Scoops . . . Modifying Them For Better Performance and Speed
Topic: Scoops - Modifying them for performance - how and why.
There are several reasons to modify a scoop but the main reason is that many times a scoop works too well. When that happens, you could experience "stuffing" and/or porpoising. If you are experiencing a "surging" at top speed, that's not a scoop issue, it's air getting into the pump cavity - see this article to cure that problem (Tech - Ski Removal and Replacement)
This discussion will focus on modifying a SUPER SCOOP and ULTRA SCOOP
The main goal to achieve is to "bleed" off excess water. There are a couple of things to consider:
- This scoop works really to well after about 35mph
- Many people have tried modifying the rear blade and have seen little change (me included)
- The biggest bang-for-the-buck seems to be to modify the front end to look like a PRO SCOOP
- There is a another option that works "almost as well" - it's detailed below.
- Finally - there's the modifications that WetbikeBrian made - very interesting indeed.
This requires using a jigsaw, handsaw or powered sawzall and a 4-inch grinder. First, you cut the front corners off like this:
Then take a suitable object and mark a nice radius on the front like this:
Then cut that radius so the front end looks like a PRO SCOOP - like this:
Now you can take that 4 inch grinder and shape the outer edges by grinding them down-and-away (to bleed off water).
If you don't want to go that drastic, you can do these modifications first - works best if you have an end mill. Here are the steps:
- With the scoop bolted down, mill the front blade back until the underside of the lip is level - and won't block any incoming waterflow.
- With that done - set your cutter back down on top of the front blade - then mill the rear blade down to this same depth. This does 2 things - it makes both blades the same height (the rear used to be higher) and it opens up the area between the blades (letting more excess water out).
- Another Optional Modification is to flip it over and cut out "vents" like an ULTRA SCOOP. This takes quite a bit of work to get scoop setup at the right angle and then bolted down level. Here's one that WetbikeBrian did a while back. Note how much he cut off the rear fin
The goal here is two-fold. First, the casting needs some cleanup. Second the front edge of the first blade needs to be cut back/leveled. Hopefully these couple of pics will illustrate the issue:
In order to cleanup the spaces between the fins, you will need to look at how "twisted" the casting is before you begin. In a nutshell the goal is to try to make the slots "parallel" with the ski (or mounting surfaces of the casting in this case). Take a look a these pics and see if you can see what I'm talking about:
Copyright 2011 Capt'n Obveeus