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RSM P51d build

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Re: RSM P51d build

Post  pkrankow on Thu Nov 13, 2014 6:45 pm

Yes, dope will continue shrinking for years. I have seen in my parents attic coverings burst with what appears large spaces, but all the material can be verified as there.

I have had tissue and dope CRUSH a rubber band power airframe overnight...months of work turned to toothpicks...

Phil
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Re: RSM P51d build

Post  ian1954 on Thu Nov 13, 2014 6:58 pm

pkrankow wrote:Yes, dope will continue shrinking for years.  I have seen in my parents attic coverings burst with what appears large spaces, but all the material can be verified as there.  

I have had tissue and dope CRUSH a rubber band power airframe overnight...months of work turned to toothpicks...

Phil

I remember the "Wakefield Class" rubber powered models and they had delicate "sticks" for frames. I use to cringe when I saw one of the chaps winding up the rubber. I know they uses a very delicate Japanese tissue that was difficult (even then - 50 years ago) but I am sure they used Banana oil. I may be wrong but I do remember frowning when I saw these things. A lot of work went into them and they coated the inside of the fuselage with something to stop the rubber lubricant softening the balsa.
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Re: RSM P51d build

Post  getback on Thu Nov 13, 2014 7:30 pm

http://www.easybuiltmodels.com/Notes_on_tissuing.pdf I cant read all of this right now but you might want to, I will check it in the morning when I do most my reading with coffee Tired w/ Coffee Read Eric What?
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Re: RSM P51d build

Post  ian1954 on Fri Nov 14, 2014 3:12 pm

getback wrote:http://www.easybuiltmodels.com/Notes_on_tissuing.pdf  I cant read all of this right now but you might want to, I will check it in the morning when I do most my reading with coffee Tired w/ Coffee Read  Eric What?

This article is geared towards lightweight tissue covering on more delicate models. I like the use of the UHU stick but it probably doesn't offer much flexibilty. I have used tissue paste previously but it doesn't allow adjustment once set.

If you use dope through the tissue and don't quite get it right. You can soften it again with dope or thinners and make adjustments.

You can even remove the piece quite cleanly after it has dried with thinner or MEK. (However, be warned - if you have used one of the traditional balsa cements - the glue will also dissolve. CA or PVA and its derivatives will be fine.)

Here you see the wet tissue after it has been applied and dabbed down with dope. The edges of the fin ahd alreadr had a copy of coats of dope (now dry). The dope soaks through the tissue and softens the dope beneath allowing a better stick. The dope on the frame work is straight dope and the tissue application thinned 50/50.

This is the second side.



As you can see there is considerable overlap. So when the tissue is stuck, I run a smidgeon of thinner where the overlap has stuck down after cutting through with a razor balde. The excess can then be peeled off.

This was already done on the first side.



I more or less did the first side straight away but as it was getting late I left the second side overnight.



It looks horrendous with the blushing. The is caused by the interaction of the water and the dope.

However the excess was softened with thinner, trimmed with a razor blade - left for the thinner to evaporate na dthen 50/50 dope applied over the whole surface.





Using dope has also enabled me to blend overlaps and edges with my thumb. It will require very little sanding when the dope has hardened sufficiently.

After seeing this, I wish that coloured dope was still available in the UK or I new how to pigment it myself.

Remember, I am just showing what I am doing - it may not be correct or the best way but I have watched a few videos, picked some tips from some scale guys (who now seem to use only glass fibre and epoxy! but were previosly dope freaks!) and selected the easiest things for me to do without aiming for that concours finish.

When the tissue is filled, I will probable start spraying final coats.
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Re: RSM P51d build

Post  RknRusty on Fri Nov 14, 2014 5:00 pm

That looks really nice. I need to start cataloging these methods for when I refinish my GB Nobler. That'll be in line after my winter 1/2A builds and possibly a Junior size build.
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Re: RSM P51d build

Post  getback on Fri Nov 14, 2014 5:19 pm

Ok . let me try this Again; Well what ever you been reading Ian is doing you right Because that really looks Great !! I had read that article before and forgot RC Plane I am interested in the preshrink part of silking / that X8-A I have needs something that want break it in half . Rusty what Jr. size not to get of subject. Eric Very Happy
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Re: RSM P51d build

Post  statorvane on Sat Nov 15, 2014 5:48 am

Ian1954 wrote: wrote:After seeing this, I wish that coloured dope was still available in the UK or I new how to pigment it myself.

Have you ever heard of aniline dyes? I have been using them for some time to shade/tone clear lacquer sprayed onto guitars. I am betting these will work fine with dope. They are extremely concentrated. I add the dye to lacquer thinner to make a concentrated mix, then dilute with thinner for spraying on the guitar. This gets covered later with multiple clear coats of lacquer. I am thinking you could do the same with dope, except add more dope into the concentrated mixture.

Here's a shot where you can see the shade build into almost an opaque color:

This is Cordovan Purple dye over flame maple. The body is ash. I later applied the toner to the ash - virtually obscuring the grain, etc.

They dyes come in liquid and powered pigments. I have had better luck with the powerded variety, but they are getting scarce.

Just a thought. Here is a link to information I originally used: Aniline Dyes Hope it helps.

Oh, and by the way that P-51 is coming along great. very nice effort.
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Re: RSM P51d build

Post  Ken Cook on Sat Nov 15, 2014 7:19 am

Ian, while were on the subject of dope. Doesn't PSAeroproducts still exist in the UK? http://www.psaeroproducts.com/psaeroproducts/Welcome.html Seeing they offer Brodak color choices is a start. Cost is another thing but it's not cheap here either. As for dope, what dope are you using? Not all dopes are created the same and the taughtening dopes can really shrink too tight. We use a product here which plasticizes the clear. Dave Brown's Flexall. I don't know if it's available in the UK but anyone using dope should be using this product. Newer dopes leave the covering in what I call the potato chip stage because that's about how fragile it can get. I use the Flexall to prevent this and it keeps the covering supple. In the past years many added castor oil to the dope. I don't recommend this as I found it does nothing more than stop the dope from drying properly. It leaves a nice shine however when it does dry. Ken
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Re: RSM P51d build

Post  ian1954 on Sun Nov 16, 2014 6:54 pm

Sorry for the late response - I have been on my travels again.

Thanks for the info on anilene dyes - I see that they are developed to be used with alcohol but the can be used with lacquer thinner. If lacquer thinner is a cellulose thinner then I can see why this can't be done. I have tracked a source for the dye and so more experimenting is on the way.

Ken - I have watched many Windy videos now and he swears by Brodak dope. I get a little confused with his statements though. His choice of Brodak dope (apart from the qualities he found in applying it) was that it was fuel proof . This would probably imply that it was butyrate, fuel proof but carries on shrinking. Butyrate also tends not to like quite a few finishes being applied over the top of it.

I will PM you (when I get some time - it is 12:45 am here and I have just driven 200 miles) with regard to the availability of Brodak products here.

I also watch Windy videos where he keeps using retarders but, again, sometimes this is not just to slow down the drying process but to fend off humidity. Nitrate dope is in plentiful supply here and I haven't come across many issues with it (either years ago or in my present experimentation). Some of my scale chums have used castor oil with it but we are talking a couple of drops in half a litre to help it flow or spread when covering large areas.

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Re: RSM P51d build

Post  ian1954 on Thu Apr 16, 2015 3:38 pm

Quite a break from posting progress on this but I have a much larger project "on the go". Even so I made progress from November onwards but lacked the time to post.

I made up coloured dope using anilene dye

https://www.coxengineforum.com/t7497-anilene-dyes-with-dope#94582

and kept plugging away with covering.

I got everything tissued and a couple of coats of dope.





I was quite pleased with myself as I hadn't used dope and tissue for many, many years. Unlike some I like the smell!

I also wanted to cover the wing with silk. I had watched one of the Dave Platt videos where he demonstrated that it was easier to do over tissue rather than a straight silk application.

So



It didn't take long and went on far easier than I remember when using nylon.

Then I decided to start using the anilene dyed dope. Here are some before and after comparisons.





Now to digress a little.

I watched many Windy videos with his meticulous sanding and thought I would give it a go.

A bowl of slightly soapy water and a few pieces of wet and dry - how hard could it be?

I noticed my hand was picking up a little colour



and the water




It got worse - caught red handed!



Now I know why in nearly every video - Windy wears gloves!

I also had a little trouble where the fin meets the fuselage. I had (as per Windy advice) left a small gap but could stop the tissue lifting.
I ended up using CA and applying filler.



Progress continued -more sanding and doping



This was all achieved before Christmas 2014. Sanding, flatting and a final coat of clear - ready to assemble.

Unfortunately - I have lost the pictures !!!!!!!

I set the parts aside and got embroiled in another non modelling project.

I was so pleased with my efforts but when I returned to it a month later  ...........................to be continued.
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Re: RSM P51d build

Post  Cribbs74 on Thu Apr 16, 2015 4:49 pm

Popcorn
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Not for the feint hearted!

Post  ian1954 on Thu Apr 16, 2015 5:37 pm

Ron,

Finish whatever it is you are eating but keep the empty bag. Yo may need it!




There I was - at the beginning of the year - with a pristine set of parts. These were left for a month and when I inspected them - they were fine.

I remembered what Ken had said

Ken Cook wrote:            As for dope, what dope are you using? Not all dopes are created the same and the taughtening dopes can really shrink too tight. We use a product here which plasticizes the clear. Dave Brown's Flexall. I don't know if it's available in the UK but anyone using dope should be using this product. Newer dopes leave the covering in what I call the potato chip stage because that's about how fragile it can get. I use the Flexall to prevent this and it keeps the covering supple. In  the past years many added castor oil to the dope. I don't recommend this as I found it does nothing more than stop the dope from drying properly. It leaves a nice shine however when it does dry. Ken

I thought "What is he talking about?", "Shrink too tight?" and Flexall - I searched and found ......

"Flexall is used by athletes in all levels of competition including major sporting events such as The Olympics, The Super Bowl, The NBA Finals, The World Series, The Stanley Cup, college basketball tournaments, and college football bowl games. Flexall (7% menthol) is a unique aloe vera gel formula with natural oils (eucalyptus, peppermint, thyme) and vitamin E.

Flexall gels provide fast, long lasting relief from minor arthritis pain, simple backache, bursitis, tendonitis, muscle strains and sprains, bruises and cramps. Flexall gels are versatile enough to aid in treating the acute, sub-acute, and chronic stages of injury.

Patients prefer Flexall gels because they deliver fast, lasting relief; offer an effective counterirritation to pain by providing a cool sensation followed by a deeper heat; and soothe and relax sore muscles by increasing local blood flow.

The Flexall aloe vera gel formulas absorb quickly and completely, are greaseless, non-staining, and gentle on the skin.

Application Method:
Directions. Apply generously to painful muscles and joints then gently massage until Flexall disappears. Repeat as necessary for temporary relief of minor arthritis pain, simple backache, bursitis, tendonitis, muscle sprains and strains, bruises, and cramps. Use before and after activity. When treating an injured area or joint, make sure to completely coat the entire area.

Additional methods of treatment may be recommended depending upon the severity of the condition and the judgment of the health professional."




There I was, feeling all smug but one month later ...............  Arrrrrrrgggghhhhhhh!!!!!!!!

Here are but a few examples of what I saw

The front tip of the fin



The base of the fin and notice the discolouration



Even worse ----- the banana fuselage!





or should I say the curly and twisted banana fuselage



The distorted and twisted tailplane and elevator. Not possible to get all the hinges flush!





The undescribeably crooked aileron!!!






and the wing!!!!!!!!




I mulled this over for a few weeks - kept thinking - replace the tailplane, aileron and fin with sheet material but I couldn't straighten the fuselage or the wing. Heat, more dope - they were unmovable!

Found looking at it depressing and so hid it in a cupboard!

At the weekend I decided to rescue the bellcrank and hinges but first I thought I would see how strong the wing was

IF YOU ARE IN ANY WAY SQUEAMISH DO NOT READ/WATCH FURTHER



https://www.youtube.com/watch?v=Tk2yLWSh51Q&feature=youtu.be

There was no sign of damage after this application of tender loving care.

This was quickly followed by



I had to jump on it to get it in here.



and three minutes later

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Re: RSM P51d build

Post  Ken Cook on Thu Apr 16, 2015 7:03 pm

Ian that hurts. Dope is a funny thing and the problem with dope is it's shrinkage. There's non taughtening dope and taughtening. Just keep in mind regardless of choice, they're all taughtening it's just that one shrinks more than the other. The non taughtening dopes however will immobilize the shrink factor. This is why and these products may not be available in the UK which is Sig Lite Coat. I use Sig for my final clear coats. It's the most fuel resistant dope in my opinion currently available. What I see on you model through your pictures is exactly what I see when some have gone to aircraft restoration suppliers to purchase dope. The shrinkage essentially crushed the model. The other side of this is the newer laser cut kits. These kits sometimes have extremely lightweight punky wood which doesn't tolerate shrinking well. Many times I substitute a lot of the wood for thicker pieces or different hardness just for these same reasons. I have a fairly large supply of the Dave brown Flex All. A little goes a long way as you only need to add a few drops. It makes the silkspan more or less flexible to the point that you wouldn't recognize the difference between it and iron on coverings.   I use this quite a bit but I'm not sure if the product is even made any more. I typed it in and copied this. Dave Brown products are quite popular with the hobby crowd especially known for their lightweight foam wheels. The link I copied shows a picture of it http://www.ohio-superstar.com/dave-brown-product-line/flexall-paint-plasticizer Ken
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Re: RSM P51d build

Post  rogermharris on Thu Apr 16, 2015 7:12 pm

Really sad to see after all that work. Sorry for your loss
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Re: RSM P51d build

Post  akjgardner on Thu Apr 16, 2015 8:55 pm

BUMMER
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Re: RSM P51d build

Post  Cribbs74 on Thu Apr 16, 2015 11:06 pm

Well, that was kind of what I was expecting to see after your previous post. That's an expensive lesson on dope. Hope it gets better.

But, whoah! That's one tough wing eh?
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Re: RSM P51d build

Post  ian1954 on Fri Apr 17, 2015 4:45 am

Cribbs74 wrote:Well, that was kind of what I was expecting to see after your previous post. That's an expensive lesson on dope. Hope it gets better.

But, whoah!  That's one tough wing eh?

It was an expensive lesson but it could have been worse. I have three other models awaiting covering and I was tempted to do them as a batch following my pleasure with the initial progress. It is a good job that I didn't. I would be more than miffed now!

Still, I hope it is a warning/guide to other members. The dope I used was "modeling" dope but the shrinking variety widely available here. It is a bit of a conundrum - was it the dope, the wood or the tissue I used.

It is difficult to find the details chemicals used for plasticisers and retarders here or commercial products. It will be a matter of trial and error but not on this scale. Whatever happened to the Humbrol dope I remember?!!

I have to say though that the kit was superb and enjoyed the build. It was my finishing that ruined it Sad

The wing was extremely strong. I laid it on the floor and stood on the centre section to remove the bellcrank. It did not break! I had to stamp on it using my heel.

Once the covering was torn a punctured with a screwdriver the wing was then easy to break. One thing I have learned it that the tissue, silk and dope finish is far stronger than the iron on stuff and adds a great deal of strength to the wing.

You live and learn!
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Re: RSM P51d build

Post  getback on Fri Apr 17, 2015 9:06 am

DAMMIT! Man That SUCKS AIR !! I see you had your Pulse checker out and the outside stove I love it , I want one but don't know why Rolling Eyes I am glad you didn't go for the other airplanes covering while waiting . I have had a lot of problems with warping lately But for the whole plane to be demolished is a real killer . Ian if you want I will see if I can get this Flexall and send it to you ! I have been wanting to do another silk span but I just don't know what I may get myself into Surprised Eric Mad
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Re: RSM P51d build

Post  ian1954 on Fri Apr 17, 2015 1:22 pm

Thank you for the kind offer Eric.

Send liquids to the UK and they will be confiscated. Especially if Her Majesties Customs & Excise combined with Border Force (or whatever they are called these days) don't understand what it is! (this is also not likely)

Then the Coup de grras - Royal Mail won't handle liquids, lipo batteries or anything potentially flammable. We live in strange days!
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Re: RSM P51d build

Post  Ken Cook on Sat Apr 18, 2015 6:44 am

Ian, I've had to discard many of the pieces using traditional finishes on laser cut kits. Dope isn't the same as you mentioned nor is the coverings used. Silkspan is no longer available at least the type that you see Windy using. I have about 12 sheets left of the old Sig silkspan. Laser cut kits with a dope finish is very susceptible to twisting. While your observations initially proved that the wing was exceptionally strong, it's short lived. The dope unless plasticized becomes what I call the potato chip stage. UV rays quickly and I mean within 2 months of use render the covering so brittle that if it doesn't split on it's own, it will even tear  with a tough weed on landing or high grass. I don't have this problem with Sig dopes when I use Sig Lite Coat as a final. Sig Lite Coat is the lowest shrinking dope currently out there and in my opinion is the clearest of clears in dope. I probably have anywhere from 12-14 coats of dope on a wing when complete which is a variety of brushed and sprayed coats the majority of them being sprayed. All attachment coats are brushed.  Another issue is like I mentioned is the taughtening part, while the outer pieces of the structure on a laser cut kit has a lot of integrity, the shrinking that takes place with the lighter laser cut wood can just explode the ribs internally. If they don't break, they bow very badly. This is very common with silk due to it's ability to really shrink and crush the model. Polyspan is something many of us switched to and I have done so myself and I find it stronger than silkspan, cheaper and I also found that it does have some elasticity to it which is a benefit. My Brodak Oriental https://www.facebook.com/PhillyFliersCL/photos/pb.513140418756097.-2207520000.1429357046./840692392667563/?type=1&theater  needed some tweaking and nursing along the process of doping due to various pieces wanting to twist. I very rarely build from kits for this reason, this kit was given to me so I built it. The cost of dope finishes for me totally outweighs the need to use it in my opinion if one is sport flying. The health hazards is another. While many enjoy Windy's videos, what most people don't understand is how it did have a negative impact on his health. Many of his earlier paint jobs was experimenting with newer and far more dangerous products. If I have a silkspan plane that is in need of covering, I find all of my crap iron on covering and go right over it. Ken
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Re: RSM P51d build

Post  JPvelo on Sat Apr 18, 2015 2:50 pm

Ken,
I am currently building a corsair that will be covered with polyspan and sig lite coat. I plan on shooting it with primer and paint after the poly is sealed with dope. Should I use a plasticizer?

Jim
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Re: RSM P51d build

Post  Ken Cook on Sat Apr 18, 2015 7:28 pm

Jim. Sig Lite Coat will be fine. I believe it already is plasticized and it doesn't shrink like Sig Supercoat. It won't shrink open bays however. You must use Supercoat first and then use Sig Lite coat to stabilize . Sig Lite Coat is also great to use on lighter structures like free flight. Sig Lite Coat can be used on planked surfaces from start to finish. It comes in the bottle like syrup and really needs to be thinned out. I highly recommend using Sig thinner as it's the slowest of them all. Ken
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