New 2" ID Diameter Scupper Drain Tubes

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DaleH

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My boat is 21-years old this year … time to replace those old ‘press in’ brass drain scupper tubes. The brass gets weak over time and they start to leak water into the core of the boat and boats made (like mine) over 20-years ago, marine plywood is the core and you do NOT want to get that core wet!

I decided to go BIGGER in diameter, from one single 1” brass tube per side to one 2” (ID) PVC tube per side. I drilled for the new holes out by putting a ¼” drill bit right above the existing scupper tube (I cut the rim off the old tube first), lying the bit right on top of the tube at 12 o’clock to use it as a guide. Then I cut through with a new 2-1/2” hole saw.

One tip for those new to hole saw use, you need to pull the bit from hole quite often and clear the chips from the teeth, as you are drilling a ‘blind’ hole and there is no where for the chips to go. I wear a thick leather glove and just swipe the teeth off. Clearing the teeth often allows you to drill the hole faster and makes the tool last significantly longer. When done, I also press the teeth into a piece of scrap ethafoam to keep it sharp and not get dulled when tossed with other tools into my tool box or ‘boat bucket’.

I had to chip out the pieces bit by bit (no access from inside the boat to fit the cordless drill) and the transom was almost 3” thick! And the transom core was dry on both sides of the boat. But when I took possession (when she was only 8-years old) I put a bead of 2-part marine waterproof epoxy around the belled-edges of the brass drain tubes. I strongly advise that you do the same. As you can see below, the brass tube was integral (at least until I beat it up and literally punched it out of the hull, from the outside to the inside), but it was only a matter of ‘time’ for it to start leaking.

Look at the layup for the transom. In total cross-section it is 2-3/4” thick! I know of no other boat in this size range with as thick a transom! I am curious about what appears to be a ‘putty’ layer lying against the transom core frp layup. My ‘best guess’ is that this thickens the hull layup from the outside so that any peripheral penetrations (small screws to mount clamshells, rigging tube collars, etc.) don’t penetrate fully to the core. What say you?

One photo shows the core being wetted out with thin penetrating epoxy, multiple coats, until the core wouldn’t absorb any more. My plan is to epoxy in place 2” ID PVC tubes ala what Bobby (Warthog) did on his 2530 refurb.

Look at the performance increase! Two 2” ID drain tubes give a 400% increase in drainage over 1" holes! For scupper covers, I’m going with the largest ball scuppers made (RaBud Marine), which will keep the cockpit deck dry. More picture later for the new tubes installation …
 

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Impressive. I need to save this post to my project file.
This upgrade is going on my to-do list for spring 2014. :wink:
 
Very cool. I have a new set of inserts and a flange tool I made waiting to redo mine. Have not had time yet....
 
Hi Dale,

The flow rate is actually to the fourth power (Poiseuille's equation), so doubling the diameter increases the flow rate by 16X, not 4X. Although this doesn't take into account the size of the opening on the scupper, which could reduce the flow rate significantly, depending on what size that is.
 
Nice project !
I need to work on mine too they are cracked on the rim
Update pics as you complete !
 
OK, to pick-up on this ... I had left off with the new holes for the 2” ID scuppers bored and wet-out with repeated coats of Raka epoxy.

Mounting Holes:
I placed the sealing gasket on the hull and marked out 4 holes to be used to mount them. The flange comes with 6 holes spaced equally, but I just went with 4 holes, 2 on the top left quadrant and 2 on the bottom right quadrant.

I drilled 1/2” holes and wet them out repeatedly with thin, penetrating epoxy. While it ‘kicked’ I used a handsaw to add grooves into the 3/8” diameter ‘nylon spacer’ inserts used. These are cool, as with the hole in the center, it gives any excess epoxy deep in the hole a way to flow out. These ensures you seat the insert far enough and prevents an air pocket.

Then I made up a batch of epoxy, that just slightly flowed, like ketchup, and put that into the back of each hole with a syringe. I added a tad more cabosil to the mix to make it the consistency of peanut butter (like the visual examples :D ?), then put a big dollop into each hole, stuck the insert into it, and then put them into the hole. While curing you need to do a check once in a while to ensure the inserts stayed straight or square to your holes.

Tap Drill for Screws:
The next day, I sanded the area and put the scupper seal back on the hull, marking each mounting hole I would use onto the new epoxied inserts. As you can see I did a pretty darn good job laying them out! I also put a ‘flag’ of duct tape on the drill bit to ensure I only drilled into the epoxy as far as needed for the body size of the screw. I just put a bit against the screw and make sure the drill bit is at least as large as the OD of the screw body. I will clean up the waterline at another time just in case Capt (Megabyte) Kevin ever vists the boat ... can't have it looking like a red-light whore now, can I?

Lastly, all done!

Performance Improvement:
Someone had told me that per Poiseuille's Equation, the flow rate would be improved to the 4th power and not 4 times by my calculations of the area of the new tubes. But I did some research here with some Chemical Engineers and it is the drag that is reduced by a factor of 16. They gave me a fluid Exit Spout Velocity Calculator, geeks that they are – haha!, and it proved that I have improved the minimum flow by my new 2” scuppers by at least a factor of 4-times that of the factory OEM 1” drain tubes.

Look at the numbers, the old 1” tubes can only shed about 9-1/2 gallons per minute, per side of the boat. The 2” scupper tubes can dump 38-5 gallons per minute. Even more important to me is the weight of the water in the boat in the event I ever took a rogue wave over the side. With the upgrade, counting both sides of the boat, I can theoretically dump ~620-pounds per minute off the hull.

Since I wanted to replace my scupper tubes anyway … this upgrade was a ‘no brainer’!
 

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Dale

Help someone like me understand why you did not just drill out the screw holes and then fill them with 5200 and then insert the screws. Why the need fto drill such large holes and then refill it with an insert. And what kind of insert do you use on a project like this ?
 
Mike Paul":35rzthpf said:
Help someone like me understand why you did not just drill out the screw holes and then fill them with 5200 and then insert the screws. Why the need fto drill such large holes and then refill it with an insert. And what kind of insert do you use on a project like this ?

5200 ...

-is not magic

-while 'good' ... it does not become a permanent part of the hull - it is a filler at best, with adhesive properties

-has adhesive properties that are best served for 2 frp pieces bonded to each other, not filling a blind or through hole with combo layers of frp & coring

-is not fully waterproof and no one can make sure they have filled the hole completely, unless you used a syringe to inject it in. And to be honest, with the mess that would be, epoxy would be the far better solution

-just isn't the 'be all' or 'end all' magic elixir some believe it to be. I have seen installs with it where it tore off glass. When I bought my used tuna tower, there was a 2" shred of roof frp layup attached to one foot. BUT, on the other hand, I can count of BOTH hands the number of times I have just pulled off 'dead' 5200 with zero effort ...

Just from my experience anyway ;) !
 
Dale

Thanks for the reply. I got to thinking more about how you did the install ( after I posted ) and it began to dawn on me that what you did was 100 % water proof with no way for water to enter the core of the boat.

Now that I understand the process and know a first class vs a cheap way it hurt my feelings that my transducer is mounted on the stern with 5200.

I still need to know what kind of inserts you put in the epoxy ?

Thanks again

MP
 
Mike Paul":2t6zvino said:
I still need to know what kind of inserts you put in the epoxy?
They were nylon inserts, called spacers at Home Depot in the specialty hardware drawers. They are helpful on blind holes.

Yes, my intent was for a permanent fix that I'd never need to worry about. Even if you just wet out the hole with a good 3 or 5 repeated applications of that thin West Marine penetrating epoxy (a best buy for this use IMHO!), and then used some 5200, you would have still protected the core better than 5200 alone, IMHO.

Blind holes can be filled best if the hole angle goes down as it orients to the horizon. But this was not possible on my transom, as there is a backward tilt or raked angle to the transom. Now I could have lowered the trailer tongue all the way to the ground to hopefully get the transom square, but I had a lot of work to do to the boat, and with recent rains, I didn't want to leave it like this.

I have done larger through holes without them, like those used on my swim platform that go completely through the almost 3" thick transom, but those were filled from the inside out, where the outside hole was taped off with duct tape, and filled from the inside, the epoxy flowed down (due to transom rake) and filled the hole completely.
 
Brent":14ym7jns said:
How are the cockpit drains connected to the PVC pipes?
Are you using hoses? Do you have pic of the cockpit drains?
No hoses on my vintage boat. The bottom of the scupper entry lower than the same plane as the cockpit floor. But immediately behind the rear inside vertical bulkhead, there is a rectangular "well" to collect water and put it to the scupper. This is maybe 5-6" by 8" fore/aft, and about 1/2" up from the bottom of the well is the scupper entry.
 
DaleH":51khsqrr said:
Brent":51khsqrr said:
How are the cockpit drains connected to the PVC pipes?
Are you using hoses? Do you have pic of the cockpit drains?
No hoses on my vintage boat. The bottom of the scupper entry lower than the same plane as the cockpit floor. But immediately behind the rear inside vertical bulkhead, there is a rectangular "well" to collect water and put it to the scupper. This is maybe 5-6" by 8" fore/aft, and about 1/2" up from the bottom of the well is the scupper entry.

I assume it is open like a gutter to the PVC pipe?
 
Brent":2o8yozv4 said:
DaleH":2o8yozv4 said:
Brent":2o8yozv4 said:
How are the cockpit drains connected to the PVC pipes?
Are you using hoses? Do you have pic of the cockpit drains?
No hoses on my vintage boat. The bottom of the scupper entry lower than the same plane as the cockpit floor. But immediately behind the rear inside vertical bulkhead, there is a rectangular "well" to collect water and put it to the scupper. This is maybe 5-6" by 8" fore/aft, and about 1/2" up from the bottom of the well is the scupper entry.

I assume it is open like a gutter to the PVC pipe?

My boat is like Dales, so I'll try to get some photos.
 
Here you go.
My boat is a 1996 vintage.
 

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