Did a Google for info on resin transfer molding (RTM) found this article. Really good overview of technical and economic stuff. Knew nothing before - know a little more now. Link goes straight to pdf:
http://www.me.gatech.edu/jonathan.colton/me4793/rtmpaper.pdf
After reading the article and searching the web, I am having hard time determine the benefits/drawbacks of RTM vs VI. Does anyone know of a good source for this information? It looks like with RTM you could work the resin at higher pressures without crushing the foam, but what are the benefits of injecting at a higher pressures? Am I just missing the point and it doesn’t matter if the resin pressure is higher or the sandwich pressure is lower.
I assume that you are refering to Vacuum Assisted RTM when you say RTM, if so the major difference is that instead of relying soley on atmospheric pressure to move the resin through the part you are going to assist it by giving it a little push by adding pressure to the infeed pot. This tends to lower your fiber to resin ratio but does facilitate wetout of the part. This method is viable for a part that doesn’t have rigid tooling, were you to do RTM or even light RTM you would need matching molds. Regardless of the process here are some of the issues you would have to cross: Resin viscosity, preferable that it is 200 cps or less. Resin Flow channels(porosity), this can be done by flow mediums, grooves on the blank, and type of reinforcements, flow distances, pressure differentials.
So to do RTM for a surfboard you would have a true “pop-out” because it would have to have a mold, but if you do vacuum assisted infusion then you can work on the same requirements as vacuum bagging. The other challenges will all be there regardless. As far as divinimat or similar products, they do or do not become a piece of the part? I would think that the layers would go DM/FG/SNDW which would only work on the outside of a foam cored board. I have seen what a solution was or maybe is, but I was just wondering if any one was sharing first hand experience.
Correct, it would be a true pop out board.
I have experience with infusion on some small parts (flat panels and longboard skateboards).
If you are using a core as your infusion media it will become part of the finished product. You can also use flow media above a peel ply that then can be removed from the part. As for the order of the lay up that can vary depending on what you want to do. I would most likely use a reinforcement on each side of the core material. I’m not real clear as to what material you are referring to as SNDW.
The theory behind resin infusion actually dates from the mid to late 1800’s and the first patent for infusing boats is from the 1950’s. What has been painstakingly slow is the development of the technology due to difficulty of spreading the information and that failures are often catastrophic. If you are going to do this in the surfboard industry you really are pioneering a new field of application for infusion.
Surfboards use such lightweight reinforcements that it is difficult to find them in non-crimped forms, this is a problem for porosity reasons. The surf industry as a whole is a microcosm in the composites world, resins need to be specifically formulated by the manufacturer for infusion, I’m not saying it is impossible to find a resin that will work, however it may not have all the characteristics that you may want and it will be highly unlikely that you can get if formulated for you if there is not a larger market that wants it.
Is it worth trying, definitely. In fact there may be some really neat things that you could do while infusing a surfboard that would change its strength in certain areas and flexing patterns.
We are presently involved in work on an infusion resin for surfboards. There are a number of issues we have to overcome the most difficult being viscosity (seems VARTM is more likly to work). The other issue, as stated above, is the availability of lightweight non crimped fabrics preferably in bi or tri axial.
If anyone is interested in persuing this, give me a call or email me and I’ll keep you posted as to our progress.
or 321-223-5276Greg,
From my experience with VIP the starting viscosity on epoxy can be much higher than with polyester. Your current resins may work fine. This is due to the fact that epoxies lower in viscosity with heat during exotherm. Also most of the epoxies I have used have been heated to about 120 F initially to lower the viscosity from the get go. Plate heater and heat temp gun work nicely for this. This is also how Andre Cocquyt (www.grpguru.com) teaches infusion with epoxy. Electric blankets and silicone heat pads can also help with heating the part. Andre also has an insane way to make a heated hard mold, problem with this is having the same exact bottom on every board.
Problem I see with infused surfboards is making the laminate to fiber rich. I think resin content is pretty key to surfboard construction, especially with compression. We are seeing resin contents going too low if you are not careful. Also, consumable waste, bags, resin lines, ect… Fun project though.
Regarding noncrimp, in this low of weight it can be very gappy, especially stitched. However, JB Martin might have some 0/90 available in the lighter weights than the traditional stiched products. They are real popular with the kayak makers. See Composites One for distribution of JB Martin products. Composites One is by far the best distributor on infusion products, they are a good resource. A lot of their sales staff have been trained in VIP as well.
Sluggo
I think your last statement really sums it up. Thanks Greg and sluggo for the input. I am going to contact composites one and see what kind of setup they recommend.
firstly i would like to apologise to daddio…
you mentioned RTM making a comeback in another thread …
and i said id like to see a custom RTM ??..
well i completly mis understood , i thought you meant rotomoulding …
as resin transfer is a more modern technique and so i didnt link it with the comment about making a comeback …
yes …
resin transfer will rattle the establishment …
greg question ???
why would you work on a resin , that was suited to VI and RT in surfboards …
have you got a crystal ball ???
has anyone in the surfboard industry actually asked for a product …
or are you just 20 years in the future again ??
im just an observer on this subject …
well not really , just silent …
regards
BERT
right…being ahead of the curve is smart business…
yea but ive known others who were that far ahead that i was there only customer …
seems like greg is thinking so far ahead that the bulk of his customers havent been born yet …
seriously tho greg …
i really believe 99.9% of surfboard industry crew have no appreciation yet , of the stuff your fine tuning and developing …
but trust me , im the 0.1% ,coz i reckon your doing the right thing , can you post my glass ball back next week??
regards
BERT
Sometimes I just want to do things just to see if I can. Challenge… and I’m developing this for use beyond just surfboards. I want to see what the marketplace would think of an RTM resin that has the same nice properties that we have in our regular surfboard resins. I don’t think that exsists in the RTM resins of today. Also, I developed a potting resin years ago, complete with R&D and testing that comes pretty close to being there. Just a little tweek needed so there isn’t that much work to finish this.
Sluggo, thanks so much for the feedback … your always a wealth of knowlege on here. Don’t ever think that your unappreciated.
Bert, the crystal ball is on it’s way back.
Greg, is the kit-built airplane narket on your list of potential customers.
Also, I remeber reading a plane builders site wherein he complained of RTM resin flow / viscosity issues. Not sure where saw it but also remember seeing a glass made for RTM that was designed to assist resin flow.
I’ll try to dig up those sites.
Problem I see with infused surfboards is making the laminate to fiber rich. I think resin content is pretty key to surfboard construction, especially with compression. We are seeing resin contents going too low if you are not careful. Also, consumable waste, bags, resin lines, ect… Fun project though.
i know exactly what your saying there sluggo …
but if you have a hard high density backing for your laminate , then your not relying on resin content to offer some hardness to the structure …
decreasing resin content allows the glass more range in movement before failing , like a bullet proof vest , if you resined it , it would weaken it …
so if you can get more range out of your glass job , it highlights the next weakest link …
get rid of that and the problem is not a problem anymore …
all the possibilities for infusion arent openly being promoted yet ,
in other words i have an infusion technique which is not like anything ive seen anywhere else …
the problem you quoted above is when infusing onto a medium that would be better suited for hand lay up …
as techniques cross over from one method to another , its common to find problems , because we are trying to apply new techniques to traditional materials …
in the end logic takes us toward new materials , which arent that practical for the old fashioned way of doing things …
infusion with consumables is promoted by those who wish to sell you consumables …
i have no consumables …
except the tape to seal the bag …
also choice of fabric , becomes essential with infusion , or else you get the problems you highlighted …
if you think of the worst fabrics you ever laminated a board with …
chances are they are still good for something …
all my boards have been infused since 97 …
they went from being light and strong to lighter and stronger …
you are right about problems …
its keeps getting refined all the time …
viscosity , pot life , flow and pressure regulation , combined with technique …
i think most would give up on it …
when i first started doing it , i thought it was a hoax …
it would take me 5 times longer than a hand lay up , because i would stand and watch …
dry spots , dead zones , resin pools , leaky systems , ruined vacuum fittings , to much pressure, poor bag material , uneven pressure ,poor temperature control, flow channels blocking off before time…
so much pain …
but now even after having a working system for so long …
the only thing left is better resins …
for years i was trying to solve a problem , which wasnt my fault …
it all came back to the nature of the resin …
with the current resins , if you want the ultimate in strength to weight , you end up with a few flaws …
but get great cosmetics , and the resin content goes up again , and you lose your strength to weight improvement …
greg ,i was thinking you either fix the gas problem with the resin formula , which i have no clue about , or i was thinking of some sort of degassing chamber before the resin was infused , a seperate process to treat the resin first …
to busy now to do anything about it …
put that on the list of things to do …
regards
BERT
No me, I’m sorry,
Read up on light RTM, all you can on Infusion and checkout soft and hard tooling (molds) and other related stuff, not so much for custom surfboards, but for other products in related sports industries cause you never know when the light will go on and a challenge will become an idea that will take us one more step into the future.
Being a knowledgeable person, means that we know more than we need for the job at hand, cause it relates to problem solving, having another door or hallway starts in your mind.
Does the T in RTM stand for tits? I certainly hope so…
Bert,
I know the issues as I am dealing with them on other parts other than surfboards. An e-glass laminate at 70% fiber can be a little scary, especially under a low density foam. A hard skin underneath would make a big difference.
Nice thing about infusion is it is a very controlled process if you follow a check list preventing most the problems you have encountered. I have seen a lot of wasted parts because someone forgot to check something real basic.
Regarding consumables, there is an infusion process called CCBM (Closed Cavity Bag Molding) that does away with tacky tape. Not enough time to explain, but you need about an 8" flange on a rocker table to use this method. Reverse flange has 2 d-seals that go over your silicone reusable bag on your mold flange. Silicone bag is made from single component silicone.
Regarding your gassing issue, can you describe? Water can be a major issue causing gassing types of syptoms. Carbon fiber, kevlar, fiberglass and a lot of epoxy hardeners really attract moisture. This can go away by pulling vaccum on your part and heating it up to 120 F for a few hours. This should be a must procedure for a carbon infused laminate. If you don’t have heat, 24 hrs at room temp should do the job. On the hardener, not sure what to do.
Sluggo
ok sluggo , ive been reading alot of archive stuff lately …
and its obvious to me you know your stuff …
question ???are you doing full clear cosmetically appealing jobs ???
why i ask is ,
im getting tiny pinhole air bubbles …
in the first few hours the whole job is beautiful and clear all the way through …
the resin pulls through it all perfect , then between the 1 and 2 hour mark , depending on the brand/pot life, tiny bubbles form in the weave , just as if you were doing a poor hand lam and it came out dry …
there is no way air is getting in the system and it always happens towards the end of the pot life …it still happens right across the job , even on glass which is all by itself acting as a flow medium …
all the resins do it , but some like the sp systems , and twin pack , man they go like bubble bath …
so i figured its the resin blowing out some gas as its kicking off …
because this has always perplexed me , and everything ive ever done to try and solve it hasnt worked , except backing off the pressure , which leaves the laminate wetter and almost defeats the purpose …
my opinion is the resin is gassing because the vapour pressure is so low …
if i use smaller weave i just get more smaller ones …
ive resigned myself to the fact that my glass jobs just have a dry look and thats what you get if you want light and strong …
i can make em look perfect , but the trade off is a loss of flexibility and strength …
if you were using a ply and bleeder , they could escape , but once the resin has wet out the glass , there is no escape route when they start to appear …
i cant think of any other logical explanation , than reduced vapour pressure …
like boiling water in a vacuum at room temperature …
basically i want the perfect glass job at the flick of a button , still havent got there …
any ideas ??thoughts?..
regards
BERT
Bert,
This seems that it should be solvable. What temperature are you at? And what’s the pressure? And what pot life is required? Actually the RTM resin I’m working on right now has reasonable resistance to foaming, about the best I’ve ever seen. Better than the regular surfboard resin we use for sure. Perhaps this resin … or a different tweeked version. Sluggos right about moisture. This can even come from the humidity in the shop. We have a customer here in Tucson that moved his operation here specifically because it can’t be done elsewhere. They close on humid days, about 10 days a year. There also may be a way to chemically solve that too.
The RTM resin is done. I finished it this afternoon. I have one small test, just to make sure and then I’ll have samples ready to ship next week.
Bert,
PM me any info on what you might need. I’ll be happy to work on some ideas. Why work around the shortcomings of materials when you don’t have to? Also I’m going to FL in about a week and a half. I have a lot more R&D chemicals there so I could send some stuff back here to AZ for use in this lab.