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Post by sf2 on Nov 14, 2007 19:48:47 GMT 10
Having built several foamies and in the middle of one now, I,ve always ended up with the same problem. Once taped,regardless of which method used,45 degree bias, long strips butted together,if there is ever an edge(predominatly with 45 bias), it shows through the covering, how do you stop the tape underneath showing through the covering ?? Also I used a fibre tape with a less than smooth surface, which also showed through, I did try sanding it, but the ensuing mess required a retape.Maybe I should use another tape, any Ideas.
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Post by ezza on Nov 14, 2007 20:00:49 GMT 10
Having built several foamies and in the middle of one now, I,ve always ended up with the same problem. Once taped,regardless of which method used,45 degree bias, long strips butted together,if there is ever an edge(predominatly with 45 bias), it shows through the covering, how do you stop the tape underneath showing through the covering ?? Also I used a fibre tape with a less than smooth surface, which also showed through, I did try sanding it, but the ensuing mess required a retape.Maybe I should use another tape, any Ideas. I think Sean should answer this one. Sean, how do you get that perfect finish? I apply the tape edge to edge with no overlaps. I find I have to go very slowly or I get little overlaps or gaps, that will show up through the covering. If there are any gaps I'll use some light weight filler. I think slow and patient is the answer but I usually loose patience!
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Post by sean on Nov 14, 2007 20:50:50 GMT 10
sf2, what are you using as the final covering, iron on film or tape? I've only done one tape job and the strapping tape showed through more than with iron on. With iron on, use one of the thicker films, Profilm is the best for foamies I reckon, Solarfilm is not good at all, very hard to get good results with and doesn't stick well, not worth the saving IMO. Monokote is easier to buy than Profilm in Bris these days but from what I understand (I haven't used it on a foamie) it needs a high temp that verges on melting EPP. As far as strapping tape goes I really like the uni-directional 75mm wide stuff you get in Windrider Bee and Bat kits! It looks cheap but gives smooth strong results under covering, and being wide it's easier and quicker to apply. I find bi-directional tape tends to show through the film a lot, uni-di gives a much better finish and similar strength IMO. If you don't have the Windrider stuff the 50mm wide uni-di tape you get from a packaging store also gives good results. I don't like the 25mm 3M tape you get frm Bunnings - being so narrow it takes ages to apply and more joins means the finish doesn't look as good. Ezza, my covering technique is as follows: For a really nice finish, first thing I do is spackle the EPP all over and sand most of it back so it only fills the voids - this can make the covering not stick well so you need to apply either goop (gives the best results but adds some weight and is unpleasant to use) or a liberal coat of 3M77. If you use goop the covering will stick like nothing else, it's so good if you ever have to remove the first layer of tape it will take chunks of foam with it! Now lay down your strapping tape - I use butt joins to avoid ridges. Personally I find it's not vitally important for the tape to butt perfectly up against the next piece, I find iron-on film will hide these gaps quite nicely though the less of a gap the better. If you overlap the tape you will get a ridge that can be seen very clearly underneath the covering. Once the strapping tape's all down I iron it. You need to find just the right temp so the tape doesn't melt or shrink a lot - you just want the tape to tighten a touch and remove the slightly wrinkly look it has when you first put it down. I have found this to be a very important step for getting a smooth finish, and it has the benefit of improving the adhesion between the strapping tape and 3m77/goop underneath. Then I lightly sand with say 150grit and a block - by using a block you take off the high spots smoothing the surface a little more. Don't go right through the tape! Just remove the shine from the tape. Now repeat this whole taping procedure for the other side of your wing. If you're using tape rather than iron-on film for the final covering stop reading here! Once all the strapping tape's down, ironed and sanded, spray 3M77 again and leave it for 15mins or so (until it goes tacky) before applying your film. With iron on films the trick is to take your time and try not to rush, do your best to enjoy yourself! . With Profilm I cut the piece out maybe 2cm larger than the wing all the way around, then position and smooth it out using the tackiness of the 77 to keep it in place. Then set your iron to the temp where it activates the film's adhesive but doesn't shrink it, or shrinks it very little. Temperature is very important to getting a good finish. Start in the middle and work your way out using a circular motion. The trick is to get the whole film stuck down evenly with no bumps or wrinkles but only very slightly shrunk. Increase the temp a bit to stick down all the edges. To get the film to shrink around compound curves (tips etc) increase the temp to almost the hottest that the film can take. You find this by placing a scrap of film on your iron - it will start to wrinkle as soon as it touches the iron. Pull the film around the corners as you shrink. Once you've done one side of your wing, do the other side before doing the final shrinking! Profilm shrinks a lot so if you shrink the film on one side you can distort your wing. Once both sides are stuck down nice and smoothly and the edges are all stuck down it's time to do the final shrinking. The smoother the finish is at this stage the better the final results will be - if you can avoid it try not to use the final shrinking step to hide severe wrinkles, do your best to get the film stuck down smoothly before the final shrinking! You can usually shrink out severe wrinkles from unevenly applied film but they tend to come back later, either soon after you finish the wing or later in hot sun. Set the iron about half way between the point where it shrinks the film slightly (the temp you used to stick the film down) and the max temp the film will take (the temp you used to shrink the film around compound curves). Run the iron lightly across the film, not stopping in one place too long, working the top and bottom of your wing. You want the film to shrink slowly and evenly. You can use a higher temp to remove stubborn wrinkles but don't go too high, it can actually slacken the film and once that happens it won't shrink again! If you take your time with the above method you can get very good results that are also very crash resistant. If any wrinkles develop after a crash they can usually be ironed out by setting your iron to a high temp. Sean.
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Post by thevon on Nov 14, 2007 21:17:20 GMT 10
I've been wanting to ask Sean his 'secret' to such sleek covering but now that I've heard it I'm a little disappointed because it's exactly the same as what I do! No, in fact there are a few difs: 1) I mix some PU with the spackle which makes it much more plasticised and it resists powdering up and you can later rip the tape off and the surface stays good. 2) I've never been into butt-joining tape. I only use bi-di tape but I tend to use an "A" pattern repeated identically top and bottom, with spacing getting wider and tape getting narrower towards the wingtips. As a result you can see the tape thru the film but so far I don't really care - I think 100% tape covering is excessive, particularly when using a tough heat film too. 4) So far I've used Monokote and I'm keen to switch to Profilm when I've used the excessive stocks I got! I think it tends to show the imperfections more. I covered one side of the Scorpian with Profilm and I think it has a "glassier" look, but you can still see the tape a bit. In future I may be able to smooth it with more sanding. I've never sanded the tape much - just a light rub to remove the non-stick coating, so the next layer sticks to it well.
I think a lot of it's patience (which I don't have). Sean takes great care to get everything very smooth. His fins look like works of art too, whereas mine look like bits of a bark slab hut, covered with Mono. But since I'm probably going to prang them up soon I can't get too worried about it ...
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Post by sean on Nov 14, 2007 21:27:25 GMT 10
Andrew, I'm keen to try the PU and spackle mix on a future build, can it be easily sanded to a really smooth finish? The nice thing about goop is it toughens up spackle a lot, so much so that I haven't felt tempted to try the PU/spackle mix in the past.
If there are any secrets to a good covering job I suspect patience and practice are the main ones, and using Profilm is the other! ;D Also temperature control seems pretty important, use the right temps at the right time.
Sanding the strapping tape helps smoothness only a little - the clear tape above the fibreglass strands is very thin so big imperfections cannot be removed by doing this.
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Post by jase on Nov 14, 2007 21:59:56 GMT 10
sean, my electron that i just built i used andrews PU and spackle mixture. your right when you say it does take practice. but patience is something you can't wait for.
it dries extremely quickly... well to the point where it becomes unworkable. i found that with a relative glob size of spackle you can be quite generous with the PU glue. i don't think i used enough, but the extra PU i think gives you a little more time to work with, if only 1 or 2 mins extra. this is why is say you can't be patient.
this stuff applies on very thickly so be very careful how u go about applying this... obviously you have to spatula this stuff on, but do it quickly and smoothly...
it is very easy to sand back. i used 80 grit glass sandpaper (on special at Big W) to sand down the really big chunks and 95% of the entire spackle covered wing, and finished it off with 160grit sandpaper to smooth it out a bit.
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Post by sf2 on Nov 15, 2007 9:10:48 GMT 10
Thanks Andrew and Sean for your input, been using profilm, some from OZ and some from states,will try your finishing touches.
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Post by skyboyken on Dec 4, 2007 20:58:31 GMT 10
Sorry for the dumb question;
where can I buy Profilm around Brisvegas? I also need a teflon iron, any ideas?
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Post by callun on Dec 4, 2007 22:08:20 GMT 10
Try Hobbyone at Tarigindi (or close to it) or Hobbyrama at Stafford - if they don't stock it they'd probably get it in for ya
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Post by thevon on Dec 5, 2007 7:41:28 GMT 10
Ken, I just got some Profilm from Budget Hobbies at Capalaba. Great service - rang one day, arrived in the mail the next day. They had quite a lot of colours. But also I know that Nitrodude online has it too, a bit cheaper but not so local.
Hobbyrama only has a few very old rolls, no nice colours. They only currently stock Monokote/ Solarfilm. They have some rolls of white labelled as Profilm but beware, it's a cloth stuff like Solartex.
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Post by thevon on Dec 5, 2007 15:51:15 GMT 10
All I can say is I wish I'd got onto using Goop and Profilm earlier.
Using my new Marine Goop, I gooped my Bat after spackling, before putting the tape on. It's dead set easy to do. I thinned it with Xylene and used a brush. I was surprised to find it dries enough to handle within maybe 10 minutes. I let it dry overnight, then this morning I taped it with a criss-cross braced pattern of strapping tape and it really stuck well to the Goop.
Then I put another coat of Goop on and hung it up to dry. Meanwhile I'd been wondering if I should spray Super 77 over the Goop. I put a post on RCG to ask, and a couple of guys said that the Profilm will stick excellently to the Goop without 77. (However I had read another thread where a guy's Profilm didn't stick well to Goop that had only dried for 20min or so). Sean thought the 77 was a good idea and I like to take his advice! But I decided to try without.
The Goop had only been drying for an hour or so. I opened my new rolls of Profilm and started with a fairly low temp. Immediately you could tell it stuck really well! You bewdy! I won't elaborate more but I can say with very strong conviction ...
1) Profilm DOES stick INCREDIBLY WELL to Goop!
2) Profilm is SO much better to work with than Monokote! It really sticks well, even to itself. Makes overlapping so much easier.
3) About 6 months ago I got some Profilm from Hobbyrama and tried it and it wasn't so great - I decided it was no better than Monokote. But the Profilm was too old! The new Profilm is completely different to the old stuff! The backing on the new stuff is tacky but the old stuff is really dry and hard and doesn’t melt properly with heat. So I really got off on a bum steer there! Profilm is definitely the way to go.
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Post by skyboyken on Dec 5, 2007 21:13:37 GMT 10
Where did you get the Marine Goop please?
Am I correct that it has UV inhibitors?
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Post by atmosteve on Dec 5, 2007 23:15:53 GMT 10
Marine goop? have links for regular goop but not marine.
Ta all for the tip on profilm too, i have many memories of monokote, not all good.
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Post by thevon on Dec 6, 2007 7:32:11 GMT 10
Look on the Goop - Where to Get It thread. To my knowledge there's no more available in Aust till Feb so you'll need to use Shoe Goo.
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Post by skyboyken on Dec 6, 2007 20:53:45 GMT 10
Thanks guys!
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