300/440/550 550sx Hull Modernization Build

[Mobile Chernobyl]

Before you read this whole thread - please realize this project was never finished. The final post is here

Interesting parts of the build are summarized below:​

Nose Rocker - and Nose Related Shaping
Adding Rocker to the nose
Reinforcing the Rockered nose
Creating a smoothed nose that matches the rockers contours - Bottom - part 1
Creating a smoothed nose that matches the rockers contours - Bottom - part 2
Creating a smoothed nose that matches the rockers contours - Bottom - part 3
Building a bond rail for a reshaped rocker nose
Coming up with a badass front section to match your newly rockered hull
Finishing up the badass front section for your newly rockered hull - part 1
Finishing up the badass front section for your newly rockered hull - part 2
Bonding your new custom nose piece back to the ski

Reinforcing the Hull
Adding reinforcement to the engine bay walls
Reinforcing the gunwale area

Creating a Custom Hood
Creating a custom hood - aka the fiero Rikter look!
Finishing up the custom hood
Reinforcing your custom hood so it's not all flimsy and poop

Refoaming the Rear Deck - and Creating a Custom Rear Deck
Using XPS style foam for the rear deck - aka refoaming
Finishing up refoaming the rear deck with XPS solid foam from home depot/lowes
Fiberglassing your refoamed and reshaped rear deck

Creating Custom Tubbies for Your Custom Hull
Creating your own custom tubbies - "Bubba Tubbies" - part 1 - cutting 2" XPS foam from home depot
Creating your own custom tubbies - "Bubba Tubbies" - part 2 - Smoothing, contouring and making fiberglass templates

Creating Custom Surf Style Bond Rails
Making wide and angled/flared surf style bond rails - part 1 - creating the layup shape
Making wide and angled/flared surf style bond rails - part 2 - smoothing and contouring the profile, creating negative shape
Making wide and angled/flared surf style bond rails - part 3 - laying up the top sheets
Making wide and angled/flared surf style bond rails - part 4 - laying up the bottom sheets

Designing a Custom Handle Pole in CAD
Designing a handle pole for this beast - part 1
Designing a handle pole for this beast - part 2

Creating Deeper Chines and Truing Your Hull
Creating deeper Chines - adding shape/profile to them, aka truing the hull - Part 1
Creating deeper Chines - reinforcing them - Part 2

Creating a Custom Spark Arrestor Box with Fiberglass
Creating a homemade spare arrestor box that is low profile and fits under a custom low profile hood
The finished product from the homemade spark arrestor

Pump Tunnel Smoothing and Stuffing
Pump tunnel smoothing and stuffing - part 1
pump tunnel smoothing and stuffing - part 2

Installing Threaded Inserts for a Dakine Footstrap
Installing a Dakine foot strap in a JS/SX series footwell (and probably others)

Painting Your Custom Hull
Painting, sanding and masking the hull for primer coat
Final paint - hazard buoy yellow!

​

Well I got a late start on this but here it goes!

Basically I plan on building a modern ski hull on the cheap. I picked up a prime 550sx and coming off a 440 it's very fun.

In the end I'd like to have a more freestyle friendly jet ski.

Day 1 - ripped off the ugly plastic that comes stock on these things (and is slippery as hell)

In the process I got a rude surprise - a crack in the top deck. This could only lead to more work!

Day 2 - defoamed that bitch. My ski was a bit Emo so it cut itself a lot too (I gave it permission with a sawzall - this was in preparation for the new top deck I planned on putting in with lowered footwells and some adjustable footholds)

Gas tank will be internal fill with a glassed over current location. I also cut off the parascope on the hood and prepared it for the new handlepole I'm making for it by starting the contour that will fade from front to back (pictured below)

Day 3 (today) - I pulled the engine and pump and everything else that shouldn't be in there when I'm glassing and pressure washing and painting it etc. etc.

So hopefully I can keep this thread updated! I plan to have a pretty nice little ski by the time this is done, with adjustable footholds (with 1" lowered footwells), polystyrene re-foaming, tubbies, "lowered" hood, new SRC aluminum shortened pole as well as complete steering assembly, lightened flywheel (thanks to #Zero) and probably other stuff if time permits.

I don't really plan on spending a lot (sans the fiberglass, foam and resins!) of anything but time on this as I'm still on a college budget, so everything I do will have to be of the home made variety.

 

[N2 H2O]

Nice work! I'm modding my 550 hull and the cost adds up quick. I've already dropped way more than I planned to just in Fiberglassing materials. Fiberglass is definitely not cheap. I'm looking forward to seeing this completed. It should be pretty sweet when your done.

 

[Joker]

I planned on doing this same exact build next year. man do great minds think alike. Are you gonna chop the hood down? And what about the nose!

 

[Mobile Chernobyl]

Well... I've got the itch

The fiberglass itch... the only cure is to remove more lol.

Tonight I decided I would clean her off...

I had already taken it to the car wash and committed a federal crime with all the foam that washed out of it lol... But i'm alot happier knowing I got most of it out (like 97%). I'm gonna work on the engine bay next and sand it. I plan on painting it with some bright orange tinted BilgeKote paint. 's supposed to be legit, and I like legit paint (previously the paint would flake off so bad it would clog the bilge outlet and pump!)

So after it got cleaned off, I laid out some lines. With some inspiration from Munkie's friends 550 build, and the more modern freestyle hulls I decided to go with a nice heavy slant on the front end, and give the backside of the hood some angle too. Here's what it came out like (only one side so far... powertools and neighbors at 10pm at night don't mix too well.)

To cut the hood up... I had to remove this damn thing!

a half hour with the heat gun and a pain scraper got it out. The fume's were not pleasant though.

I'm planning on stuffing the front end with foam now too since I can get to it. I'll have to figure out a way to keep in it place.

I'm going to have to start laying out the foam now to remake the hull shape.

I decided to just nix the stock handle bar mount and make a new one... that will give me some freedom of placement and hopefully better maneuverability.

's gettin real! next week I put in the us composites order...

 

[315rider]

Killer! I wanted to do this to a 550 hull but fix steer it lol totally checkin this build out next time im on the x

 

[caseville9036]

Subscribed for a cool build!

Some of that area that you cut off of your hood is a clearance area for the flame arrestors, do you a solution for this in the works too?

 

[Mobile Chernobyl]

You are right!!!

I noticed that my bulky K&N flame arrestor/air filter would top out on my modified hood. It also had velocity stacks on it. My friend notified me that i could take all of them off and run a setup akin to a stock superjet flame arrestor - and that is what I plan to do. I may need to fabricate it or maybe I can just buy it but either way I'm not afraid - now that I have taken off both the air filter and the velocity stacks I have gained nearly 3-4" of clearance to play around with... Lots of stainless sheet welding planed in the near future!!

Day 5

Sanding down the ty ass ing "reinforcing" done to this ski when I got it (actuallly from the guy before the guy that I got it from)... 90% resin, 10% fiberglass... wtf!! the front areas had mad air pockets too, some good they would do... (I sanded it all off today - day 7)

Sawzall was hungry!

Day 6

Closing in on the Fiero/Rickter look!

Just got confirmation from #Zero that My flywheel has been lightened, powder coated and return shipped! This guy is a machine! I highly reccomend him for engine part customization! He had my part for like a day and already was ready to return it! Can't wait to ride with a 1lb lighter flywheel now.

Will be posting day 7 sometime soon, once it happens. I traced out the hood so I can keep a .75" constant gap on the height between the pole lowered area and the side wall height - again, inspired by the rickter design. In the end this ski will take a lot of it's inspiration from the Rickter hood and nose, and the B.O.B. tray (with adjustable footholds)

 

[Sanoman]

Nice build!

l think yours is the first one l have seen cut down like that. Keep cutting away............

 

[Mobile Chernobyl]

I've already cut it some more (day 7 now) and I'm going to pick up some materials now at the local material yard. Some of which is going on the tray walls for the adjustable footholds! I cut down the hood a slight bit more and now its a pretty slant angle (fiero rickter inspired!). It really doesn't have any more material than is needed. I hate how bulky the stock 440/550 is! I'm thinking for the front end, fiberglassing in a "floor" on the bottom of it and then building up from it to hopefully achieve greater strength in the long run. I'm going with appx 3 sheet thickness of 1708 for the sidewalls and 2 sheets for the front bottom half of the floor to reinforce this pig for the gnarly nose stabs I plan on doing in 12" of stone bed infested river water. Also so I can ram into alligators at 45 mph, you know start my own gator' hunting show and .

 

[MADMAT]

Holy crap man! Lot of work!!

 

[Mobile Chernobyl]

Holy crap man! Lot of work!!

Hell yea! Just ordered a load of fiberglass from US composites! nice people to deal with. Hopefully it all comes together within my planned date of a month from now - otherwise I'll be stunting the 440.

 

[MADMAT]

Very interesting build. Motor? Pump?

It seems like if you are going that far then a motor/pump transplant has to happen too!!??

 

[-cowboy-]

verry nice work

 

[Mobile Chernobyl]

Very interesting build. Motor? Pump?

It seems like if you are going that far then a motor/pump transplant has to happen too!!??

Possibly next year. It's motor is already pretty pimped out. If it performs well with all the body work and other bits it'll be a good candidate for a bigger motor!

I think I'm going to plumb in a scupper tube, but fiberglass over it in the mean time and put a knock out cap in the engine bay side - maybe also plumb in a line for a trim cable - I might put a versiplug in it, but doubt I'll have a need for trim for a good while.

 

[Mobile Chernobyl]

Well day 7 brought some more progress!

To start with, I got this 3/8" fiberglass board from the materials yard

Perfect for reinforcing the walls for the adjustable foot holds, which have been mocked up and will look something like this:

Not going too crazy with the design, pretty much exactly what the BOB design uses. I need to address bending moments created in the walls due to tip loading of the footholds - I.E. I don't want to come down on the top inner edge of the hold and snap the wall off, or bend the hold. I want them to sit about 1/2" or so right above the inner tray so it can touch it if need be. I'll be able to address some of this with the sunken in foot hold tray's. I'll also need to give the holds some angle downwards possible, or just fold the tip down.

The nice thing so far is the width of the tray - about 22 inches right now, but more like 21 inches when all said and done - at the foothold area. I'll reduce it down to about 16 inches up forward of the holds.


I laid out a few other components. Here's the battery box:

Kinda small? yea I'll be using a Ballistic Evo2 12cell, so it's only got a footprint of 3.5"X4.5" and weighs under 3lbs lol.


I carved up the floor by the stock siphon bilge a little. I removed the stock mounts and I'm going to make a new siphon bilge out of 3/4" PVC tubing with holes in it and a sealed end on one side, with a threaded barb in the other.

I'll be able to fit 2 tsunami's in it right by the drive shaft now, and still keep the stock siphon bilge.


The hood is now finished - perfect .75" recess on the pole area vs. the side walls so I'm ready to start laying out the fiberglass mold.

I also finished sanding the inner walls in preparation for some 1708 reinforcing layers.

The person that owned this ski 2 people before me did a horrible job lol. There was almost a solid air bubble under 3/4 of the fiberglass that was supposed to be reinforcing the walls, so unfortunately it wouldn't have done much good if needed. Glad I took all the time to sand down to fresh SMC, I can now be more confident that this build will take a trashing.

I had to cut out part of the engine bay/hood centering walls (as seen in the foreground) - I did this to better clear the pipe. Before it was rubbing the wall so this should alleviate some if not all of that.

Next I have to lay out the front nose and pole mount - It will be using a lowered mount now so I'll have to abandon the conventional JS pole front end I had designed for our SRC aluminum poles and go with something more akin to a super jet with a lower pivot location. The goal is to have the pole bracket fairly close to the bond line - for more strength and so I don't need to depend so much on the ty front ends that the JS series have.

 

[Mobile Chernobyl]

Day 8:

Received my lightened flywheel from #Zero - awesome looking and I'm sure performing once it's all back together! Highly reccomended.

Decided to make a foam cutter from a guitar string and a battery charger - the basic beginner model everyone fools around with. First thing I discovered is I can't make a straight line worth a damn... May have to use a guide rail to make a straighter cut, but for this object (the tubbies) they were cut big anyways - I'll be sanding them down to shape mostly.

Side view of the un-shaved tubbie on the ski. It's symmetric about the hull's natural arc starting point. Figured that would make for a good start. With 2" foam - I'll have to see if it's wide enough.

 

[Mobile Chernobyl]

I'll just keep updating this in case someone wants to do the same thing later on!

Well I decided to put all the cards on the table... i.e. rocker nose and superfreak/trinity matrix style bond rails (and tubbies)

I figure if I get around to doing the 750 conversion next year it will need all the handling help of a real ski!

First off - US Composites order came in! Might not be enough, but will surely get me well on my way!

The nose - after being cut up in preparation for the rocker mod (2 inch slices with spacers)

The bond rails after being cut up

and I'm going to increase the distance the "reverse strake" travels down the front end for the same reasons that they claim in the matrix ride report... cuz it seems legit.

So I'm getting to the point were if I cut any more... this hull will fall apart lol.

Hopefully I can find a 750 cheap in a year!! would love to add trim and just be set for a few more years till I can shell out the money for a real custom hull. or at least the materials to make one!

 

[Edwardsjr1]

Are you an engineer student? Crazy work dude! I wish I had the juevos to hack my ski's up!

 

[MikeyB]

He's gotta be in engineering if he's talking about bending moments lol, nice work dude!

 

[Mobile Chernobyl]

Are you an engineer student? Crazy work dude! I wish I had the juevos to hack my ski's up!

Yea just about an engineer lol. Professional student too. It doesn't really take juevo's to cut up a ski, just a sawzall blade that's not dull, a $15 harbor freight grinder and the realization that you can't afford a RN superjet yet lol.

As it turns out... doing the nose like I want to - putting a floor in at the new "plane" I created by cutting off the nose, this will not allow me to use my current waterbox, I may be able to, but I gotta figure out how to route the pipe that comes up out of it - by putting in a new "floor" for the pole bracket on the nose, it's too low to clear the outlet pipe.

So time to get creative even more!

just glad to be rid of the flimsy big honkin stock nose. Gonna need to make a new splash gaurd once the rocker nose and nose top are done tho - I've not heard any good coming from a splash-gaurd-less designs and saltwater lol.