as722

My Feedback: (1)

I just got an auto vac system from aerospace composites and have some questions.
I'll be doing a set of wings for a 40% carden extra 330.

1. How much pressure?
2. Is pro-bond OK instead of epoxy?
3. Do I need breathing material and how do I use it?
4. Where do I place the hose, corner of the bag, wing tube hole, center of bag, etc.

Thanks in advance.
Albert

DMcQuinn

My Feedback: (13)

About 5 - 10 pounds of pressure is about right for 1/16 balsa over beaded styrofoam (this is the foam typically used for 35 - 40% airobatic planes). Use polyurethane glue (gorilla glue or Elmers polyurethane. no mask needed. you must put the reinforcing plywood and phenolic tube inside the foam before bagging. You can put the tube from the vacuum pump anywhere into the bag. I use window caulk as a sealer around this joint.

dreadnaut

My Feedback: (5)

I usually use 8 lb and epoxy resin. Tried Pro Bond once, and didn't like it. The nice thing about vacuum baging is that you can use a lot less of whatever adhesive you choose. I apply the epoxy to untreated wood skins, then squeege it off before it soaks in too much. I stick my vacuum line into the hole for the wing tube/spar. This enables the foam core itself to act as the breather, and pull the glue that has soaked into the wood onto the foam for a really strong bond.

The first time I did this, I did some destructive testing on the strips that were cut out for the aileron hinge line. One one, I simply bent it till it broke. The glue joint did not fail. The other one was flexed back and forth for several minutes, and put back on my work bench. That was over a year and a half ago. When ever I notice it, I pick it up and wiggle it some more. Hasn't failed yet.

russian

My Feedback: (23)

Albert!
First of all thanks for info about control horns for my 40% Carden Extra 330S!
I just finished the wings, stabs and everything that needed to be sheeted with balsa using the vacum bag. I used Gorilla Glue and it works fine, don't put to much of it because it expands a lot, spread the glue evenly on surface. 15 - 19 pounds will be OK! Do everything like sandwich - foam then balsa than your outer cores - align them, tape to prvent them from slide and put into the bag. If use Gorilla Glue you can get out your parts in a 3 hours. I didn't try ProBond but what I know is that it almost the same as Gorilla just drys longe and you need keep the parts in vacuum bag overnight. As for sealing the bag I use the old method I learn in Russia, if you use just regular plastic film (I do), to seal it quickly have the iron, set it to hi temp, cut the 1-1.5" paper stripes from news paper put them on the place to be sealed and iron them it takes a few minutes and you done. What these stripes doing is they protect melted plastic from stick to iron. When I do this I do it on MDF board.
If you need more details, feel free to call 5187561155 or email: [email protected]
Vadim

dreadnaut

My Feedback: (5)

A note on sealing the bag. I use the green bagging film from cstsales.com. I seal it by rolling up the edges and clipping it with clothes pins every 3 inches or so. No kidding, it works. The only tricky part is getting it to seal good around the vaccum line. The great thing is re-useability. I once skinned 12 2m pattern wing sets for a guy and used the same two bags for the whole job.

as722

My Feedback: (1)

Thank you guys.

Vadim. Did you finish the bottom of the fusealage yet? If not you might want to make a removable hatch like I did on mine. Check out "carden 260" under giant scale, I posted some pictures there.

crook

you can try to seal the bag hundreds of different ways, which maybe 1 or 2 of them actullly giving bag a good seal without making a mess(caulk or silicon sealents) Best thing it to find bagging tape, also called cromate., tacky tape or others. i think a company that makes it is actully called tacky tape...do a search of it. also with your new vacuum pump, you will get no pressure out of it...only vacuum which is Hg" (inches of mercury) sounds kinda dorky saying it..but you get used to it. and last is fitting for bag, you can get a vacuum fitting get a threaded pipe bout 3 to 4 in. long , tape on some breather material around the pipe and then hanging a few more in. off the pipe, the hangin part needs to come into contact with the other breather mater'l you have around part or/and around your bag.if you use a sealent tape, just put a piece around the pipe open side of your bag and tie in pipe piece to existing baggin tape.....also check for bridged areas of your bag or release films.you will not get good vaccuum in these areas and eill be more then likely filled with all resin.

funkydrummermike

Hi,

According to the video that George Spar put together, you only want to pull 6 inches of mercury. That's 6 on the vacuum gage. Pulling more than that will crush white foam and ruin your wing. I have seen him at the WRAM show and I have heard him say it time and time again. If it's white foam, you don't want to pull more than 6 inches.
If it's spider foam, you can pull up to 18 inches of mercury I think.
DOW Chemical rates their Square Fit foam at 15lbs per square inch before crushing. That is more than atmosphere.

You do need the breather cloth. It won't suck all of the air out without it. It is just felt I think.

Place the hose about 4 - 6 inches from the end. You need room to seal the bag and you don'e want it up against the wing.

You might want to pop a few bucks for George's video on vacuum bagging. It spells everything out.

Mike

Newc

Here's a good video to watch for free! Jim Young - the guy in the video - is very good at vacuum bagging and sheeting, and his projects result in very light and strong structures.

http://www.rcgroups.com/links/index.php?id=4901

dreadnaut

My Feedback: (5)

I never use breather on wings and I get 8 inches easily. Where I need a breather, like when laminating end grain balsa sandwich panels, I use Brawny paper towels. They work as well as felt, and cost a lot less.

WHANNAH

Want to try vacuum bagging for my winter project.... Giant scale (40%) wings etc. Anyone have recommendations for equipment needed.... bags, adhesive, vacuum pump etc.

hayman

Here is a "must have" for beginner vacuum baggers.

[link=http://home.paonline.com/hayman/video.htm]Click Here[/link]

Bill

Larry S

My Feedback: (6)

Simple question:
What is vacuum bagging?
Larry

Newc

If you take a look at the free video on the following link I think it will answer your question extremely well. Short answer is that it is a technique for sheeting foam with balsa to form a stronger and lighter structure than by other means.

http://www.rcgroups.com/links/index.php?id=4901

Larry S

My Feedback: (6)

JL,
many thanks for the comeback. I just watched the videos and must say learned something new. My last two projects were Jemco models, both with foam wings. Wish I new then what I know now, would have been easier to do but I will say, both planes did come out nice. What I did was about the same as the video as far as the epoxy goes but instead of bagging, I use 1/16 sheets of plywood to cover the wing and rubber banded and taped the sheets on. Then I used sand bags to lay over the whole assembly till the epoxy dried. I only did one surface at a time this way but it glued the wing sheeting down nice and smooth.
Larry
PS: On the video, he used a food bagger. By using one of those, how do know how much vacuum to use? Is there a way to regulate the vacuum on a food bagger?

Newc

Don't know what the vacuum is for the various food-saver type systems, but Jim has had very good luck using his wife's system! From my very limited knowledge of the system, the fact that there is a vacuum - at least enough to compress the plastic bag as is shown in the video - is more important than how much vacuum, at least up to a point. From the various reading that I have done, you can get too much vacuum - enough to crush the typical white foam that's used for wings.

I'd be most interested in other inputs on this.

Larry S

My Feedback: (6)

I went on line and checked the price for various food baggers and found they are priced anywhere from $50 on up to over $250 for some. The problem I found is that you are limited to 11 inch bags where if you purchase the basic vacuum system from APC www.acp-composites.com/acp-vbs.htm , you can get much larger bags and at a very affortable price. I guess it would depend on the size of the wing panels you plan on doing to which system to go with.
Larry

Newc

The other advantage I see of the vacuum systems versus the foodsavers - beyond the width of the bag - is the ability to control the amount of vacuum.