MV catapult

Build logs from members building catamarans, trimarans and other multi-hull variants.
groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: MV catapult

Post by groper » Tue Mar 05, 2013 8:37 pm

44c wrote:
groper wrote:The problem with duflex is that the surface quality is poor (pinholes etc) and i dont like the idea of a balsa cored boat. Balsa has brilliant mechanical properties, but boats being boats means inevitably water will get in somewhere somehow someday... for this reason i prefer foam. The total materials cost for my boat shell is looking like going a touch over $40k as i have just about everything i need to finish the boat on hand. This is only glass reinforcements, infusion consumables, resin and foam. A duflex kit for this size boat probably would have been around $70k including furniture, so there is a considerable money saving.
The kit for our Oram 44C was about $65k. Not including furniture. I doubt your boat would have run to $70k even with the furniture.

The reason Duflex has pinholes is because it has extremely good glass/resin ratios. Every drop of excess resin is squeezed out. Because hydraulic presses are used, pressures available are far higher than can be achieved with infusion, where pressures are limited to around 0.8 of an atmosphere, or around 10 psi. Pulling deeper vacuum than this risks "boiling" the resin.

The weave on Duflex is easily filled - just a squeegee of a runny glue mix.

I disagree that water ingress is inevitable. There are balsa cored boats 30 and 40 years old still in perfect condition. And many of the early boats used polyester resins, which are nowhere near as good as modern epoxies.

Not knocking your methods or the job you're doing, which is excellent. Just that some of your comments about other materials needed correction IMO.
The platen pressing prepreg method of producing the duflex panels is very good, the structural mechanical properties are excellent. Its the cosmetic properties of the panel that i have a problem with - they need extra work which is not nessesary with infused panels off a table. This extra work (and resin = weight + cost) offsets some of the time savings achieved by using it in the first place...

Your point on infusion vacuum pressure is not complete. Polyester and vinylester resins do need the vacuum pressure reduced a touch to prevent boiling of the styrene. Epoxy resin does not contain any volatiles and as such can be infused at 100% vacuum - the gauge pressure i typically see on my infusions is -101kpa as my boat is 100% epoxy laminates, although i have done some vinylester stuff aswell and have observed the resin boiling in the catch pot if the vacuum is too strong. Absolute vacuum at sealevel is -101.3kpa btw, so im 30mbar off absolute. I have measured and weighed individual components which make up the test samples of the panels i have produced. By measuring carefully the before and after weights, of foam, resin, cloth, resin absorption in the surface of the foam etc, i end up with a 68-70% fibre volume fraction in my laminates - which is considered very good even by commercial standards. Due to the different densities of fibre VS resin (fibre being heavier per unit volume), this equates very closely to half the weight of resin to fibre in the laminate - and i get this with no pinholes or extra filling required afterwards - its ready to start painting.

Compare this to a hand layup, i typically use equal weights of fibre and resin to get the job done. At the end of the build, this adds up to ALOT more resin, something like and entire 200KG drum more... a drum of epoxy costs around $3500 - this pays for all the infusion consumables used with money left over, plus your boat is 200kgs lighter - so infusion will actually save you money compared to a hand layed build - which contradicts another misconception floating around... what im saying is, infusion is not expensive provided you shop for your consumables wisely.

Back to the balsa thing, if your a perfect builder- then sure, you will never see water ingress into your balsa... but how perfect are you? I know myself well enough not to trust my perfection :)

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: MV catapult

Post by groper » Tue Mar 05, 2013 9:02 pm

dennisail wrote:Thanks for the lengthy reply. I think you made the right decision designing it yourself. Not that this would be a good idea for most people. But for someone with your capabilities I think it would be a rewarding experience. It will give you the confidence to do your larger more expensive sailing cat, not that this is a small project.

Can you explain what is happening in pic 2 on your first post? You have a blue board of some type. Is this a mold you are using to hold the table infused bottom and side panels together with prior to infusing them together at the bottom with a curve that contains no foam? What causes the dark colour? Do you add a die to the resin when infusing so you can see where it is flowing or is this carbon :shock: ?
This infusion was done in a "temporary female mold" - what i mean is, the mold was not built to last more than 2 infusions as i only needed the lower bow sections of each hull. So i tried to build the mold on the cheap rather than a full blown proper mold which would have taken more time and money than i considered was worth it.

So it was just a frame and batten setup on a strongback - same start as a transverse foam strip plank mold. Rather than laying the foam on this and doing one side at a time - like the fram build - i wanted to be able to infuse both sides at once. So i transverse striped the battens with a 3mm plastic signboard material. I painted it blue as i had some old blue paint lying around. I didnt want to leave it white, as you cannot see air bubbles in the laminate easily when on a white background. I handlayed a light laminate over the wax and PVA mold release and let it cure in order to achieve a vacuum tight membrane. Afterwards, i peeled off the peelply, then setup the infusion as per a normal infusion setup using much heavier laminates, the foam core, and the inner laminate etc. I added a heavy laminate on the bottom of the entire hull to allow beaching of the boat and reduce possible puncture of the laminate if i end up sitting on a rock or peice of coral in the sand etc... to lay this much glass (5 layers 750gsm triax on the outside) by hand would have been hours and hours of nonstop hard work. Instead, it was all setup and infused same day light work, inside and out, next day it was demolded and ready to join into the rest of the boat as a rigid peice - the peice im holding on my shoulder on the first page :)

dennisail
Posts: 61
Joined: Tue Feb 19, 2013 1:42 pm

Re: MV catapult

Post by dennisail » Tue Mar 05, 2013 9:57 pm

Cool, so when you infuse panels like this you are able to infuse both sides at once? How can do you know if the outside is getting good resin flow? Did you extend the 3 layers of 750 all the way around the corners where there is no foam?

The only prob with this method is most designers don't seem to cater for it since its not so popular yet with homebuilders.

Romeo
Posts: 49
Joined: Sun Nov 09, 2008 10:32 pm
Location: Western Australia

Re: MV catapult

Post by Romeo » Wed Mar 06, 2013 1:14 am

Look up Kelsall Catamarans. He has been doing resin infusion catamarans for the home builder for the last six or more years. He does workshops all over the world, I nearly got to one in Busselton five years back but saw what was acheived in a weekend a few weeks later Its a good way to build if your building in foam.
YIY Romeo

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: MV catapult

Post by groper » Wed Mar 06, 2013 5:54 pm

dennisail wrote:Cool, so when you infuse panels like this you are able to infuse both sides at once? How can do you know if the outside is getting good resin flow? Did you extend the 3 layers of 750 all the way around the corners where there is no foam?

The only prob with this method is most designers don't seem to cater for it since its not so popular yet with homebuilders.
Yes, the method im using is basically the same as kelsall`s KSS build method. If you want a design done for this build method, contact him for sure and see what he can do for you. Im not sure if many other designers will do it for you, some might if you ask, but i know of another in QLD his name is John Sayer - http://www.sayerdesign.com - a friend is building one of his catamaran designs. John is very knowledgeable with infusion aswell and can also make patterns for direct female molding. My friends boat is all infused foam sandwich aswell.

That was 5 layers of 750 btw... yes the radius corner where there was no foam had this laminate all the way around... so it was a solid glass laminate where the inside and outside laminates come together with the core tapered at 45degrees and it has adequate stiffness from the tight curvature. On the other hull, i did it a bit differently... i simply made the panel with all the foam intact, then kerf cut the radius areas and bent the panel before restoring the laminate in the bent area. This proved to be a better method all things said and done.

Image

Image

Image

44c
Posts: 1148
Joined: Tue Aug 08, 2006 5:08 am
Location: Hervey Bay, Qld

Re: MV catapult

Post by 44c » Thu Mar 07, 2013 8:34 am

Hey I know Andrew too. Years ago he had his boat at Hervey bay marina, next to our old one.

He started building his cat a couple of years before I did.

Very nice guy, and extremely helpful.

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: MV catapult

Post by groper » Sat May 18, 2013 7:11 pm

Edit: this forum always seems to crop images from top left rather than resize... can this be changed red666??? you cant frame the photos so you can show what you need...

A bit of sandwich panel origami...

The kitchen, ahem galley, is beginning to take shape... Half of the bench top will go in next, which also boxes in the bathroom below... you can see the stuff up to the left where ive moved the doorway too :D
The back deck, a piece which forms part of the seat and icebox...
And the other side, just a seat which boxes in the bedroom below;
And yes i know, theres dust and crap everywhere... ill clean up one day when im done glassing maybe...
Last edited by rexd666 on Sat May 18, 2013 10:17 pm, edited 2 times in total.
Reason: FYI tested the hsimg tag on this post so if you want to fix any just edit them and change the img tag to hsimg and it will work like this.

rexd666
Site Admin
Posts: 157
Joined: Tue Dec 15, 2009 7:15 am
Location: Melbourne, Vic

Re: MV catapult

Post by rexd666 » Sat May 18, 2013 9:38 pm

Groper,
Couple of options with the pics, as everyone has multi-mega pixel cameras these days and most images are much bigger than the forum layout allows. I am forcing the pics to stay within the design, which stops threads that suddenly go wide and beyond peoples screen width. It used to scroll the image, but stopped doing it for some reason.

1. Use the Upload Attachment Tab underneath the text edit box to upload the images. This will create a thumbnail that fits within the design and then when you click on it launches a lightbox to view and zoom on the image.

2. Using the img tag in your text and linking to an external image as you are doing. However the forum software doesn't support dynamic resize, so you have to resize the image to fit within the forum design. Not ideal doing that I know, I should see if I can make the lightbox code work for these also.

EDIT
There is now a third option, instead of img tag use the hsimg tag, the button is above the edit window to the right of the img button. I used that to fix your post above, but comment below still applies.

My preferred option is using the attachments method as it uploads the pictures to our server and means that I have control over the image and can keep it working. The other option we end up with threads full of missing images when someone drifts off and forgets to keep their image account active.
I am playing with some new designs for the forum that will be responsive designs (sized to screen) so it may improve, but sometimes the images are bigger than peoples screens and not much you can do then.
Steve

rexd666
Site Admin
Posts: 157
Joined: Tue Dec 15, 2009 7:15 am
Location: Melbourne, Vic

Re: MV catapult

Post by rexd666 » Sat May 18, 2013 9:43 pm

Here are the images as attachments.
image_zps79f99ded.jpg
image_zpsa16ecd87.jpg
image_zps7f3a57a7.jpg

puremajek
Posts: 751
Joined: Thu May 04, 2006 7:36 pm
Location: Brisbane Australia
Contact:

Re: MV catapult

Post by puremajek » Mon May 27, 2013 11:02 am

Curves certainly make a statement, looks nice.
James
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http://www.diycatamaran.com
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