skipjack 24 flybridge fuel tank support

808hazmat

Well-Known "Member"
May 17, 2012
63
9
Kaneohe/ HI
Name
sean
Boat
Therapy-24' Skipjack Project
I am in the middle of a Skipjack 24 flybridge "renovation" and found something I didn't expect. As shown in the attached photos I uncovered twin spars of metal running under the original fuel tank area (spars are approx 4in wide x 1/2inch thick x 4ft long and spaced 6in apart on either side of the keel stiffener). The previous owner had bedded a new tank with pour foam (I know, a no no and sure death for aluminum tanks). My suspicion based on their orientation is original fuel tank supports.

-can anyone confirm what these metal spars are?
-can anyone tell me how they are bonded to the hull?

I wish to remove them without destroying the hull. They just scream "hard spot" on the hull. I know folks will ask so...there is a fishbox going down the center and I am going to saddle/ twin fuel tanks to lessen the roll moment of the hull.

Mahalo!
 

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apogee

My name is Apogee and I am a Squidaholic
Jan 29, 2009
3,046
2,016
Bakersfield
Name
Apogee..
Boat
Boston Whaler Outrage 28 (End Game)
I would leave them in place. If you do not want them start grinding them out. One heck of a project.......
 

cvjarrod

Freshie
Aug 6, 2003
749
155
53
Chula Vista
Visit site
Name
Jarrod
Boat
24 Diesel Skipjack Flybridge
I am in the middle of a Skipjack 24 flybridge "renovation" and found something I didn't expect. As shown in the attached photos I uncovered twin spars of metal running under the original fuel tank area (spars are approx 4in wide x 1/2inch thick x 4ft long and spaced 6in apart on either side of the keel stiffener). The previous owner had bedded a new tank with pour foam (I know, a no no and sure death for aluminum tanks). My suspicion based on their orientation is original fuel tank supports.

-can anyone confirm what these metal spars are?
-can anyone tell me how they are bonded to the hull?

I wish to remove them without destroying the hull. They just scream "hard spot" on the hull. I know folks will ask so...there is a fishbox going down the center and I am going to saddle/ twin fuel tanks to lessen the roll moment of the hull.

Mahalo!
The original skippies had steel tanks. A lot of people that converted to aluminum tanks would put additional ballast in the boat to make up for the loss of ballast going from steel to aluminum. 24 Flybridge is a tippy boat and as long as you have the power to push it, the additional ballast will help your stability at rest. Most of the roll moment of the hull is coming from a deep V coupled with a flybridge. This is the perfect combination for a tippy boat. Not sure going to saddle tanks is going to overcome this in the least.
 

FINADDICT*

SKIPPER
Jul 22, 2008
1,496
237
California
Name
Fingers
Boat
Finaddict*
im just curious to what happens when one tank is almost empty and the other is full in a decent swell,drifting?i would think it might make it worse?not sure.
 

FINADDICT*

SKIPPER
Jul 22, 2008
1,496
237
California
Name
Fingers
Boat
Finaddict*
got a 24 skippy too so am very interested in your project and hope too see all the pictures so keep them coming.are you going to keep the floor at its original height or lower it some?are you closing off the back hatches/doors where the batteries were at?how about the floor?what is your plan as far as material?1/2" 3/4"marine pw?glass then gel?non skid?looks like you have made some progress and should be real nicewhen your done.
 

ALUMINATOR

I've posted enough I should edit this section
Sep 16, 2003
3,874
206
North San Diego County
caspsolutions.com
Name
Dennis
Boat
27' self built
I also might leave the tank in the center and fish boxes on the side. You might be able to redesign the tank with a V bottom to pick up a few more gals. As you said no foam! One way to attach is to use a heavy piece of angle welded to the ends or sides and rest the angle on a glassed in support. This way the tank can sit an inch or so above the hull allowing complete air flow around it.

What are you replacing the deck with?
 

Saluki

.
May 10, 2003
9,483
196
HB
Name
Mika Tan
Boat
"MoorZilla"
Wait a minute...........

You are planning on cutting dow the stringers (the backbones of the hull of your boat) to only 3" high???????


Seriously????

If I was your insurance agent, I'd drop your policy like a hot rock.
 

cvjarrod

Freshie
Aug 6, 2003
749
155
53
Chula Vista
Visit site
Name
Jarrod
Boat
24 Diesel Skipjack Flybridge
Wait a minute...........

You are planning on cutting dow the stringers (the backbones of the hull of your boat) to only 3" high???????


Seriously????

If I was your insurance agent, I'd drop your policy like a hot rock.
Missed that part of the insanity. X2 that cutting the stringers down is a bad thing.

If you put the fuel tanks outside, you'll be raising the center of gravity of your fuel and the boat will become even more tippy.

Abandon this engineering abortion.
 

808hazmat

Well-Known "Member"
May 17, 2012
63
9
Kaneohe/ HI
Name
sean
Boat
Therapy-24' Skipjack Project
Sorry it has been a while and I really appreciate all the experienced input.
Actually, I totally agree that taking out the backbone of a boat would be a bad idea. An alternative construction method to full length stringers is a box grid system. In this case I'm redoing it as a grid construction (yeah...here we go with the Parker Boats debate). Grid construction is a very common method of construction in hawaii and many well known boats here use this method. One significant advantage I see over the conventional skipjack layout is compartmentalization of the hull cavity. When I look down the original bilge there is just one big void...very had to control a water leak from hull breach or other problem. Compartmentalization (with a grid system) prevents an issue from becoming a catastrophy.
I haven't been on here (or progressing much on the boat) due to work, but I have had a lot of time to think out the project. Integrated saddle fuel tanks will increase the outer stringer height to full deck level. The grid system will "box" the hull to the deck and create a very rigid system (I'm not saying the factory method was inadequate. I'm just modifying a great hull to suit my needs.) Saddle tanks will increase the center of gravity slightly (I measure about 3"), but...the mass of each tank has resistance to movement opposing the other. Essentially they will dampen the movement of each other in the direction of the beam and also centralize the mass fore/aft. This should decrease the roll moment about the keel. If the water is rough time to troll. If the water is calm then we bottom fish.
I have gone back an forth regarding fishbox in the center or fuel tank. I have decided to build the fishbox in the center because that is the way I want to fish it. A guy can dream about needing a big fishbox for 200# ahi, right? Well on the more serious side in rough water I also want there to be a big fiberglass box in the center of the boat so an inexperienced crew has something to lean on instead of having to go gunnel to gunnel.
On the brighter side I found an purchased an running and rebuilt volvo AD41...wow that is a neat engine! More safety and range with diesel were my objectives in changing from gasoline to diesel.
Hope I answered everyones questions and concerns. Looking forward to the feedback and making some progress this summer (if work lets up).
Aloha!
 

808hazmat

Well-Known "Member"
May 17, 2012
63
9
Kaneohe/ HI
Name
sean
Boat
Therapy-24' Skipjack Project
Forgot to add construction material will be 3/4" 3M fiberglass reinforced polyurethane sheets at 20# density. Strong stuff similar to Coosa and Penske boards. Should give a stable core and I'll just glass the hell out of it. I'm using this for the transom (should be good regarding compression resistance), grid system and deck. I may go to a lower density foam sheet for non-structural components like hatch covers and such. I know this this create a stir, but I will just be using regular polyester laminating resin. Bottom line is polyester works very well and with good surface preparation does a good job at secondary bonding (I'm sure this stirs the pot too). For the integrated diesel tanks I will finish the interior with vinylester using a resin rich layup schedule for the added chemical solvation resistance.

If anyone in HI is looking for a takeout volvo 5.7 (about 300 hours, original owner repowered then let it sit, local termites are very hungry and ate ALL the wood in the boat.) or a 110gal aluminum fuel tank from a skipjack let me know. Mahalo!