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Depron, brown paper, pva glue and issues!

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Nick Farrow10/01/2017 12:31:15
157 forum posts
9 photos

Hi

I'm building a 3d 'starter plane' from the FliteTest crew http://www.flitetest.com/articles/ft-3d

Not having access to US dollar tree board, I have used depron and covering each bit with brown paper (using PVA glue). I have spend my time on this build and the brown paper seemed soundly bonded onto the depron

However, when I put a thin sealing coat of water based varnish, some sections of the brown paper covering bubbled on the wings, which have not really gone away when they have dried out. I can cut them with a razor blade and bed them down but I was determined to 'build this right' and I dont understand what has gone wrong.

Any pointers for next time would be good, this seems a great plane and I was hoping to give it a decent finish!

Thanks

nick

onetenor10/01/2017 12:39:24
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1900 forum posts

Most likely the glue hadn't dried properly being trapped between the paper and the Depron is not absorbent so glue takes longer to set.Leave it a few days next time

McG 696910/01/2017 13:01:53
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2543 forum posts
973 photos

Hi Nick,

It seems indeed following your explanation that the PVA glue hadn't the time to fully dry as Onetenor is writing.

I suppose that you diluted your glue before applying to the paper so in that case it can even take longer.

An alternate solution is to skip the PVA and only use WB varnish. You first give a light coat of diluted varnish - around 40 > 50% - to your Depron.

Place your brown paper - with the shiny lines facing down - on a sheet of plastic and paint it over with the diluted solution and let it soak in while the varnish applied to the Depron is drying slightly. Place your paper onto the foam and dry brush out any trapped bubbles. Let it then dry completely hard.

If you prefer you can always apply a second non diluted varnish when done, but it adds some extra weight of course. wink

Cheers

Chris

TigerOC10/01/2017 21:32:02
309 forum posts
13 photos

Personally as a prolific builder in depron I would skip the paper and use packing tape.

This is the reason; Depron is closed cell and has a hardened surfaces. Covering in packing tape gives the depron quite a lot of strength. We have a club build that is used for competition and they get a LOT of abuse and are incredibly strong. If you're worried about the impact areas like the nose section line it in some 1/16 balsa on the inside which will re-enforce it. The tape method will make it even lighter and a better 3d machine.

Rob

Gordon Nicol10/01/2017 22:35:01
81 forum posts

Spooky... I have spent to-day also building the pod (body ) of a flite test Bronco . I have used 6mm grey depron and and using UHU Por , and also I'm "Nailing the fuselage sides , bottom etc etc with cheap cocktail sticks , dipped into waterproof PVA , and it has dried as hard as "nails"and as solid as I needed, but I was going to post on here for advice about coating the whole airframe with varnish and craft grade brown paper

so where can I buy good quality brown paper. the stuff i have in the house is pretty naff , i have used BP and watered PVA before with fairly decent results , but I really want this plane to look good also

previously i have soaked the BP in the bath first , left it over the bath side to dry out a bit then painted the fuselage with PVA , laid the wetted paper onto it, and then painted the whole assembly with thinned(watered down) PVA always has dried tight and hard.This will be my first time using (Ronseal) varnish

onetenor11/01/2017 05:10:10
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1900 forum posts

B,P. from/////Staples in fact any stationers ,even the local post office for a parcel pack with a fair sized sheet of B.P. and string and or tape and WH Smith

Chris North 311/01/2017 06:17:32
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302 forum posts
498 photos

Hi Nick,

This is not really an answer to your specific question but I have built a number of the FT plans (Spitfire, Old Fogey, Baby Blender etc) and have a similar problem getting suitable foam board here in Thailand although depron is easy to get hold of. I did look at brown paper but like TigerOC I found that packing tape is a much easier, quicker and cleaner method which gives loads of strength and good puncture and moisture resistance for little weight gain. I have also had good results applying self adhesive vinyl paper, although this is a bit heavier.

I apply tape or vinyl to one side of a sheet of depron and then stick my printed plans onto the other side using pritt stick or spray adhesive which don't tend to make the plans wet. Once the glue is dry you can cut you pattern out and this leaves you with tape on the outside and paper on the inside making the depron nice and strong. Hot glue can be used on both the paper and tape surface as required, although be careful about shrinking the tape if the glue is too hot. The way the plans are printed, if you make the half cuts and scores etc on the paper side, they will always end up on the inside.

For areas like tails and fins etc, I apply tape to both sides before sticking the paper plan on to one side using a pritt.stick. once dry, this can be cut out and the paper plan peeled off to leave a depron piece with tape both sides.

Using coloured packing tape, it is fairly easy to get a striking design without too much hassle. I doubt whether this would help if you intent to have a camouflage finish but for contrasting wings, fuselages and star bursts its fine.

Chris

Nick Farrow11/01/2017 12:52:14
157 forum posts
9 photos

Hi,

Many thanks for the advice and help, some really good tips here

When I used the brown paper, if was left to dry for at least 2 days with an air gap top and bottom. It was also heavily wieghted on the edges to prevent warping, so it was definetly dry. Perhaps, it was the cheap tesco brown paper, although it seemed thick

The balance seems to be to use tape (certainly cut out the long drying times and warping), but I have a few questions:

1) When applying it, do you overlap the tape runs, or if not how easy is it to carefully 'butt' the edges together?

2) Is there a method of reliably over painting the tape, or are you restricted to the colours available?

3) Do you pretreat the depron surface to ensure the tape does not lift/bubble (other than a quick wipe!)?

4) Are there any tapes that are fully opaque, most of ones I have see are translucent, which is not great if the edges were overlapped.?

I think I might peel off the brown paper on the wings and tape them once I know what I'm doing!

Gordon - I had found that drying the brown paper produce massive warps on a single 6mm sheet part, so be careful with the airframe! I also sealed it with ronseal 'diamond hard' varnish but I the brown paper just seemed to soak it up without giving a decent finish. This was when it bubbled, so I only gave it a single coat.

nick

IanR11/01/2017 13:32:11
775 forum posts
4 photos

Could I add to Nick's questions, please:-

What is "packing tape"? Trade names and where to purchase, please. The only packing tape I know is the thin brown stuff, about 75mm wide, which the missus uses when wrapping parcels.

Thanks. Ian

TigerOC11/01/2017 14:09:21
309 forum posts
13 photos
Posted by Nick Farrow on 11/01/2017 12:52:14:

Hi,

Many thanks for the advice and help, some really good tips here

1) When applying it, do you overlap the tape runs, or if not how easy is it to carefully 'butt' the edges together?

2) Is there a method of reliably over painting the tape, or are you restricted to the colours available?

3) Do you pretreat the depron surface to ensure the tape does not lift/bubble (other than a quick wipe!)?

4) Are there any tapes that are fully opaque, most of ones I have see are translucent, which is not great if the edges were overlapped.?

I think I might peel off the brown paper on the wings and tape them once I know what I'm doing!

Gordon - I had found that drying the brown paper produce massive warps on a single 6mm sheet part, so be careful with the airframe! I also sealed it with ronseal 'diamond hard' varnish but I the brown paper just seemed to soak it up without giving a decent finish. This was when it bubbled, so I only gave it a single coat.

nick

Here is the routine for covering with packing tape;

1. Wipe the area with methylated spirit/isopropyl alcohol.

2. lay the tape and wipe the surface with alcohol to remove release agent. Rub over with a cloth or tissue to ensure smooth adhesion

3. overlap the previous run by about 6mm. When doing wings start at he trailing edge and work forward so the edge is with the flow and not against.

All the coloured tapes provide good cover with exception of white. HobbyKing have the cheapest range of tape in the UK but alternative is:

**LINK**

I have used the above supplier's product extensively and it is good quality. HK tape is comparable but much cheaper.

You shouldn't need to paint it with the correct planning. Would be a challenge to find a suitable type of paint as well. If you want to put patterns or shape of one colour over another, make a stencil and apply the colour over the area and then place the stencil over the colour and go around the shape gently with a scalpel and peel off the excess.

Rob

Edited By TigerOC on 11/01/2017 14:10:44

Gordon Nicol08/02/2017 08:03:31
81 forum posts

I have the FT Bronco fuselage(pod) wings and tailplane covered, and very strong

they are too, there was a slight curve upwards on the wing , end to end,but when it was folded and the spar fitted it pulled itself straight , there is still a little at the tips where there is no underside but it has given washout , so may be a good thing, pod is solid, and tailplane is flat (papered both sides)

thing is , I have decided not to cover the booms or the vertical stabs , it has just become a lot heavier than I want, especially at the rear of the airframe and that is just with the tailplane covered

next time I may use heavyweight tissue, just a thought

Edited By Gordon Nicol on 08/02/2017 08:04:13

Andy G.08/02/2017 09:18:04
avatar
413 forum posts
215 photos

Hi Nick..

Wondering where you're based, as if it's UK then Foamboard is easily available. It doesn't go under the name Dollar tree as that's an American chain company. I use quite a lot Foamboard which I get from a local Independant office supplies company in 2 thicknesses an in a choice of white or black paper cover. The only difference I can see is that unlike the stuff FT use it is hard to get paper off like they sometimes do. I haven't looked in Staples, but would imagine they would stock it.

Nick Farrow08/02/2017 13:00:29
157 forum posts
9 photos

Hi,

Andy.G, yes i'm in the uk. I have seen something similar in a recently opened hobbycraft. I was wondering about the weight of the board compared to native depron and what you then did to paint/cover the plane?

I peeled off the brown paper from the wings but it stuck stubbonly to the fuz, anyway I coved the whole lot in hobbyking cheap packing tape (attached photo). I found that I had to cover it twice to get rid of the very obvious tape overlaps (but not on the stab as can be seen)

. I guess the tape is not as good as that recommend by TigerOC.

covered.jpg

Andy G.09/02/2017 08:32:35
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413 forum posts
215 photos

Nick,

That's the same stuff, it'll weigh more than plain Depron but will be on a par with Flight Tests stuff. For decorating I use packing tape or leave it in it's natural colours. There's some pics of my efforts in my albums or in my Fat Fighter thread in the electric ducted fan section.

Mark Kettle 109/02/2017 10:59:33
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2367 forum posts
1382 photos

Just a quick mention everyone -

FliteTest foam board available in the UK size of approx. 75 x 50 cm (30 x 20 inch)  £2.99 each. 

**LINK**

20170209_102220.jpg

20170209_102234 (1).jpg

Edited By Mark Kettle 1 on 09/02/2017 11:00:19

Edited By Mark Kettle 1 on 09/02/2017 11:00:42

Mark Kettle 109/02/2017 11:31:34
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2367 forum posts
1382 photos

I've done a **LINK**

Nick Farrow09/02/2017 16:48:59
157 forum posts
9 photos

Hi Mark,

Thanks for the heads up. The FT board has long been an issue because of the postage to UK/EU so this is really useful as its at a good price

nick

Mark Kettle 109/02/2017 18:14:51
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2367 forum posts
1382 photos

Nick have you sorted you build and covering problem?

Baz.B09/02/2017 22:39:17
4 forum posts

Hiya Nick,

Thought you might be interested in foam board. I buy 5mm foam board in a 10 sheet pack of A1 size for £19.99 plus £6.95 delivery with 2 days from a uk company called Paper Gourmet. Just type in the name and it goes straight to it. I've been using it to build some of the FliteTest models, and it works great.

Andy G.11/02/2017 08:53:49
avatar
413 forum posts
215 photos

Two of my Foamboard attempts. Fat Fighters mk1 and mk2. Mk1 from black Foamboard, mk2 from white with parcel tape decoration. Mine's 3 is currently on the building board, being bigger and twin fan powered.

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