Shocked by hull material catamaran

[Colin A]

Originally Posted by Stumble

Colin,

Those were probably not autoclaves, but were postcure ovens. I a man simplifying here, but basically really high quality (high Tg - Glass transition temperature) epoxies need to be baked at between 140-150F for a couple of hours to reach full strength. It's similar to annealing metals.

Autoclaves, while they also raise the temperature do so under high pressure, around 600KPa to consolodate the laminate stack. It's the laminate equivilant of HIPing cast metal parts.

No they weren't auto claves. They used a vacuum bag and the oven for the cure. Looking online the must have brought it to 200 for most low temp prepregs. Lyman Morse and Goetz were the two yards I saw this but looking online it seems somewhat common, seems some Carbon spars are done that way as well.

[UNCIVILIZED]

DIY ovens for post curing/curing are pretty common. For example, at one of the teams I worked for, the guys insulated a CONEX box, added a couple of heaters, fans, & some thermocouples, & used it for "small" projects. And I've even seen where holes for dozens, & dozens of hair dryers were cut into the (plastic) wall of a temporary boat builder's tent in order to postcure an entire hull, or the integrated structure of a catamaran's 2 hulls & bridgedeck.

You need to make sure that you use heat that's free of contaminants, such as particulate matter, or oils & hydrocarbons. Along with having a means to monitor temp's at multiple places so that no one area gets too hot, or too cool. And multiple vacuum gauges if you're bagging the part as well.

So for really small things, you can even get away with using a few lightbulbs, so long as you monitor the temp of the part. Multiple atmospheres of pressure (bar) isn't necessarily a requirement, unless specified in the engineer's designs.

[GordMay]

Greetings and welcome aboard the CF, TerryO.

[minaret]

Originally Posted by UNCIVILIZED

DIY ovens for post curing/curing are pretty common. For example, at one of the teams I worked for, the guys insulated a CONEX box, added a couple of heaters, fans, & some thermocouples, & used it for "small" projects. And I've even seen where holes for dozens, & dozens of hair dryers were cut into the (plastic) wall of a temporary boat builder's tent in order to postcure an entire hull, or the integrated structure of a catamaran's 2 hulls & bridgedeck.

You need to make sure that you use heat that's free of contaminants, such as particulate matter, or oils & hydrocarbons. Along with having a means to monitor temp's at multiple places so that no one area gets too hot, or too cool. And multiple vacuum gauges if you're bagging the part as well.

So for really small things, you can even get away with using a few lightbulbs, so long as you monitor the temp of the part. Multiple atmospheres of pressure (bar) isn't necessarily a requirement, unless specified in the engineer's designs.

Hair dryers?! It's all about the TuCo for us. These guys build heaters for large buildings like gyms and auditoriums as well as industrial stuff like this. Top shelf. Pro solution for post curing, with this kind of gear you can hit pretty high temps in a simple bag. Also allows you to paint and laminate in winter no problems, warm and dry in the tent. I can't imagine the wiring nightmare trying to get enough amperage for enough hair dryers to do much...


Construction Heaters | Temporary Heating Solutions | Lynnwood, WA



Bring yer checkbook though! $$$$$

[44'cruisingcat]

Currently under construction: Schionning G-Force, 20 metre. All carbon, epoxy and balsa cores. Multimillion dollar boat.


Guess they're using balsa 'cause it's cheap.

[tp12]

I'd guess that well over 90% of all Schionnings are balsa and definitely not due to price considerations.

Jeff talks about materials (options, considerations) here,for anyone who is interested: http://www.schionningdesigns.com.au/material-choices

[Seaslug Caravan]

Originally Posted by 44'cruisingcat

Currently under construction: Schionning G-Force, 20 metre. All carbon, epoxy and balsa cores. Multimillion dollar boat.


Guess they're using balsa 'cause it's cheap.

NO NO Mr C time , its because , IF Mr Schionning admits that balsa has problems and changes to foam it then makes him look like a goose and devalues all his boats already built.

There is now enough boats out there with repaired rotten core for the Balsa brigade to see, even with their heads buried deep in the sand.

[valhalla360]

Originally Posted by Just Another Sa

There are a lot of inflatables with hardly any stiffness, the air pressure provides tensioning of the fibers in the skin, providing bending strength, but still not stiffness, as that is not required. Just push the surface with your finger to see that yourself, the skin deflects very easily.

On most rigid materials there is no need to have stiffness to span between bulkheads, only bending strength. Stiffness is just a byproduct of providing the strength unless the skin is in compression, something decks of monohulls have around the mast due to rigging loads. Multihulls use tramps for save weight, because there is no harm done by their lack of stiffness compared to solid panels.

Depends if you are talking stiffness of the hull or stiffness of the skin.

The skin needs almost no stiffness because it has infinite bulkheads but the hull still has significant stiffness

[valhalla360]

Originally Posted by Thenaz007

Fiberglass is a great material, but it will not deflect very far before resulting in brittle failure. The thicker it is, the higher load it will resist before deflecting and failing in said fashion. We purposefully engineer thin areas in fiberglass hoods on cars so they will fail in a front end collision rather than come through the windshield.

I hope that it is safe to say that a cat hull requires bending stiffness, especially unsupported by water or maintaining structural integrity in rough seas. It certainly requires some degree of impact strength. You may want some wear resistance if you beach it on occasion.

As you introduce a composite core you save weight or add stiffness at a given weight. Depending on the properties of your core you may compromise (or improve) impact strength, interlaminar shear strength, or moisture wicking through damaged, improperly installed, or severely aged fiberglass. Theoretically, composites save weight with minimal compromise.

I would say go with foam core if you trust your luck, skill, and the manufacturer's engineering and build quality. If you have reservations, holding out for no foam beneath the waterline, regardless of pros and cons, is the right decision if it brings you piece of mind.

Although arguably improvements, without doubt foam cores are installed in higher volume cruising cats because they are a cost savings.

Actually fiberglass can deflect quite a bit before it fails. I have a man overboard pole that will deflect a couple of feet in heavy windand spring back when calm.

In general terms the thicker and stiffer you go the less you can deflect without falling but that applies to any material.

[44'cruisingcat]

Originally Posted by Seaslug Caravan

NO NO Mr C time , its because , IF Mr Schionning admits that balsa has problems and changes to foam it then makes him look like a goose and devalues all his boats already built.

There is now enough boats out there with repaired rotten core for the Balsa brigade to see, even with their heads buried deep in the sand.

Ever tried dealing in facts? NO NO NO mr clown!

Schionning's kits are available with foam cores if that's what the buyer wants. This client has CHOSEN balsa because it has superior mechanical properties to foam. Simple as that.

[markpierce]

Originally Posted by barnakiel

One thing is I am not 100% sure it is legal to take images of somebody else's boat and post them on the forum without explicit or implicit indication of obtaining the owner's permit to do so.

Cheers,
b.

Of course one can post a photo of something in public view. If not, you couldn't take any photo unless in your home.

[arsenelupiga]

Originally Posted by markpierce

Of course one can post a photo of something in public view. If not, you couldn't take any photo unless in your home.

not so sure. only IT companies get away with free spying these days.

If owner establishes that because of these pics and comments he can only sell L57 for 300K less than if no pics published, he may decide to chase the guy publishing them for the 300K & fees.

[Cruising4Christ]

Originally Posted by arsenelupiga

not so sure. only IT companies get away with free spying these days.

If owner establishes that because of these pics and comments he can only sell L57 for 300K less than if no pics published, he may decide to chase the guy publishing them for the 300K & fees.

Nope. I deal with this at our law firm. In this case, NOT disclosing this type of structural damage would be considered fraud, and the only party with monetary damages resulting from these photos are the 'would be' buyers. The owner may not be stoked, but he has no recourse...not to mention international statute nightmares.

[daletournier]

Originally Posted by Seaslug Caravan

NO NO Mr C time , its because , IF Mr Schionning admits that balsa has problems and changes to foam it then makes him look like a goose and devalues all his boats already built.

There is now enough boats out there with repaired rotten core for the Balsa brigade to see, even with their heads buried deep in the sand.

Wow....Geoff Schoining told you that? , or?' please elaborate?

Sent from my vivo Y35 using Cruisers Sailing Forum mobile app

[Cruising4Christ]

Random question and I know there would be drawbacks, but has anyone ever built, purchased, or seen any type of 'skid plates' for use in heavy coral or rocky areas where running aground is more of a consideration than performance?

Maybe just a removable nose cone with a deeper draft to absorb a lot of energy like a car bumper? It could be a 'V' shape that connects to the bow, lightweight, stowable, sacraficial and relies on geometry for strength. ???