hmmm this is interesting stuff. i am new to infusion - most previous work was on part which were wet layup and just needed functionality Yes parts should have low void resin fraction, etc. but in an 80/20 scenario…
thanks for the response.
also if i surround my part completely with MTI why not just tee both ends together and pull down? i’ve seen setups where ends were adjacent but they chose to tape one end shut and only use other.
You could T it. But doesn’t really make a difference I think. I’ve done the sealed Mti hose since I’ve been using it and never had an issue. Why waste or potentially waste a T when you don’t need it!
My first attempts with MTI were misguided as i was using it same as spiral - can’t really look at MTI like that - it functions differently. I misinterpreted my errors as those of the MTI hose.
Good stuff.
and i do believe that tryng Stretchlon 200 was a bad idea.
The Mti hose cost is high up front but I’ve been using it for a while now and don’t have an issue. It’s worth the cost up front if you factor in failed parts and wasted time.
I build RC racing sailboats for hobby use with hulls that are 1 meter (39 3/8") long, about 175 mm (7") wide and about the same deep in female fiberglass molds. To date, these have been wet hand layups with multiple layers of glass. In order to make lighter hulls (low weight is king in the class this is for) I want to infuse a single layer of 5.9 oz/yd^2 3K carbon twill as I have seen done by commercial builders. (I know this is will make a very thin part, but it works in this application) One shop backs 1K carbon with 2.2 oz Kevlar, but I think that is too expensive for my first attempt at infusion.
After reading this entire thread, I have some questions for the infusion wizards.
With the mold I am using (picture attached) should I feed from the center and put the MTI hose around the perimeter, go from end to end, or go side to side?
I usually use regular peelply but can source a nylon based silicon coated peelply that is supposed to be easier to release. Should I use that with the red Airtech mesh?
The finished surface of the hull is generally cut and buffed to get a super smooth low friction surface - think show car finish. That requires a hard resin and I am not sure that either the infusion resins or in-mold coating sold by GAC will be hard enough. My wet layups were done over a two-part SprayMax rattle can clear coat which polishes out great. This is a touch up product for minor autobody work. Is any 2k coating like this OK or should I purchase the GAC product?
My pump is a rebuilt lab pump and will probably not get down to a 20 mbar level, but it does fine bagging on a glass plate when making carbon sheets. I don’t need aerospace quality parts. What are the issues with not having the recommended level of vacuum?
Any suggestions and source for the appropriate resin that is available in pint or quart quantities? I can get Adtech 114, but only in gallons and with hardener that is about $225 - Ouch!!! Plus it would go bad before I could use an entire gallon.
Is 3M77 Spray Adhesive OK to use in place of the one used in the videos? These would be light dusting coats to hold the peelply in place in the dry mold.
Any and all suggestions would be great.
BTW, for those on the West Coast of the US, ACP in Livermore CA is stocking MTI tube. http://www.acpsales.com/Vacuum-Bagging-Resin-Infusion.html
Looking to start doing infusion for 1-meter model sailboat hulls for hobby use (not production) using the MTI tube. The goal is a higher Vf than either hand layups or vacuum bagging. Lighter is more important than pretty as this racing class has no minimum weight.
[ul]
[li]The mold: My mold (similar to the photo below, but with a larger flange) is about 1 meter long by 140 mm wide and with a max depth of 140 mm. It has a PE tooling gelcoat with a 1/4" (6mm) PE/glass backing.
[/li]
[li]The pump: I have a Harbor Freight two stage 3 CFM pump that is rated at 22 microns and is reported to pull below 10 microns in actual use. I will purchase an absolute pressure gauge before doing the infusion.
[/li]
[li]The epoxy: This is a hobby build of just a few hulls so 5-gallon quantities of expensive brand name epoxy are out, but carbonfiberglass.com (also known as Illstreet Composites) sells a 150 cps resin with a 90 min pot life @ 77F in gallons. It is repackaged from an unnamed manufacturer, but they say it is a “spec” resin they use it to make their auto hoods (bonnets for those in the UK 
) and car parts. I will degas the resin before infusion.
[/li]
[li]The cloth: I plan to try both aramid and carbon layups following the schedule of some successful hulls by commercial builders. Aramid hulls will be 2 layers of 1.7 oz (58 gram) with addition ribs and patches at high load locations (see “Connections” photo). The carbon hulls will be a single layer of 5.9 oz (200 gram) twill with small 3.7 oz (125 gram) load patches.
[/li][/ul]
After reading this entire thread, I have the following questions:
Should the resin feed from the end, middle or across this mold? If across can I only run the MTI down one side to save costs?
Use red flow media without perforated release film or use the green flow media with Airtec perf release?
Most of the discussion is this thread is how to make parts with great cosmetics. What should I do (feed bucket height, resin flow, etc, to get high Vf parts?
Anyone have a source for the multi-layer bag material DDCompound recommends in small quantities? All I can find on-line is single layer Wrightlon 6400.
German Advanced Products is out of stock on the In-Mold clear coat. Is there any other source?
I plan to use Frekote 700-NC as a release agent after treating the mold with FMS and I know I will need to do some testing to assure the resin and clear are compatible with the Frekote.
Other suggestions are welcomed to increase my odds of a good part the first try.
SS//
[/li][/ul]
That sound ok, Maybee you should double bag it the first time. Seal the first bag on the flange and the second bag make envelope bag. So you make sure your mould is tight and possible pores are infused with resin so that the mould will be tight next time.
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The pump is fine, works perfect. More important than the volume is the absolute pressure, but 10 microns is perfect. They smoke a little when first pulling air out and when there is a leak in the bag!
[/li][/ul]
The resin should be fine, at least on such a small part. Degassing is important.
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The layup is very thin, I think the Aramid might be little too thin, but test it. A infused Laminate will not be as stiff then a wet layup because your wall thickness is less because of the higher VF.
You can infuse across, should work. I would prefer to infuse just from a spot in the mifddle and use MTI around the perimeter. I think that this will give the best result because you have a slower infusion. One layer can be quite tricky.
I would use a slower infusion mesh with perforated release and a coated peel ply. If you don’t use a perf release you will not be able to get the flow media off the part without cracking the laminate, same with the peel ply, thats why I would recomend a coated very fine one.
Use the MTI valve or place the bucket 1-1.5m deeper than the part. That will give you a high VF with a still perfect surface.
If you double bag you can also use single layer bags, but I don’t know where you can get small quantities.
Only in Europe, but don’t they get new one?
In Mould Coating and Frecote is not that easy, always fisheying. I had good results with waterbased release. I mostly use the HP HGR5 from HP Textiles, can be shipped to the states, no dangerous goods.
Make sure your bag is tight (100%), the resin degassed, use MTI hose (preevacute by resin feed, that is faster and easier to find leaks) and that your vacuum is perfect <20mbar or better <10mbar.
Then you will get a perfect part.
Regards Dominik
Use peel ply. I use it under the media flow and never an issue.
Acp composites sells bagging tube. One I believe is 60 inches wide but you can buy smaller ones as well. I typically buy 60 meter bags and cut them down or use them since some of my parts I need an envelope bag.
Peelply is fine, but if you have to pull it out together with the flow media and only have a prt that is 1layer thick you will break the part.
Oh only 1 layer? Never mind. I guess you could use Mylar coated stuff since that releases far easier?
Thanks for the replies.
I will purchase some coated peel ply and perforated release film. ACP stocks both and is an hour’s drive way. I need some other supplies so I will add that to my list.
The Frekote does tend to fisheye unless you first apply a very light misting coat, let it flash off, and then apply several more light coats. While wax and PVA certainly works, this mold has almost vertical sides and in my other similar molds when using the Frekote the parts almost dropped out rather than needing wedges and prayer ;). I would rather take a chance on the Frekote than damaging my mold due to a stuck part.)
I am still building the new mold so I will wait to see if GAC restocks the IMC. If not, I have two other automotive spray clear coats I can test. It may work better to coat after the part is removed from the mold anyway. If the part comes out smooth enough without the IMC that will save a little weight.
Double Bagging:
After reading the referenced work on double bagging, there seem to be two ways to do it. One method uses one pump connected to both the inner and outer bag and the other uses two separate sources.
The stated reason for using different sources is to use just enough vacuum to draw the resin through the media, less than 19 inches Hg, so any volatiles that might remain after degassing don’t form bubbles in the layup and the bubbles that remain in the fabric weave have time to migrate with the resin front. The full vacuum in the outer bag is used to apply the compression and for vacuum redundancy. This makes more sense to me as with this small thin part I can control the speed of the infusion with the level of the vacuum in the inner bag. If it has a leak, the outer bag can still be used to draw in the resin and save the part. I have a single stage pump that can pull 27" Hg that I could use as a second source of vacuum for just the inner bag.
Dominik, what would you say to the following as a process?
[ul]
[li]Double bag with a resin feed line of spiral tubing running the length of the keel with the MTI around the rim, drawing the resin up the mold walls (feed line goes into a T at the center of the mold, with a little breather fabric under it to prevent an artifact on the part.
[/li][li] Use silicone coated nylon peel ply http://www.acpsales.com/Econolease-Super-Release.html
[/li][li] Use perforated release film http://www.acpsales.com/Perforated-Release-Film.html
[/li][li]Use the green Airtec flow mesh http://www.acpsales.com/Infusion-Mesh-Green.html
[/li][li]Degas the resin to below 19" Hg for a minute or two after it foams up.
[/li][li]Use the single stage pump to apply only enough vacuum to draw the resin slowly through the part to the MTI - about 3"/min ?
[/li][li]Once the resin is completely infused, clamp off that vacuum line and lower the resin supply to 1m below the mold.
[/li][li]Then apply the full vacuum of the two stage pump on the outer bag to at least 20 microns until the resin in the feed line gels.
[/li][/ul]
How long should I leave the part in the mold after the stated 24 hr “drying time” (sandable and at 90% of full cure)? I have read that people do not demold for up to a week.
Steve
Hi,
first off all please also read the double bag thread here in the forum! It does not make a difference if you use one or two bags! The second bag is always just for vacuum integrity, for nothing else!
You must have nearly full vacuum in the first bag, always! That means nearly 29"Hg vacuum or better measure in mbar absolute.
When degassing also do it at the same vacuum 29" Hg.
The difference between a single and double stage pump ist the amount of air that can be evacuated with no vacuum. So a double stage pump sucks the bag faster down but will create the same end vacuum.
I only use 2 pumps if I have a to big leak in the second bag to get the perfect vacuum in the first bag.
I would place a maximum 30cm spiral in the keel and place the resin pot 1-1.5m deeper than the part from the beginning!
Hi,
A little about me. I am a newbie in MTI or RTI molding. However i have practiced quite a lot of hand lay up (vaccum wing bagging - vaccum mold and some other hand lay up little molds)
I want to drop the vaccum hand lay up molding for MTI
The CNC mold looks like this one : http://www.globalcube.net/imgcontrol.php?p(clients/flybiwo/content/medias/images/J2-wingandstabmolds.jpg), not mine but quite close : 60 inches x 8 inches.
My first question, as a newbie, is where to put the resin inlet?
1/ surround the part with MTI (around 145 inches of tube) and put the inlet in the middle of the part, in the bottom, but so how long should be the inlet??? 
2/ put some MTI on the right elliptical wing tip and install the same lenght of inlet ramp on the opposite wing tip
So, what’s the best place to install the inlet and how it should look like?
My second question is due to the very specific materials i am going to use :
A sandwich composed of carbon non wooven of 0.13 ounce followed by a triaxial carbon of 1,4 ounce, rohacell 31 IG-F in 1 millimeter and a biaxial carbon of 1 ounce (no typo in the numerals!).
Is MTI capable to deliver a nice product at the end? Any advice to get the best result?
Thank Alexis.
I just read all 51 pages of this thread, 
a couple hours well spent I hope. I just called German Advanced Composites and left a message, I am hoping to get my hands on a couple feet of this stuff to try, it looks very promising. If it works half as well as most people seem to say then the cost seems almost insignificant compared to the cost of scrapped parts.
I never heard back from German composites despite leaving a message last week, any chance of getting a small sample?
hello dominik, have you received any of my pm’s to place an order for some mti hose?
so the MTI hose works… period. I am now almost afraid to NOT use it since the parts simply come out nice. here are pics of large flat panel
Definitely worth the cost of MTI Hose, i’ve been using it for about 2 yrs now, Parts come out cleaner, lot less pin holes, witch saves labor . Also their Digital meter is a life saver, Measure Millibars , to find any minor Air leaks before infusing.
For infusing large cylinder shapes (2m length x 0.5m dia) what is the recommended routing of the inlet and MTI hose?
I will upload a drawing of 2 options shortly. The mandrel must be in a horizontal orientation.
