SeamusG

Ifind that as Iam tacking film covering I put tension on the film by holding it with my thumb and fore finger knuckle. While holding it Irotate my wrist away from the film in the direction that removes wrinkles. I find that pulling it tighter is better as it doesn't rely solely on the film's ability to shrink to eliminate waves and rolling-type wrinkles. That part of it works as advertised. But, Ihave a habit of putting my knuckles or extended little finger on the backside of the piece to provide leverage. As it turns out my knuckles are harder than the balsa. Result? Dents. This is not a problem when the piece has some structure - only when the piece is a chunk of balsa.

Any constructive suggestions as how to avoid the dents?

Oh, of course, the pieces are very narrow and difficult to hold steady.

BTW - buying ARFs is NOTa constructive suggestion!

Tall Paul

Take a sanding belt to your knuckles!
Or, just be more careful.

Minnreefer

You are much more experienced then I am, so take this with a bag of salt )))))))) could you use a scrape piece of balsa to help hold on the bottom side? or better yet, just keep trying and I will take all of the dented ones off your hand for just a small fee >

Gray Beard

My Feedback: (-1)

I sometimes use a couple of towels on top of my building board and try to cover on that instead of my lap, doesn't help though, I have been doing it on my lap for way too many years. I don't dent wood very often but I have been known to break out ribs.

Live Wire

Latex gloves you do not have to grip so hard

SeamusG

Hey LW - the way I flail around with my hot irons I'll melt the latex to the back of my hand. [:@] Yea, I'm a bit tough on that old Ultracote.

I'm a lap guy myself. I try to leverage the piece between my legs (wearing shorts not advised).

I'm leaning towards Minnreefer's idea. Maybe a cotton towel.

Ya think ya have a handle on something - then, poof - you don't.

Thx all ...

Live Wire

You better watch that hot iron where your working Sound like you are like me don't like to wast covering.
Larry k

Edwin

My Feedback: (2)

I tried to think of a way to describe it then gave up and took a picture, worth all those words. Basically two stands with foam and rubber bands to hold it in place while I cover. Works for fuses too.
Edwin

Lnewqban

Tips copied from http://www.gmaa.org.au/tips.html

"If you ding your balsa while building, place a few drops of water on the dent and steam out with a covering iron. If the piece is covered (Hanger Rash) use a small diabetic needle to inject a few drops of water under the covering and they use your heating iron. The dent will come right out."

"Covering Table

Another use for hollow core doors. With the home renovation craze, hollow core doors can be found for free. If the door isn’t perfectly straight though, you could end up with built in warps in your bird. Don’t throw it out though. Cover the door with a couple of old blankets (a few dollars form garage sale) and you now have a great covering table that won’t scratch or dent your plane as easy. Fold the blanket over the sides and under the tables edge. Secure it with upholstery tacks or nails."

airbusdrvr

Please don't let this response start a Monokote/Ultracote war. Just sharing my thought on the subject that might help in the future. If you are using Monocote, you may find Ultrcote is much easier to work with.

Tall Paul

Friends don't let friends use the Othercote!

JohnBuckner

My Feedback: (1)

Probably the most common mistake of all, making the sections and the overhang to small without sufficient material to pull from.

With most new folks first attempts at covering its uncanny you can tell which ones tried to save to much money by cutting the film without enough overhang.

Just an opinion from a contented long time Monocoat user

John

SeamusG

The piece that I'm struggling with is an aileron that's 30" long and 3/4" wide. I tried using something on the back - no room because the film "wraps" itself around the back of the aileron when tacking things down. The only technique that I could come up with was to use finger-tip only contact with the leading and trailing edges while pulling across that huge 3/4" wide stick. No dents but there's a lot of slack (as compared to the other approach) that needs to be taken up. Bottom line - new "finger tip only" technique worked. Just need to be aware of density of the stock being covered. Soft balsa - beware!

On using water to "pull dents" has a downside. If there's only one or two dents, the drops of water will be isolated. If, on the other hand, there's a bunch of dents separated by no more than an inch, those drops now saturate the entire side of the piece. What happens next? A warp. Time to "de-warp" and aileron.

Next time I will be very aware of control surface density relative to the size of the surface - thinking about covering with film. Or, maybe it's time to try a paint & film combination ...

JB- the piece of film had plenty of grab surface - limited width was the wood piece itself.

Lnewqban

If I remember correctly, MinnFlyer has explained several times a CA tack technique that he uses for many construction tasks, including covering, for parts hard to hold in place.

I wonder if it is possible to extend the film over a flat surface, tacking the covering and the aileron, and placing the aileron on top of the cover before applying the heat.[sm=confused.gif]

Check this post from Mike:

http://www.rcuniverse.com/forum/fb.asp?m=317725

SeamusG

Lnewqban - you amaze me! You're access to such a broad range of reference materials just blows me away.

I read the post. Not sure that it's applicable.

Here's the challenge - see pic

1: press and tack the entire end to the piece (a whoping 3/4")
2: pull the film tight and then tack the entire end
3: press and tack a center point on the LE
4: pull then tack the TE

repeat 3 &4 until entire LE&TE are sealed (except for a small section on the TEto allow hot air to escape during shrinking process).

It's number 4 that's the tough bit. As you pull the film against tack point 3, you also want to wrap the film "down over the trailing edge"to create a tight corner over the TE. I was putting a knuckle against the bottom and rotating the film "down and away" from the surface being covered.

Again, this piece isn't much wider than my thumb. Doesn't provide much surface area to "shrink away" any slack so you want it nice-n-tight before hitting it with a hot iron (or heat gun).

Lnewqban

Nothing amazing.

I just remembered a technique of my times of free flight with which very delicate airframes can be covered with Mylar: extend the film first and place the frame over.

You have much more practical experience than I; maybe Mike or somebody else will help you here soon.

What if you tack the whole lenght of TE first and continue going over the LE (stronger to hold your hand), working from the center to the ends?
(I feel weird advising my teacher[sm=bananahead.gif])

SeamusG

I tried your suggestion before I realized that I was dentin' the wood. I started with the LE. That way I could lay down a nice straight cut at exactly the needed location - to save a treacherous cut of film-over-film. I wasn't happy with the slop left in the center so I went back to the way I pictured it.

cloudancer03

My Feedback: (22)

the best way is......STOP DOING IT!!!!!

SeamusG

Yea, yea - I think Iheard that one ...

Me: "Doctor, doctor - it hurts when Ido this ...."

Doctor:"Well, then don't do THATanymore ..."

HighPlains

My Feedback: (1)

I cover a strip aileron with a single piece of covering to do both sides. Start by tacking down the covering at the hinge line.

SeamusG

HP - I thought about that. Makes for a nice clean leading edge. The thing that stopped me was shrinking the film over the tips. Not comfortable with shrinking the bottom to top with the top film in the way. Maybe I'll give it a shot if I have enough covering to make a mistake.

saintcreed

My Feedback: (205)

On narrow ailerons and other small solid surfaces. The way I approach this problem is this way...cut the covering so that you have suffecent overhang on all sides that will meet YOUR needs to cover the edges plus some...like mentioned earlier I take a large beach towel, an old one so I don't get it from the WAR DEPARTMENT..Folded double, I lay it on my building table, lay the covering face down (adhesive side up) lay the piece being covered on top of it, get it lined up where you want it..carefully rotate it 180 degrees with the covering now on top of the piece being covered....start in the middle and work towards the ends and sides...all done with an iron with a sock covering the iron...no dents or extra covering that one cannot shrink enough to get wrinkles out, because you are shrinking it and adhering it to the word surface all at one time....works on all flat solid surfaces for me..The only time I tack and seal the edges and then use a heat gun is on open surfaces or very large sheeted wings, on which I also incorporate the iron..This is what I've found works for me...but might not work for someone else... everyone is different and do things different ways and still get the same results...

For the third hand one always seem to need to hold these items being covered in place. I use plastic freezer bags (why freezer bags,,simple they are made with heavier plastic) filled with play sand or like here in Florida just step outside and get a handful of sand..fill them as full as one sees fit for the job being done, bleed the air out, seal and then place on the piece being covered and the bag confoms to the contour of the piece...works great when covering a one piece wing, I use a gallon size bag for that job..these also come in handy when working on the fuselauge. The best thing of all they don't mark up the covering or put dents in the wood...

Just my 2 cents worth of ideas..

MinnFlyer

My Feedback: (4)

I think LNEWQUBAN is mis-quoting me. My CA technique is for old covering where a corner has lifted and won't re-stick.

As far as doing a strip aileron I think your first problem is that you're pulling the covering too tight. This is the way I do it:

Tack one side well (let's say the left side). Now, snug the covering - don't pull it TIGHT, just snug and then tack the right side LIGHTLY. Don't tack the center at all.

Place the aileron flat on your workbench. Place the iron flat against the left side of the aileron, and with a single motion, slowly move the iron all the way to the right, BUT, not all the way! By the time you have reached the right side, the covering will probably have developed a wrinkle - that is, the remaining covering (between the iron and the lighty-tacked right side) will have bowed up (I'd draw a pic, but I'm away from my regular computer).

So now, you lift the lightly-tacked right side to un-stick it and finish ironing down that last inch.

Now, for the reason the covering buckled at the end...

You must remember that everything expands when it is heated. This is basic science that you were taught back in grade school. Covering has a unique property that when it is heated TO A CERTAIN TEMPERATURE, it will shrink.

HOWEVER... As the covering directly under the iron is being heated to its shrinking temperature, the covering just forward of the iron is being heated also, but not enough to shrink - only enough to expand. This is why when you place a piece of covering on a flat surface and tack the center with your iron, wrinkles will develope around the outer edges of the iron - that area has expanded.

Another way you could do that aileron is to tack both ends (again, pulling the covering snug, not tight) then tack the edges until the covering is sealed on all edges, Then shrink it all with a heat gun before giving it a final sweep with the iron.

SeamusG

Yea, MinnFlyer, I do pull the covering pretty tight. I am now the proud owner of an addition roll of silver - so - it's time for some trial-n-error ...

Practice is just practice, but perfect practice makes for perfection (or something like that).

I stole some gawd awful guest towels and some gallon freezer bags filled with sand (Maine has nice sandy beaches, right?).

Thanks for the input!

SeamusG

saintcreed & MinnFlyer - you guys are like Gods amongst us mere mortals!!!

Securing the "thing" being covered freeing up 2 hands for covering is so valuable! Saintcreed, I used your approach of towels on the table (pink, white and gray guest towels - hehehe - no accounting for taste) and 3 ziplock gallon freezer bags full of coarse sand (2 on each side of fuse for lateral stability and 1 on top with very dense packing bubble sheeting protecting the fuse). Yea, had to rotate the fuse a bunch of times but, man, it was secure. THX.

MinnFlyer - I was definitely pulling too hard. With the thing being covered secured, it's so much easier to shape and position the piece of film before tacking to the wood. Much less effort is needed during tacking than what I was doing. I'm guessing that while I was supporting the thing being covered with hands, knees and legs, I didn't have much "fine" control left - resulting in "too much" effort.

Kinda cool when you take that next step ...

pic 1 - das setup
pic 2 - der tail feathers (in silver of course)