Latest News: Forums Technical Outboard Bracket

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  • #3851

    I have a Mk1 GRP Wayfarer to which I want to fit an outboard bracket. Boats ‘N’ Bits of Norwich sell a bracket which, looking at past magazines, appears to be used on many boats. Unfortunately I cannot see how to fit it to a Mk1 Wayfarer and the company selling the bracket were unable to advise. In brief, how do I attach the nuts to the ends of the bolts inside the transom where space is minimal as a consequence of the polystyrene flotation blocks inside the rear compartment? Any advice would be gratefully received. Mike Norris

    #7661
    Swiebertje
    Participant

    Foam out, bolts bracket, foam back in. 😉

    Except for the foam part, the procedure is discussed in detail on the WIT:
    http://www.wayfarer-international.org/WIT/cruise.daysail/motors/motor_matters_index.html

    #7665

    Thanks for your prompt advice. Much appreciated. I had come to the same tentative conclusion although, not being “over practical”, I was hesitant in reinventing the wheel if there was an alternative, simpler solution (often the case).
    I have now looked at the references you gave and communications in respect of a similar previous enquiry. Only two further queries: (a) the polystyrene foam is encapsulated on two sides by a thin glass fibre wall/support. Presumably no choice but to cut this together with the foam and then re-fibreglass back as best one can? (b) any tips on cutting/joining the foam to ensure a solid bond – is there, for instance, a particular waterproof glue that expands to fill irregularities in the foam caused by the cutting?
    Again – thanks for your advice. Mike

    #7667
    Iain
    Member

    We fitted the same bracket one our Mk1 as follows
    We drilled the fixing holes in the transom, then fixed a spanner to a steel rule with tape so as to make a long thin handled spanner that will reach up behind the bouyancy tank.
    we then fixed the nut into the open ended spanner with a little blue tack
    also sticking a washer against the nut with a little blue tack, this will hold it all onto the spanner while it is pushed up behind the tank.
    With one of us pushing the bolt through the hole and the other holding the spanner up behind the bouyancy tank we managed to screw the bolt into the nut, the spanner can then be pulled off the nut.
    Its a bit awkward but with patience it works

    #7669

    Thank you for your advice. No end to human ingenuity! I now need to decide which route to take – unless of course in the meantime someone else comes up with another ingenious solution. Thanks, Mike

    #7671
    Swiebertje
    Participant

    I removed the foam and didn’t put it back. Any type of foam will eventually take some water and create a moist atmosphere in the tank. Even the expensive hard PU foam takes on some water. I rather use plastic (Coca Cola) bottles or cubitainers like Hartley uses on new boats. Bottles are cheaper though. Even if you decide to re-use the foam, why not take the opportunity and relocate it to a more convenient position inside the tank and create more storage space? Or replace it with a foam board (with the same volume of course) that is glued against the entire ceiling of the tank, creating more convenient storage space. Or do as I did and replace the foam with two waterproof plastic barrels, the sort that is generally sold to store pet food. Not only do they serve as safety buoyancy, should the tank spring a leak, but they also provide safe and dry storage space for sensitive equipment (camera, cell phone, etc), spare parts, a sleeping bag and/or dry clothes. Obviously, while racing I empty the barrels to minimize weight. The buoyancy isn’t much different between filled and empty barrels. Though the barrels are not held in any position, they don’t move around much.

    You need a buoyant material in the tank for safety but there is no reason to fix it in a position unless you want it fixed, or fix it in the current position (unless you want it there). Anything that floats and does not take on water will do the job, closed cell foam, bottles, barrels. Just make sure you have sufficient volume as specified by the class rules (MK1: rule 34.4a – 40 liter minimum).

    #7674
    tempest51
    Member

    Mike,

    Why not just use self-tapping bolts to secure the upper half of the outboard plate and going through the foam, and use bolts and nuts for the lower half? All the weight and force will be centred on the lower bolts anyway.

    #7675
    tempest51
    Member

    Mike,

    Sorry I meant to add that you could also use an epoxy mix to secure the plate to the transom, and then add an epoxy layer or 2 to the whole assembly to ensure a waterproof and physical seal. Your outboard would disintergrate well before anything weakened on the transom, and it would save you tampering with any of the buoyancy designs on the original boat.

    #7677
    Swiebertje
    Participant

    @tempest51 wrote:

    Mike,

    Why not just use self-tapping bolts to secure the upper half of the outboard plate and going through the foam, and use bolts and nuts for the lower half? All the weight and force will be centred on the lower bolts anyway.

    Au contrare mon amis, the upper bolts take most of the weight as the weight of the engine tries to break the bolts away backward, in a horizontal plane. It is a thing called torque. The lower bolts are just there to hold the bracket in place.

    Obviously this is only true in a stationary situation. Once the motor is started we have vibrations and when we start sailing a whole array of other forces is at play. Even if we are using only 2 hp the forces far exceed anything a sailor could do to the boat. Your suggestion to use self trapping screws is dangerous. The bracket is usually bolted with four M8 bolts and nuts, using a backing plate if one is not already laminated in to the transom by the builder. No self tapping screw can replace an 8 mm bolt and will be torn out in weeks if not days, leaving a severely damaged hull. The GRP is simply too thin to hold a self tapping screw firmly and the forces are not distributed but will damage the screw hole instead. A bolt and nut will sort of clamp the GRP between the bracket and the backing plate distributing the forces over a large area. Almost no forces work on the holes itself.

    Use bolts and a backing plate. Everyone else does and for good reason.

    #7678
    Swiebertje
    Participant

    @tempest51 wrote:

    Mike,

    Sorry I meant to add that you could also use an epoxy mix to secure the plate to the transom, and then add an epoxy layer or 2 to the whole assembly to ensure a waterproof and physical seal. Your outboard would disintergrate well before anything weakened on the transom, and it would save you tampering with any of the buoyancy designs on the original boat.

    No, Epoxy does not stick to aluminum nor does it stick to Stainless Steel. It also is far too brittle and will tear under motor loads and vibrations. Further more you need to protect it from ultra violet (UV) rays (sun light).

    Covering the entire bracket is also a bad idea. It will compromise its function which is that it allows us to remove the bracket leaving only a small shoe on the transom. Once the shoe is covered by epoxy the bracket will not fit properly anymore.

    As for waterproofing you need something flexible like Rubber or Sikaflex. The dynamic forces and vibrations created by the engine will constantly move the bracket relative to the transom, no matter how tightly it is fixed. Hence we need something that is flexible enough to guarantee the bond between bracket and transom stays waterproof for many years, yet flexes with movement. As an added bonus Sikaflex (or any other brand of PU based sealant) does bond reasonably well to steel, aluminum and very well to GRP. But Sikaflex alone will not be strong enough, you still need the four 8 mm nuts and bolts and a backing plate.

    #7680
    tempest51
    Member

    Seemed like a sensible idea with the bolts when Ian Porter suggested it to me mon amis, maybe the bolts and self threading bolts are the other way up?

    #7681
    Swiebertje
    Participant

    Not even Ian would use self threading screws to put an engine bracket on, though he seems to fix anyting with self threading screws 👿 . It seems you are confusing the engine bracket with something else?

    Most of us have re-fitted or repaired many parts of our boats after we counted our losses. Don’t use Ian as reference for craftmanship, not when I am around!

    #7683

    I appear inadvertently to have sparked an “international incident” regarding my outboard bracket. It’s encouraging, however, as a new member to note that Wayfarer owners care! My only contribution to this lively debate is the warning, learned from personal experience with boom rash, that blood left on GRP is very difficult to get off and is therefore best avoided. May I take this opportunity of thanking mes amis Tempest51 and Swiebertje for their interest and advice. Mike

    #7684
    BluTak
    Participant

    I put the bracket on my boat and it has done at least 500 miles under outboard. I didn’t access the back tank and used a ply pad. If you can wait a day or two I will look at it and describe it to you. I put one on for a friend and he used it with a 15hp motor so I guess its strong enough!
    Robert

    #7685

    Thank you for your input. I look forward to hearing more in a day or two. It sounds a good idea. Mike

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