Direct female molding

sorry if im frustrating you... ive never seen this done before so its all new to me... ive cut the grooves into the foam on a scrap peice of 15mm 80kg/m3 klegecell in my garage... it still springs back... hence the question...

ply strap screwed to the blocks/plugs and all this under the bag... then what, bag it again for the inside skin laminate? wouldnt it just be easier to bog up the grooves of the core and let it sit in teh mold to take shape whilst it cures with sand bags or whatever holding it, then proceed with the bonding and laminate after to make sure its not going to move in a 1 step infusion?

Im not sure how many people you are using with your method tunnels, but i have only 2 hands, more would be nice but thats all i got... and this whole system is asking for disaster with only 2 hands unless an infusion can be setup or done in many smaller sections - no way can i do a 35ft hull like this on my own...

ive been thru all this thinking and figured its just easier, safer and cheaper to just do it the old fashioned way, at least for this particular part...

 

I usually hold foam with drywall screws. When the fiberglass sets, you just rip it off.

 

Not only that, Grouper, but I just put up 1/2 of a hull in foam today, by myself. Well, not half a hull literally. Just half of a 1/2 hull mold from my pictures above. It's my final hull half and I got half of that done today in 7 hours, taking an hour for lunch.

Not only is it way faster to thermoform foam, it also makes a lighter boat. Instead of many small rivers of heavy epoxy in all those little channels, you have just foam, which takes many kgs off a boat.

Can you imagine how many hours all those little cuts take? (I tried that process when learning)

Definitely use drywall screws to hold the foam in place.

If you are thermoforming, screw them in from the front, using wooden blocks to get them to hold to your mold battens. After that, go under your mold and screw more in from the back. That holds the foam 100%.

Now you take the blocks off the front and bog up any cracks and lay glass.

You'll be done a single shoe in a week, all by yourself once you get the system down.

 

yep, this is the "old fashioned way" i am talking about... however you cant do this when trying to lay foam into a proper full female mold - not just a frame and batten mold... you cant just put screws into your otherwise finished/polished mold... this is the part i was trying to get tunnels to explain... how you hold it all together before you get the bag on seems a bloody nightmare...

 

What part of Australia are you in ??
Seems a bloody nightmare!!! thats only because You are not reading what i have written!! If you are reading ,then read again !! you are not understanding !!
You are only using 15mm thick foam !! so try making your cuts and leaving just 3mm uncut . the uncut surface goes against the glassed surface I am picking the sheets will bend so easy you will have trouble lifting them off the cutting table !! .
i would take it you still havent grasped the hot glued plug (or biscult as was reffered to) into the glassed surface yet to hold the sheets tighly in place have you ?
Exsperiment!!!!!understand !!! make it work for yourself !! grasp the idea !!understand and modify it to suit your own needs !!

If you are working alone break the whole job up into bite sized bits 1/3 at a time or even a 1/4 to start off with !! But before you start baging cut fit and do everything you need to do to all foam sheets Then just make one big bag to cover the lot!!, but divide it into 3 or 4 sections so when the first section is done and gelled hard peel back the peel ply and scrim and bag and carry on with the next section and do the same right to the very end !,
If you have two half moulds to work between it could almost be a ongoing process work on one side then work on the other . Epoxy resins are a little slower than Vinylester or polyester .Most important is to Know what your gel time is at the temprature where you are working and have a timer so when you start you know how much time you have to work with the catalysed resin aways allow to have plenty of time to pull it down the bag and check the vac pressure !! and leaks etc etc then keep a eye on it till its hardened completely .

I am always working in a contnuous production enviroment and we always have female moulds to work inside of !! things like screwing and stapeling cores is an impossability and wouldnt even consider it any way so is never an option and is real agricultual and primative way of doing things .

AS for the little rivers of resin within the core from the saw cuts and adding weight is not even worth thinking about . In reality its helping to strengthen the core and make it stronger Some infusion foams have millions of cuts chris-crossed and all interlinked with each other so its sort of the same concept .
Take more time to boil water and make a cup of coffee than to do all the cuts in a sheet of foam when you have the straight edge and the saw set .
If its what you have to do to get your sheets to fit and lay properly then get on with it and stop thinking about what you cant do !! you should have had all this sorted before you started the job !!.

 

Ah damn it... the light bulb has illuminated and i understand teh whole process now, thankyou for sharing tunnels...

- ill definately put some of this knowledge to work on the next part i need to do like this,

Thanks again...

 

Yahoo at last !! My partner was getting frustrated with the tufts of hair laying about the apartment .
Its worked well for what we were doing and has been used a few times not just a one off Finding a nice thin bladed saw is the difficult part

Heating foam there is a issue of first building a oven and getting the whole sheet hot enough and a former to bend it over till it cools then theres the other issue once its cooled it is inclind to get really hard and goes brittle so what density you had in the begining is now much harder .No one ever mentions that when they tell you to heat it !!

I been round and seen and done to many things over the years to listen to silly things .
I wake up at 3;00 just about every morning and do a days work in my head before my feet touch the floor . I have thought of and sorted problems before i even get to the office door at work .
Over the years i have worked with some very clever and extremely inventive and inovative people and there attatude has rubbed off !
When all else fails think simplicity !, get back to basics and make things simple !!.
We are all of us here to help ! everyone has been there and done anything you can name just takes time to find and grasp what the hell they are talking about !
Take care !

 

one more thing, the vac pressure... need to pull it down reasonably tight so its consolidated well and the resin fills the grooves etc, but not so tight that you pull too much resin out and leave it dry/poorly bonded/bedded.... how do you quality control this and determine the best vac pressure?

 

You got to do test laminates.

 

If you are just bagging into a layer of wet glass then the glass needs to be uniformly wet out all over plus roll a coat of resin on the back side of the foam lay and hold in place etc etc . Get the bag down and pull slowly but consistantly never pull down and back off for any reason . the foam will squash out the resin and will not return if you slacken the pressure for any reason .
Is best to have a coule of vac gauges and place then away from each other and away from the vac point . better to do a 1/4 of the panel size at a time if you only got a small pump ! The bag needs to be firm when pulled down not really tight .The pressure could be differant for each panel you do . No one i know of can tell you what pressure is the ideal !I did some exsperimenting of my own way back and it was amazing at how little pressure you actually need to get a nearly perfect job .
You can do a little exsperimenting of you own !
Us a sheet of 4 mm thick glass about 400mmx 400mm and suck your core onto it so you can see both sides !! suck down slowly and use a vac gauge and record the pressures as it gradually pulls tighter and tighter !! A video camera is best as you can see what happenng and talk into it at the same time .Now pull to the max and then hold and after a minute slowly slacken the pressure off !! look and see what happens !! Then re-apply and check what you got !!

So many things can and do affect what you are doing !!Flat panel or curved makes a differance ! Density of the core makes a differance ,the core thickness makes a differance , the type of resin you are using makes a differance, slowly in you mind you begin to get the picture there are no hard and fast rules as such !!!just every one has there own opinions and fixed ideas of what should happen and every job is differant!! .

If you want to see something interesting and dirrectly related to vac and resin ,use a plastic syringe any size ,without a needle of course and suck up about enough uncatalysed resin to half fill it , Hold it up and let all the bubbles out !! Slowly suck a small amount of air ,just enought to make one nice small bubble ! place you finger tightly over the end and seal it !!,watch the bubble and then slowly pull the plunger out , see what happens to the bubble as the vac pressure builds !!, the harder you pull the more vac pressure you create and whats happened to you tiny bubble ??.
Its absolutely amazing and gives you some sort of an idea and a much better understanding of what going on under the core when you start to bag panels !!!. so if there is a problem you will understand and know what caused it !

Think of the untimate vac as 100% !!Ok
Now to get the closest to near perfect suckdown and best panel ,you could only need less than 5% of the vac you have on hand !!!!
Something to thinkabout !! Some flat panels 3 mtrs by 8 mtrs using 20 mm perfirated core i was making long time ago using core bond we got to 2% of vac and they were 99.9 % Perfect all over !!
At the end of all this you will know more than the average seasoned laminator will ever know in his dull boring life !!

Catbuilder is going to have kittens when he reads this i can just imagon the look on his face already !!

I never take things as being gosple and always do my own exsperimenting as to manythings are never the same as what others are using and doing !!!.

 

well i bit the bullet and decided to go for it - direct female molding (not taken from a plug)

I had some time before my materials arrived so i built this...



Its your standard female frame and battten mold, transverse stripped with with 3mm "foamed PVC sheet" sometimes known as celluka board or such like... this stuff is cheap and easy to thermoform around tight radii... simply stapled it down to the battens... could have used thin plywood or similar but the pvc sheet was cheaper and its very flat with a nice glossy surface... i did a resin test on it and epoxy does like to stick to it so you cant release straight off it - ill be spraying PVA before the layup...

Several options could happen from here, but the way i think i will proceed is to sand down the bog joins you can see in the pic, then paint the whole inside with a dark colour paint so i can see the layup when im working - white is no good, too hard to see the air bubbles or poorly wetted out glass etc.. then apply the mold release and do a hand layup skin coat - this will form the inside seal for the infusion to follow i know alot of you will freak out when i say that- but lets just see how it goes shall we it only has to last 2 hulls for my cat - i dont care after that...

The steel table frames underneath are for the flat infusion table once these hull shoes are finished... wish they wernt so high as its a PITA to work up on tressles all day - should have set this up closer to ground level...

 

And this is the first peice of 16mm corecell kerf cut (hows that tunnels!!!) and checked to see if all this will go in... it fits quite nicely with nothing to hold it down at all in this pic...

 

Way to go !!!! yeah some one with some get up and go !!
I see the foam sheets bend in the corner and fit ok !!! Remember the closer you make the cuts the better and smoother it will bend and you are less likely to get flat patchs that could cause print through to the outside !!.excillent job !! the saw cuts fill with resin so makes a strong corner thats for sure !

The pva thing you had better do a new teat sample bits !!
Ever used pva before ??
There a few little tricks with pve you could try and see how it works for you !!

 

How to apply PVA !!

Try this and see if it works for you !! I wrote this a while back !!

Ok throw away all that you have read and what you think you know about PVA !!
This is so simple it stupid !!
Ready ??
Always spray pva !!!
brushing !
wiping !
pouring !what ever is a total waste of time and materials!

Take the bowl off your spray gun and pour in 1/2 cup of pva straight from the bottle ! take the same cup and pour in 1/2 cup of cold water straight from the tap !!
Mix together !
Its enough to spray on A 35 foot Yacht hull mould you should have about 1/4 or a little less of the mix still in the gun when you finished !!
I hope you have a good air supply with lots a air !
Wind the air pressure to max 100 psi or more .
On the gun wind the flow controll needle in so its completely shut off so there is nothing coming out when you pull the trigger back !!.
OK!!
Now ready to adjust the gun !!
Hold the gun up to the light so you can make sure there is nothing coming out when you pull the trigger back .
Gradually and slowly wind out the needle till you see a fine even misty spray coming out !!,Usually 1/2 to 3/4 of a turn !
Ok !! thats all you need to come out of the gun!!
Use max air pressure and spray your mould !!
visulise what you are doing quickly and evenly !! stay away from the mould about 600 mm or a little more !
Most important to remember is if you can see the pva on the mould you have to much on !!!
You should not be able to see the pva at all . release the trigger till the spray stops and just air is comng out of the spraygun and blow the air across what you have sprayed !! this will eveaporate the water and dry the pva !when it has completely dried very gently with just the air still coming out of the gun blow dry your hand as well and you will be able to wipe your hand softly across the surface of the mould coated with pva dont stop you hand any where or the moisture from you skin will melt the pva you have just sprayed on .
The finer the spray the better !!
Takes practise and as i say the finer the spray the better it works . If you can see it you have to much !! Remember that !!!!

I have posted this maybe 4 times for people having pva problems and has worked for the every time for them .
When i worked in Australia and i was shown this technique and have taught and show people for the last 20 years ! The place we worked in Queensland we never waxed a single mould all the time i was there we only ever used pva 100% of the time on everything . New Plugs and making moulds . products out of Glass moulds ! even old moulds been laying about the place after a buff and polish !! works really well on boats deck non skid and dosent get dirty wax marks when a deck comes out of the mould . !!
Takes practice !! dont be tempted to doing a heavy spray !!
Spray fine and if you can see you have to much on !!!!
ONCE YOU MASTERED THIS AND SEEN HOW EASY ITS WORKS POST SOME FEED BACK !!FOR OTHERS TO PICK UP ON !!
Just think 50% of what you are putting on is water so when it dries its half of what you think it is !! the thinner the better !!
Its no real advantage at all trying to spray a second coat !!!. just picks up dust and sticks to the mould , so dont be tempted !!!
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Thanks mate!

Ive tested the acrylic paint im going to spray on the PVC sheet, it sticks like **** to a blanket so no problems there...

my only last concern is what will happen when the vacuum is pulled... the skin coat of glass on the mold sealed to the bag on the other side of the stack... the mold is a bit flexible but my reasoning tells me the outside of the mold will only pull in until its pressed against the foam core and the plastic bag will do the same from the other side... the mold should be a little stiffer than the foam so the foam should pull more so against the mold rather than pulling the mold too far inwards... i really dont know how successful this will be, suck it and see i guess - pun intended