Mini OB Boat conversion to Mini Jet Boat

Discussion in 'Fiberglass and Composite Boat Building' started by LilWake, Feb 16, 2012.

  1. LilWake
    Joined: Feb 2012
    Posts: 149
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    Location: Minneapolis, MN

    LilWake Senior Member

    I like the purple a lot too, and the color used would be HOK Passion Purple. The problem is is that it is VERY hard to find Bimini (Sunbrella) material and vinyl for the upholstery to match it.

    here are 3 cars painted in the same purple. When light catches that paint the color explodes.
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  2. LilWake
    Joined: Feb 2012
    Posts: 149
    Likes: 7, Points: 0, Legacy Rep: 53
    Location: Minneapolis, MN

    LilWake Senior Member

    I thought I'd be cutting by this weekend but I didn't get the tools needed from my buddy and was also busy getting other spring things done. I did take all measurements needed to place the motor, and planned the cut lines. After taking a good look at where the cut lines will be and how things will align, I determined I could not have picked a better ski. The footprint of the bottom of both boat and ski will make this a seamless swap. All of the lines match nearly perfectly and boat flattens out near the front into a flat 5.5" strip all the way to the back of the boat at which boat the flat parts widens more. The width of the 5.5" strip matches perfectly to the channel that leads to the pump intake on the ski, and the wider flat part near the back of the boat will make a perfect surface to glass the pump intake in. I'll explain more when I start cutting so I have better pics for reference.

    This pic shows the bottom of the ski nicely and you can see the 5.5" flat strip that leads to the pump intake. The boat has nearly the exact same design which will provide a smooth water flow/channel to the pump.

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    These 2 pics show the rough placement of the motor. I left about 1.5" clearance to the back of the seat. Also the motor will drop about 1.5" once we notch the subfloor between the two stringers. We will be moving the cross support between the stringers to right under the seat back. We will then put another cross support between the stringers right behind the motor and notch it for the Impeller drive shaft.

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    I'm thinking this type of placement for the waterbox, and run a splitter hose off the exhaust outlet into two exhaust tips

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    Here you can see there is nearly 17" of room behind the motor for the pump to fit. That is exactly what the pump needs, so the pump shoe (where the pump nozzle mounts) should be nearly flush with the boats transom.

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  3. LilWake
    Joined: Feb 2012
    Posts: 149
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    Location: Minneapolis, MN

    LilWake Senior Member

    Started by seperating the top of the boat from the bottom with a reciprocating saw (AKA Sawzall).
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    Exposing the inner structure. to determine cut lines.
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    Where I am cutting in these next photos is recessed channel where the motor will be mounted. We had to lengthen this recessed area so the motor will sit level with the boats bottom and in turn let the pump sit flush with the bottom of the transom.
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    Above, you can see I cut a little peep hole to see what else I was getting into. Good thing because this is when I found out about the LARGE center stringer.

    I didn't get a pic of the section removed, but you can see the area in these pics showing how the motor now sits flush with the bottom of the boat. The recessed channel now runs the entire length of the rear hatch area.
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    There was a lot of sweat, dust, and itchiness. I can't wait for a couple more weeks of this!

    PS: I am relatively new to boats so please help me with boat terms along the way if you can. If I refer to something incorrectly it would help me to know the correct term. Don't be afraid to chime in.

    Thanks for following my build so far!
     
  4. LilWake
    Joined: Feb 2012
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    Location: Minneapolis, MN

    LilWake Senior Member

    So we started Friday night by hanging some plastic to section off our workspace in my apartments underground parking. Who said you need a shop? haha.
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    Next we masked off the XP where we wanted the cuts.
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    This morning (Saturday) we started by removing the speed sensor hardware.
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    Then used a small jack to pry the ride plate from the XP hull.
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    Drilled through the corners to locate the cut lines on the inside of the ski hull. This XP is multiple layers thick in some areas so the angle grinder would not cut through both sides at once.
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    Then it was all cutting from there.
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    Next we cut the lines anywhere it didn't go through both layers of the hull. (No pics of cutting the inside)

    The hull hole
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    The section that will be glassed into the ski. It needs to be refined first. More pics of that to come...hopefully tonight.
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  5. LilWake
    Joined: Feb 2012
    Posts: 149
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    Location: Minneapolis, MN

    LilWake Senior Member

    Here are the photos showing how we refined the shape of the ski section that will be grafted into the boat. What we did was just remove any fiberglass that stuck up (the inner layer of the hull) from the bottom layer of the ski's hull. The exception was the motor mounts. We left those and will then reinforce them by glassing from the top of the mounts outward, towards the boat, once that section is grafted into the Addictor.

    Here you can see we removed some fiberglass near the top left and bottom left corner of this photo. We hadn't cut one of the rear raised sections out yet.
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    Now you can see that we cut the rear raised sections out, removed the foam that was in between, and then grinded it smooth with the lower fiberglass layer.
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    And in these two you can see how all raised sections, except the motor mounts, were cut off and grinded smooth, with all the foam removed.
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    And that section of the ski placed in the boat, with the engine sitting on the mounts. The ski section is set inside the boat in this pic, and won't sit flush in the recessed area until I cut the hole in the bottom of the boat, and also out the back where the pump shoe will exit.
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    So what do you all think so far?

    I should have more work done tomorrow. Hopefully the boat will be completely cut and ready to glass!!
     
  6. LilWake
    Joined: Feb 2012
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    Location: Minneapolis, MN

    LilWake Senior Member

    Sundays progress was held up by an unforeseen problem. How to get the boat bottom flipped over. My brother, Nate, and I can barely lift it, let alone flip it while holding it up. So we thought of every way possible to flip this beast of a hull. It probably weight 400 lbs. So since we don't have a hull rotisserie we had to improvise. We built an inner structure to support the sides of the hull and distribute the pressure from the weight of the boat. Then we tilted it up onto one of the sides and then went to the other side to lower it back down. The skeleton we built definitely help and there was no bowing/stress cracks/etc at all. We also put old couch cushions down on the concrete to distribute the pressure that would have otherwise been directly on the lip of the hull where the top and bottom of the boat meet.

    Here is that wood structure we built.
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    Then we measured the length of the section of the ski and determined we wanted it to sit back 3" from the back of the boat. So we took that length measurement, subtracted 3" and marked a line on the boat that was that same distance from the back of the boat. At that line we measured how wide the flat part in the middle was, and we made the ski section angled so it would be a nice gradual blend from the flat part of the boat to the flat channel in the ski's hull that eventually flows into the intake grate. Any abruption in that surface would decrease water flow to the intake.

    Here you can see the angled lines marked on the ski that angled inward towards the front to create and nice gradual/dynamic blend.
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    We eventually cut the ski section along the lines in the previous photo, and then transferred the shape of the ski section to the bottom of the boat.
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    From the outline on the boat we measured inward .5" from all sides and cut that shape out. That left a .5" trim where the ski section and the boat overlap. We then feathered the edges of both the hole in the boat and the ski section so they mated nicely. We still have some refining to do so they sit perfectly flush.

    This is where we got to tonight.
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    With Rideplate set on
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    ^^This was a GREAT feeling seeing how well they mated, after all the work we put into creating these shapes.

    All in all tonight went very well. It was a LOT of measuring. We probably spent 3-4 hours just measuring and drawing lines, transferring the shape of the ski onto the boat. It was very difficult because of how lines get skewed over curved/angled/odd shaped surfaces. We triple measured everything and it payed off. A lot of fitting, grinding, fitting, grinding...until everything sat flush.

    I owe my brother Nate greatly. He has been plugging away at this with me every time I have worked on this project so far. And this is hours and hours of being covered in fiberglass dust and being bundled up in particulate suites, respirators, protective glasses, gloves....sweating, itching, bleeding a little here and there. So big THANKS to you Nate! The labor intensive part is nearly done though...thank god! :)
     
  7. tinhorn
    Joined: Jan 2008
    Posts: 575
    Likes: 20, Points: 18, Legacy Rep: 310
    Location: Massachusetts South Shore.

    tinhorn Senior Member

    Those two parts DO appear to be matching nicely. Nice work, on the boat AND on the forum updates.

    How dry do you think the hull is on the inside? Yours sounds a lot heavier than mine--I can pack mine around by myself, and it isn't like I'm all that powerful.
     
  8. cor
    Joined: May 2008
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    Location: Alaska

    cor Senior Member

  9. LilWake
    Joined: Feb 2012
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    Location: Minneapolis, MN

    LilWake Senior Member

    Tinhorn- The dryness is something we have been considering all day. I am sure the floorboard and foam is all dry as can be up front. The part that has me concerned is the transom. After cutting the hole for the pump to exit in the transom we located some wood that is not solid. We also noticed that the the transom was either originally made from two separate boards that were glued together, or that at some point in its life another board had been added to cover up the existing transom wood. Either way, this wood has been bothering me ever since. I know the right thing to do would be to replace it now while everything is torn apart...and never have to worry about it again. But the task seems really daunting! The only area we have even inspected is where we cut the small hole for the pump to exit. We will need to make that hole larger soon and cut it to a nicer shape, so I am hoping that as we cut out further (further away from the holes where the outboard attached) that we reach dry wood. If we do not it seems like the only smart move would be to replace it...
    Also, I appreciate your compliments...thanks!

    Cor- Your welcome. Thank you for checking it out! It will be fun when it's done! haha, jk I am definitely enjoying it. This is my first boat project so I am learning A LOT!
     
  10. LilWake
    Joined: Feb 2012
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    Location: Minneapolis, MN

    LilWake Senior Member

    I was thinking tonight...the boats transom is relatively small. If I do decide it's necessary to remove all of the wood would it make sense to lay up fiberglass chop mat up to about .75"...basically creating a composite transom? I think i have plenty of material to do so. Would there be any drawbacks?

    Thanks!
     
  11. LilWake
    Joined: Feb 2012
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    Location: Minneapolis, MN

    LilWake Senior Member

    So my brother and I had been discussing the transom issue for a full day. We were going back and forth on whether we should replace the entire transom, patch repair it, or just hope it was just a little rotted where the outboard bolt holes were (where we would be cutting a section out for the pump nozzle to exit). What we concluded was that we would go home, cut another small section from the top corner of the transom to see how far the rot had gone.

    We went home to my apartment last night (Weds) and exposed the top corner of the transom. What we found was that the original transom board was completely rotted. It also made it clear that at some point some idiot just slapped another sheet of plywood over top of that rotted board and glassed it in. We were very intimidated at this point. We saw a lot of cutting, grinding, chiseling, sanding ahead of us.


    We went ahead and made a cut with the angle grinder all the way around the transom, through both layers of fiberglass that were containing the two boards.
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    We started prying gently all the way along the top cut that we made. immediately the solid board start pulling away from the rotted board.
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    It took some muscle, but we grabbed the solid board and just pulled and ripped that F***er off. Came off surprising easy, but what shocked us even more was HOW ROTTED the original board was...it was flakey MUSH.
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    It was such a relief because with a chisel and crow bar we were able to just skim it off the outer fiberglass/gel coat skin.

    This did, however, leave us with a lot of fiberglass to grind down. I didn't get a pic before we started grinding, but in these pics you can see we grinding the extruding edges of fiberglass down level to the floorboard and transom skin.
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    The Newer Board
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    The Original Board
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    We're getting VERY close to GLASS! Check out the inside view of the ski part in place.
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    Back View
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  12. LilWake
    Joined: Feb 2012
    Posts: 149
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    Location: Minneapolis, MN

    LilWake Senior Member

    So tonight we made a little progress.

    Cut the hole in the transom for the pump to exit.
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    Variable Trim System (VTS) test fit. Had to make sure it would clear when we fiberglass the void between the pump shoe and the transom.
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    Then we finished cleaning up all the extra extruding fiberglass from where they glassed in the two transom boards. In the next two you can see we grinded out the transom board where it was tucked behind the stringers.
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    We cleaned up the top part of the transom, and grinded all the extra glass.
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    One of the first steps in this build was to cut out the subfloor and cross support between the stringers to make a larger channel for the motor. In this pic you can see we grinded that area that we exposed, cleaning up all the left behind fiberglass, wood, and foam.
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    Tomorrow we will start sanding all of the surfaces to remove all of the gelcoat. We will take it down to the fiberglass with 40grit to get a nice tooth to bond to. I just purchased this bad boy to help!
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    Now I am just hoping for decent weather this weekend so we can get everything done that I wanted. I am hoping to have everything glassed.
     
  13. LilWake
    Joined: Feb 2012
    Posts: 149
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    Location: Minneapolis, MN

    LilWake Senior Member

    I'm seeing little interest in this project here on BoatDesigns. I am currently updating 3 forums with this build. It's a lot of work doing each update on 3 forums. I am considering stopping the updates here, and may provide a link to the other forums so the few that have posted can keep an eye.
     
  14. beachcraft
    Joined: Nov 2011
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    Location: Marinette

    beachcraft Junior Member

    Please keep updating this.
    I've been reading it from the beginning.
    This boat is right up my alley.
     

  15. tinhorn
    Joined: Jan 2008
    Posts: 575
    Likes: 20, Points: 18, Legacy Rep: 310
    Location: Massachusetts South Shore.

    tinhorn Senior Member

    This thread has nearly 1500 views, man. Thing is, there isn't a lot for us to say. It's an awesome project.
     
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