1970 Boston Whaler 16.5 pilot house build, answers and ideas needed

Discussion in 'Fiberglass and Composite Boat Building' started by shizlenut, Feb 16, 2011.

  1. shizlenut
    Joined: Aug 2010
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    Location: Seattle

    shizlenut Junior Member

    Hi All
    I have been hard at work building the male mold for my pilothouse and using cardboard to make templates for cutting my contourable foam to shape, but I have many more questions than answers still lingering.

    I have been planning the build as such.
    1 setup stations and lathe to secure my foam onto
    2 template foam pieces from cardboard
    3 secure 1/2" 5lb, Baltek contour foam pieces to wood structure and secure them too each other also.
    4 putty edges and spaces between contoured foam on outside to make nice radius on windshield and other parts to make glassing easier with foam or putty
    5 Laminate outside of foam with +/- 45degree 17 oz, bi-axial, knit mat. then a .75 oz mat on the outside for ease of sanding.
    6 once the outside is finished, pull the mold off the boat and flip over removing wood.
    7 begin fairing the inside with putty etc... and laminate inside same as outside.
    8 put the finished pilothouse back on boat and laminate onto gunwale inside and out.
    9 sand and paint or gelcoat blah blah blah another days forum topic I'm sure.:rolleyes:

    So thats the jist of my plan so far, problem is I spoke with a fellow from Fiberlay and he has begun to convince me that it will be easier to make a true male mold, Using formica or masonite on the outside of my lathe frame, putting on release agent and going that route.

    I hadn't put much thought into that route until now and I'm not sure if it is easier for a layperson or not, especially because it is a foam core. I guess I am asking what route you would take and why?


    Other questions I have if I go my original route are as follows

    1 when securing foam to wooden structure should I use small dots of hot glue or brad nails with thin discs of cardboard? will hot glue cause small pits that need to be filled, are there any other problems with brad nails etc...

    2 when I go to putty over the foam seams and gaps if i have high spots will they sand out easily of will i destroy or abraid away the foam trying to remove the higher, harder putty.

    3 should i use vail in place of the .75oz mat to make sanding easier or is the thin mat going to have properties I want that the vail doesn't.

    4 I have figured my total foam at around 110 sq. ft. how can i figure the weight of my completed part, assuming I use the 45 degree 17oz w/knit mat backing and .75 oz mat.

    Please look through the pics of the build and tell me what I should do, where I've gone wrong, how you would do it etc... and if you think I should make my lathe structure into a true mold please tell me why and how because that process will be new to me.
    http://www.flickr.com/photos/madgregory/sets/72157626064430806/

    Thanks for any input your willing to throw my way, and thanks for your time.

    Oh and are these decent prices for supplies
    5 gallon pale laminating resin 139.94$
    .75 oz mat x 38" sold by yard 2.32$
    knit +/- 45 degree 17oz w/mat 38" 8.90$ per yard
    Fiberfiller putty 1 gallon 46.72
    1 case, 175 sq. ft., baltek, c70.75 1/2" contour foam 926.94$
     
  2. TeddyDiver
    Joined: Dec 2007
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    Location: Finland/Norway

    TeddyDiver Gollywobbler

    Don't listen your Fiberlay friend.. it's much better as you planned. Others might have something to say about your laminating schedule etc, I can't fig those imperials without calcs. What resin? Poly?
     
  3. shizlenut
    Joined: Aug 2010
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    Location: Seattle

    shizlenut Junior Member

    Thanks Teddy, I was hoping to hear that from someone. Is it going to be difficult to fair out putty on the surface of the foam if a guy has high spots? I will be using polyester resin.
    Thanks again
     
  4. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member

    In the long run it is in my opinion your better off to use the male mold and forget about making a female mold.

    You can use short dry wall screws screwed from the inside of your lathe to hold the panels in place, use a small spacer so they don't pierce the outside of the foam.

    One thing that is going to make more work is using ALL contoured foam I think it would be far less work to use solid foam sheets for all flat panels. The 1/2 foam is very bendy so if you need to crown the roof line if will conform easily to your male frame mold

    Fiberlays fiberfill will be hard to sand you might want to use a light weight polyester or vinylester filler to fill all the gaps in the foam and use the fiberfiller for structural radius.

    Your list of procedural methods sounds good, except I would go with 1.5 oz 450 gsm matt as a final layer for the outside and the inside surfaces instead of the .75oz
     
  5. indianbayjoe
    Joined: Nov 2010
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    Location: Lake Champlain

    indianbayjoe Senior Member

    why not cold mold the entire thing. Your half way there with what you have done so far. Weight?
     
  6. shizlenut
    Joined: Aug 2010
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    Location: Seattle

    shizlenut Junior Member

    I like the idea of the screws Pescaloco, I have also decided to use only a small amount of contour foam, and build some of my panels flat on my layup table. why would you go with a 1.5 oz final mat, just to make it smooth or to give extra strength?

    Hey Indianbayjoe, What is entailed in a cold mold? is that formica on the outside of my male form and radiusing, fairing and using release agent. etc etc.? I believe by my recent calcs that I will have roughly 88 sq ft and around 285 pounds, maybe 300 with windows installed.
     
  7. indianbayjoe
    Joined: Nov 2010
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    Location: Lake Champlain

    indianbayjoe Senior Member

    No Just build the structure out of lumber, plywood and epoxy over the entire thing with some cloth or mat. from your pictures you have the basic form already created out of plywood. The only thing is the weight may increse a little when the overall project is done.
     
  8. pescaloco
    Joined: Feb 2006
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    Location: so. california

    pescaloco Senior Member


    The 1.5 oz matt will not be sanded through as easily as the .75 oz and provides better hide of the Biax fabric underneath.
     
  9. shizlenut
    Joined: Aug 2010
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    Location: Seattle

    shizlenut Junior Member

    1 person likes this.

  10. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Nice job
     
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