Affordable seaworthy cruiser

Discussion in 'Boat Design' started by goodwilltoall, Jul 31, 2010.

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  1. Tinklespout
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    Tinklespout Junior Member

    "Great Minds ..... ......"

    Funny, I thought the same thing. Very similar to the Pilgrim. The Pilgrims high bow and stern would be much more comforting to me in rough seas but I am kind of a wimp when it comes to that; I had some rough times out there, 17 foot seas with short wave periods will make anyone respectful of Mother Nature. Goodwill, what are your thoughts if you should encounter a similar situation? My back of the napkins mathematics says that your bow and stern would be underwater; 1) causing your bow to "nosedive" into the coming wave, 2) your stern held down by the passing wave, resulting in 3) a fulcrum effect creating stresses that would snap your boat in half. Please don't take this wrong, I am impressed with your tenacity, just wondering if you've considered this. I noticed that someone else mentioned it.
     
  2. goodwilltoall
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    goodwilltoall Senior Member

    Well Buehler had an influence and pilgrim is his best design.

    Last year i did a comparative study of at least twenty boats and their relation of waterline beam at bow areas and several stations back and I think only one boat (don't remember which one) had more area. I did this because during lofting the batten I used needed more spring and as a result it ended up making a sharp entrance which got me very worried. Even now did a few more comparisons and it still looks good. Bow height is fine also but it lacks flare and hope the bwl makes up for this.

    That concern was also an additional reason for the cut water. If necessary (which I doubt and hope not) the added bow platform can be used to feather back about ten feet for more flare.

    Should stay away from conditions you mention but would definitely head off and slow down if caught in a similar situation. As far as boat breaking in half, it a logical concern for a long boat but you also have to factor in balance and not making it to full at stern which would excarerbate nose diving. Strong scantlings with proper balance will avoid breaking apart.
     
  3. goodwilltoall
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    goodwilltoall Senior Member

    One more thing about the longer boat vs shorter boat that got me to think was as it encounters the wave it takes more time for bow to rise on longer boat because the wave doesnt impact the wider areas aft as quickly as with a shorter boat. This contributes to less pitching but more chance of stuffing the bow.
    Will find out but I think my comparative calculations showing plenty of bwl even with my mistake gives me atleast some relief. Also if it was designed wider there would be more pounding but the full keel n cutwater would have mitigated that.
     
  4. goodwilltoall
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    goodwilltoall Senior Member

    Need to correct statement about shanty trawler. The full keel would help minimize rolling but the flat bottom would handle that I think well enough anyways. As said before its to break up full wave impact but also to keep boat on course and prevent excessive leeway drift. That's one reason typical houseboats need those big engines to overcome loss of control.
     
  5. nzboy
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    nzboy Senior Member

    Ive been very reluctant to comment or critique this build as seas trials will be the ultimate test. While a chine would please the idealists and me ,Epoxy will save the day with cloth inside and outside over chine area. Pre 1975 majority of ply homebuilds just used oil house paint seemed to work for a while! My father didn't do things by halves, dynel and glass inside and out side and 2 pot epoxy, boat is still floating somewhere
     
  6. goodwilltoall
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    goodwilltoall Senior Member

    Understand your reluctance. Have buehlers book with pilgrim and did a qiuck calculation. At his station 11'-3" which corresponds to 13'-2" on jubilee. the beam wl is 4.23' for pilgrim n a little over 5' for jubilee, but pilgrim has alot more flare. To figure the bow height comparison i made both max beams at 8.33' and the result is both have bow heights above wl at 4.75'.

    This is one of the ways i learn, its unorthodox but you have to have some foundation to make comparisons.

    Would like to see somebody build pilgrim i think it would make a fine boat, but knowing what i know now, think jubilee will be better.
     
  7. frank smith
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    frank smith Senior Member

    You have got me completely stumped . Many expectations based on your own assumptions. Reminds me of Harley and his little Around in ten boat. I am looking forward to the launching.

    F
     
  8. peterAustralia
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    peterAustralia Senior Member

    gwt,,, I know you are keen to do your own thing

    I guess if you want to build a second boat, heaven forbid the 50ft one does not work out as planned. I might suggest building Pilgrim as per plans, over doing another boat to your own design. Harley and AiT,,, oh dear,,, thats not nice.
     
  9. Tinklespout
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    Tinklespout Junior Member

    Goodwill,
    My comments are provided with the greatest respect; you have obviously learned a lot and put much effort into your build. Hats off to you for this. "Ignore the man behind the curtain". One more comment though wrt to strength and worst case weather. When I was caught in the 17 foot seas, we watched the weather and were in the safety zone. However, we had to straight into it to save a fellow boater and thank God were successful in all respects. My point is that while we "have the technology" nowadays to avoid bad weather, stuff happens. It would be easy to do a "three point bend" test of your boat on land. If it breaks apart, oh well! This would simply show you where the weak points are and you can then strengthen them and head to sea with your mind at ease; this is a very important consideration to me: boating with confidence in my boat. Oh well, that's my two cents.
    Take Care, Kim
     
  10. SamSam
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    SamSam Senior Member

    [​IMG]

    There's this photo with the description "box keel tab". Is that 1/2" plywood scab all that holds the keel onto the hull?
     
  11. peterAustralia
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    peterAustralia Senior Member

    hmmh, thats does seem a worry. I guess the term 'keel bolts' was new to gwt when the bottom was built. In Australia we call items called coach screws, however for this job normal bolts would suffice, if it were me I would use 10 inch coach screws or bolts of 3/8 diameter to tie the lenghtwise stringers into the transverse frames. I think quarter inch would be a fraction too small but would probably be OK if cost were an issue.

    I am also a bit worried about the linkage between the bottom of the box keel sides and the bottom of the box keel itself, by this I mean the last inch of wood coming off as opposed to the major timbers separating. I guess it could be fixed retrospectively by adding stainless steel coach screws.

    Coach screws point upwards when the boats is upright, (go down in this photo), to add them after the woodwork you would have to get inside the hull, drill straight up through both major timbers and the capping piece, because if you tried to add them from the outside you would not know where the transverse frames were.

    Thus get inside, drill a quarter inch hole all the way through, go to the top, widen the hole to fit the coach screw top and a washer, then add your coach scews and washer, then fair it back with a thickened epoxy paste.

    apparently you in the US call a coach screw a 'lag bolt'. Using conventional bolts would be a two person job, lag bolts could be a one person. I dont know if the make long stainless steel lag bolts or not. Whereas I am pretty sure they make long ss bolts.


    [​IMG]
     
  12. peterAustralia
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    peterAustralia Senior Member

    try image again

    [​IMG]
     
  13. goodwilltoall
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    goodwilltoall Senior Member

    Good day to all.

    Thankyou all for your suggestions as they will help much. NZboy comment about using cloth at chine is much better than what I had planned by using wood blocking.

    Tinkles: How would the three point test be done? Would you elevate the boat and put a bearing in middle and then pull down on ends?

    Sam: Thats a very good observation you made. When the installation of tabs began the first four stations had thinner ply and then thought - why is this? So from there on it was only 3/4" and when turned upright will possibly lay an additional layer over them however, the cutwater will extend to the fourth station and the plan is to make it solid wood/epoxy. It will act as a butress and tie it to the rest of the hull.

    The rest of the box keel area as shown in pics at #1123 post show how wide it becomes as the keel goes aft until it reaches the prop where it narrows but is deep, there is substantial 1x treated wood atttached to framing by about 2'. The first layer of 1x longs is on with two more layers of ply over that and then at least two 10oz.

    Before the cloth is added plan to add a signifigant fillet at hull/keel joint.
     
  14. goodwilltoall
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    goodwilltoall Senior Member

    Do you think the solid cutwater will be to heavy? As designed its an additional 264lbs of displacement which will add to the bouyancy fwd at sametime guessing an additional build weight of 150lbs. I put it there to bring more displacement fwd, it will also provide better handling and collision protection. Dont feel comfortable having an unaccesible air void below the wl thats the reason for making it solid.
     

  15. goodwilltoall
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    goodwilltoall Senior Member

    Went back and quickly looked at drawing and it shows the sole 21" above the waterline at aft area. You see this on modern ocean going sailboats, fishing boats, and rescue boats. Was wondering what some of your thoughts are about this?

    Sam, This is one reason I prefer graph paper as its much easier to design for ergonomics than constantly having to pull out a ruler. You can sit back, look at it, and then contemplate how the dimensions will fit.

    And Frank Im glad you used the word assumptions as it refers to taking control and responsibility rather than presumption which means without fact.
     
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