SJ build - removing bulkhead entirely?

SuperJETT

SuperJETT

So long and thanks for all the fish
Location
none
I'm toying with the idea of getting rid of the bulkhead in my ski almost entirely on my topdeck conversion.

I need the middle section for the intermediate housing obviously, so I'd leave that rectangular section between the bottom and tray, but the sides would be open. I'd install the footholds with the topdeck separated still, then foam the gunwales and glass over that to seal it, and foam/seal the nose as well for floatation.

The bottom section would be open all the way to the back. No scupper tube required, only duckbills or the pwcdoctor versi-plug in each side.

I'd connect hoses right at the pump cavity using some good crimp connectors so I don't have to worry about them coming off.

I have thought that the sides might need some strengthening, but the bondline gives a ton of strength. I could leave the upper portion of the bulkhead too.

Sitdowns are/have been built this way forever, and our skis are much smaller, so why not?
 
the only couch rider

the only couch rider

Location
Jersey
SuperJETT said:
I'm toying with the idea of getting rid of the bulkhead in my ski almost entirely on my topdeck conversion.

I need the middle section for the intermediate housing obviously, so I'd leave that rectangular section between the bottom and tray, but the sides would be open. I'd install the footholds with the topdeck separated still, then foam the gunwales and glass over that to seal it, and foam/seal the nose as well for floatation.

The bottom section would be open all the way to the back. No scupper tube required, only duckbills or the pwcdoctor versi-plug in each side.

I'd connect hoses right at the pump cavity using some good crimp connectors so I don't have to worry about them coming off.

I have thought that the sides might need some strengthening, but the bondline gives a ton of strength. I could leave the upper portion of the bulkhead too.

Sitdowns are/have been built this way forever, and our skis are much smaller, so why not?
Click to expand...


i know nothing about standups but i would think there might be some sacrifice of structural integrity. but that is just me.
 
tom21

tom21

havin fun
Location
clearwater FL
hmm very interesting. I like it. don't some newer flatwater skis have hollow bottoms that are open from the back and sealed at the bulkhead? I swear I have seen a few.
 
SuperJETT

SuperJETT

So long and thanks for all the fish
Location
none
On the exhaust, I'm going to do a side exhaust anyway, either in front or in back, so I won't utilize the stock exhaust tube anyway.
 
G

Goose

Guest
Highroller just built a new boat that has something like that setup.youll see how flimsy that bottom is when you take the bulkhead out so it will need a fair ammount of reinforcing
 
tom21

tom21

havin fun
Location
clearwater FL
I would think as long as you properly reinforced you would save weight, never have to refoam and be lighter. I see no downside (except the bottom is smc).
 
SuperJETT

SuperJETT

So long and thanks for all the fish
Location
none
Goose said:
Highroller just built a new boat that has something like that setup.youll see how flimsy that bottom is when you take the bulkhead out so it will need a fair ammount of reinforcing
Click to expand...

tom21 said:
I would think as long as you properly reinforced you would save weight, never have to refoam and be lighter. I see no downside (except the bottom is smc).
Click to expand...

Having the center section still would take care of that issue I think, plus I'm probably going to have a new stronger piece of material to use as the bulkhead anyway.

Like this:
IMG_6537_with_cutouts.JPG
 
Endo

Endo

Non-tree hugger
Location
Northeastern Indiana
What about the strength at the front of the tray? Also (to lazy to run calcs) would you have enough buoyancy to keep it afloat if something catastrophic happened. I really like the idea.
 
Mark44

Mark44

Katie's Boss
Location
100% one place
Don't think I would cut that much out all you need is roughly 1" up and 2"-3" wide.

See black in photo

Mark44
 

Attachments

  • cut.JPG
    cut.JPG
    86.4 KB · Views: 82
Last edited:
Mark44

Mark44

Katie's Boss
Location
100% one place
You can also calculate the ski's weight and the buoyancy of the foam to determine the amount of foam needed to keep the ski a float while it is submerged. I would not guess at this equation for peace of mind.

Mark44
 
WFO Speedracer

WFO Speedracer

A lifetime ban is like a lifetime warranty !
Location
Alabama
As the resident flotation tester (yes I have sunken many boats ,I have experience in the field)I would have to say that no ,it will not be enough flotation to keep the boat from sinking.Heres why,its not just the amount of foam you have to take into consideration it is the amount of water displacement.

Obviously with the boat fully foamed it can take on x amount of water and the foam has enough floatation to float the boat with that amount of water in it.Now if you remove all the foam from the bottom of said boat you have greatly increased the amount of water displacement in the hull.Enough that the boat will no longer float.If you don't believe me do the calculations for the cubic feet of foam removed,subtract that from the total amount of foam in the ski,then figure in the weight of the water needed to displace the amount of foam you removed.

If you are going to do this I strongly suggest you come up with some alternate means of flotation with less weight.Here is what I came up with ,it is just a suggestion and you can take it or leave it at will.Boat fenders,they come in various sizes,they are made of a very tough material and the newer ones are capable of being refilled with a football needle,just like you would pump up a basketball.

Now if you can come up with a way to permanently attach a couple of needles to the fenders and run a tee line to them you can air them up with an air chuck and check their pressure,an air line kit for air shocks should do nicely for this.I would also suggest figuring the weight of the installed components and putting the hull together with a couple of screws and use concrete blocks ,bricks sand bags etc to check your flotation before sealing the two halves of the deck together for good..
 
Last edited:
Flash-FX

Flash-FX

No Square..No Round..FX-1
Location
South Jersey Shore
You might be able to fabricate a bearing/bulkhead support like we used in the 440-550 days. They worked well with the old school flimsy bulkheads.

Be cool with that side outlet exhaust design. If the water is allowed to cover over the outlet when running, it will make the motor bog and hesitate (enough to make you crazy).
I ran a side exhaust (above the bondline) for awhile, it was LOUD even with a stock waterbox...and black exhaust goop covered the side. Then I re-located the same outlet below the bond line. It was a little cleaner but ran like crap.
In the end I'm back to the rear exhaust.
 
onlyFX-1

onlyFX-1

Jace Forest...BRAP!
Location
Lake Travis,Texas
Yeah, dan(highroller) is building my ski like this with no bulkhead. I cant wait to see how it comes out. Should be a couple more weeks and it will be done and I can post some pics
 
Q

QuickMick

Guest
SuperJETT said:
Having the center section still would take care of that issue I think, plus I'm probably going to have a new stronger piece of material to use as the bulkhead anyway.

Like this:
IMG_6537_with_cutouts.JPG
Click to expand...

Jet that idea will work. However I think you should beef up under the tray between the tray and lower hull to the pump with a perpindicular bulkheads that run the length of your tray that attach to the front existing bulkhead. That should help beef up the existing bulkhead as Glen described.

These bulkheads are very simple to make on some wax paper, then trim and glass in place.
If you foam in the side of the hull for better floatation is a good idea too.
before you foam lay in a piece of pvc pipe to foam around so the water has a way to get to the drains.
 
Last edited by a moderator:
You must log in or register to reply here.
Top Bottom