Carbon Fiber skinning foam glider wings with FoodSaver

[MK-Ultra]

Hey everyone! Names Mark but Dogbastard or any name will do just fine lol. I'm new to Aloft forums, so happy with this hobby shop and their service I had to further join, nice meeting yall! ?

So I have 2 glider/sailplane wings roughly 4ft in length for total span of 8ft or so. Wing chord is about 9" in length, so these are fairly decent sized wings. I'd like to SKIN them via the VACUUM INFUSION METHOD which utilizes a vacuum pump of some sort to initiate a vacuum while the composites cure with epoxy in bags for some unit of time. Since I have never done any DIY composite forming myself (I'm extremely familiar with aerospace composites and autoclaves however as an aerospace engineer which utilize similar methodology but curing takes place within an autoclave which is beyond the scope of what I need!) I'm not very keen on spending too much for an entire "vacuum composite setup" as they can be quite pricey, so... I remember I have an unused FoodSaver vacuum sealing system ? Aha, maybe this can work Mark...

I'm writing this post to seek any helpful guidance on how to go about such a process with a FoodSaver? I've read others do it online but have not seen the exact "steps/materials" per say in how they did it ??‍ everyone seems to do things differently which is ok, but my goal is to ensure that:

- Carbon Fiber/Kevlar skins are permanently embedded within the epoxy matrix structure and conform to shape with minimal epoxy resin.
- I'd prefer a smooth and clean finish, why not make it look good, right? My saying is, dont halfass a fullass job if unless it ain't a full moon ?

Materials/Equipment are:
-A brain, and 2 capable hands with 10 fingers ?
-FoodSaver Model VAC820
-FoodSaver roll of bag material (the kind with diamond patterns on it, some supposedly said this eliminates the need for breather and such? I'm unsure)
- AeroPoxy if its decently (which one for RC uses btw? Heres my problem in everything in life: I have Boeing and Tencate AS9100 epoxy cans, same stuff they use on 787 Dreamliners, but these are specifically rated for autoclave use and are too costly/overkill for this prototype! I ain't using no primo with a FoodSaver, its be worse tbh lol)

- Is thick mylar or anything else actually needed? I just want the wings to be skinned, with minimal epoxy, and smooth/purdy (if possible but I'd like to think it is) which brings me to another question I'm confused with:

Usually with vacuum forming, there are epoxy drain tubes/valves that come out of the bag and go into a drain reservoir of some sort. Now with FoodSaver bag roll, Martha Stewart didnt speak of any such drainage procedure with this "jerryrigged-somehow I did" method ?. I've never even used a FoodSaver, I use my stomach to save fresh food I eat! But luckily I have one and I thought what the frick, dont overthink this Mark, u know how u get (my paranoid line of work folks, if I design something wrong, people die or correct targets arent hit and per AS9100 and various MIL-STD protocols, that's a big ol no-no ??).

Composites being used:
- 3K twill weave Carbon Fiber at about 220g/m^2, Made in Merica of course (btw, dont buy foreign/Chinese composites off Ebay folks, its chicken shit and I wouldn't even wipe my a$$ with that stuff and its technically illegal, at least for US composites being sent out fyi ?). This will be used for majority of the wings and control surfaces.

-3K twill weave Carbon-Kevlar hybrid cloth of similar 220g/m^2 density/weight. This to be used for fuselage and outer wing portions for structural rigidity (my design intent calculations indicate higher levels of potential aeroelasticity/harmonic vibrations... last thing I want is for this thing to be zooming by in a friggin alloy EDF jet and catastrophic event occurs and bam, I'm that guy on KTVU who started a wildfire with 6S battery packs... I DONT WANT TO BE THAT GUY folks ? hence all this precautionary voodoo). Also, I have pure kevlar cloth as well; the kevlar shouldn't impose any RF interference with the onboard antennas unlike CF, so this why it goes on the fuselage and such and also for hard strike landings or whatever.

So to all my new friends (hopefully haha), can anyone give some insight and perhaps maybe with some pics if any of yall have done some jerryriggin like this? I'LL BUY BEER for help??‍? ANY help is appreciated as I only know the "advanced method" to make a friggin airliner and such, but I honestly dont know about the "Jerryrig method" and Jerry's a good friend of mine in anything I do from fishing to whatever, skies the limit.

[Note: I'm avoiding the usual "lay the cloth, slather epoxy, rollbrush, let airdry" Sopwith Camel method as this results in an inferior composite that's overweight, has air pockets, and doesnt allow the composites to do their thangs, especially with thick coats of epoxy being used, no matrix will be formed. It may LOOK LIKE a job well done but it ain't, and so I wanna use vacuum to "squeeze" that epoxy into the filaments to form a unified composite.]

With any help, I'd be down to make a pictorial guide for future references for any other people to refer to in the future showing how this goes (if its chicken shit I'm signing off this forum and quitting my job ?). Jokes aside, any advice is helpful but if someone's done a full A-Z jerryrig FoodSaver vacuum skinning job for somewhat larger wings, I'm all ears and I have good beers, yeeyee ?

Thanks for yalls time, insight, and glad to be part of the Aloft Hobby group to say the least. Where all my hobby shops gone??? Chicken shit Bezos ruined everything, so... I prefer my local goods like my local produce, u gotta get them ripe non-GMO servos and whatnot so Aloft will be my hobby farmers market to go to 1st. I got SAME DAY 1950s customer service, they actually care what I'm making, they answer EVERY QUESTION I asked (we all know when we ask 5 questions and only 4 get answered, not with Aloft, they're just good folks. Everyone take care and be safe and seek cover... cuz Mark's bout to get all Boeing in his jerryrigged cleanroom garage ??

Btw, if anyone has aerospace/aerodynamics questions or whatever that ain't classified, heck even fishing questions even, gimme a holler as I dont a charge a dollar. Thanks to Nigel and Chris for putting up with me, I gotta get em some beer haha. Yeeyee ?

 

[Konrad]

Can't tell by your writing how serious you are. But I've used a fish tank air pump as my vacuum pump. Yes you will want mylar. Yes you will need breather cloths (don't know about diamonds). And yes you will want a catch tank if you want to use that pump again.

The only issue I've had with bagged wings is the LE and some advanced wing tips have needed some hand shaping when pulled from the bag.

Don't forget to have some bias cloth in the Lay up going around the LE to tie the top and bottom skins together.

Try using glass as you develop your technique.

 

[MK-Ultra]

Can't tell by your writing how serious you are. But I've used a fish tank air pump as my vacuum pump. Yes you will want mylars. Yes you will need breather cloths (don't know about diamonds). And yes you will want a catch tank if you want to use that pump again.

The only issue I've had with bagged wings is the LE and some advanced wing tips have needed some hand shaping when pulled from the bag.

Don't forget to have some bias cloth in the Lay up going around the LE to tie the top and bottom skins together.

Try using glass as you develope your technique.

Morning Konrad,

Actually, I'm EXTREMELY SERIOUS, lol bit of humor never hurt nobody, especially in sometimes rather serious work, cant let it change you tbh. Also new to the forums, dont know how strict yall is but ok, I tend to be a funny countryboy and am serious about this thing not breaking apart as were in wildfire area and I have a very powerful EDF which will have loads of electronics onboard so YES, HIGHLY SERIOUS about safety.

Interesting, an aquarium pump, nice as I have an aquarium! Do u mean like one of those small Aqueon air pumps with 2 outlets used to make bubbles and such? Is that strong enough? To me a FoodSaver seems stronger but ok I'll look into my aquarium pump to see what vacuum can be drawn.

Do u happen to have any pics of how this setup works and is laid out by any chance? Type and order of mylars and breathers, where u placed the tube, the catch can, etc. Reason I ask is because the wing has a blended geometry and so placement of these components is critical as some areas are better than others. On a large aircraft wing structure, wed have several vacuum drain tubes in key areas depending on the structure being formed.

U say "hand shaping" when pulling from bag? Then wouldnt this indicate that the curing hasnt finished? It should be hard for the most part so Im a bit confused but I'll keep an eye out for that. Perhaps different bags? Not sure, these FoodSaver bags arent smooth on inside and have tiny rid pattern which supposedly eliminates need for some equipment some of have said, but I'm not sure.

Lastly, u mention a bias cloth to tie both top and bottom skins? I'm going for one piece cloth tbh were the cloth will be folded over the LE as a "midpoint crux" where half the cloth goes over the top, and other half folds over onto bottom side, resulting in a true 1 piece structure. The idea is to preserve the angled weaving of the cloth, not to manipulate it, unless for different section requiring different angles of weaves so to speak. U change the weave, you've changed the dynamics, so I'd like to preserve the twill weave angled pattern throughout except for the outer wing portions which will be from Carbon-Kevlar.

Could you please elaborate and/or show such a build that you've done like this whenever you get a chance friend? I'm curious how the outcome result looks and the overall setup with an aquarium pump, seems pretty interesting.

Thanks for the input Konrad, I now learned I have 2 sources of vacuum devices in my house lol. Take care and have a great day, Mark

 

[gp49]

Here you go, someone tried to skin this cat before. And it worked.

Vacuum bagging elevons with a Food Saver machine. - RC Groups

Discussion Vacuum bagging elevons with a Food Saver machine. R/C Blogs

www.rcgroups.com

 

[MK-Ultra]

Here you go, someone tried to skin this cat before. And it worked.

Vacuum bagging elevons with a Food Saver machine. - RC Groups

Discussion Vacuum bagging elevons with a Food Saver machine. R/C Blogs

www.rcgroups.com

GP49, ur my savior! Exactly what I was looking for, I'm sure same can be used for CF and Kevkar and such.

Since writing initial post, I've been looking at nice smaller industrial pumps that hold nice vacuum like those GAST pumps... u have any idea on those small industrial type of vacuum pumps out of curiosity? I figure this may future proof my composite needs if need be haha.

Thanks for the link friend ?

 

[gp49]

GP49, ur my savior! Exactly what I was looking for, I'm sure same can be used for CF and Kevkar and such.

Since writing initial post, I've been looking at nice smaller industrial pumps that hold nice vacuum like those GAST pumps... u have any idea on those small industrial type of vacuum pumps out of curiosity? I figure this may future proof my composite needs if need be haha.

Thanks for the link friend ?

Depending where you live you can try ACP composites. They have nice stuff for vacuum bagging including pumps:

Fittings & Equipment - ACP Composites

ACP carries a variety of fittings that will meet all your vacuum bagging needs.

store.acpcomposites.com

Custom Composite Manufacturing - Fabrication & Products | ACP Composites

Providing custom composite manufacturing, including applications for radiology, UAV, robotics, and other custom parts needs.

store.acpcomposites.com

And you are welcome!

 

[Konrad]

Ok, the uni-skin can be done but is difficult to control. With the heavy weight cloth getting true fidelity to the LE might be a problem.

You say you have 4' wings but I failed to read what is the core. I assume it is extruded polystyrene. If so you will find that the limit to your wing will be how much shear the foam core can take. Even with glass I've failed the core not the bond or the matrix. Take a look at incorporating a spar (shear web) to hold the top and bottom skins together. Use the core only to define the airfoil shape.

As I recall I got 4 maybe 6 inches of vacuum with the fish tank pump. Even with this I could crush expanded bead polystyrene foam.

Disclaimed I last did composite manufacturing around the turn on the millennium.

 

[MK-Ultra]

Ok, the uni-skin can be done but is difficult to control. With the heavy weight cloth getting true fidelity to the LE might be a problem.

You say you have 4' wings but I failed to read what is the core. I assume it is extruded polystyrene. If so you will find that the limit to your wing will be how much shear the foam core can take. Even with glass I've failed the core not the bond or the matrix. Take a look at incorporating a spar (shear web) to hold the top and bottom skins together. Use the core only to define the airfoil shape.

As I recall I got 4 maybe 6 inches of vacuum with the fish tank pump. Even with this I could crush expanded bead polystyrene foam.

Disclaimed I last did composite manufacturing around the turn on the millennium.

Hi Konrad

I'm a fool for not saying what the foam material was, my apologies bud. The wings are made from EPP or "expanded polypropylene". This may clear that issue up a bit.

A uni structure is a bit difficult I'll agree with u on that but the wings are essentially straight in geometry for most part and so I THINK I can achieve a uni or "mostly uni" structure. The leading edge sparks as a joiner is a plausible solution though if I may run into some trouble or I may make 2 uni sheets per wing with one covering the larger inboard area and another sheet covering the smaller outboard area, with the CF-Kevlar hybrid cloth as a 3rd smaller sheet covering the the outer most 20% of span all the way to the tips. Still deciding thinking of layout but u did mention some good points, especially the LE spar as a "joiner" which I may also consider.

I had no idea that those tiny aquarium pumps could pull such a strong vacuum! That's pretty impressive to say the least. In the end though, I'm going to make a smaller practice mockup and see how the various arrangements/methods are being influenced. "Measure twice, cut once", right? Haha

Thanks for your added input Konrad, feel free to mention any other ideas as I'll be relaying whatever route I go with and its respective findings. This forum is cool, everyones helpful and offers interesting perspectives on how to go about a problem, THANKS EVERYONE! ?

 

[MK-Ultra]

Depending where you live you can try ACP composites. They have nice stuff for vacuum bagging including pumps:

Fittings & Equipment - ACP Composites

ACP carries a variety of fittings that will meet all your vacuum bagging needs.

store.acpcomposites.com

Custom Composite Manufacturing - Fabrication & Products | ACP Composites

Providing custom composite manufacturing, including applications for radiology, UAV, robotics, and other custom parts needs.

store.acpcomposites.com

And you are welcome!

Hey GP49,

I'm a South Bay Area resident and so ACP being in Livermore is doable. I viewed their products and they're a LITTLE PRICEY for my first DIY go-around with these wings and so I think a good used unit may be best?

U have any idea on GAST vacuum pumps btw? I found one in AWESOME condition for like $50 with shipping and it pulls 28mm/Hg... costs around $500 new yet it looks new and is listed as a working unit but without gauges.

Thanks for the ACP reference bud, everyones extremely helpful here and I'm loving it. I might make a few wings with different methods and plan on relaying my DIY findings back for anyone else who might be curious. Konrad mentioned he did well with an aquarium pump which didnt cross my mind tbh! Was thinking of refrigerator pump off Craigslist or something but I like the aquarium pump, good used industrial pump, and hopeful FoodSaver routes (their bags are reusable according to the rocketry community who are making NICE CF ROCKET TUBES with FoodSavers as 6" tubes are rather pricey!) in the meantime.

Once again, thanks everyone for your input and USEFUL ADVICE. ?

Hi Konrad

I'm a fool for not saying what the foam material was, my apologies bud. The wings are made from EPP or "expanded polypropylene". This may clear that issue up a bit.

A uni structure is a bit difficult I'll agree with u on that but the wings are essentially straight in geometry for most part and so I THINK I can achieve a uni or "mostly uni" structure. The leading edge sparks as a joiner is a plausible solution though if I may run into some trouble or I may make 2 uni sheets per wing with one covering the larger inboard area and another sheet covering the smaller outboard area, with the CF-Kevlar hybrid cloth as a 3rd smaller sheet covering the the outer most 20% of span all the way to the tips. Still deciding thinking of layout but u did mention some good points, especially the LE spar as a "joiner" which I may also consider.

I had no idea that those tiny aquarium pumps could pull such a strong vacuum! That's pretty impressive to say the least. In the end though, I'm going to make a smaller practice mockup and see how the various arrangements/methods are being influenced. "Measure twice, cut once", right? Haha

Thanks for your added input Konrad, feel free to mention any other ideas as I'll be relaying whatever route I go with and its respective findings. This forum is cool, everyones helpful and offers interesting perspectives on how to go about a problem, THANKS EVERYONE! ?

 

[Scott Page]

I'm inspired to try this. Read through the RCG thread referenced above and looking forward to making a mess.

 

[bracesport]

I pulled a line of the domestic bagger and added a non-return valve to the line, so I could blip the bagger without losing vacuum - it also enabled me to bypass the sealing process using the bagger,

 

[Konrad]

"Expanded polypropylene" this is the stuff that has a slick (oily feel) skin to the beads? If so it is my experience that this family of plastic doesn't take well to bonding with epoxy.

I hope you are a process engineer and can share what techniques/processes are used to prep polypropylene to accept epoxy bonding. Heck it would be great if these processes could be used to obtain a good bond with paint.

4" of vacuum is from "0" being atmospheric pressure.

 

[Wayne]

You should be able to score a very nice but used vacuum pump online. Ebay or similar. Most of these comes from medical or dental labs and have been rebuilt. I prefer the Dental lab units. I have bought a few of these over the years, they are MUCH better than the home built or small but new things from china.

You will probably want to get or make a pressure switch to turn off the pump. Typically we only need to run the pump for a small amount of time and we shouldn't have too many leaks if done well.

I don't think you will have good results with EPP foam cores for bagging. First off it is too soft and will crush under a vacuum, next the epoxy would saturate the foam. The good news is EPS foam costs less and can more than do this job!!

@thenated0g Should be able to give you some good pointers as he recently did something very similar to this project, and he has a nice CNC foam cutter, he could probably be talked into cutting the foam for you.

For resin infusion I strongly suggest you do some tests. Start off simple and just pull some water into a bag around a piece of wood. Once that is working well, then try your resin on a scrap of similar foam. Once you have that working well, then go for the wing. No point in learning and wasting expensive materials. There is a learning curve to infusion.

As I recall there are some good write ups on this subject from Wyoming Wind Works on RCGroups about 10 years ago. He shared everything he was doing and eventually got great results. Well worth finding and reading. May be in the slope or in the tool section there. They used to have some very good tech over there.

 

[bracesport]

Given I will probably bring my ships home is a body bag I do everything as simply as I can - using the lead off of the food vacuum bagger with a non-return valve in the line I get pretty good results - I have also had plenty of plastic foil at work so I construct my own bags - I am jet to try a mylar on the surface, instead, I have used two layers of the foil, primarily to allow me to get the wet epoxy into the bag - my foam cores are just $3 per sheet DTFB.

 

[Konrad]

Not sure folks caught the key term here. That is " VACUUM INFUSION METHOD ". This is thought to be the next step up from the basic vacuum bagging. This is done to try to get a higher fiber to matrix ratio. It is understood that most composites actually have about 30% more epoxy than actually needed. Now don't confuse this term with a dry lay up. Take a look at this video at about the 12min mark.

 

[MK-Ultra]

Given I will probably bring my ships home is a body bag I do everything as simply as I can - using the lead off of the food vacuum bagger with a non-return valve in the line I get pretty good results - I have also had plenty of plastic foil at work so I construct my own bags - I am jet to try a mylar on the surface, instead, I have used two layers of the foil, primarily to allow me to get the wet epoxy into the bag - my foam cores are just $3 per sheet DTFB.

View attachment 4992View attachment 4993View attachment 4994View attachment 4995

Those are some nice wings ?

Were these done with a FoodSaver? The bags seem rather larger than the 11" max I knew of?

Nice outcome tho I must say, u prob baked them during vacuum stage?

Yeah materials seem simple, it's the pump I'm concerned with atm (looking for good/used decent pump or whatever gets job done lol)

? in the wings, Mark

 

[MK-Ultra]

Not sure folks caught the key term here. That is " VACUUM INFUSION METHOD ". This is thought to be the next step up from the basic vacuum bagging. This is done to try to get a higher fiber to matrix ratio. It is understood that most composites actually have about 30% more epoxy than actually needed. Now don't confuse this term with a dry lay up. Take a look at this video at about the 12min mark.

Hey Konrad,

Yeah I totally get/implied such a method but with original FoodSaver machine + FoodSaver bags. Was figuring there was some "standard DIY build" for using a particular kitchen apparatus ?

Anyhow yeah, I'm fine with basic even but infusion is preferred to reduce excess resin content. I've been "playing around with some S glass and even CF-Kevlar on a piece just cuz why not? ?) and thought I did ok, we'll see results in near future ? although wrinkles under vacuum appear to be an issue to be played with in place while undergoing vacuum, 2 hands helpful as FoodSaver is pressure activated, so perhaps I'll use a weight on FoodSaver next go around lol ?

Thanks Konrad, Mark

 

[Konrad]

Yep wrinkles are a problem. Mylars help a lot as the bag wrinkles never make contact with the lay up. Now in my day I didn't have a CNC foam cutter. So there were more issues with the surface finish of the foam core than I'd like. Without the mylars these lines would show through the lay up. I use the mylar to define the surface finish of the part. Now like I said there were some issues at the part line for these mylars, particularly if the wing had a lot of curves (leading edges and wing tips). Most of these could be cleaned up with wet and dry sandpaper ending at 600 grit. followed by some hand buffing with compound.

 

[bracesport]

Thanks - I made my own bag - if I used the food bags I would have done the wings one at a time - no baking, just 24hrs in the bag at a decent room temp - the food vag machine does me well for the vacuum side.

I am not sure if I would bother to vacuum infuse - I would imagine you will end up using more resin - wetting out the CF then rolling it between plastic sheets to remove excess resin is a great way to get to a decent prepreg (poor man's prepreg) - works well!

Those are some nice wings ?

Were these done with a FoodSaver? The bags seem rather larger than the 11" max I knew of?

Nice outcome tho I must say, u prob baked them during vacuum stage?

Yeah materials seem simple, it's the pump I'm concerned with atm (looking for good/used decent pump or whatever gets job done lol)

? in the wings, Mark

 

[Konrad]

It is generally understood that the infusion method results in a light stronger product. It also is cleaner (less tools exposed to the epoxy) it is safer (less fumes). The only down side is that it might take a bit more time to set up prior to the introduction of the epoxy.