I don't think I could apply a vacuum without a female mould. My mould is just mdf frames with some stringers.

I have some basic resistance vs speed values for my hull if anyone is interested. Things to note though:

1. One hull only.
2. The hull is upright. (No heel)
3. There is no sinkage or trim. (It is fixed in space at the design waterline and the waves rise and fall around it.)
- Hydrostatic nor hydrodynamic effects are accounted for to support the hull
4. There is no leeway angle.
5. Speed is in knots.
6. Resistance is in Newtons. (divide by 9.81 to give kilograms)
7. The results are not validated. They're just for fun.
8. It was done in Michlet so all its standard restrictions apply

Speed Resistance
1.0, 1.57
2.0, 5.89
3.0, 12.86
4.0, 25.77
5.0, 42.48
6.0, 83.01
7.0, 114.35
8.0, 138.48
9.0, 161.14
10.0, 184.42
11.0, 208.78
12.0, 234.25
13.0, 260.70
14.0, 288.10
15.0, 316.38
16.0, 345.56
17.0, 375.63
18.0, 406.69
19.0, 438.72
20.0, 471.73
21.0, 505.78
22.0, 540.96
23.0, 577.16
24.0, 614.63
25.0, 653.11

I used FreeShip to do all the hardwork of creating the Michlet "in.mlt" file. Was done in about 1.5-2hours including reading the manuals to figure out how they both work. Also got a couple of wave plots saved and opened in FreeShip, but was only playing with these and hence only did them at lower speeds.

you can.. by using the foam and epoxy/micro mix as the vac barrier... Extend the foam below the gunwale line.. apply glass to the gunwale line and put the bag over.. double sided tape in the extra zone... well hope you get the idea...

I'd be dubious about the support offered to the foam by my mould with a vaccum applied to it. I reckon the foam would deflect.

There would have to be some more photos by now nick <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />
Hows the project going?

Nah, sorry, no photos since I started fairing. I'll get some soon though.

The decks and hull sides are faired, hull bottoms were started yesterday. Fairing is one problem with the method of construction I've used. It is very time consuming.

Also started laying up the new centreboards. NACA 66-010 section, about 1.7m long (about 1.2m below hull), 240mm chord (so aspect ratio of about 5), rectangular planform (easier to make mould). They are this long so that we can pull board out to find a nice balance for the conditions.

When carrying out this exercise are you using Salt or Fresh water. I predominately race on the sea so when I go inland I'm sure that I can notice a difference with the boat due to less buoyancy. Or is it just the fact that when I capsize the water tastes different?

You are building a F16 right ?

Then those boards have FAR to much surface area. You have more surface are then any of the F18's.

All other F16's are between 0.144 and 0.188 sq. mtr surface area per board and you are at 1.2 * 0.240 = 0.288.

As a comparison the F18's have an area per board of 0.200 - 0.255 with the larger area belonging to the older designs.

I expect your boat to feel like it will trip over the boards easily, as the FX-one had as a tendency. These boards were the same size as the Tiger F18 (initially). You have even more then that.

As such I expect you to pull up the boards by 1/3 most of the time ending up at :

Area : 0.192
Depth : 0.8
aspect ratio : 3.33

I have made this prediction before with the nacra I-17's and since a few years their class rules allow the boards to be shortened by 30 % after they too found that singlehanded sailing with too much board area makes the boat feel like it is tripping.

Wouter

sea water

Oh yeah, i know they're too big, but I'd prefer to be oversize than undersize. It won't be hard to cut them down later once I know what I want.

They're gonna be huge, nearly as tall as me!

This is not being "just oversized" this is being rediculiously too large.

You have to cut off so much board that it with result in a big hit in aspect ratio. Why do it ?

You'll end up with a pretty mediocre design after the testing and cutting.

If anything start with a 200 mm width and a 1000 mm board instead. That 0.200 sq.mtr is oversized without going overboard and if this has to be cut shorter then you still have asn aspect ratio of at least 4 or heigher (200 mm by 800 mm)

Wouter

The plates on my boat project approm 1m below the bottom of the Hull, but I do not have them with me so cannot measure them. I could ask John to do so if you want a comparisonm for the longer plates

Hi all,

don't know about you guy's, but I hate having the boards up above deck line. They get in the way of moving around the boat and hurt like anything when you slide up the hull and hit them <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />.

I don't (so far) find it a problem as when they are up, it's so windy I'm either on the wire or at the back of the boat. So far, it looks to me like they are better when the wind is below about F4, and then I just (when I remember <img src="http://www.catsailor.com/forums/images/graemlins/smirk.gif" alt="" /> ) pull them up a little.

I agree the higher aspect boards are a complete waste of effort... <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

Well, if that's the way you feel...

These are a set of experimental boards with which I can test a couple of theories.

If these ideas don't work I can easily modify the boards or easily build new ones. My centreboard cases are rectangular so they don't require too much modification. I will cost me about AU$200 to build this set out of carbon.

Plus I don't think they will be too far off the money. The chord length is a fraction longer (10-25mm) than what seems to be around atm, the board length can be adjusted to suit. Aspect ratio isn't everything, I think the Taipan boards have a ratio of about 1.5-2, just from looking at them.

I agree that they do get in the way when they're up...but it's sail area! <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />

As long as you are aware of this then it is all fine.

Good luck,

Wouter

Nick,

you are a brave man going where you are. Even if the boards turn out to be too long and not fast, the class will have final and real-life information about how large boards should be. Theory and experience from other classes is one good, but a full scale test is even better.

Ncik,

How long are these plates ?

Mine project approx 1050mm below the hull on my Stealth.

I think they are about 200mm wide, not sure what the cord is.

Should be about 1.1m below the hull, with a chord of 240mm and thickness of 24mm.