Transom rebuild questions

Discussion in 'Fiberglass and Composite Boat Building' started by Presty, Sep 10, 2014.

  1. Presty
    Joined: Sep 2014
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    Location: Gold Coast

    Presty Junior Member

    Gday all!

    I have just recently started my first transom rebuild on my 80 model Stejcraft half cabin.

    Cutting off the top half at rear of my boat (engine well + 2 seats either side of well) to gain access to the transom, I really like the look of how much room there now is without the engine well being there!

    My question is, is it possible to cut the engine well and seats right back to the transom and just leave the top edges of the sides that will continue to the back of the boat and then across the transom, sorry if this is confusing. :confused:

    Basically I want the top rails of the boat to continue to the rear as they always were and then I want to glass the transom in as the final finish at the rear plus flow coat of course.. no engine well or fibreglass seats in the rear corners.

    Im hoping someone can let me know if this is possible as far as structural integrity goes?? and any ideas that could help

    also would it be a bad move to remove the engine well, as far as taking in water?? I think this would only be minimal

    Its just an idea I had to maximise the fishing space on the back

    this is my first boat project and decent glass job so I apologise if I am struggling to paint a picture of what I mean, but I attached photos which Im hoping will help.

    Cant wait for some advise :) Thanks fellas!

    Mitch :)
     

    Attached Files:

  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Yep, you can cut out the "splash well", but except on very small boats, the well is a safety feature that shouldn't be removed. In you boats case, the stringers and other longitudinal stiffeners are sparse, suggesting the liner/deck cap (the part you cut) is part of the structure. The side decks don't show much depth, so they wouldn't add enough longitudinal stiffness, so the liner, uses a flange, molded in seats and an engine well to both save weight and reinforce the load transfer from the transom. All these angles greatly stiffens things up.

    To be technical, you can cut out this well, but the reinforcement it provides needs to be replace somehow. A horizontal brace about half way up the transom, maybe support by a couple of vertical knees from the brace to the bottom will go a long way to replacing what is removed. You'll gain a good bit of space, but (and it's a big butt, much like my other half's) I would only do this on a long shaft (20") outboard and never on a short shaft. You simply need the transom cutout to be high enough to prevent swamping. I've seen boats sunk from a boarding wave through the transom cutout. As a result, I don't design any boat without a 20" shaft cutout, except for the most very small power skiff.

    The horizontal brace and the knees will need to be well tabbed to the transom, hull sides and bottom. If you're going to screw up anything, do so on the too much side of the equation, as the results are less costly then going to light on the tabbing.

    What's the length, width of the transom, shaft length and engine HP on this puppy?
     
  3. whitepointer23

    whitepointer23 Previous Member

    I am familiar with stejcraft. Par is spot on. You must strengthen the transom if you remove the seats and well. They are not very strong to start with. I knew one that split the transom from the auxillary motor weight and my uncles touched the sand on a bar crossing and split from the gunnel to the chines. We had 3 in the family back in the late 70's. Good boats but the construction was of a fairly low standard.
     
  4. Presty
    Joined: Sep 2014
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    Location: Gold Coast

    Presty Junior Member

    I really appreciate your replies :) PAR, my transom is about 70 inches from side to side and 19 inches from bottom centre to the bottom of the engine cutout, my engine is a 50hp long shaft 20 inch leg.

    I have no problems with over strengthening my transom for peace of mind, is there any chance you could explain the bracing you are recommending in some sort of a drawing and rough dimensions?…….. would extending the stingers back and bracing the transom into the stringers with knees create more strength?

    Also if I was to attach my motor to a custom made alloy pod which mounts on the transom (local alloy boat builder makes them) would this require even more strengthening of the transom to support it?…..

    Im thinking doing this would allow me to build the transom right up and no longer have the engine cutout plus gain all the space at the back of the boat for fishing.

    I have attached a photo of a similar pod I would like for my boat (if possible!!!) only a smaller version for a 50hp

    I would love to know you thoughts

    Thank you!

    Mitch :)
     

    Attached Files:

    • pod.jpg
      pod.jpg
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  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    A bracket (like pictured) will allow you the things you want, in regard to additional cockpit volume, no splash well, etc., though you'll still need to reinforce the transom, as you suspected.

    Cut the side decks off the removed portion of the liner and bond them back onto the boat, which will finish up the look. Some sort of horizontal brace just above the bolts for the bracket should be bonded in and I'd bond in two plywood knees to the bottom stringers, well tabbed in place to transfer the bottom loading. The horizontal brace could also be at the top of the transom, maybe looking like the side decks wrap around. You have to rebuild this area where the cutout is anyway, right. Two layers of 3/4" plywood the full with of the transom is the minimum, with 3 layers of 1/2" being stronger. Of course, this too is well tabbed to the hull shell, the knees, brace and stringers.
     
  6. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The engine well prevents water from entering the boat. It is an important safety feature in smaller boats.
     
  7. whitepointer23

    whitepointer23 Previous Member

    Is it a 15 ft stejcraft. I was talking about the 18. Do you have the skill to build a ply and epoxy pod. You can make it how you want and for a fraction of the cost of an ally pod. If you fit new floor stringers run the 2 middle ones thru the transom and use them to build the pod on. I know a boat builder that does this with glass boats and it works well. The 2 beams carry most of the weight so the transom does not bare all of it. Also google home made pod for stejcraft. A bloke has a you tube video on a bolt on pod he made step by step.
     
  8. Presty
    Joined: Sep 2014
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    Presty Junior Member

    Thanks heaps Brendan I will def check this out :)
     
  9. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I wouldn't carry the stringer through the transom, for one reason. Though they would provide good support for a pod, they also would be a potential leak point and not an easy one to see. Think of the hull as a waterproof shell. You want to maintain the integrity of this shell, so penetrations need to be carefully thought out, if not avoided if possible. If the pod is bolted and/or bonded to the transom, you only have fasteners to worry about, which unlike stringers that are going to flex with bottom load (hopping wakes, slamming over chop, etc.) changes. If the pod is all laminate and the stringers are similar, with an inert core, some justification could be made for carrying them through, but not if the pod is plywood, sheathed in 'glass with wooden stringers penetrating a plywood cored transom.
     
  10. whitepointer23

    whitepointer23 Previous Member

    The 1 the boat builder showed me looked like it would last for ever. HIs pods are fully glassed to the hull. Not bolt on.
     
  11. whitepointer23

    whitepointer23 Previous Member

    My own pod is the opposite . I made it to protrude into the hull 230mm so I could bolt it to the inboard engine beds. That way I did'nt have to build the transom up to outboard specs.
     

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  12. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I'm confident both you and I could insure the transom's integrity, but a novice, doing this sort of thing the first time? This is my only hesitation in this regard, considering the previous questions the OP has asked, I felt a prudent course.
     
  13. Presty
    Joined: Sep 2014
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    Presty Junior Member

    Im thinking the custom alloy pod would be a wise move for my level of experience.. and I think the price of $750 Australian is pretty good… Im just in the process of drawing a design for the strengthening of the transom… Ill post a picture of it when Im done, would really appreciate both of your opinions if possible, I want to make sure I have all guns loaded before I start this job :) thanks fellas!
     
  14. whitepointer23

    whitepointer23 Previous Member

    $750 is a good price. Point taken par. Hey presty have you got any of jeff websters books. Most newsagents carry them . I think the second edition has an excellent article on transom rebuilds including lots of pics.
     

  15. Presty
    Joined: Sep 2014
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    Location: Gold Coast

    Presty Junior Member

    I just ordered the second edition of Jeff Websters... its in the mail… thanks Brendon :)
     
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