Building in Triaxial vs Unidirectional - Which is better?

"The structural bulkheads are specified as (literally) 8 or 10 different layers of uni. I wonder if I can use triax here? I guess that's probably a question for the designer."

...wow, why not use structural foam and less layers, this will be quite heavy...you can laminate them on a sheet of glass to get a nice finish, also cover with a laminex type plywood sheet and vacuum bag down the layers to get a perfect and glassy look without any fillers.

 

These comments about weight are confusing me. You are not the first person to say this. People keep saying my boat will be heavy, but the numbers show it will be quite light. It is known to be one of the top performing catamaran designs available.

The bulkheads, of course, use structural foam as a core. It is either 5lb or 6lb foam.

Also, my hulls use 3 layers of 20oz triax on the outside and 2 layers of 34oz triax inside. People keep saying my hull will be too heavy. YET....

All materials for my entire boat, taken straight from the material list, weigh only 12,000lbs (5,433Kg). This includes nearly 400 gallons (1500 liters) of epoxy as well as all of the glass and foam core. How is the boat heavy for a 45' ocean crossing catamaran? Seems rather light to me when the Gunboat 48 with all carbon fiber has a lightship displacement of 17,700lbs (8,028Kg).

So why is everyone saying my boat is going to be too heavy when I talk about laminates? I am very confused.

 

...mate, i am commenting on your post of 8 or 10 different layers of uni, there was no mention of any core there, so I thought that possibly it could be a viable suggestion.

...cats are meant to be light, that is why they go so fast, not many heavy cats are designed, though there are a few very good ones that can handle quite heavy loads and still be at their designed waterline.

 

Triaxial cloth is a good choice for the connecting beams/bulkheads. Although I was saying not to use UD for the hull laminates its a different story for bulkheads as they are made on a flat laminating table and are relatively small so many layers of UD is not such an issue.
You can deviate from the suggested cloths as long as the orientation and weight remain the same in total. So you are free to choose what ever style of cloth is most economical to use, but include the time factor in that choice.

Weight is a relative term, your boat is not going to be heavy. But it will be heavier than some of the local designs, we do seem to be building lighter in Aust & NZ.
As an example the total displacement for the Oram 44 is 5,500kg , same as your material list alone.

 

It is just the general impression of the readers. You originally said the laminate was designed for resin infusion.
With infusion, you are aiming for about 30% glass content. With hand layup, 50% Gc is the best you can do. Thats about 20% more resin you will use.

 

Sorry there, mate. I didn't mean it in a bad way. I have just had a lot of people say my boat was going to be heavy. I was confused because I sought out a boat with the best sailing performance I could find. I should have posted that there was a core involved as well. Sorry to be confusing.

My hull (and rigging) weighs about 12,000lbs (5,433kg). Her designed WL displacement is 18,292lbs (8,315kg). Her sail area for main and genoa only is 863sqft (80.2 sq meters). I think these numbers are ok. Now I must go off and compare them to other boats! ha ha ha

I think my boat is designed to carry more load, which is something I needed and my designer suggested because I am doing charters. There will often be a lot of weight aboard that we will ditch when not working. (People, excessive water tanks, provisions, etc...)

 

Thank you, Andrew. Time factor is very much included. I would much rather do everything in as quick a manner as I can. No extra work. Several thousand hours is enough already.

I will have another look at the Oram 44. I guess (see my post above) that my boat is designed to carry more payload than an Oram 44C, which is probably why the numbers are different. My designed waterline displacement is much higher than the Oram 44C.

 

Yes, I know. I was curious why the general impression was that my boat was going to be heavy. That is obviously a very touchy point when you are building a high performance cruising catamaran.

I wanted to see why people kept saying that, is all. It has been said several times when I revealed my lamination schedule.

Anyway, I was going to do this with infusion, but have decided against it because of the risks and expense. I think (given my low skill level), building a hand layup might be best.

 

i don't feel your expertise is high enough to gave some advises.
i read your posts you seams quite a fake in boatbuilding.
but the beauty of any forum is you can pretend to be anything.
i will not touch anything with you involve, you don't have the "gravitas" will have said karl rove, to be on a yachting community.

 

Hey! Please don't wreck my thread by insulting someone who has answered my questions. War Whoop did contribute to some of my questions, especially in the resin infusion thread I started. He is just as entitled to propose an answer to a question as the next guy.

Where is your answer to my questions? You have given none - only insults and BS.

Do not carry your "off topic" BS into the on topic areas. :!:

 

Make sure you get a sample of the needed triax first. There is a lot of difference in wet out between different constructions.

Also a possibility is to use a biax +/- 45 and a UNI on top or below. Make a list of what you can buy easily, send that to the designer, and let him work out a decent laminate schedule using these materials.

 

accept my apologies.
and to redeem myself accept a good feedback point

 

Ok, I will do this. Thank you, Herman.

 

Wow, I am impressed. Thank you for such a good response.

Please accept a positive feedback point for understanding. I was a little hard on you, but it's important to keep the boat building information separate from the emotions in off topic areas.

 

no you were not hard on me, you reminded me how to behave, and you are right.
my beef with a member should not be display on a thread.
thank you for your kindness