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Thread: Changing bunks

  1. #1

    Changing bunks

    Probably a stupid question but can bunks be changed with ski on trailer? If so how can the ski be jacked up and supported? Thanks

  2. #2
    Click avatar for tech links/info K447's Avatar
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    Yes, but one must be careful.

    I sometimes adjust the bunks while ski is on trailer. Bow roller supporting the bow, winch strap tight. Hydraulic jack under the watercraft ride plate (centered), with a stiff flat board to protect the ride plate and spread out the force.

    Update: Hitch trailer to tow vehicle. Set parking brake.
    This prevents the trailer from moving while you are working.

    Jack up the ski at the ride plate until you have clearance to work on the bunks. Be aware that the ski is heavy and there is always some risk of it shifting unexpectedly. The entire weight will be supported by the jack under the ride plate and the bow roller. Make sure the bow roller and winch stand are up to the task of holding that weight.

    If you can, add some long boards across the trailer frame to hopefully support the hull if it should drop suddenly while a bunk is out of position.

    I would suggest doing one bunk at a time. Keep hands out of potential crush zones.
    Last edited by K447; 07-05-2020 at 02:48 PM.

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  4. #3
    Xspook's Avatar
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    If you don't have a maintenance cart, it would be easiest to put the ski in the water and work on the trailer near the boat ramp.

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  6. #4
    Quote Originally Posted by K447 View Post
    Yes, but one must be careful.

    I sometimes adjust the bunks while ski is on trailer. Bow roller supporting the bow, winch strap tight. Hydraulic jack under the watercraft ride plate (centered), with a stiff flat board to protect the ride plate and spread out the force.

    Jack up the ski at the ride plate until you have clearance to work on the bunks. Be aware that the ski is heavy and there is always some risk of it shifting unexpectedly. The entire weight will be supported by the jack under the ride plate and the bow roller. May bear site the bow roller and winch stand are up to the task of holding that weight.

    If you can, and some long boards across the trailer frame to hopefully catch the hull if it should drop suddenly while a bunk is out of position.

    I would suggest doing one bunk at a time. Keep hands out of potential crush zones.
    Thanks, great idea/suggestions.

  7. #5
    Quote Originally Posted by Xspook View Post
    If you don't have a maintenance cart, it would be easiest to put the ski in the water and work on the trailer near the boat ramp.

    That was my first thought, but if I needed something unexpected (which tends to happen when doing something for the first time), then I'd have to leave the ski in the water, unattended, to get what I needed.

  8. #6
    Thanks for the help guys, I was able to swap out the bunks with no issues. I could have done it at the river with the ski in the water as it turns out but it would have been my luck that I would have needed something that I didn't have there. Anyway, jacking it up from the ride plate with plenty of support worked out great.


  9. #7
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by AirborneSilva View Post
    Thanks for the help guys, I was able to swap out the bunks with no issues.

    ... jacking it up from the ride plate with plenty of support worked out great.
    Any photos or tips for the next guy?

  10. #8
    I always forget to take photos, didn't even think about it this time. The only tip I can think of is before you get it up in the air make sure you have everything you think you'll need and work as quickly as safety will allow.

  11. #9
    steve45's Avatar
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    I've done this at the beach before. I think I may have pics, I'll add them later if I find them. Get your wood. I do NOT use pressure treated lumber because it warps and splits so badly. Just plain old 2x4s (I use 2x6s). I use the Tiedown Engineering Glide Ons, and they fit a bit big on a 2x4. I think they're designed to go on over existing carpeting. Anyway, I rip the 2x6 to get a good fit with the Glide Ons.

    Get your hardware ready. Use stainless steel hardware only. Do not use lag screws, they get loose and fall out. Use carriage bolts. Carriage bolt heads will protrude from the wood, so you'll have to counterbore the holes so the 'Ski (or carpet or Glide On) will go over the bolts. Use stainless steel washers and stainless steel locknuts.



    You will need 8 nuts, 8 bolts, & 8 washers per set of bunks. You will need a small drill bit to drill pilot holes for each bolt, a Forstner bit that is slightly larger than the carriage bolt head, and a drill bit the same size as the bolt shank (I use 5/16").

    Take a cordless drill with a freshly charged battery, as well as a spare freshly charged battery.

    Remove the old bunk rails. Take a pair of C-clamps and clamp the first bunk rail to the trailer brackets. Use a marker to mark the holes. Repeat for the second bunk rail. At this point you can remove the bunk rails to work on them in a level place. A drill guide helps you to drill the holes perpendicular to the rails. Drill the small pilot holes first. This will help you keep the Forstner bit centered so you can counterbore the holes for the carriage bolt heads.



    Next, use the Forstner bit to drill just deep enough for the bolt heads to sit below the surface of the boards. The bottom of the bolt heads are square, they won't go all the way into the wood. When you assemble them, you will hammer the bolts into the holes and the square part of the shank keeps the bolts from turning.



    Place the bunk rails back on the trailer brackets and install the washers and nuts. GREASE THE THREADS! Some stainless threads will gall and seize up before you get the nut threaded all the way on if you miss this step. It's possible that the bolts will spin inside the holes, in spite of the square shanks. In this case, wedge a flat screwdriver in the hole next to the bolt head, or try some needle nose pliers. Do not use a drill/driver or impact tool to install the nuts, it's too easy to get the threads hot and cause galling.

    When you get all the rails in place, it's time to install your carpeting, Glide Ons, or whatever you put on top of them. Use stainless steel hardware.

    Go play!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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Name:	Countersink Holes With Forstner Bit.JPG 
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    Last edited by steve45; 07-08-2020 at 04:38 PM. Reason: Added photos, specified Forstner bit

  12. #10
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
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    Quote Originally Posted by steve45 View Post
    I've done this at the beach before. I think I may have pics, I'll add them later if I find them. Get your wood. I do NOT use pressure treated lumber because it warps and splits so badly. Just plain old 2x4s (I use 2x6s). I use the Tiedown Engineering Glide Ons, and they fit a bit big on a 2x4. I think they're designed to go on over existing carpeting. Anyway, I rip the 2x6 to get a good fit with the Glide Ons.

    Get your hardware ready. Use stainless steel hardware only. Do not use lag screws, they get loose and fall out. Use carriage bolts. Carriage bolt heads will protrude from the wood, so you'll have to counterbore the holes so the 'Ski (or carpet or Glide On) will go over the bolts. Use stainless steel washers and stainless steel locknuts.

    You will need 8 nuts, 8 bolts, & 8 washers per set of bunks. You will need a small drill bit to drill pilot holes for each bolt, a spade bit that is slightly larger than the carriage bolt head, and a drill bit the same size as the bolt shank (I use 5/16").

    Take a cordless drill with a freshly charged battery, as well as a spare freshly charged battery.

    Remove the old bunk rails. Take a pair of C-clamps and clamp the first bunk rail to the trailer brackets. Use a marker to mark the holes. Repeat for the second bunk rail. At this point you can remove the bunk rails to work on them in a level place. A drill guide helps you to drill the holes perpendicular to the rails. Drill the small pilot holes first. This will help you keep the spade bit centered so you can counterbore the holes for the carriage bolt heads.

    Next, use the spade bit to drill just deep enough for the bolt heads to sit below the surface of the boards. The bottom of the bolt heads are square, they won't go all the way into the wood. When you assemble them, you will hammer the bolts into the holes and the square part of the shank keeps the bolts from turning.

    Place the bunk rails back on the trailer brackets and install the washers and nuts. GREASE THE THREADS! Some stainless threads will gall and seize up before you get the nut threaded all the way on if you miss this step. It's possible that the bolts will spin inside the holes, in spite of the square shanks. In this case, wedge a flat screwdriver in the hole next to the bolt head, or try some needle nose pliers. Do not use a drill/driver or impact tool to install the nuts, it's too easy to get the threads hot and cause galling.

    When you get all the rails in place, it's time to install your carpeting, Glide Ons, or whatever you put on top of them. Use stainless steel hardware.

    Go play!
    Excellent writeup, only thing I would do differently is to swap the carrage bolts out for regular bolts and countersink the head and a washer into the bunk.

    I loathe carrage bolts.

    Sean

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