New design - opinions / idea's wanted

[JCF]

Originally Posted by Steven Prince

Hi J.

I've been working on the current design for about 4 weeks, but I had been working on a different design before that but was not happy with the look. Before these boats I had been designing a 45ft monohull but I finally decided that I would look into a catamaran properly rather than just going of the magazine articles warning ppl away. Once I started looking into Cats I realised there many advantages and was sold.

I've read through part of your thread, haven't managed to read all of it yet. I have to admit that I haven't looked at the mathematics yet. I've mainly been trying to get a boat that I like the look of. The program I'm using to carry out the design allows for very easy manipulation. I believe that I currently need to move the Centre of Buoyancy slightly further forward by 300mm but I'll wait till I've finished the design so that I can apply the materials to the hull and check where the centre of gravity is in relation to the centre of buoyancy.

I've modelled my boat from a variety of designs but the biggest influence has been Darren Newton at Dazcats, particularily his D15R. I'm hoping to get in contact with him soon and see if he'll help with the design and eventual building of the boat.

I'm currently hoping to get a scale model made, although it'll be a lot smaller at 1:100. I hope to get a few made as the design progresses to show the different stages. The final model will be painted with the same paint as the main boat and will be used for carrying out test. The final model will be larger to show the details more clearly and to allow for some testing.

I was wondering what you have used to work out the hydrostatics.

Steven

Hello Steven,

Freeship works out the hydrostatics for you including CG and weights for all components. It is incredible and easy manipulation is the understatement. You can get it here. Try it...the worst that can happen is that you will fall in love with its ease and very satisfied with the result.

Freeship - Reviews and free Freeship downloads at Download.com

Four weeks? Well, you're doing excellent then. I don't think I had nice lines in place until way after my learning curve.

Unless you intend to have a qualified NA or NE do the work for you, it would be a good idea to get an understanding of the different design elements which include much math and pain to the noggin. If you have any intention on floating the design, it is imperative.

To start, learn the different design elements that assist you to understand how she will perform so you can design her well. For example. You mentioned that you will wait to move the CB.

Thats a no no. The CB on a cat should be at 50% of the LWL or dead center longitudinally. Therefore the CG of the design must at its final position be directly above it. If the CB is not centered and the CG of components are manipulated to be above the CB, not at the center, then the footprint changes as will stability, the LCF, increased pitch aft or forward, hobbyhorsing and other elements etc. That is ofcourse the ideal, but you should strive to always stay as close to center as possible right from the start.

If you like, I will look over your thread with more care and will offer my thoughts on her so that you have another "opinion" to keep you open about the design.

I don't understand the paint part of it or why? Can you elaborate some more?

Keep it going.

J

[Steven Prince]

Hi J,

The CB of my current design is 300mm back of centre line. This of course will move slightly further forward with the addition of the rudder and a small keel running from the centre of the hull back to provide protection to the rudder / prop when beaching.

Can you import models into freeship from other programs do you know. I'm hoping to haval a NA look over the final design either way as I'll be spending alot of money to get the boat built although I'll be carrying out alot of analysis on the model and CAD model.

The boat is to be painted black but due to the temperature the boat would reach in the tropics it will be painted with a special paint that changes from black to white when it reaches a set temp.

Alsa Corp | Eclipse: Product Information

[JCF]

Hello Steven,

Yes. Freeship will allow you to import different formats...DXF, Carlson.hul, fef, surface, chines, Carene xyz, vrml, polycad and michlet waves.

It is an excellent idea to have a NA or NE take a look at the design and call out the scantlings or at least confirm their integrity. I also did that with my design.

Black paint to white paint when temperature changes sounds koool. But if she will be in the sun in the lower lat's, why not just go with the thicker white gel coat with strong UV inhibitors? What is the purpose of having the colors change? I'm not being critical, and it's your pickle, but you should reconsider the colors and reject them.

Here is something for you to consider. Sunshowers that keep the temperature just below the color transition but the sun is beaming on deck. Given enough time you will be in an oven and although the heat build up may be slow, it will not dissipate as fast as you may think. Just some food for thought.

I know that exploring different things is always good (I have fighter sticks for steering in my design), but, sometimes it's good to stick to the tried and tested.

J

[Steven Prince]

Progressed a bit more with the design this week. Here's a few pics. Will try and put into Free ship to do the Hydrostatistics sometime this week, if i can import the model into it.

[Steven Prince]

Ok, I'm trying to import a wrl file into freeship but I just get a msg saying not a valid vrml 1.0 file. Has anyone got any ideas as to why i get this msg.

[JCF]

Originally Posted by Steven Prince

Ok, I'm trying to import a wrl file into freeship but I just get a msg saying not a valid vrml 1.0 file. Has anyone got any ideas as to why i get this msg.

Hello Steven,

The only thing I can think of is that the file is not saving in vrml 1.0 format. It must be 1.0 for the import to occur. You will either need to save it as such or perhaps get one of those free converters from the net to convert it for you.

Have you tried importing in a different format? Are you able to do so?

J

[44'cruisingcat]

Originally Posted by Steven Prince

Hi J,



The boat is to be painted black but due to the temperature the boat would reach in the tropics it will be painted with a special paint that changes from black to white when it reaches a set temp.

Alsa Corp | Eclipse: Product Information

the boat will likely turn from white to black at sunset. Not the best safety feature I could think of.

[Southern Star]

Steven, from a quick glance at your preliminary drawings it would seem that you would not have interior access from the bridgedeck accomodation into the hulls (or at least, not access permitting steps and headroom). And I tend to agree with the comments about black - especially for the decks and coachouse.

Further, I am not aware of any 2-part polyurethanes (or epoxies) that change colour as you describe. IMO no other paints are sufficiently durable and repainting any boat, let alone a cat of that size, is a VERY expensive proposition.

Brad

[KIWI]

Have a look at Pelin designs, He is a NZ designer and would be one of the best known designers in NZ , I have seen one of his cats a 40ft and even though I am not a cat person I was impressed this one was home built and the owner did a amazing job, I was also impressed with the bridge deck to water clearance of about 4 ft , He has a 40ft and a 45 ft in the cat designs and can be built out of ether cold molded marine ply or FG
Pelin Boat Plans - Build Your Own Boat

Graham

[JCF]

Originally Posted by Southern Star

IMO no other paints are sufficiently durable and repainting any boat, let alone a cat of that size, is a VERY expensive proposition.Brad

From my calculations, with paint, clear coat and uv inhibitors... thinned 2:1 with 3 coats recommended, minimum of $3,200.00 per gallon of coverage, whatever that coverage may be. Primer and special base coats not included. That is a prohibitively expensive yacht R & D venture.

Do a pro job and it will last 10 years in the tropics and then it's time to do it all again.

J

[Steven Prince]

Well I've finally managed to get the model convert to a wrl. 1.0 format so will look at running some of the hydrostatistics on it tonight or tomorrow.

[JCF]

Hello Steven,

How is it going with Freeship? Make sure all the layers contain accurate data and that all required fields in project settings and layer boxes are accurate and complete or the hydro may not run or be accurate.

Keep it going...I want to see more.

J

[Steven Prince]

Hi J,

Managed to get it converted but it comes up with an error message and won't load it. I think the model all though converted is to complex for the program.

I'll have another go soon but rather busy at mo, got a few uni assignments to get done. Bit of a juggling act between work, uni and designing the boat.

Got a bit stuck on the back of the bridgedeck, not to sure howi want it.

Steve

[Steven Prince]

Ok. I've finally managed to get some time free to do some more work on the design. I've also finally managed to get the model into Freeship using VRMl. Could any1 now give me some pointers on how to run the various hydro calcs.

[Abaco]

Steven,

Here is a design for a 55 footer that you may find interesting. The design incorporates a small forward cockpit for handling all the sail control systems and an inside steering station like the Gunboat. The design was a joint effort between Dudley Dix and Phil Harvey. Phil Harvey was involved in the building of some of the early Gunboats and designed this boat for him and his family to live on and cruise.