What are the likely issues if bagging glass cloth to a polyurethane blank using sun cure resin?
Apart from having a see-through bag 
Thanks for input.
absolutely no point!
OMG!
Experimental value aside I have to askā¦ WHY?!
And what the hell are you doing up so late āsillyā?
hi doug had to wack together a 7.6 yesterday
need to ready by end of week
id just finished some stuff!
maybe you could ring up wonder woman
and she can supply u with some invisible peel ply and invisible breather fabric
so you can try your completely pointless excersise
Why bag glass to foam?
Flex - you have to reduce the resin loading to get flex without cracks - Itās the traditional way of building spoons (and some aircraft!).
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quote Andrew Marshall from his book Composite Basics. āBasically, the resin matrix is the key to the whole operation of producing composite structures. It was noted earlier that the resin matrix is the mass in which the fibres exist, but the resin does much more than just contain the fibres. Its primary job is to carry the load from one fibre to the next, and from the bundles of fibres or groups of reinforcements into an adjacent structure which may either be embedded in the composite during manufacture, or adhesively bonded to it at a later stage. The resin material thus distributes and transfers the load within the structure so that each reinforcing fibre carries a proportional share of the load.ā from http://www.pilotfriend.com/experimental/build_10.htm
These days guys mostly use negative molds to build spoons. Using a positive blank is a more direct route to getting the project done, especially if your mold building skills are non-existent, like mine. Excess foam is cut away once the bottom is solid. Then the top deck is applied.
Many people use bricks, small cars and spare children as weights to squeeze out excess resin, but I think baggingās the way to go.
Why use sun cure?
I think UV provides a superior polymerization reaction to other catalysts. You can read more here (Iām not pushing this brand) http://surfsource.net/asuncuremfg/UVC2000usersguide.htm
- I love the strength and finish it gives.
++ And if the resin trap is kept dark I can re-use the resin :>
Hi Condition_Red -
I think it was Gary Young (the bamboo veneer composite guy) who developed a UV resin vacuum bagging system for surfboard laminating. The advantages are obviousā¦ smooth finish, quick turnaround, higher strength to weight ratio, etc.
Iām surprised no one else seems to think itās valid.
I canāt seem to open the link I had to his website to verify but I think he holds a patent on the process.
that relates to the use of epoxy resins not polyester.
if you dont want cracking use epoxy its simple
even if you did a hand layup as opposed to baging
the weight difference would be neglible
uv resin would be a waste of time
for a start to get the best use of bagging u need a breather and a bleeder which would block out the light
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Iām surprised no one else seems to think itās valid.
john
it just overcomplicated with very little or no gain in strength or weight
a carefully hand layed up postcured epoxy lam could be easily stronger and as light
bagging epoxy lams on bigger project becomes relevant where 5 to 10% makes a difference.
whats the point in saving that weight if your using a heavy pu blank
lam strength gains are neglible in a surfboard with a stringer pu blank
The juryās still out on epoxy spoons. Epoxy flex is whole new area of flex experimentation across the surf industry.
But it is a consideration. Thanks for the feedback.
By the way, UV resin is being used in laminations - some MEKP is added to cure those hard to get at areas.
Red
Now if someone has an idea how thick the PU, EPS blank will need to be to prevent distortion in the bagging process Iād be grateful.
Otherwise i will just over engineer.
I donāt think its altogether crazy.
I made a balsa compsand without any epoxy, once. Yes, over EPS. At least that was the original plan. The reason the project wasnāt completed as planned had nothing to do with adhesive or resin problems, but with unrelated equipment setbacksā¦
It was last winter & my shop was so cold & damp that epoxy was troublesome. But I still wanted to make something.
I pre-made the balsa skins with 1/16" balsa & 4 oz e with UV poly resin. I taped down a one-sided bag & pulled vac, and then turned on full-spectrum plant grow lights hung above the skin & bag. That worked just fine. The skins with glass on the outside only seemed just as light & flexible as they do when made with epoxy.
Then I bagged the skins to the EPS blank with foaming PU glue. The first one was fine; on the second one I had bag leaks, my pump ran until it failed, the pu glue expanded creating voids under the skin, and I ended up tearing off the whole skin. I had to sand off the PU glue & fair out the blank before putting a new skin back on. By the time that was all done, I got some warm weather, and just used epoxy to make the second (third, really) skin for that board. But the board came out fine & is still in use - one side epoxy, one side uv poly & pu glue:)
It figures that a simple question regarding vacuuming UV resin might turn into another Epoxy/EPS vs Polyester/polyurethane debate. LOL
Cut/paste from Fiberglass Supply online catalog - note recommendation for use with poly, vinylester and epoxy resinsā¦ Why?
Stretchlon 800 .002" X 60" Stretch Film is a thin strong (8000 psi Tensile Strength) orange polyurethane film with over 500% elongation that is recommended for use with polyester, vinylester, and Epoxy resins for vacuum bagging or infusion. After it is stretched it will return to approximately 80% of its original size. Stretchlon 800 Stretch Film is a perfect vacuum bagging film for multiple contour parts. Little or no pleats (rabbit ears) are needed so even the least experienced bagger can use this product. Do not exceed 400Ā° F. (204 C)
what do you mean wrt to distortion
foam will distort under higher pressures
epoxy is engineered with variying degress of flexibility
and can handle repeated cylces of flex without cracking
perhaps to use resin infusion with epoxy would be the easiest method to make a spoon
sounds somewhat complicated though
when careful handlayup would achieve similar results
with litle hassles
unles the flexy base was made with a core foam or balsa
that could be interesting
and pre glass the skin as benny suggests(bagging is unneccsary in this process however)
than use vac to attach skins effectively to foam
i bag boards reguarly for relevant reasons
but avoid unneccesary bagging
sorry i so rude before btw
this can be done but their our a few steps you have to take, and what type of light source are you using, and at what nm range, and what uv photoinitiator you are using ,the surf industry standard is ciba irgacure 819 photoinitiator their are others that work better depending on light source, i use a blend of a few ciba products and a mercury vapor lamp, which will cure through almost any vac bag material.
their is to much info to type if you need help call me at my office 949-361-9199 and i will give you all the help i can, i have been doing uv cure product for over 12 years now
god bless Richard
Hi Richard -
Do you know anything about UV cure acrylate resin used, in this instance, in vacuum bagged aircraft repair? Sounds like interesting stuff.
http://d67576.u25.creativedg.com/members/member_documents/Pages%20from%20RT_N_D04-5.pdf
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this can be done but their our a few steps you have to take, and what type of light source are you using, and at what nm range, and what uv photoinitiator you are using ,the surf industry standard is ciba irgacure 819 photoinitiator their are others that work better depending on light source, i use a blend of a few ciba products and a mercury vapor lamp, which will cure through almost any vac bag material.their is to much info to type if you need help call me at my office 949-361-9199 and i will give you all the help i can, i have been doing uv cure product for over 12 years now
god bless Richard
Uhā¦yeah. I, like, bought these lights at ACE Hardware that said āsunlightā or something. They work tooā¦
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and pre glass the skin as benny suggests(bagging is unneccsary in this process however)than use vac to attach skins effectively to foam
Necessary, though, if you want the resin to get all inside the balsa & stuff - the tradeoff for weight gain is better waterproofing & flex retentionā¦ Balsa, dry, between sheets of glass is prone to staining from dings & splitting over time; resin-saturated balsa is pretty much a synthetic deal
But Iām back to epoxy anyway because of the VOC issuesā¦
Howzit Benny, Kind of sounds like the bulbs used for indoor plant growing and not really sure if that;s the kind. Fiber Glass Hi sells 4ā UV bulbs for about $18 a bulb. My set up uses cheap Walmart fixture with the F.H. bulbs and they work great. I have 4 fixtures and 8 bulbs and you need to warm the bulbs up for about 10-15 minutes before putting a board under them.Aloha,Kokua
Yeah - Iām dismally cheap. But it did work. Iāve since tested it with āopenā uv (not in a bag) and its about an hour before its rock hard - it would be 15 minutes in direct sun. Iāve always attributed it to that I only have 2 100W bulbs over a 12ā workbench kind of like a foggy day. But it worksā¦
Thanks for the response, guys, in particular RichardL for your kind offer. I was hoping that I could just cop a sunny day
Benny1, when you say make up the skins do you mean hand laminating something like a 4oz cloth flat and then bagging it to the blank? Just checking. I think Iām going to 18 layers of cloth in places (they get successively shorter, to induce progressive flex).
Silly, no worries, mate. I realised it was a response to a blow-in asking seeming uninformed, meaningless questions 
You think bagging UV is an issue - think of the flak Iām copping for suggesting modern intake rocker, another foot of length and complex rails (eggy to down transitions) may be the way to progress spoon design!!
Red
im starting to get you now
yes bagging would kill it in no time
infusion even better
is it a male mold right??
look for a slow cure epoxy with a flex agent perhaps
you can get awsome flex with epoxy layups
and it wont micro crack
im not usually that rude
sorry again
spending to much time online and not enough in the water
give me a few links to some spoon projects so i can see the molds and layups
and ill try and figure something wrt to fast layups
ive tried a few different methods by now
and think that the quickest are the best
i still think suncure is trippin though!
I think this is the definitive spoon site http://www.flexspoon.com/
These spoons were made in molds, but the surfresearch link http://www.surfresearch.com.au/1977_McT_Spoons_SW_Jan_v24n4p64.html talks about the āoldā days which is where Iām hoping to head with a computer designed, machine cut blank (my āpositiveā mold).