Shrinking Dacron over foam

[Martinup]

Thanks Scott: Neet looking plane

Martin

[IASCOTT]

Hi KC;

I was on the Owens Corning site researching this and for roof application they recomended using the therma pink product line. I read through the spces really quickly and menteioned that it can take temps up to 250 degress.

Anyway the videos I saw on Dacron suggest to get shrinking the temps are around 250 degress. To get adhesion to a metal frame they recommend I beleive 275 degrees to 350 degress.

The temperatures may have to be played with but the glue applied to metal is one application and the same glue put on polystyrene may not require such a high temp to get good adhesion.

From what Dan from, "Stewart Systems" mentioned to me that he thought this might be possible to do.

I've invited him to join us here and share his knowledge and skill with this product. Might save us all some trial and error.

Also search it on You tube to see a whole bunch of videos on Airplane Applications.



Martin

Martin

If you go through all the videos you will see that they shrink the fabric in stages of 250, 300, 350 degrees. Now a person could stop at 250 degrees as these little campers aren't exposed to the air flows an airplane is. They want the fabric pretty tight to maintain the shape of the airfoil of the wings. I don't think it would hurt to stop the shrink process sooner for a camper if you achieved a tight smooth cover at a lesser degree. When I was attaching the fabric to the airframe I was running a cooler iron and didn't have any bonding troubles. The true bonding is done when you apply the top coat and by wiping off the excess you are pushing clue down through the fabric to adhere to the first coat of glue.

Scott

[Martinup]

Scott: Question # 1 When you covered that plane did you use the glue on large flat surfaces or just wing parts? The reason I ask is if I wonder how everything will behave . . . a) I have my spars on One Foot Centres ( 1/2" Baltic Birch, " EDGE UP") , b) and then 1" wide by 1/4" thick cedar, Every 6" On Centre, dattoed into the spars ( 1" FACE UP, " and Flush To Top Of Spar ) Note: These 1" strips will run the legnth of the Trailer to make up a !2" by 6" grid over all the whole roof and underside of the ceiling. c) I will fill everything else in the remaining 12" by 6" grid will Polystyrene Insulation I am thinking about expansion and contraction rates of A) different materials B) the movement of the trailer C) rapid temperature change . . . say driving in a desert and then driving up to a cold mountain top. Question # 2 Do you think it would be a good idea to use Dacron for the CONCAVE ceiling of my trailer? I am very keen on your insight as you have worked with this material and I have zero experience with it? Thanks, Martin

[IASCOTT]

Martin

The Cub is totally covered in fabric. So I was working with flat areas and round tubes. If I were to cover your trailer I would start by covering the sides first. I would make a glue line around the perimeter of the plywood sides of 2 inches. On the bottom I would wrap the fabric under and clue it to the bottom of the floor. I would also glue and wrap the fabric on the inside edges of all door and window openings. Once the fabric is all glued on and dry I would the shrink it to 250 degrees starting in the middle and working my way out to the edges. Now to the roof I'm not sure how wide you trailer is but my guess would be that the fabric isn't going to be wide enough to drape over the whole roof. So I would cover this half at a time I would start by gluing the fabric to the center stringer. Then I would glue and over lap the side fabric the 2 inches. This is going to be the tricky part I would leave the fabric wider than needed. So I can pull or shrink the fabric a little bit at a time to get it to lay nice. Then I would mark it cut it and finish gluing it down. Once the glue has dried and just like the side walls I would shrink this the same way. Then I would do the other half of the roof. Then I would continue shrinking the fabric through the rest of the process 300 then 350 degrees. Once that was done I would glue a 3 inch wide pinked edge tape where the fabric was glued down over the center of the roof. I would also reinforce all the areas where it was wrapped around a corner. Like the door and window openings and around the bottom of the trailer. For the doors and windows I would cut my reinforcing patch from a sheet of fabric. Oh I would make all my cuts with a pair of pinking shears. It just makes a nicer edge for looks plus it help with the unraveling of the fabric.

As far as temperature concerns. This isn't going to be an issue. Once the fabric is shrink temperature changes has little effect on the fabric. Plus what you decide to use to fill the weave is going to some what bond with what ever is underneath it. The fabric kinda acts like a stretched rubber band.

The concave parts inside is going to be the hardest part. Shrinking of any fabric is going to want to pull away from the concave areas. So I think shrinking of any kind is going to be out of the question. What I would do is have a bunch of pieces sheared out of roof flashing material so the edges would land in the center of each ceiling joist. I would then form the aluminum to conform to each concave. I would glue what ever I wanted for a ceiling fabric to these pieces. I would install them and cover the joints with a contrasting trim piece. Maybe a interior guy who works on old cars could give you an idea how the headliners where installed in old cars. This might be an option.

Scott

[Martinup]

Thanks much Scott:

I will post more pictures of the roof and ceiling preperation and I will remeber this and perhaps we can go over it again then.

As with everything the substrate reflects throught the finsh and critical.

Martin

[Corwin C]

It has been many years, but back in one of my airframe classes, we attached dacron to an undercambered wing surface using rib lacing which was covered with pinked surface tape. I vaguely remember about 12" needles and special knots, but we were able to attach the fabric to a concave surface.

[IASCOTT]

Sorry all for taking so long for doing my little test panel but here's what I have found out.

First I started out with all the materials I needed. Which was a teardrop shape rough handed out and the hard corners rounded over with some sandpaper.
The Stewart glue water based very little smell. A cheap paint brush and the dacron fabric cut to shape. I was using the 2.7 oz fabric which I think if I was doing this for myself I use a little heavier fabric. Stits has a fabric that is 3.4 oz that is 72 inches wide I think I would use.


First I started by applying the glue to the edge of the foam


Then after letting the glue dry to the touch I started to apply the fabric.


I started to use the iron set at 250 degrees to shrink the fabric around the curved parts. This is the nice thing about dacron no need for darts to get the fabric to lay flat around a curved surface. The excess fabric just shrinks and conforms to the curve.



I had a little trouble getting the fabric to shrink enough around the tight radius at 250 degrees so I bumped it up to the 350 max and found out that if I let the iron set to long in one spot the foam would start to melt.

The next step should of been painting glue on where I had used heat to stick the fabric to the glued area. The process is to apply the glue over the top and then wiping off the excess with lint free paper towels. I used what Stewart recommend Scott lint free blue shop towels .

I then proceeded to shrink the flat areas at the 350 degree setting always keeping the iron moving I was able to shrink the field without any troubles.


With a little caution with the iron this will work on a foamie. And for covering plywood and protecting it from the elements this would be great way to go for a painted teardrop. With the width being 72 inches there would be no need for a seam on the roof. Pinking shears soften the looks of the seams and well give it that airplane look. Plus it help with the fraying of the fabric and would even be good to use on canvas.

Scott

[eaglesdare]

i think that is pretty cool scott!