Props4ever

Hi,

I want to know what is the best glue to use for Sheeting balsa skins to the foam cores, both wings and fuselage?, i will starting to sheet my S Connie but before i do that i want to know best glue that won't come apart in few years time. I have been told to use white glue and hold sheeting with rubber bands till its completely dry for the fuselage, but i want something faster curing then white glue, what about using 3M 77 black spray can glue for this purpose. I really don't want to use lapage's contact cement!, i don't trust this cement for sheeting purpose.


Regards,
Sammy

ptxman

My Feedback: (2)

White glue is a bad idea. Rubber bands is even a worse idea. Use a good grade of laminating epoxy, West systems if you must. Spread it thinly & evenly on the balsa skin. The cores should be sanded smooth & vacuumed dust free. Use the female shucks & weights like patio blocks to press the skin to the core with plastic or wax paper in between the skin & shuck. Some guys are using urethane (foaming action) glue too, personally I favour epoxy. Then there is vacuum bagging, but this method will get the jobdone for 80% of all applications.

Props4ever

What is Shucks?, this is the first time i have read this term. To be honest i not in favor of using white glue for this purpose either. As for Lamination epoxy (west systems) how long does it takes to fully cure? and same question for Urethane?....

http://www.rccanada.ca/bb/download.php?id=26397

My problem is that inner wing of this model is already glued togather and i have glued spars also, this piece is 60" in length with flat center wing and both inner wings glued to it at 6.5 degrees, so how could i sheet this center wing?....specially applying the weights to high angled wing core won't be easy task....

You can see how inner and center wings are glued togather, center wing is under fuselage and inner wings is where you see engine necelles cut outs are, this is one whole assenbly with 6.5 degress of diehedrial on both sides.....

ptxman

My Feedback: (2)

The shuck just means the outer 'remainder' portion left over from the rectangular foam block after you (typically) hot wire the cores. Hmmm... probably the part you threw away! <g>. The reason why its good to have is it is a perfect match to the wing core shape so that when you apply weight it presss teh skin quite equally liek a form.

If you dont have them, then the next best method is vacuum bagging the skins on. But even that method still uses the shucks to ensure warp free lamination as the bag is great for applying pressure but you still want to be sure you are not building ina warp.

If you dont have the vac pump & goodies Im guessing its make-do with what you have. Now I see your original problem. I hate to say it but maybe soem form of spray adhesive will get you through it. Just recognize its not an optimal solution at all:
- the adhesive itself is much weaker than epoxy
- the act of bonding & pressing the stronger skins to teh more flexible core can often build in unwanted warps. Once its down, its too late.
- spray adhesives like this have low tolerance to heat, you might see delamination on a finished model from the sun's temp or just fromflight loads

Anyway, epoxies like West Systems typicaly have overnight cure times althouh the working time (pot life) can be anywhere from 15 min to 1 hr depending on teh hardener you purchase. On foam core laminations I recommend a slower cure like 1 hr. It gives lots of working time to adjust, align, press etc

Urethane glues are also an overnight cure thing. I think they probably have in teh order of 30 min working time. Some guys lightly water mist the skin to promote foaming action. As a bonding adhesive it seems ok, I just prefer epoxy.

Your center sheeting issue can probably best be handled by sheeting that panel seperately from teh others. I guess make a scarp templat efrom paper & superimpose that on the sheet stock after its been edge joined.

I hate to tell you this but in all honesty you have kind of painted yourself into a corner compare dto conventional modelling methods. There are some solutions but they involve more work. If the cores are sufficiently thick that they dont get distorted by teh sheeting procedure, you should be OK with the aforementioned caveats. We used to do it this way in the bad old days. A light epoxyglass finish coat might help with the strength (say 0.7 - 1 oz/yd glass cloth) but liek any strcture, its only as good as teh foundation bond.

Props4ever

Ok i see what you mean by Shuck, i might still have those in some boxes but i am not 100% sure at this time.

The thing is once i sheet the cores, then i will apply 3-4 oz fiberglass cloth on the whole structure, i may also evporate certain area's of the cores in fuselage by using gasoline. A fellow club member mentioned to me about vacuume bagging the whole aircraft, he does have vacuume pumps for this purpose, I think i will go with 3M Spray adhisive to attach sheeting to the wing cores and then vacumme bag them, i am not sure how well the results will be, mind you i have 3 "I" beam type plywood and balsa spars in the center section. I don't think with 3 spars there will be big chances of any warpage!.....

As for fuselage your methord is preety good by using west systems epoxy, i guess 15 minutes would be sufficent as i will lay 3"-2" x 36" strips to sheet the whole fuselage. I do have some shucks for the fuselage though. I wish i could lay full 3''-4" x 36 sheets on the fuse but Connie's have high compound curves to its fuselage.

mmattockx

This sounds like disaster in the making. The 3M-77 is CONTACT cement, which means that it sticks permanently at first contact. If you miss, too bad, because it's there forever. And laminating epoxy (what you want, it is the thinnest consistency for a uniform thin layer on your sheeting) cures in hours, not minutes. Usually, when sheeting wings they are left overnight or longer to ensure a complete cure. You do not want to rush this step or all of your work to date will be for naught. If you are sheeting the entire fuse, you will edge glue the sheets together to form large enough pieces to sheet entire sections at a time. Laying in individual sheets will leave gaps, nasty edges and a heavy, weak completed structure.

To see an excellent example of how to sheet wings, take a look at Terry Brox's site:

http://www.mackrc.net/patternwings2/index.htm

I do not mean to sound critical or like an ass, but you sound like you have never sheeted a foam structure before and what you are suggesting is not going to produce the results you want.


Mark

Props4ever

Hi Mark,

Yes you are right this will be my first time sheeting foam cores, i don't want anything to go wrong with this project, now i understand that 3M-77 is not the way to go, i am sure being first time i will make mistakes here and there initially, but through the whole process and by the end i should be able to do sheeting with my eyes closed. You are not being Ass here but guiding me through right process. I will try to find the shucks for the wings, this way laminating epoxy process could be done nicely and accurately.

I will also check out Terry Brox's website and go from there.



Regards,

mmattockx

Just wondering, what's your hurry with the sheeting? You were looking for a contact adhesive and then the shortest cure time on the epoxy. Is there a constraint on the sheeting that doesn't allow you to let it sit overnight to cure? I can testify from experience that time is your friend here. It takes a while to spread epoxy or PU thinly and evenly over the sheeting, get it all lined up and taped in place, then get the shuck/skin/core/skin/shuck sandwich into a vacuum bag and then get your vacuum lines hooked up and running, or your top board in place (without disturbing the sandwich alignment) and the weights evenly placed and balanced. Then you need to check alignment again and if it is off, you need to be able to unload things and adjust as required. I would say the minimum reasonable pot life for the epoxy would be 1 hour to do a 500sqin wing panel. More for your first time, as you will have something not be quite right the first time you run through it all with the clock ticking...


Mark

Props4ever

I was thinking to do wings fast and get over and done with as i still have to do stab, fuselage and outer wings with tip tanks, thats why i was in bit of rush there, as it stands this job is not a rush job and if i rushed i could easily distroy all the work put into it so far. Ok i'll ask my frient to lend me his Vacuum pump and now try to find bag big enough to secure whole center wing assembly in it. I will go west system epoxy way to do this sheeting. Thanks guys for your help, i will ask more questions as i go along with sheeting job...

TLH101

My Feedback: (90)

Jack Devine models are made from foam, and sheeted, like you are doing your Connie. Here is a link to info he puts out, on how to do it.
http://www.jackdevinemodels.com/foam...technology.htm
Works really well, I have built his models.

Props4ever

Hi Terry,

I just checked Jack devine's webpage and its excatly what i was looking for, his foam bulding methord is very simple yet to the point.
One thing that i coulden't understand is a need of capping round sides of the wing cores with balsa stips and then tape em!, other then that every thing is self expalinatory to the fullest.

He uses Sig-bond to attach sheets edge to edge and then to apply sheets to the cores, he used his Foam bond cement. I really liked the idea of using foam-bond cement for my sheeting, this way if i can't find my Shucks for the wing cores, i don't have to worry about that too much, i can still sheet my cores w/o shucks...

Thanks for the link, i have booked marked it also.

TLH101

My Feedback: (90)

The caps around the edges create awood surface to shape, instead of trying to curve the sheetinf around a tight radius of the edge. You can probably find a good bit more info in the Jack Devine building forums at rcscalebuilder.com.

Props4ever

Ok now there something i should have mentioned before but diden't, foolish me![X(], I have basically covered whole fuselage with Lepage's light weight speckling compound to hide all imprefections on the foam cores, now i am wondering if Foam bonding cement will actually work on this compound or not!, its smooth porous surface now!......

Ok i'll check rcscalebuilders.com for more info....

charlieoneseven

Give Shorgum a try, it will go over spackle, foam, wood and plastic with good adhesion. brush the glue on both parts, let it dry clear and press in place. No waiting, no drips to clean off like epoxy does and it sticks way better than the 3M that is suposed to be not compatable with EPS. I use a sheet of wax paper to keep the skin from sticking to the core until I have it in the right spot tack one edge together and lift to remove the wax paper and the sheeting will go down easily. you can wet the wood if the curl is too much it won't affect the glue at all.

Props4ever

Charlie,

What about PU glues like Gorilla glue!, i really don't want to use any contect cement type of glue in the begining, i am sure there will be mistakes made initially but after few attempts i can certainly go to any of contact cements.

mmattockx

Careful with the PU glues for this, they expand as they cure and will shift sheeting around, push things out of alignment, etc. They work well if you can clamp and hold the pieces in place while the glue cures, but will not work well with little support. OMP use sheeted foam for their profile fuselages and they comment that the PU glues can lift and move well over 100lb on a medium sized fuse if not used with care. If you want to try PU, I use Elmer's Pro Bond, it is much cheaper than Gorilla glue and performs the same. It's worth picking up a bottle just to have around and to test out on some scraps, the stuff is amazing for some uses.


Mark

Wayne Miller

Hi Sammy,

Although I haven't tried it yet, Ron Forester has advised me that a good method of sheeting balsa to foam is using a household iron and white glue. The process is to put white glue on the foam, and on the contact side of the balsa. When the glue dries, you then "iron" the balsa to the foam. Apparently it sticks immediately.

You may want to try this on a scrap piece of balsa and foam.

Has anyone else tried this?

Hope this helps.

Fly4Fun,

Wayne Miller

Props4ever

Hello Wayne,

Nice to hear from you, i like your suggestion and methord too but hoestly now i am confused!, there are so many types of glues to use, i am not sure what is the best way go at this point. I am going to ask Peter EICAS also, i knew he did sheeting on his A321 and said somethingon using on similar lines as you did. If i use this methord i am wondering if i can also use Monokote iron to do this job and what kind of heat should be there that foam under 1-16th balsa dose not melt.

Wayne Miller

Hi Sammy,

I've PM'd you Ron's email address, you may want to contact him regarding the method. Hope this helps.

Fly4Fun,

Wayne

Props4ever

Hi Wayne,

I have sent email to Ron and have Pmed EICAS, so let see what they have to suggest. I am confused as what route to take and what glue to use, so many ways and glues to this job, its just confusing.....hard to decide what my best option here.

TAZ

Hi for to cents worth i use COPYDEX (available in the UK) it is a latex glue that you use for crafts and hobbies but it is great at sticking the skins down (as long as you have the shuks).

Props4ever

Hi Guys,

After reading and talking to many guys about this subject i have decided not to do sheeting anymore, instead i will be taking different route. I will be glassing the whole foam airframe with 4-6oz cloth and West Systems leminating epoxy, i know its messy process but results are rewarding. I would like to thank every one who suggested me there ideas and knowledge, i highly appreciated it and your time too but, sheeting would have been too much for me at this time, i just want to get over this step and move on with the build....


Regards,
Sammy

KI8FR

I would like to ask on the glue. If I am going to put dope on it a fabric can I just use a good wood glue...

simhatus

Hi

I to have always used copydex for sheeting foam.

With some food coloring added so that on white foam you can tell where you have already put it.

Simon

KI8FR

what is copydex