing factors that want attention. 30 degrees at station 2.5 will tend to cramp the interior of a cruising boat but is fine for some others. 10 degrees aft is fine, depending on whether the aft hull is a warped bottom or monohedron.
     
  12. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    Gentlemen , good thread so far . This is a early Huntform hull . Closer to this is what I am thinking . Not to sure about the bell form sections .

    [​IMG]
     
  13. michael pierzga
    Joined: Dec 2008
    Posts: 4,862
    Likes: 114, Points: 0, Legacy Rep: 1180
    Location: spain

    michael pierzga Senior Member

    Axe Bow
     

    Attached Files:

  14. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    Micheal , That is an interesting shape , Where would it be used ?
     

  15. frank smith
    Joined: Oct 2009
    Posts: 980
    Likes: 14, Points: 28, Legacy Rep: 185
    Location: usa

    frank smith Senior Member

    On the warped bottom , where would be the best point to start the transition of the warp ?
     
Loading...
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.