I am wondering about my hull shape speed wise

Discussion in 'Wooden Boat Building and Restoration' started by sdowney717, Jul 6, 2015.

  1. PAR
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    PAR Yacht Designer/Builder

    I haven't frequented the WoodenBoat forum for several years, because of the "bilge" overflow and other rather closed minded contributors. I am an very old member there, with a 3 digit membership number, but it's changed enough to just not want to put up with the BS anymore.

    I don't think the bottom needs to be changed, in regard to the hook, unless you add a good bit more power and wish for a higher top speed. The hook is designed to help the boat's trim through a narrow range. If you over power this range the drag increases exponentially, though it can make a great wakeboard thing if desired. A convex shape wouldn't be desirable either, though less of a drag penalty than the hook, you'd probably just have to install tabs to replace what's lost with the hook's removal. The addition of tabs with the hook will widen the speed range a bit, but this is a dog chasing it's tail sort of thing and eventually, you just need more power or a different hull form.

    If you're interested in fuel efficiency, skip the tabs and keep the speeds within the range the boat was designed to operate at. That hull just isn't well suited for speeds much over the mid 20's and it's efficient range will be 18 - 22. The spray knocker could be removed, though you're not going to see much speed improvement. Any improvement wouldn't be visible on a speedo, though a GPS might show a .2% change comparing before and after. At 20 MPH this is less than a 1/2 a MPH improvement, which hardly makes their removal worth it.
     
  2. Easy Rider
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    Easy Rider Senior Member

    Got a lot out of your post PAR,

    I had no idea the hook was designed in … I assumed it was hogged sitting on blocks. "The hook is designed to help the boat's trim through a narrow range." Heaven help the guy that goes surfing at an ocean inlet. I was probably thinking of a 12 knot boat commenting on convex aft.

    Thanks as this boat w the hook was a mystery to me.
     
  3. sdowney717
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    sdowney717 Senior Member

    Yes, the hook was an intentional OEM design feature.
    And it would be somewhat difficult to remove and not worth the effort I think.
    From what I have read, it is supposed to help force the nose down and lift the rear, but as Par says, this also means hull cant go over mid 20's. I have read where Egg's with a hook like this when owners overpowered with lots more HP, the bow would dig in and they would be difficult to maneuver. The boat is not hogged, it is in good physical shape about the same underwater shape as it was made.

    I would say, definition of 'sedan cruiser' is not high speed sport fishing boat.
     
  4. PAR
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    PAR Yacht Designer/Builder

    If the hook was filled in (read gallons of putty), you could install tabs and get a wider speed range, but you'd be playing with tab angles for each sea state condition. It would be possible to get more speed this way, but it wouldn't be a big improvement, maybe with enough power to get you into the upper 20's, though fuel use would dramatically increase too.
     
  5. Easy Rider
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    Easy Rider Senior Member

    But PAR the extra hull volume, support or flotation aft would reduce the squatting, angle of attack and probably a lot of drag. Foam and stringers ect would be much less weight than "putty". Haha

    I'm about to consider this a bad design. But as I recall they were considered good boats.
     
  6. sdowney717
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    sdowney717 Senior Member

    Well it is what it is in't it?
    The hook does not extend all the way across the stern, There is no hook at the round chine. The hook extends slightly past the struts at an ever diminishing amount.
    So say hook is pronounced at the keel, hook continues as it moves outward and then vanished right past the strut, this from what I recall from holding straight board up against hull.

    I think to get rid of the hook, the strut mounting would perhaps be an issue.
    If you dropped struts to eliminate hook, then strut would be too long, by maybe 1/2 to 1 inch, which means the angles would change and engine alignment, I suppose might be possible to compensate. Maybe strut could be shimmed in place, press up to hull to see what needed with shaft connected, then an angular wood piece cut to reestablish a correct angle.

    I think maybe boards could be fitted and then ground-planed off and the some kind of filler used to smooth the hull.
    Last time out, I was contemplating if I wanted to how would I do such a thing. But this likely I wont ever do.
    Although I might someday.

    Another way would be to leave the strut as is, and shape the hull around the strut leaving a strut sitting in a pocket. This would prevent any issue with alignment and strut angles. But I don't like that idea much.
     
  7. Easy Rider
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    Easy Rider Senior Member

    717,
    You could build a box-hole for the struts so they would be undesterbed and fill the hole w foam or some other material that could stand the hydraulics but could easily be removed for service.

    I wonder if using solid wood would be effective. WR Cedar may not weigh all that much and if treated w CPES may not soak up much water. Could be bedded w Dolfinite for easy service/repair. Just a thought. Would be cheap and easy.
     
  8. Jamie Kennedy
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    Jamie Kennedy Senior Member

    Interesting discussion for sure. I like Easy Rider's idea of trying to clean things up as much as possible, but maybe focus more on things like weight reduction, and streamlining stuff like the sacrificial anodes, rudder, and maybe even the keel and stern post as well as the spray rail. I also agree with PAR about sticking with the general full shape and stick with the speed it was more or less designed for, but perhaps making it more efficient at speeds below that as well. You can't have everything, but weight reduction is one thing that tends to lift all boats, so to speak. ;-)

    I wonder how much of that keel might come off.
     
  9. sdowney717
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    sdowney717 Senior Member

    The skeg (lower) keel is white oak timber beams thru bolted with 1/2 inch long bronze bolts into the upper keel. And each timber is also bolted with hidden inner bronze bolts. What they did was assemble the skeg off the hull with bolts, then using more bolts attached it to the hull. It is about 4 inches in width.

    It may do nothing to prevent rocking, the boat can rock a lot due to round chine. It may exist to help protect the running gear? I suppose it may strengthen the backbone bottom of the hull.

    I imagine the rearward parts could be shortened up closer to hull. Maybe drop the keel bolts, then saw off some of it, then rebolt.
    Doing that likely would cut through some of the hidden bronze bolts.
    Only way to remove the hidden bolts would be to gouge out a pocket for where the nuts might be found higher up, good luck finding them without x-rays.

    Of course shortening the skeg might negatively affect the hull rocking more, which I would not like.

    How many inches in the aft part of the keel would need to be removed to make a measurable difference?

    I think getting rid of the hook instead is better.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    If the boat is running bow-high while going nowhere particularly fast, the hook is "not guilty, your honour". Hooks only slow boats down by forcing the bow down and increasing wetted area, and ploughing and bogging when running with the sea. The speed difference between what you once had, and what you have now, rules out anything to do with the shape of the hull, whatever skegs are there etc, it has to be more related to engine output you'd have to think. Look at everything you have changed, whatever remains the same as before is seemingly not implicated.
     
  11. DennisRB
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    DennisRB Senior Member

    What is the CFM rating of the old and new carburetors? Maybe the new ones are not letting the engine breath as well limiting power compared to the old ones. Also the slightly lower power density of E10 fuel will not mean you will loose power. It will mean you just need to use slightly more fuel. E10 fuel has a higher octane rating than regular which means you can increase your ignition timing and actually produce MORE power. I would wind a few degrees in. Alcohol blended fuels a big favorite for hot rodders with many people specifically tuning their engines for it so they can take advantage of the better performance.
     
  12. sdowney717
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    sdowney717 Senior Member

    http://www.nadaguides.com/Boats/1970/Egg-Harbor-Yachts/MOTOR-YACHT/10063253/Specs

    I found a listing for the weight, and it is 17,100 lbs. The NADA guide is not showing the same HP engines as mine are 265, and these 225, but weight should be close enough to be around 17,000 and 18,000 lbs.

    The quadrajet is a variable cfm carb which can go to 750 -800 cfm, while the motor cfm requirement is more like 400 cfm. The 4GC carb is also variable CFM, but not as obvious, the air valve is inside mid section on the secondaries.

    The only real changes i can think of at the moment are
    gas to to E-10 gas
    4gc carb to quadrajet carb
    trim tabs to no trim tabs

    However, the starboard fuel pump did fail, and I got a new better pump. A pump which cant pump enough fuel will lean out the mix, starve the carb, and the engine will loose power ( I think so ). So in a few weeks I will know some more about the speed.
    i pulled the distributor to work on it and found it needed shimming, the shaft end play was too great, not that it would matter. However the advance weights, the plastic bushings had failed, I repaired that, not that it may matter much.
    I will also verify the ignition timing is good.

    I pulled the plugs, here they are. This was after the pump failed and the engine quit while running about 1200 rpm.
    After the second time of coming in on one engine, I decided I had to get a new fuel pump.

    [​IMG]

    other side
    [​IMG]

    Plugs are Autolite 303, engines are IH 392

    Couple years earlier, I rebuilt the port motor which works well.
    here is an album of pics. Shows how I pulled it out. I worked on it right in the main cabin during the winter.
    https://picasaweb.google.com/105248...rnational392Engine?authuser=0&feat=directlink
     
  13. PAR
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    PAR Yacht Designer/Builder

    The top photo shows normal, though slightly darker than normal color. The bottom photo shows some fouling, but not a lot.

    When checking plug reads, it important to make it a fair test, so you get good readings. The plugs should be new or machine cleaned, so they don't add anything to the read. Install and run the engine at WOT under load for a few minutes, then shut down with the kill switch (disconnect the coil wire if you have to) and immediately pull the plugs. Don't let the engine idle, just shut it down and yank the plugs. This will give you the condition of what's going on. If the engine idles, it'll clean off the plugs and a lot of what's going on, so the read will look different.
     
  14. Easy Rider
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    Easy Rider Senior Member

    Instantly shutting down an engine working hard is not good for the engine but it is common practice.

    Re the hook it's only effective if enough speed is attained. If no it's lots of drag. Witness a planing hull just below "hump" speed.
     

  15. sdowney717
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    sdowney717 Senior Member

    I have often thought a hull that could change the under shape, morphing one way then another as needed would be a good idea!
     
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