Vacuum infusion and splitmold?

[Danielsan]

Had some talks with some people and I would like to hear some more about this.

When using VAI what could one recomend? Is it enough to have a mold build upon stations spaced at +/- 45cm covered with some 3mm multipex faired and painted, ready to wax with mold release? Or won't this be strong enough?

Extra problem It would be a splitmold Is it possible? I would say if you could put some sealant in the mold joint(s) It can?

What about mold release wax, it seems that there are diff release factors when using VAI to prevent antisipated release?

Many questions, would be nice to see some more ideas about this

Greetings,

[yokebutt]

Multipex? What is it?

Yokebutt.

[Danielsan]

should have been multiplex, sort of plywood


Sorry my bad ;-)

greetings,

[Herman]

Strength is not a real issue. Airtightness is. Get this thing really airtight can be a tedious job. However, I have seen both a thick coat of epoxy and a 300 grams woven cloth with epoxy which worked fine.

Split molds are even worse. It is very well possible to use a split mold. However, the split molds I have seen in use have a specially designed flange which allows for a seal to be blown between the two flanges. Smart, but not practical for a one-off. For a one off use a double layer of tackytape, and pull a vacuum in between to prevent any leaks from destroying your part. (make sure the flanges can withstand the forces)

[wet feet]

You need good quality ply and no leaks to get any level of vacuum.You could try to achieve a vacuum on a small area.It can help to apply a coat of resin/paint/sealer with the vacuum applied to fill the voids and leaks.There will be some,there always are with wood.If your mould was 3mm thick grp with a vacuum flange,you would be more likely to get a good result.If the mould has sufficient rigidity,which does not seem too promising with the thickness and the frame spacing,you could try wrapping the whole of the outside with polythene and sealing to a bag at gunwhale level.

[Danielsan]

Let's say the joining area of the molds have both a flange. Can't I put a kind of thick squeezable PU foam between them like the ones used to seal windows etc.? Put the flanges together and bolt them together every 20 cm so the mold has no more gaps and the foam (sealant) is sqeezed to the max.

Using the 3mm plywood not directly on the stations but on battens spaced @ 10-15 cm. nailed on the stations, would be more rigid I think?

Airtightning the mold? have been thinking of glueing the plywood seams to eachother before nailing them on the battens? so they will be sealed? then applying various layes of DD-coating (paint) to the plywood mold, sanding than app. release agent.

What about the release(wax) agent?

Maybe I am complicating things to much for a one off hein?

greetz,

[wet feet]

I don't know whether you have ever tried to apply a vacuum to a wooden assembly.It is not easy to achieve.If you can produce your intended boat without the need for a vacuum,you are likely to be afloat sooner.Your flange seal looks reasonable but do you really need the tensile strength of all those 10mm bolts when you might have several hundred kilos of atmospheric pressure pushing the flanges together?You can get a seal by running a strip of tacky tape along the edge and around any nuts and bolts as the pressure differential between the vacuum inside the bag and the atmosphere will push the mastic into any gaps.
Any release wax ought to work.Can I make the suggestion that you try to produce a small component first before risking a lot of time and effort on a complete hull.When you are confident that you have a good chance of success you are less likely to have an expensive disaster.

[Danielsan]

you are quite right about making some test parts I will do this for sure.

The only thing that tempts me wit the VAI is the time needed to get the thing done

put some gelcoat, layup the necc glass, the waste materials, the resin (flow tubes) cover it up and open the valve and 40 min later thing is done? HeHeuHM in a simplified way he? the stakes are indeed higher when the thing results in a complete disaster.

Have to tell I got no exp with this kind of techniques, and yes I want to make a boat

I think some must be on the floor from laughing when seeing this?

I do really apreciate the replys on this site it is most helpfull!

greetz,

[yipster]

Danielsan, i start wondering if your plans are in production or a nice one off?
having looked at your drawing i mentioned the stich and gleu in a basket mold method becouse you drew a hard chined hull
made for that system. no need for a mold and vacuum infusion than. yet planty of glas and resin if you like.
if you dont like wood use hardfoam. $ 235 for these 25 ft patterns there is a forum etc.
if you did not read my reply or didnt realise what i meant then read this this site
for the rest i'll like learning more on vacuum infusion just as much as the rest.
once made an excursion to medemblik seeing it done.
hope to have been of help.

[Danielsan]

Ypster, dont get exactly what you meen? Might be the Cuba libre gooing up into my head. LOL
You sugest I should buy an existing design from bateau.com instead of doing this myself?

What about those 235USD they are only for the plans, no?

The basket mold thing looks like an easy way, and will be ok for the hull, what about the deck? Note that I would like to use a mold so I won't need fairing the end piece.
If I can control the shape of the hull-mold this will be ok even if I have to correct it but if I make it according the stich and glue I will need to do some fairing on the endpiece which in worst case get's totaly F#$%ed up. Same thing with the VAI it can get totally messed up.

PS it is a one off for myself design has changed somewhat, remember the beam being over 3m!!! I had to start over again to go to 2.55m, as my solidworks didn't want to scale the the design, so this will be version 3.01 of my design and hopefully the last one for this boat.

greetz,

[yipster]

in my eye its a hard chine hull and deck? when you can make patterns of your own design with solidworks you dont have to buy, i merely pointed to a nice similar hull. fairing, long as it inst convex or concave can be done with stich and glue. offcourse anything can get totaly F#$%ed up specially specially on cuba libre. you should take a deeper look into ways of building your hull, i belive its designed for S&G.

[Danielsan]

Ok that is what I tought you wanted to say. I should have a look at the patterns of the stations, but as far as I know it has concave as well as convex areas. that is also the reason for the split mold.

The only reasons why I would do the vai is for not having to roll out every single layer off glass time after time and the better resin / fibre ratio.

But the mold will stay I think, or I should move over to version 3.02 and make developable chines? But then I would shurely make flat GRP panels with VAI.

What about stresses in the joint areas of the stich and glue?

Thx for the replies, will go to sleep now....

Greetings,

[John ilett]

I have built a 40ft female timber mould for vacuum infusion a few years ago. This was female frames with stringers, then double diagonal 1.5mm ply, 300g fglass cloth with epoxy resin, epoxy faired, epoxy primed, two part polyurethane paint finish with a semi permenant release system like Frekote. No leaks, infused well and released good too. Lots and lots of work though!