pod design

Discussion in 'Boat Design' started by Ev1, Dec 29, 2017.

  1. Ev1
    Joined: Feb 2017
    Posts: 19
    Likes: 1, Points: 3, Legacy Rep: 10
    Location: Uk

    Ev1 Junior Member

    Hi guys. I have a tinker 20 ft long. I've ripped out the motor and want to Repower with saltwater series Yamaha 250 If any off you remember I had issues with my pod on a regal empress porpoising well that boat went on fire and I lost the lot arwell. So we have a new project. I want to make another pod. What sort of angles should I aim for
    transom angle
    Negative angle on keel or follow boat lines
    It would have to be about 24 " set back from boat transom
    How wide the bit closet to the water should it be flat or vee shape copy keel angle
    My last pod was nearly full width followed the keel angles basically a hull extension
    I don't want the rear to dig deep on trying to get on plane want to get on plane in24" water so want maximum rise what I achieved with last pod but if I had to much weight at stern it would porpoise because COG went further to the transom
    Would a negative keel dig deep
    Cheers
     
  2. Ev1
    Joined: Feb 2017
    Posts: 19
    Likes: 1, Points: 3, Legacy Rep: 10
    Location: Uk

    Ev1 Junior Member

    So basically what is the best pod design for maximum bouyancey at stand still
    Best pod design for holeshot
    Best pod design for reduced porpoising
    Or do all of these contradict each other
    Or would it be best to cut out an engine well in the transomof the boat what I really don't want to do
    Any info be appreciated thanks
     
  3. jorgepease
    Joined: Feb 2012
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    Location: Florida

    jorgepease Senior Member

    I would step and angle up so as not to prevent bow from rising to proper planing angle and it will also help with porpoising acting like a wheelie bar. The amount of buoyancy lost by angling up won't be that much. I would also be prepared to shift batteries or other weight around as needed. If the mod throws things off that much, then also be thinking trim tabs.
     
  4. Ev1
    Joined: Feb 2017
    Posts: 19
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    Location: Uk

    Ev1 Junior Member

    Cheers jorgepease. Any idea what sort of angle to rake he pod up min max. As I'm seeing it the more rake up the more he stern is going to go deeper on holeshot The last pod I made followed the keel line no rake up counter acted the weight of Honda 225 didn't dig in massively helped get on plane 2/3 seconds up and on my way I fish shallow water so can't be digging deep so trying to find what would min angle rake But having made a couple pods before followed the keel line with 50 mm step up it would sometimes porpoise at high speed if I had to much weight at the stern what I sorted out by outboard wedge and removing the rear weight. I would make new one almost full width beam and being 24" long is going to be real small angle if stepped say by 50 mm
    Pods are quite complicated t seems that the more one goal is achieved at the expense of another goal
    So what would be rake angle for 20ft boat
    What be best step up hight.
    Cheers for any help
     
  5. jorgepease
    Joined: Feb 2012
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    Location: Florida

    jorgepease Senior Member

    Cheers,

    I took the following from the internet -
    Boat bottoms have the least drag at an angle of from 3 to 5 degreeswith the water. If they run flatter than 3 degrees, as most light planing boats tend to do, or steeper than 5 degrees, as stern-heavy boats just barely on plane may do, efficiency suffers.

    So what I did with mine, since I drew the design, was to angle my boat about 3 degrees and then set the pods (one each side of transom) so they would be parallel to the water at that angle. I had a slight bit of rocker in my hull so I didn't bother stepping it, just followed the hull line. It's a minimal amount that is why I said it's not going to affect your static draft much.

    If you wanted more buoyancy and help flatten your hole shot you could extend the bracket on either side of the outboard but you have to continue angling it up
     
  6. Ev1
    Joined: Feb 2017
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    Location: Uk

    Ev1 Junior Member

    That's a good idea instead of having a transom that's straight it could be stepped effectively having buoyancy in front of motor and along the sides as well. With the same rake angle

    I was also bouncing this idea around in my head dropping the pod below the keel say 50 mm. Do we think that most ov the boat would not even touch the water at speed stepped hull don't they do something like this on racing boats for less drag or is that far to complicated if it's not design right wouldn't it be something like a riser keel pad
     

  7. jorgepease
    Joined: Feb 2012
    Posts: 1,568
    Likes: 40, Points: 48, Legacy Rep: 75
    Location: Florida

    jorgepease Senior Member

    You are talking about a pad but no it's not stepped down ... imagine a v hull boat held at the proper planing angle and the keel shaved flat to the water. If you step down you are going to cause lift and bury the bow, avoid that at all cost ))
     
    Ev1 likes this.
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