Reducing boat weight

[justgary]

22 hours ago, SkiPablo said:

my boys ski 28 and 15 off and it's great - I would think your boat would be similar, maybe you are being too picky ?

Or something else is up with your boat.  Like I said before, I ski 15 off 29 MPH behind a Response and my Sunsetter, and the wakes are very comparable.  I don't spend a lot of time in the middle, though.

The first time I ever barefooted behind a Response (yes, faster than 29) I couldn't believe how flat the wake was,  so I just instinctively crossed it a few times.  That's what started my own quest to find a Malibu.

[Nick in the TC]

I agree the wake is pretty good at 15 off. Like I said before half just board and like to have a winter project and I really hate stepping over that trunk all the time. The way I use my boat is 100% business.  Only thing I have seen with the trunk how we use the boat is it is always wet in there and not really space I can utilize. We only ski and drive back to the dock. I have a different family boat that is more user friendly. 

[Eagleboy99]

I guess you are trying to turn your RCB into an Infinity ZX-1

[Nick in the TC]

Do you have a used v-drive for sale?

[solorex]

Sounds like you need to buy a Malibu Tantrum.  My ski wakes are perfect and no worries about weight 

[Chaabo]

14 hours ago, Nick in the TC said:

I agree the wake is pretty good at 15 off. Like I said before half just board and like to have a winter project and I really hate stepping over that trunk all the time. The way I use my boat is 100% business.  Only thing I have seen with the trunk how we use the boat is it is always wet in there and not really space I can utilize. We only ski and drive back to the dock. I have a different family boat that is more user friendly. 

Ok then, ... get rid of the trunk, backseat and fuel tank and replace with a small(er) fuel cell somewhere in the bow area. Get some matching marine carpet and build a “skirt” out of it to cover the open gunnel area in the back you are left with when ripping out all the above. Cover the middle floor section above the rudder with some carpeted HDPE board and you should be good to go. 

[Nick in the TC]

That’s the plan. Already got a good start.  The hardest part was taking out the hidden screw that held the bottom of the side panels to the bottom of the seat backrest.  Eventually I will get a total weight number of removed parts.

 

 

 

[Eagleboy99]

I wonder what will happen when the stern is lightened so much?  Prop angle changes, etc.  I doubt there will be much inthe way of weight savings from the removed parts, save for the gas in the tank.  In which case, you could have just  capped off the current tank and added a new pony tank to the front and piped that to the motor.

Edited November 4, 2019 by Eagleboy99
Spelling

[Nick in the TC]

Again I would be just stepping over an empty gas tank?

[Chaabo]

1 hour ago, Eagleboy99 said:

I wonder what will happen when the stern is lightened so much?  Prop angle changes, etc.  I doubt there will be much inthe way of weight savings from the removed parts, save for the gas in the tank.  In which case, you could have just  capped off the current tank and added a new pony tank to the front and piped that to the motor.

No more need for bow weight. 

 

[justgary]

So the grilling is apparently over and we can get back to your original question.  Sorry about that. 

I think it might be good to consider moving the blower with the tank to get the flow of fresh air reversed.  In other words, you still want to draw it from the engine area to the gas tank area and out.  Might need a reverse scoop on the deck to help route flow. 

[Eagleboy99]

1 hour ago, Nick in the TC said:

Again I would be just stepping over an empty gas tank?

Well, I would test a pony tank before I did all that work only to find it makes no diff.

[Nick in the TC]

Yes I was thinking about adding another blower. Maybe dump from the nose to the engine area then the regular blower would clear the engine area.  I always run the blower couple minutes before start up and leave it on the whole time running. 

Edited November 4, 2019 by Nick in the TC

[Eagleboy99]

4 hours ago, justgary said:

Might need a reverse scoop on the deck to help route flow.

Like this? 

[justgary]

1 minute ago, Eagleboy99 said:

Like this? 

Exactly.  Except backwards to help pull air toward the front and out.

[justgary]

And use small wake stickers instead of those go fast ones. 

[MadMan]

A benefit of replacing the short wide fuel tank with a narrower, taller one is that you can have much less fuel (weight) in it and sloshing or turning won't cause the pickup to become uncovered.  Also, the fuel gauge might become useful.

[UWSkier]

while I could never give up my trunk, I would be a fan of getting the fuel weight moved forward.  Something that I could install from the front would be swell.

[Woodski]

To answer a few of the points brought up in this thread:

• Removing transom weight via any means but to this thread getting rid of the 30# gas tank and any of the fuel in it (pretty much can't run below 5 gals / 30 #) makes a very significant difference on the slalom wake, much flatter at all line lengths.  FYI - my fuel tank is in the ski locker between the driver / spotter seats.  I also made a carbon fiber platform that lopped off an additional 20#.  Outer chine draft at the transom is less than 1".
• Getting rid of the trunk and installing a vertical panel at the transom makes a really nice 'dressing area' behind the motor box and an easy step over to the platform.  I really like how that opens up the space back there and provides a short step over ala ZR1.  I use that cavity to store my ski and since a Goode always desirable to hide it from the sun.
• Tracking actually gets a bit better as doing the transom area weight reduction actually pitches the nose down a bit.  No additional rudder torque was needed for the slalom course, which is cool.  I have moved the water break off the front part of the chine quite a bit (forward by a foot).  In my case, lopping off 475# in total, and moving the CG forward by slightly more than a foot (calculated, measured and validated) so my conclusion is the weight loss is not a detriment coupled with the increase in wetted surface and forward CG.  That was one of my concerns as I migrated along the weight reduction project.
• You won't need to augment airflow, the removal of the tank will actually open up the airflow path to improve air evacuation.  The high pressure at the base of the windshield is the inlet source, the low pressure at the transom provides the delta P (drop in inlet to outlet pressure) to ensure airflow through the engine compartment.  If you are going to go to the trouble of an engine box scoop, do a reverse NACA duct on the top, that will draw better:-)  A better solution is to provide a cold air source to the engine air inlet, which will keep your early / late season peak speed performance in tact rather than losing some when the hot air under the hood steals some performance.

Hope that answers some of the questions or comments, doing that certainly has been very rewarding at least for the slalom aspect.  It also makes the handling a blast, 180 bat turns ala early PS190's are a snap & the boat feels a lot livellier (383 cid & 500 hp doesn't hurt either).  It does make one heck of a terrible wake / surf boat!!

[justgary]

@Woodski - My only thought on changing the air flow was safety, and only on startup, not after you get pressurized flow from speed.  I figure it's better to draw air over the gas tank last rather than pick up fresh fumes and blow them past the engine.  In reality, it's probably just as well to leave the flow as long as the blower actually moves plenty of fresh air across the engine and you don't have a leaky tank. In other words, don't just open the transom and not fix the blower hose to properly draw from the bilge and stringers. 

I think I would also inspect the tank regularly to make sure that it isn't leaking so that you don't have a situation where you are unable to clear fumes that the blower then pulls past the engine.

 

[Eagleboy99]

31 minutes ago, Woodski said:

pretty much can't run below 5 gals / 30 #

Other than this, I agree with what you are saying.  We routinely slalom with <10 liters of gas.  No issues whatsoever.  

[Nick in the TC]

Thanks for the reply @Woodski  I have read many of your posts and gotten some good ideas from you. You said in one thread you made a lighter motor box but couldn’t find more info on that.  Did you have more info on that somewhere?

[Woodski]

@Nick in the TC - I made one using carbon fiber with a foam core, the standard ones are pretty heavy as they are chopper mat fiberglass.

@justgary - excellent point, I don't draw air over the tank, I fully separate the two compartments and vent the tank separately.  I also isolated it from vibration and chafing and as you note, keep a close eye on it.

@Eagleboy99 - that is excellent, no way I could start our sets with only 2.6 gallons in the tank.  I was surprised how much was actually in the tank when it appeared empty.  Our sets routinely take 5 gallons to complete so need to start with at least 7 to avoid paddling.

[formulaben]

16 hours ago, Woodski said:

 @Eagleboy99 - that is excellent, no way I could start our sets with only 2.6 gallons in the tank.  I was surprised how much was actually in the tank when it appeared empty.  Our sets routinely take 5 gallons to complete so need to start with at least 7 to avoid paddling.

@Woodski if that's the case, then I'd say it's worth your time to install a small quart-sized hopper tank in line and down low in the engine compartment with a small vent line back to the main tank to keep the supply line and hopper tank air free.  That should keep a steady supply of fuel regardless of the sloshing in the main bow tank.  

[Woodski]

@formulaben - new tank works fine, can run it down to a thin film on the bottom although you don't go far under power when at that level.  It is a relatively narrow tank so minimal sloshing happens. I didn't need to add internal baffling although I thought about doing that and did make sure the pickup was at the rear of the tank for acceleration slosh.  I should have been clearer that I was referencing the original tank, my error.