Study for Sail Area / Displacement Ratio of some cats

[ldrhawke]

Originally Posted by fastcat435

What I see on the picture is vacuum bagging not resin infusion at all You probably do not know the difference but I will tell you.
With vacuum bagging the already hand laid up parts are after the lamination job vacuum bagged to get excess resin out.
With Resin infusion all the laminate fibers and foam etc is put in the Mould dry and all is put under vacuum , in our case 24 hours to compact the laminate than we open epoxy lines and the epoxy is drawn in under vacuum .
Another difference I see is that we do a complete hull and deck in one shot while here the hull sides are first made separate and than glassed together and that takes a lot of extra tabbing and fairing , probably 100 kilo,s per hull.
If we where to build the Atlantic 48 we would get it in under 15000 LBS in our technique and make it even stronger.
Greetings
Gideon

I beg the differ again.....you are playing on semantics. The method used is building the Atlantics shown is called resin infusion. It is slightly different approach than liquid resin infusion, which many experts feel does not always produces as uniform product as prepreg and resin film infusion. Atlantic uses prepreg foam and resin film infusion.

I would love to see photos of your two mold system in operation, the heat curing system, and a hull under construction using the methods you have described using to build the FastCat hulls.

I don't question that there may be some slight savings in weight using only two molds, and eliminating bonding together of several large parts, but I am not sure if improves quality or is more cost effective building a large cat.

Love to see some photos.

[fastcat435]

Originally Posted by ldrhawke

I beg the differ again.....you are playing on semantics. The method used is building the Atlantics shown is called resin infusion. It is slightly different approach than liquid resin infusion, which many experts feel does not always produces as uniform product as prepreg and resin film infusion. Atlantic uses prepreg foam and resin film infusion.

I would love to see photos of your two mold system in operation, the heat curing system, and a hull under construction using the methods you have described using to build the FastCat hulls.

I don't question that there may be some slight savings in weight using only two molds, and eliminating bonding together of several large parts, but I am not sure if improves quality or is more cost effective building a large cat.

Love to see some photos.

Hallo IDRhawke Prepeg foam does not excist, just prepreg fibers exhist.
With Prepeg film the resin to fiber ration is around 42 to 58 % instead of 32 to 68 % and the chance still excists that there are air inclusions .
I am in South Africa right now and have all the pictures of the building of the FastCat in my office in Amsterdam.
Yes you are right to build in one large mould is not cost effective but it does make a stronger lighter boat and that is all I am interested in
200 kilos saved on this item alone is a lot , just imagine that over a lenght of 18 meters or 60 feet you have to tab in glass , filler , gell coat or other means of making the boat look nice on the outside uses a lot of weight , we did that on the Fastcat 395 , the first boat we build this way and the extra weight was slightly over 200 kilo,s for a 39 footer
Having the fibers run continues instead of patching fiber on top makes the boat stronger .
Resin infusing a boat is a costly affair , much more expensive than building a hand laminated or prepreg boat but the weight savings are tremendous and the strenght is the best possible .

I wish you happy voyage with your Atlantic 48 and hope to meet you one day on the water so we can compare these 2 lovely and fast cats.

Greetings

Gideon

p.s. your words!!
A new negative hull mould has been made available and the vacuum bagged multiaxial glass/ carbon fiber/ epoxy/ foam cored construction has started.

What you showed on the picture is actual vacuum bagging 3 steps behind resin infusion

[Frank Artville]

Greetings Gideon,

I noticed this cat for sale on Yachtworld.com , a Lavranos design.

Apart from some details, the hull shape looks identical to your 43' (now 45') catamaran.

Did you purchase their moulds?

The interior is quite different, but the aft cabins again look identical to the pictures you posted previously.

2003 Wright & Lavranos 4300 Boat For Sale

[fastcat435]

Originally Posted by Frank Artville

Greetings Gideon,

I noticed this cat for sale on Yachtworld.com , a Lavranos design.

Apart from some details, the hull shape looks identical to your 43' (now 45') catamaran.

Did you purchase their moulds?

The interior is quite different, but the aft cabins again look identical to the pictures you posted previously.

2003 Wright & Lavranos 4300 Boat For Sale

Hallo Frank

This is a design that dates back to 1999 , built for charter use , 11 berths totally different with long keels and a weight of well over 10000 kilo empty.
No we designed and build the FastCat from the ground up in 2003/2004 build as a performance cruiser with only 4 to 6 berths the moulds where build by us here in New Germany South Africa and the first FastCat was finished in late December 2004.
The only thing these cats have in common are the designer ( only one since mr Wright had left the company and the fact that it also has 2 hulls )

Greetings

Gideon

[ldrhawke]

Originally Posted by fastcat435

Hallo IDRhawke Prepeg foam does not excist, just prepreg fibers exhist.
With Prepeg film the resin to fiber ration is around 42 to 58 % instead of 32 to 68 % and the chance still excists that there are air inclusions .
I am in South Africa right now and have all the pictures of the building of the FastCat in my office in Amsterdam.
Yes you are right to build in one large mould is not cost effective but it does make a stronger lighter boat and that is all I am interested in
200 kilos saved on this item alone is a lot , just imagine that over a lenght of 18 meters or 60 feet you have to tab in glass , filler , gell coat or other means of making the boat look nice on the outside uses a lot of weight , we did that on the Fastcat 395 , the first boat we build this way and the extra weight was slightly over 200 kilo,s for a 39 footer
Having the fibers run continues instead of patching fiber on top makes the boat stronger .
Resin infusing a boat is a costly affair , much more expensive than building a hand laminated or prepreg boat but the weight savings are tremendous and the strenght is the best possible .

I wish you happy voyage with your Atlantic 48 and hope to meet you one day on the water so we can compare these 2 lovely and fast cats.

Greetings

Gideon

p.s. your words!!
A new negative hull mould has been made available and the vacuum bagged multiaxial glass/ carbon fiber/ epoxy/ foam cored construction has started.

What you showed on the picture is actual vacuum bagging 3 steps behind resin infusion

Prepreg doesn't necessarily mean the foam is purchased saturated with resin. The prepreg can be made on site.

I'm an engineer and I can't picture a resin infusion system layed out in a one piece mold that is capable of guaranteeing resin will 100% saturate all areas and in very tight corners, like in the bow of a cat. You'd have to have a zillion vacuum and feed lines, with no kinking or blockage of any of them.

I would still love to see photos of your building a FastCat using this process in a two piece mold followed up with high temperature heat curing you say you use. You don't have the digital photos on your computer? Please post them after you get back.

[fastcat435]

I will send them we post cure after the complete hull structure is completed with all furniture in place, the post curing temeperature is 80 C. for 8 hours
we use a zillion tubes for both the vacuum and the resin and after the infusion process is completed we put vacuum to all the lines to get even vacuum suction all over , this takes another 150 kilos of resin out , before starting the infusion we keep the complete part under vacuum for 24 hours in order to compact the laminate even more and this also saves a considerable amount of resin.

Greetings

Gideon

[schoonerdog]

BTW, i for one find this discussion extremely informative on the different types of resin infusion methods. I know that PDQ had been using vacuum bagging since the late 1980s (the picture of the Atlantic looks like the same exact process). Simon the owner of PDQ mentioned that when trying to make an much lighter boat for strictly racing that he added several steps to the vacuum bagging to remove extra resin and that reduced the hull weight considerably. I've never seen resin infusion Gideon does, it will be interesting seeing the pictures. The sophistication of the process would seem several leaps ahead of the vacuum bagging operations I've seen used before.

[schoonerdog]

And yes Gideon, I'd put a LOT more information up on your website, showing in detail all of the aspects of your boats that are competitive advantages. You've got sooo many, from the dyneema standing rigging and mesh, the retractible electric engine technology (in my mind the benefits of having a retractible engines are at least equal to being simply electric), the resin infusion process, the low weight batteries, the carbon fiber cabin tops, margard lexan, etc.

[ldrhawke]

Originally Posted by schoonerdog

BTW, i for one find this discussion extremely informative on the different types of resin infusion methods. I know that PDQ had been using vacuum bagging since the late 1980s (the picture of the Atlantic looks like the same exact process). Simon the owner of PDQ mentioned that when trying to make an much lighter boat for strictly racing that he added several steps to the vacuum bagging to remove extra resin and that reduced the hull weight considerably. I've never seen resin infusion Gideon does, it will be interesting seeing the pictures. The sophistication of the process would seem several leaps ahead of the vacuum bagging operations I've seen used before.

Actually the process has been around for many years. it's called the SCRIMP resin infusion process. It is patented and cost big bucks to use legally. If you're a boat builder it is smart to pay the license fee, if the patents are still in effect.. It give about a about 20% increase in strength and a very slight decrease in weight compare to PrePeg vacuum bag and a nice decrease compared to hand layup.

All of these vacuum process came about because of new environmental air pollution and working conditions laws. It just happened that they also were a major structural design improvement.

What’s Unique About J/125’s Construction?
The J/125 is built to ABS offshore specifications by TPI Composites using the SCRIMP resin-infusion process. Tests conducted by the US Naval Surface Warfare Center at Carderock, MD established that the properties of laminates produced by TPI's patented SCRIMP resin-infusion process are superior to low-energy pre-pregs used by many custom boat shops and twice the strength of hand lay-up. J Boats was hesitant to enter the lightweight race boat market until something like SCRIMP/Carbon technology became available. In our judgment, SCRIMP construction greatly reduces the chances of warranty claims due to laminate failures resulting over time from pounding into waves and/or rig tension or ballast loads.

SCRIMP Process The entire laminate is placed in the mold dry. A high vacuum eliminates any air voids, then resin feed tubes draw in only enough epoxy to "wet" the laminate. This is the TPI patented SCRIMP resin-infusion process. The last step in the process is to post-cure the hull and deck at 140 degrees in a closed oven. As can be seen from the chart, SCRIMP laminate properties in terms of compression strength, flexure, and tension are twice the strength of hand lay-up and significantly stronger than low energy (vacuum bagged) post-cure pre-pregs. There is no entrained air in a SCRIMP laminate. 1% void content reduces flexural strength by 10%. Note that 50% fiber content in a carbon laminate equates to 67% carbon/33% resin by weight. See the comparison of composite properties of low cost fabrication methods in the chart above.

Weight of Construction, after subtracting weight of keel plus 1000 pounds of rig, engine and hardware, J/125 at 2700 pounds is as much as 1500-2500 pounds lighter than competitive designs. Not all of this has to do with the J/125’s narrower beam.

Hull & Deck Laminate Design of the J/125 is stronger for its weight than E-Glass/epoxy laminates using slit CoreCell foam. J/125 uses epoxy with a combination Kevlar & E-Glass for the outer skin with two layers of carbon fiber (bi-axial & unidirectional) for the inner skin. The higher strength of these exotic materials allows a thinner, lighter skin than the equivalent E-Glass structure. The CoreCell A500 and A600 foam cores of the J/125 laminate is further processed for strength and to save weight by (a) thermoforming to the shape of the boat in a second set of tooling to avoid having to slit the foam to bend it to the shape of the boat, and (b) perforating on 2" centers to form epoxy rivets between hull skins. If the core is slit to bend to the boat, then either resin fills the slits and adds weight, or there are air pockets in the laminate which reduce strength. Hull & Deck Laminate Design of the J/125 is stronger for its weight than E-Glass/epoxy laminates using slit CoreCell foam. J/125 uses epoxy with a combination Kevlar & E-Glass for the outer skin with two layers of carbon fiber (bi-axial & unidirectional) for the inner skin. The higher strength of these exotic materials allows a thinner, lighter skin than the equivalent E-Glass structure. The CoreCell A500 and A600 foam cores of the J/125 laminate is further processed for strength and to save weight by (a) thermoforming to the shape of the boat in a second set of tooling to avoid having to slit the foam to bend it to the shape of the boat, and (b) perforating on 2" centers to form epoxy rivets between hull skins. If the core is slit to bend to the boat, then either resin fills the slits and adds weight, or there are air pockets in the laminate which reduce strength.

[BigCat]

Let's just say that if you design for every intended stress and nothing more, you are not prepared for unintended stresses.

Also, if the designer takes the minimalist approach seriously, the owners better do so too, or you just end up with a racehorse doing pack mule work. A light boat over its marks doesn't perform as well as a boat designed to carry a lot of weight in the first place.

[Therapy]

Originally Posted by BigCat

. A light boat over its marks doesn't perform as well as a boat designed to carry a lot of weight in the first place.

How about a light boat designed to carry weight?

[BigCat]

Let's put it this way-a boat will perform best when at the displacement intended by its designer, no matter whether the weight is from structure or contents. However, you will find that very light boats were not, typically, designed to carry much weight. When in doubt for a specific design, ask the designer what its intended payload is.

[David M]

BigCat,
Do you use the MT1 calculation for yachts? I learned about it in my stability and trim classes for ships relating to loading cargo. I was just thinking it might be a way of explaining things in here?

I found this website which may help explain some of the terms being thrown around in here. the boatbuilding.community - Sailboat Design Ratios Looks like I just answered my own question as well.

David

[David M]

Originally Posted by BigCat

Be careful you don't give your poor boats Anorexia / Bulimia! It's a slippery path!

Yes, that's an obvious downside to lightness that is not really being spoken about. Possibly removing weight in the wrong places where there does need to be strength.

[fastcat435]

Here are some pictures of a resin infusion in process of a complete hull mould and the result , the tent build over the boat for the post curing etc . And offcourse the end result of 5800 kilo or 12760 lbs ready to sail

Greetings

Gideon