Scrubbing the bottom of UL1 hull?

[kwizz]

I've read in the instructions about taking the shine out of the underside of the hull to release surface tension. Do you just do the sponson area or the entire hull?

Has anyone got pictures of this please?

Thx

[G-UNIT]

I believe its just the sponsons, the bottom of the boat hardley has any contact.
I'm going to try this myself once I get a good base line run in, I ran my boat yesterday but conditions were way to choppy, even for my bj, could'ent even give it full throttle with out blow overs, but the BJ looked so cool catching air.

[kwizz]

I was seriously cut between three boats UL1, BJ26 and Arpro. The BJ looks such an awesome machine for cutting thro the chop. On ly reason I didn't go BJ was thro lack of knowledge of upgrading the machine to UL1 standard.
Love those narrow tall cat hulls!!!!

[kwizz]

So what would happen if you scrubbed the whole underside of the hull would it effect it anymore then just the sponsons?

[m4a1usr]

So what would happen if you scrubbed the whole underside of the hull would it effect it anymore then just the sponsons?

Nope. When on plane only the ends of sponsons and the driveline are supposed to be in water. Scuffing the bottom of a properly setup hydro is not so critical. Just look at what the real hydros use. If its out of the water when at speed then it becomes aerodynamic effects, not hydrodynamic. Scuffing does nothing for aerodynamics.

John

[G-UNIT]

The BJ was my first boat and I learned alot about fe boats from this one, there are alot of mods you can do, like scuffing the bottom, shortening the stuffing tube for more adjustment,
but with the UL-1 not much is needed except a prop change, strut adjustment, air dam if needed and shortening the stuffing tube if needed, love the UL-1, fun boat out of the box.

[kwizz]

Added an air dam last night and scuffed the sponsons, took it for a test this afternoon, OMG it was amazing!
The waters in this area are never smooth, always a little chop. On the few runs i've had with boat it's bucked around a bit, yesterday I added a lead weight to the nose which helped but not like this air dam. I had the boat flat out in both directions with just the dam fitted it was so fast and stable!
Looking forward to getting a 40x57 balanced prop next.

Thanks for the help guys.

[FEJohn]

What do you use to scuff the hull with and how much should you take off?

[martin]

What do you use to scuff the hull with and how much should you take off?

Use 600 wet & dry in linear strokes ( front to back in straight strokes), You only need to do it fairly lightly to just take of the shine of the surface which leaves the very fine scratches. Thanks Martin.

[martin]

Buy the way only do the running surfaces that are in the water at high speed, Dont do the entire under side of the hull. Thanks Martin.

[dreamland s4]

Added an air dam last night and scuffed the sponsons, took it for a test this afternoon, OMG it was amazing!
The waters in this area are never smooth, always a little chop. On the few runs i've had with boat it's bucked around a bit, yesterday I added a lead weight to the nose which helped but not like this air dam. I had the boat flat out in both directions with just the dam fitted it was so fast and stable!
Looking forward to getting a 40x57 balanced prop next.

Thanks for the help guys.

wouldnt air dams cause drag? just wondering because im thinking of getting one.

[martin]

wouldnt air dams cause drag? just wondering because im thinking of getting one.

The very small amount of drag youd be talking about is far out weighed by the hulls capability of travelling a lot faster before lifting, Thats of course that you have the power to go faster either in motor or props. But it will still also run better even at slightly lower speeds if its breezy. But its not going to turn a 45mph boat in a 60mph just by adding a dam. Thanks Martin.

[Fluid]

The important thing when sanding the ride surfaces of a hydro is to get them flat and smooth. You can't do that with 600 grit paper, you need to start with 220 or 320 and wet sand the surface flat and smooth, without any low spots. You will probably go through the paint, so what. This will also help to sharpen the edges of the ride surfaces, very important to low drag. Once the surfaces are flat and smooth, finish with either 400 or 600, makes no difference.

An air dam can certainly increase the speed of a hydro or catamaran - by allowing it to stay on the water at higher speeds. If your boat is stable at full throttle a dam will do nothing but add drag. If your boat blows off at 50 mph, adding a dam may allow you to run 60 mph if you have enough power and prop.


.

[FEJohn]

Thanks guys for your answers. A good weekend project!

[pescador]

I finally got around to truing the ride surfaces of my UL-1 and sharpening the edges, I didn't think they were too bad but after my JAE build I figured the edges could be waay sharper.
It took a fair bit of sanding and filler to get them flat and sharp, the rear edge of the front pad was the most work to square up.
Ignore the belly pan work, I was cleaning up a previous little ding.
I had filled the sponsons with pour foam a couple seasons ago so they are pretty solid.
For the paint, Topflite Lustercoat yellow is a pretty close match (it's on the bottom anyway)
We'll see how she runs in the spring.