Bullet Scuppers

Tuesday, 09 June 2009 05:47 | Written by  Dale Lippstreu and Rob Mousley
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Red7 Bullet Scuppers Red7 Bullet Scuppers Credits: www.surfski.info

I made a comment in my recent review of the Fenn Elite Double and the Apex Double skis that the balers on both were not at all effective.  Here's how to solve the problem - with the aid of a set of Red7 Bullet Scuppers.

My benchmarks for baler performance are Red7 Surf70 Pro and a V10 which I paddle regularly and both of which have excellent balers.  [Editor: Red7 pioneered the concept of the bullet scuppers described in this article and they were first seen on the Red7 Surf70 Pro.]

Subsequently I made my own scupper caps and bullets which I fitted to my Elite and the improvement was dramatic.  However making the moulds and fitting the scuppers was a laborious process so I was immediately interested when I heard that Republic Sports has come up with a bullet baler kit.  I called Andre Botha and he agreed to send me samples for evaluation.  That which follows is first a description of the fitment process (on Rob Mousley's Fenn Elite single) and Rob's evaluation of the performance of the scuppers. 

Fitting the scuppers

To fit the Red7 Bullet Scuppers, you need:

  • Bonding paste or epoxy cement (see note below)
  • 25mm hole saw
  • Small angle grinder
  • Bolts, fender washers, wing nuts and plastic tubing as described below
  • Sandpaper and sanding block
  • Matching spray paint to finish

The kit includes the bullet, hood and flanged linking sleeves which if properly fitted should make for a highly secure watertight seal. 

Step 1 - Remove the old scuppers

The first step is to grind off the old baler caps.  I used a small angle grinder and finished off the job with 80 grit sandpaper on a sanding block. 

Step 2 - drill new baler holes

The outside diameter of the baler sleeve is 25mm and is much larger than the 12mm of the standard Fenn balers so the next step is to drill out the holes using a hole saw - do not use a spade drill which will chatter and make a mess.  The fact that one is drilling into a pre-existing hole creates an issue for a hole saw as there is nothing for the central locating bit to "locate into".  I solved this by first filling the existing hole with bonding paste but the same result can be achieved by taping a piece if 2-3mm ply wood over the hole to act as a locator. Once the hole is drilled you should clean up the area with fine grit and paper. 

Step 3 - position the balers

Before you install the link tubes you need to draw 2 lines running through the centre of the baler holes and parallel with the centre line of the hull.  This will help you get the balers properly aligned when you bond them in place.  You should then hold the components in place, mark out their locations with pencil outline and complete with a light sand inside the lines to establish a good bonding surface.

Step 4 - Install the sleeves

This done you are ready to install the link sleeves.  The bottom component (with the foot for the scupper cap) should be put is place and marked out so that the excess length can be cut off.  The sleeves can then be fitted from above and below bottom with liberal amounts of bonding pace to make sure that you have 100% coverage - bear in mind that you can always wipe away excess later!  You now need to squeeze the sleeves together bearing in mind that the excess length of the top sleeve will be sticking through the bottom of the hull.  The easiest way to pull these components together is to use a bolt with fender washers at each end and a piece of plastic tubing over the linking sleeve expending beyond the bottom of the hull. 

surfski bullet scuppers

Suggested clamping method

Before leaving to cure make sure that the bases for scupper caps are aligned with the lines drawn on the hull. 

Step 5 - Add the scupper cap and bullet

Once the link sleeves are fully bonded you can fit the scupper cap and bullet in their marked locations using the same bonding paste (Andre uses superglue).  In order to ensure that the bullets and caps were tightly fitted to the hull I taped them in place with clothe tape and then pressed them to the hull with low density foam squeezed into place using roof ties.

Step 6 - Finishing touches

I finished the job by touching up the area with matching white enamel paint which so the sake of convenience was applied to the scuppers as well.


Some words of caution

Andre told me that he generally uses epoxy cement for attaching the scuppers.  This is lot easier and is most probably perfectly adequate but I am rather paranoid about developing major leaks far out to sea. 

One needs to bear in mind that skis are sometimes subject to quite high shock loads (e.g. as when launching over waves) and the interaction between hull and deck can generate large shear loads on the balers when this happens.  If a baler were to "pop" in big conditions it is likely that the ski would fill very fast and you could find yourself in serious trouble if you are far out to sea at the time. 

You therefore need to make sure that you achieve a very secure bond line around the installed baler. Fenn put quite a bit of bonding paste around their baler holes (for the above reasons) so if you are lucky you will find that the new enlarged hole is still surrounded by solid donut of resin. 

If not I strongly suggest that you grind out a bit of the space between the hull and deck and fill this with bonding paste. The hull and deck connection must be very secure.  You can buy bonding paste or make your own using 50/50 cotton flock mixed with aerosil (available from all composite suppliers).  Remember to use epoxy for epoxy skis and polyester for polyester skis.

NB: Even a small angle grinder is a vicious tool which can gouge a hole really quickly if you are not fully familiar with it.  If in doubt grind away the old scupper cap by hand as the last think you need to do is damage the laminate at the start of the job.

And the Performance?  (Comment by Rob Mousley)

Flooding the cockpit

There are many advantages to a single footwell in a surfski - but there's one major disadvantage: when flooded it holds a LOT of water.  There's nothing as discouraging as trying to accelerate a sluggish waterlogged ski onto the next wave - you want to get rid of that water as fast as you can.

My Fenn Mako Elite was supplied with conventional scuppers - and had average drainage. After the experience of paddling the Red7 Surf70 Pro, which pioneered the "bullet" scuppers, the relatively slow drainage of the Mako Elite was quite pronounced. When Dale told me that he'd obtained some sample bullet kits from Andre Botha, I leapt at the opportunity to have them fitted to my ski.


I've paddled the ski several times now - including a (gentle) downwind session and I can report that the bullets have made a major difference.  On flat water the scuppers start gurgling at about 9.4km/h and at higher speeds the water seems to vanish in an instant.

There is no doubt the bullets radically improve the performance of the scuppers.


Another benefit of the bullets is that they reduce drag.  The original computer simulations commissioned by Red7 showed that three bullet scuppers have approximately the same drag as a single conventional scupper.

Traditional surfski scupper flowSurfski bullet scupper flow

Water flow and turbulence Conventional scupper (L) v Bullet scupper (R)

Surfski Scupper Resistance

Resistance Comparison - conventional v bullet scuppers

So by replacing the conventional double scupper with a double bullet scupper, the drag is reduced by about 60%.  Is that significant?  I read somewhere that the drag of a single scupper reduces speed by about 0.3%.  That's 36 seconds in a two hour race.  Two scuppers?  A deficit of 1:12.  How cool to claw back 60% of that time by fitting bullets!

Whether or not those figures are accurate...  it feels great to know that the ski is slipping through the water more efficiently - every little helps!


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