Ski boat project questions

Discussion in 'Powerboats' started by aussiebushman, Sep 22, 2012.

  1. aussiebushman
    Joined: Oct 2009
    Posts: 269
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    Thanks Tunnels

    I'll get rid of the cav plate and old rudder as recommended. I'm going to see if the motor can be mounted to avoid a transom cutout because I do not want to cut into the existing stern if it can be avoided. One reason is that retaining the existing fibreglass right round the hull will elimiminate the need for timber coverboards and all of the tricky work (and cost) involved. The picture here shows how the new timber deck is fitted flush with the the glass that will be faired and finished with 2 pack. New deck beams will be rebated to ensure this flush fit. The days of prep work will still be easier than making timber coverboards.

    If this means using a bracket for the outboard, so be it. Obviously, the motor must be able to lift and tilt, also swivel for steering. I'll make up some scrap ply templates to check this. The 150 Merc came with all the control cables and goodies so any old cables (found them in a box I forgot I had) can be dumped.

    The transom is sound - no sign of rot. 2 layers of 20 mm ply and glass, plus knees will fix that and yes - I have mega-hours of glassing experience (I have built 4 boats to date).

    To repair the minor hull scrapes and dings, Polyester resin and fillers will do but for everything else I shall use only epoxy. It is false economy to use polyester on ply or timber. I coat all ply surfaces with 3 coats of unthickened epoxy, epoxy thickened with microfibres between ply layers, plus S/S screws to eliminate voids, then fillet all joins with epoxy thickened with microspheres. 440 gsm double bias cloth is reasonably priced here and will make the entire transom very strong. We are going into summer here (ha,ha - it snowed today) so slow hardener is best to give decent working time. In the mountains here, the late spring/summer temperature is generally between 20 and 35 degrees C.
     

    Attached Files:

  2. tunnels

    tunnels Previous Member

    Ok ! i printed the pictures this morning but for a change i have a load of things to be done !,working that is !! good to hear also you done glassing before and not some one that hasent got a clue and have to start from square one !!.

    Looking quickly as the print was coming out of the printer i see the back of the hull has a recess where the cavitation plate has been right across the back of the hull not just a small place like that plate that you got with the rudder on it !!!.
    Looks also like some one has done a glass panel cover up job along the top sides of the hull and looks like black resined the rest for what ever reason !
    As i said the prop shaft hole will be some where along the bottom and covered over !! its would not have been very big any way but there could havebeen a stuffing box inside with a shaft gland etc attached to it .

    The plate recess across the back needs to be ground back to glass surface and glass filled level and straight to the back of the transom ! also bring the ends of the strakes back and finish them flush to the transom corner ,need to be square and best with no radius at all, a corner sharp enought to cut paper is whats needed.sharp square corners shed water quick cleanly and easy and reduce drag . In the case of chine edges and strake corners etc they collectivly add a hint of better drag resistance !

    The glass gunnel/deck edge that looks about 80mm or so wide id carry on with the cut the same width for the rest of the way right to the transom then just lift it up and peel it off across the back Its a good edge to keep and you can add to later !! You will need to add to the transom inside any way and there'll be a new splashwell to be made etc etc and lots new building happening in that area so it needs to be gone to be able to get in there and clamp and screw etc etc then glass over the whole thing !!. so you can marry the old and new together plus the old gunnel will hold the hull shape much better than not having one at all !!
    Have a good day !!
    :):D:p:p
     
  3. aussiebushman
    Joined: Oct 2009
    Posts: 269
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    Thanks again Tunnels - I'll have to hire you as a consultant!

    I'll grind the area where the old cav plate was attached. The strakes can be extended with shaped timber and the area between them filled with chopped mat, then fairing compound.

    Hard to tell what happened right along the sheer, but the line extends evenly all the way around the hull. No amount of grinding will hide this so after fairing and painting the entire outside of the hull with 2 pack finish I'll butt up to the line with a 50 mm 3M vinyl stripe in a colour that contrasts the new hull colour - it will look as though it was designed that way.

    I disagree about removing the 70 mm deck-edge at the stern because it will be feasible to fit the transom reinforcement without removing it, then add a couple of knees under it plus a serious epoxy fillet all round. This will be stronger too. The other merit of leaving this deck edge in place is the visual continuity. I'll rebate a vertical strake to fit snug under the inboard sides of the deck edge and this will provide a good fixing surface for the interior lining panels. Will probably make the latter in 6 mm ply (epoxy coated) and either painted or upholstered.

    Looks like 2 years work to me!

    Alan
     
  4. tunnels

    tunnels Previous Member

    2 years ! yeah takes a while and i spent hours just sitting in my boat looking and thinking what can i do and what should i do ! i made all my panels out of glass as in total throughout the whole rebuild . I didnt want wood any where at all. I used plasic pipes to get rounds and a sheet a meltica board to mould over and make panels amost exactly the size i wanter so to not have to much waste . i did use gel coat for the surface to keep the glass fibres away and not show up i used a heap of hot glue sticks and small strips of ply to hold things together in the right place and then laid glass over the back side .
    Have you ever used peelply ?? Its laid over the wet glass and rolled down with the last layer when all is hard can rip it off and leaves a nice smooth surface 100% ready to sand lightly and undercoat over .
    It also helps to get rid of surplus resin and compacts the glass fibres some places i worked we used it every where and i mean every where . !! saves lots and lots of time even use it with epoxy as well ! can finish working inside the boat and rip it off and takes all the rubish like paint drops foot prints and glue spills and resin all comes off and have a surface ready to paint 100% clean and smooth ! i use it all the time !dosent matter what glass you put it over top of still get the smooth finish !
    Got to go :)
     
  5. tunnels

    tunnels Previous Member

    Thanks again Tunnels - I'll have to hire you as a consultant!

    I'll grind the area where the old cav plate was attached. The strakes can be extended with shaped timber and the area between them filled with chopped mat, then fairing compound.

    After a really close took at the picture the hull at some time had had trim tabs in each side of the plate as the recess is slightly deeper to accept the hinge and fold over plate so would be a good idea to have a close look and see if the screw hols been filled properly every where !!:(

    Hard to tell what happened right along the sheer, but the line extends evenly all the way around the hull. No amount of grinding will hide this so after fairing and painting the entire outside of the hull with 2 pack finish I'll butt up to the line with a 50 mm 3M vinyl stripe in a colour that contrasts the new hull colour - it will look as though it was designed that way.

    I disagree about removing the 70 mm deck-edge at the stern because it will be feasible to fit the transom reinforcement without removing it, then add a couple of knees under it plus a serious epoxy fillet all round. This will be stronger too. The other merit of leaving this deck edge in place is the visual continuity. I'll rebate a vertical strake to fit snug under the inboard sides of the deck edge and this will provide a good fixing surface for the interior lining panels. Will probably make the latter in 6 mm ply (epoxy coated) and either painted or upholstered.

    Looks like 2 years work to me!

    Alan
     
  6. tunnels

    tunnels Previous Member

    The other thing i missed thinking about is the transom is vertical so its deffinitly always been a inboard all its life .
    So yes you will need a bracket or rebuild a new transom and get rack angle for the outboard to bolt to and thats a bit of a major !! Just off the top of my head 16 degrees seems to stick in my mind !! will have to check !!

    Yip been and checked , there variations from 12 to 20 degrees of transom angle ! 12 to me is not enough and 20 is way over the top its good to have a little more than less so you can tuck the motor if the boats heavy and stern down so rather than digging a big hole ttuck the motor in and it will simply get going forward and up quickly on the plan and goes for it i would invisage the spray out the side of the hull coming out from about half the length of the boat or less the more you trim up the further back the spray will come out . To find the optimum angle of trim use the rev counter set the boat to run at 3500 rpms right on the button and trim up slowly ,the spray will move back as the nose comes up and the reves will come up as well a little more and the rev's stay the same back down a little ! thats it !! if you trim to high the rpms should drop just a little same the other way as well to far down they drop also . its that magic place that your boat likes to be !!! so mark a fine light on the trim gauge and go there everytime !! If you add people and weight it will change so its up to you to figure out where it likes to be in differant situations . spend some time and just drive seat time lets you get the feel of it .
    Theres nothing better than the feel of going quickly on water . High speed is scary and can be dangerous if the boats not set up properly and you dont know what you doing !

    Its friday and my mind is on other things !!! we are moving factories and everything is going !!:)
     
  7. tunnels

    tunnels Previous Member

    :idea:My thoughts on splashwells is we dont really need them or if you insist they should be a small as possible or even smaller . its a place that if you get pooped from the rear instantly you have the weight of a couple of extra people and so the backs lower and pooped again !, i will do anything to do away with a splash well !!. same thing with hull drains they are a legacy from the dark old days now we have electric bilge pumps that can empty 20 litres of water in just a very few seconds . !! all boats i have had i have glassed over and no more leaks of forgetting the plug !! . no more smelly bilges and the sound of water sloshing from side to side . I dont like holes any where in my hull at all !!! but thats just me .
    So whats the progress for the weekend ?:?:
     
  8. aussiebushman
    Joined: Oct 2009
    Posts: 269
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    If I have understood the various bits of advice received over the last month, I agree the splashwell is unnecessary. I have yet to make up a template but it is pretty certain that with the long leg, the outboard will sit high enough to tilt back without a transom cutout, though it will almost certainly need a 200 mm bracket to put it clear of the transom.

    Over the weekend, I drained out a heap of (rain) water from what were supposed to be flotation chambers along each side of the hull. Some goose had taken shortcuts when adding these - no bog at the joins - just glass cloth applied over ply with polyester resin, so is it any wonder the glass peeled off alowing water in? Now they are dried out, I'll put in a proper epoxy fillet and reglass over the joins.

    I also ground out all of the chips in the hull and it is now obvious that the red colour is actually 2-pack sprayed over the original (white) gelcoat. When I go to town this week, I'll purchase some Flowcoat and filler (more likely a proprietary brand repair paste) to fill all of these before sanding and refilling to a decent standard for later application of 2-pack.

    Meanwhile, I have pretty much worked out the internal layout and deck plan -I gave up on Freeship and did it in Excel - see attached PDF. There will be plenty of room to move the fuel tank fwd or aft for weight balance. The aft well is NOT a splash well but a place for the dog (German Shepherd) to travel without destroying the upholstery as he has done in the car), plus lockers for ropes and diving gear. If some future buyer wants to make a ski boat out of this vessel, he can add the bits needed.

    Won't get much more done in the near future, because I'm still sorting out post-launch issues with the trimaran and they take priority so I can sail this summer, As previously mentioned, the powerboat is a project for when I'm at the farm in the mountains and it might take 2 years, what with the engine rebuild.
     

    Attached Files:

  9. tunnels

    tunnels Previous Member

    boats are fun !!

    Hi
    Its amazing the things you find that others have done !!
    makes you wonder what they were thinking about !!

    The wee bracket for the motor 300mm out from the transom will do more good and look better like its meant to be there and not just a after thought !
    Plus will make the boat just that little bit better performance and handling wise . The power trim will work better and be more sensitive to the touch
    Keeping the transom hull edge sharp and clean water coming out the back will cut down on any spray hitting the outboard legs and splashing up onto the back of the boat . The underfloor tank i would possition almost where the drivers seat is now , front of the tank ,front of the seat !.

    Summer is coming again and i will get 2 summers almost one after the other . its autumn here and the best time of the year in China summer is hot and seems to go on for months and months . the cooldown takes a while ! Now it just what i like !.
    Im outta here begining of next year and back to New Zealand for a month ! will see the end on the nz summer and autum as well and the best weather is feb to april !!! ! Theres a possability i could be back here in China agian to pick up another job making small power boats yet again . As usual they are older boats and need some add-ons to bring them up to date . Have nice hulls and reasonable interiors just both need modenizing and the cabin boat needs a hard top on stainless steel frames !!

    I cant wait to get back in my own boat and get it back on the water again and do some fishing !!!:D:p:p
     
  10. aussiebushman
    Joined: Oct 2009
    Posts: 269
    Likes: 18, Points: 18, Legacy Rep: 132
    Location: Taralga NSW

    aussiebushman Innovator

    150 HP Mercury 2 stroke 1975 model

    Just got the Seloc merc manual - $20 on ebay. It may be that the manual is more daunting than the motor because it is a reminder of the countless things an owner should do as rountine maintenance.

    The good news is that this motor is in bits so it will be fairly straightforward to check all of the components and fix anything that is under spec.

    There IS a score in the liner of the number 3 cylinder where a ring cracked and it looks too deep to hone out. Does anyone happen to know if a single liner can be changed or must all liners be replaced at the one time? Personally, I shall never run this beast at high speed and would like to keep the rebuild cost down.

    Cheers

    Alan
     
  11. tunnels

    tunnels Previous Member

    Check on line sometimes there are small oversized pistons availible 2.5 or 5 thou oversized . look in the manual you just got it maybe listed there !!have the feeling also its possible to just re-sleeve one cylinder and use the old piston if the ring groove is still ok !
    Have a friend with a 140hp vee4 yamaha and a sparkplug came apart and damaged one bore and it was re-sleeved and as far as i know the motor is still going !! that was 20 or so years ago !. :p
     
  12. Frosty

    Frosty Previous Member

    2.5 --5 thou over size!!!!! thats less than the clearance.

    I think you mean 20 30 40 oversize.
     
  13. tunnels

    tunnels Previous Member

    no they were made for bores with scratchs that could be honed out . long ago we used to use quite a lot not all just the odd cylinder !! but yes a 10 would clean it out and fix the problem nicely !!:)!
     
  14. Frosty

    Frosty Previous Member

    Nonesence .015 is the first oversize the next is 030


    http://www.ebasicpower.com/c/ob-merpistons/piston

    Weve done this back at the start you cant hone out to an oversize.

    Well you can but it will seize before you get in gear and is a botch up job.

    Pistons are not round you know!!!!!
     

  15. powerabout
    Joined: Nov 2007
    Posts: 2,901
    Likes: 61, Points: 48, Legacy Rep: 719
    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    all the outboard manufacurers are happy for you to rebore one cylinder if you need to
     
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