My transom fell off

Discussion in 'Fiberglass and Composite Boat Building' started by Cebu, Oct 22, 2010.

  1. Cebu
    Joined: Oct 2010
    Posts: 18
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    Location: Cedar Rapids

    Cebu Junior Member

    My transom fell off - well it will if someone doesn' help me design it

    Not really but it worries me as how to design my transom to hold one big outboard or two smaller ones. I mean the weight and vibration needs to be dispersed into the hull. I had thought of making a 1 inch square tubing frame for the transom and bolting on 1/4" steel plate on both sides and attaching it to a steel keel running the middle of my 22 foot long Jon boat design. Then fiberglass the whole thing in.

    This I am sure would work but it seems also overkill.

    How do the commercial fiberglass boats make their transoms for outboards?

    Any transom info would be helpfull as this is one of the last parts that I am still designing.

    ThanX

    Cebu
     
    Last edited: Oct 24, 2010
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    As I've aged, my ability to read minds has diminished considerably, so, if you would tell us the make, model and year of your boat, any alterations, upgrades, the engine(s) you wish to install, etc., plus any photos you might have. This would make things wee bit easier for old clairvoyants.
     
  3. Cebu
    Joined: Oct 2010
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    Location: Cedar Rapids

    Cebu Junior Member

    Yes you must be aging. I'm the guy who wants to build his boat out of cardboard. So I am still in the middle of the design phase and want to know how the commercial guys do it and how I can apply their technology to my boat.

    That's a 22' x 7.5' fiberglass Jon boat.


    CEBU
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The "commercial guys" hire an NA who engineers the laminate schedule and scantlings for the project.
     
  5. apex1

    apex1 Guest

    And they do not follow exclusively each and every of Cebu´s posts to know what he is talking about.....................

    You cannot apply our (professional) technology to your (unprofessional) boat, Cebu. Your method does not allow for that.
     
  6. Cebu
    Joined: Oct 2010
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    Location: Cedar Rapids

    Cebu Junior Member

    I really thought this was a forum where a newbee could go for some technicial help with his design. I thought this site was to help increase the number of boatbuilders and help them build boats. Instead you just insult me by throwing out obscure design terms. Why not offer some useful references, technicial documents or names of members who have expertise and willing to help. Do you really expect me to look up the terms "laminate schedule" and "scantlings" and study them and magiclly know all I need to design a transom.

    Please some one give some help and direction to the sources I need. I am an engineer with no working knowledge of marine structures, help point me in the right direction.

    ThanX

    CEBU
     
  7. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    Don't shoot yourself in the foot. You are "designing" your boat but you are asking how to do so. Be patient and don't run off.
    Generally, a transom is laminated from layers of plywood. How many and of what thickness depends on many factors, especially what kind of power it is expected to transmit to the hull.
    Rules of thumb do exist and a bit of overkill ensures you won't see your boat fall to pieces as soon as it hits the water.
    Here's an example of a good question:
    Hi, I am building a skiff of my own design from plywood. It is 19 ft long and 6 ft wide. I would like to run a 60 hp outboard on it. The boat will be pretty sturdy. I calculate the weight at 600 lbs not including outboard and crew. She'll take some hard use as a full time fishing boat. The transom is 5 ft 6in wide. I've drawn a picture (see below) of the boat.
    my question regards the transom's thickness in plywood, and whether I'll need to add bracing as well and where to put that bracing.
    I'm a novice when it comes to both design and building but I have studied skiff design some and I'll have a lot of experienced help from friends.
     
  8. Ike
    Joined: Apr 2006
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    Location: Washington

    Ike Senior Member

    Don't give up on us. PAR is just tired. Like me, he's involved in too many forums.

    Typical structure. The transom is a sandwich. on a fiberglass boat its generally plywood sandwiched between glass. Usually about 2 inches thick but that depends. However some builders make solid glass transoms. On a metal boat it's a metal backed by plywood. or wood sandwiched by metal.

    For strength, a pair of longitudinal (lengthwise) stringers running forward from the transom to some point farther forward in the boat. They don't necessarily run the full length. A pair of braces from the transom at about a 45 degree angle tied into the stringers. The size, shape, strength and how they are tied in differs depending on, size of the boat, size of the engine (weight and HP) height of the transom (20 inch, 25 inch) and the material and so on. So we need specifics, otherwise you get general answers or wisecracks.
     
  9. srimes
    Joined: Sep 2008
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    Location: Oregon

    srimes Senior Member

    Well, yeah. Maybe these will help:

    http://lmgtfy.com/?q=laminate schedule

    http://lmgtfy.com/?q=scantlings

    I'm as ignorant as the next guy, and when I don't understand a term I'll try to look it up before asking for the definition.
     
  10. apex1

    apex1 Guest

    Do YOU really expect us to give advice in unprofessional terms? The right terminology is what makes such a Forum possible for worldwide exchange of knowledge. Why would we give that up?
    If learning the right terminology is already too much for you, how about the secrets of boat design? That is a much wider field to comprehend, and a very difficult one if one does not know what people are talking.

    It seems you are out for a short 101 in heart surgery, without seeing any blood!

    And worse, it seems you don´t like contradictions to your preconception.
    Do not ask experts if you don´t like experts replies!

    Richard
     
  11. Cebu
    Joined: Oct 2010
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    Location: Cedar Rapids

    Cebu Junior Member

    Apex1 why don't you leave me alone and find another thread, your not welcome here or in any of my threads. If you cannot be constructive and polite go somewhere else. I am going to block you again. As for you being helpful with throwing out nautical terms and expect me to be impressed, think again. I made it clear from the start I was a engineer and clueless to marine engineering and just wanted to design and build my boat and needed some help directing me to resources so I can design my boat. This is kin to asking the librarian where the therodynamics texts are and not asking my TA to design my term project. As an engineer I work like this. I brainstorm and develop my first design and then redesign it over and over again to work out the errors. But I do freely admit when I am clueless or do not know where to find the answer. Or maybe I am not even aware of questions I should be asking. But you Apex1 claim to be an expert at everything and sit around all night posting to every thread. You obviously learned you knowledge from hands on, and not in a structured setting like school. So it is apparent we are not compatable, therefore let me continue my design discussions with those who interested in helping me finish my design of my cardboard boat or discover the structural flaw that will redirect me to the path 2 design of foam fiberglass.
    Before I started this transom thread, I had a finished design and came to the realization that I had overdesigned it and decided to request help finding some free transom plans or of design notes some member would share. Or even a freeflow discussion of a redesign of my transom design. Also hiring a NA is not in my budget, that is why I am here in this forum.

    My next post will describe in detail my transom design as of 2 months ago.


    CEBU
     
  12. Cebu
    Joined: Oct 2010
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    Location: Cedar Rapids

    Cebu Junior Member

    As promised this is what I had in mind for my transom design.

    It starts with steel frames made from 1 inch square tubing. A square metal frame encloses the transom. A outer steel plate 1/4" thick, is welded to the frame and a inner matching 1/4" steel plate is attached with bolts to the outer plate. The size of the steel plates are only large enough to cover the area needed to attach one or two outboards. They are held seperated from each other by steel spacers. The spacers are 1 inch steel round bar stock with a center drilled hole to match the attachment bolts. The length of the spacers equals the laminated fiberglass and core sandwitch thickness. There would be 4 or 8 bolts respectively. This frame would be welded to an additional box frame made from 1 inch square tube. It will be placed approx. 1 foot forward of the transom and will be enclosed to hold 1 stainless gas tank on each side of the boat. In the center will be the Battery boxes and other misc items. Next will be the keel made from again 1 inch square tube. It will be two parraell bars running forward, and stopping 4 feet from the front of the boat. This is the intersection of two critical design elements. This point is where the modified V bow starts it upward taper and it is also the forward bulkhead of the wheelhouse. The wheelhouse is the whole width of the boat and is 7 feet high and enclosed on three sides: front and sides. Open to the rear. A steel frame will rise from the four corners of the wheelhouse and be attached to the keel. I had also planned to attach two additional beams of 1 inch square tube to be attached in the middle of the keel measured from the trailing edge of the wheelhouse and the forward edge of the gas tank/battery box enclosuer. If I seem to explict in my discription I have be told my detail is lacking. Also I will be making a mock-up of my boat and keel and posting photos so as to further help those watching this thread see my vision.

    Thanks for being here with me.

    CEBU
     
  13. WickedGood

    WickedGood Guest

    Alan Post some pictures of your "skiff of my own design from plywood. It is 19 ft long and 6 ft wide."

    I would like to make a 18/20 ft skiff 8 ft wide for Duck Hunting and Ill push it with a 25 hp Merc

    Object is to use Plywood, Cheap!
     
    1 person likes this.
  14. apex1

    apex1 Guest

    CEBU

    you do not design a boat! You are dabbling with senseless ideas! There is a little difference, you know?

    The cardboard idea is as mad as the steel structure in your transom. If you cannot afford a proven design, you have to buy a second hand boat or give up on boating. So easy is that!
    Throwing some premature thoughts in the ring and assuming that the experts are willingly make something buidable out of it is not just optimistic, it is impertinent in this case.
    A open minded person would have asked first, and not tried to get a mad idea confirmed.
    And a engineer would know about his limitations and ask instead of "designing" first!
    Your unpolite approaches here, (see your first post) and the unwillingness to use a worldwide agreed terminology do not bring you any further. And sure, that holds most of the experienced members away from your threads!

    I am not sitting at my computer all day long (you don´t even grasp that we have different time zones?), but my internet connection is open all day while I am sailing, and BD.net runs in the background.

    Go for what you want to go, I don´t care. We have similar approaches here every week, all fail in the end.

    Good luck anyway, maybe someone opens your eyes (like going for FRP sandwich in foam, not paper).
     

  15. WickedGood

    WickedGood Guest

    CEBU


    how you pronouce that? SaBout?


    I worked with an guy who took all the old Cardboard Packing from the VAX computers that were unpacked and was going in the dumpster. He took this Free cardboard and built himself a nice big barn up in Vermont using nothing more than Elmers Glue ( Which is made from Horse Hoves that is too tough for the Jello) and he had a dandy barn

    He sparyed it down with a mixtuure of old Motor Oil and Tar to make it waterproof.

    It all worked out real well and was low cost. Lasted a while before it caught on fire. but Hey

    A Cardboard Boat? Go for it! maybe you can use the Tar idea to keep it waterproof. Now thats a "Slick" Idea!

    Steel is a good strong builing material and you should have no problem holding a couple 100 hp outboards on it. However maybe it would be better to go to the junkyard and buy a couple VW Bettle engines foe $20 bucks. As they are Air Cooled it would be just the ting to mount on your boat and just bolt on an old wood propeller from a scrap airplane.

    Be sure to stand on the Port side when you pop it over and yell Contact before you do.



    <removed>

    Here is a German design that works with just One Oar in the Water!


    [​IMG]
     
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