Monday, June 21, 2010

Stability Trial

video

With the ~220 lbs of steel plate ballast secured to the floor, it was time for a stability trial. The video shows 2 trials with the mast below water level.

In the first trial, there are also a couple of sand bags (~ 2 x 60 lbs = 120 lbs) lashed to the floor in addition to the steel plate (6 pieces, ~ 220lbs total).

The second trial is without the sand bags, steel plate only. The difference is pretty subtle.

We also did a couple of tests with me in the boat (no video) and from my view it didn't seem like there was much difference in observed stability.

It is noteworthy that I was able to enter the boat when the top of the mast was in the water. The cabin coaming was still a few inches out of the water even with my weight on it while entering. If the boat were heavily laden, this might not be the case, but the hull would likely be even stiffer in that condition.

The boat is pretty tender when upright but stiffens up remarkably when heeled. The second trial was in deeper water. The boat stiffens up even more as soon as the deckhouse is in the water. It is a very noticeable increase. You can see in the video that I was trying to push the mast to the bottom but was not able to do so. All very encouraging.

Note also that in these first trials, the sail is down. In a real knockdown, the sail would be up, there would be more weight aloft and the rig might catch water and dig in as the hull is pushed toward it by wind and waves.

5 comments:

Anders said...

Nice to see you're still working on your boat. Keep up the good work!

Dave said...

First of all, what is the temperature of that water! I assume that is a dry suit you are wearing?

Fantasma recovers nicely. I imagine with 1 or 2 people aboard, she will be stiffer. Did much water come in thru the closed hatch?

What is the theory behind the gripe for more weather helm? Does it effectively increase the waterline length of the boat and thus change the moment arm?

When you post pictures of the steel plate ballast and hold down strips, can you post a picture of the mast step too? Does the base of the mast just rest on a reinforced pad on the hull bottom?

More pictures and video !!!
Dave

george said...

thanks for the encouragement, guys.

Yes, the water is COLD. Definitely a dry suit.

The gripe provides lateral resistance forward which translates to weather helm. We talked about adding a small centerboard forward but the fixed gripe is simpler, lighter, doesnt use up interior space and adds protection to the hull.

Will put in a photo of the wood mast step. It held in place now with a single bolt so it can be moved around but will eventually be epoxied in place and reinforced.

Mark said...

Hi,

Any idea (even a very rough idea) of when plans will be ready?

I'd love to get started on one in our (southern) winter.

Regards,

Mark

Mike Hayes said...

Hi George

Great sustained effort and build quality !!!

Keen to build an Enigma 460 here in New Zealand.

Any idea when Plans will be released ???

Cheers: Mike Hayes