HK B-17...C 5/4 sweating the metal

[bdthoresen]

Craig-

I remembered a build here from way back when from the great Brian Cauchi, where he had built Revell's Corsair, and had used tissue to detail the fabric control surfaces- It looked as though he used Tamiya tape for the rib lines, and then overcoated it with tissue and cement; Check out his build here, the technique starts to be discussed about post number 250-

http://forum.largescaleplanes.com/index.php?showtopic=7290&page=17

Still one of the best builds I have ever seen- But the ideas might help you-

THOR     

[Gerhard]

Oh my goodness,  That is superb

[brahman104]

Hi guys,

 

Thanks for all the great advice and suggestions. It would certainly seem that tissue paper may be the wsy forward. I have already ordered a specialised heat iron rather than the clothes iron I was using. I'm also drawing up some laser cutting files to rebuild the structure in fine plywood so I can investigate the heat application without fear of melting!

 

Unfortunately I have been called away on short notice for work and could be gone for a while, but please keep the suggestions and comments coming. Hopefully I'll be back to my bench soon!

 

Craig

[airscale]

Hi Craig - I have a bit of form doing this and may have a few thoughts that will help..

 

if the covering you are using has the same properties as the solartex I use (ie for RC planes with heat activated glue & shrinks to give a tight cover) then from the looks of it the temp you are using is too high. I think I have my wifes iron on a low temp (dot 1 of 3 dots) and it works fine. Now you have ordered a specialist iron see how you get on with that, but not much heat is needed for the activation of the glue & shrinkage to occur..

 

..in terms of melting plastic - I have never had this happen, any heat you apply is literally brushing the part against the metal plate - you would need to hold the part for a long time for the plastic to distort (unless you had very high temps).  I stand the iron up and hold the part up to it as its much easier to work that way, sort of sweeping it over the plate and pressing more firmly around the outer edges - it is only here you need real adhesion so start on one edge (the straightest) and try and work the adhesive and the cover bonding around the edges first. Any sagginess in the middle, or undulations will come out by sweeping the whole form against the hot plate tightening up the cover...

 

it takes a little practice, but I would just try at a much lower temp and with edges first & you will soon get the hang of it

 

..the model is looking fabulous by the way

 

TTFN

Peter

[brahman104]

Hey Guys I'm back!

 

I had to duck away for a few weeks with work. If anyone is interested, this is what I got up to....

 

http://video.army.gov.au/play/5580

 

For the Easter long weeked I took a quick road trip down to Mackay to visit some friends. Passing through a place called "Bakers Creek" I came across this:

 

 

It's a memorial to a crash during the war in which an overloaded plane crashed on take off. I believe it still ranks as Australia's worst air disaster, even worse being that they were mostly guys on leave from the New Guinea campaign. What's the significance here? The aircraft involved was actually a B-17C. Strangely, 40-2072 actually carried a VH registration at the time.....

 

 

 

 

 

Anyway thanks very much for all your suggestions regarding the covering process. As I still had the coverlite, I still wanted to do some experimenting with it. I made a little test piece on the laser cutter out of plywood.

 

 

Looked promising, and now I had the proper iron to apply it with. I was going to try and make a complete structure in plywood for the rudder, but given Peter's experience with no melting of the styrene, I decided to go straight onto it. This was the result:

 

 

Not entirely terrible and no apparent damage to the underlying structure. I played around for a bit trying to get the wrinkles out but to no avail. I re-read the instructions and it mentioned that coverlite has only minimal shrinkage, so perhaps I was asking too much of it. I decided to remove the covering and have another go at it. I figure this time I'll try to put a bit more tension in each piece initially, instead of just draping it over and hoping for the best. The heat sensitive glue does work very well though!

 

After a little effort, all the covering was removed and apart from some glue residue, no damage!!!

 

 

Once I clean it up I'm going to have another go. I've seen the results first hand that can be obtained from this material, so clearly this is an operator error!

 

Cheers, Craig

 

 

 

 

[Gigant]

Keep at it, and you will get it! 

 

I don't believe any of us doing this for the first time could do much better.

 

Also, thank you for the memorial photos.

[Jim Barry]

Good work on the experiments there. I have some covering of the Bearcat control surfaces I have not worked out yet so watching you closely. Cool intersection of your build and your weekend visit. I have a B-17 crash story here in Maine, USA. During WW2, Maine was a fuel stop on the way to deliver the B-17 crews and their planes to Europe. One of them got lost in heavy clouds and decided to get a recon on their position by descending for ground view and perhaps locate a city on the map. They unfortunately descended into a valley surrounded by mountains and in their attempt to get back above the mountains, failed. It was like a death trap, really.The plane was a lawnmower through the thick mountain forest it crashed into and there were no survivors. A small memorial on a remote logging road is all that is left today. My visit a few years ago really impressed me. The memorial has parts of the plane just laying in a tiny pile, a few small memorial flags and stone with a plaque. It's very amazing to be able to touch the parts and imagine the drama. Goosebumps if you have a good imagination. Though I did not give it a try, they say it's not hard to find more parts deeper in the woods, though nothing like a full prop or anything. 

Edited April 2, 2018 by Jim Barry

[airscale]

hmm - sorry to see it's still proving a challenge Craig.. I guess keep at it and try different approaches

 

.. I can't quite work out what is happening as looking at the sample it seems there is not enough shrinkage to tension any slack - I assume it starts life flatter & smoother than it looks now so the heating factor seems to be if anything stretching & slackening it. I can see pinches on where it has adhered to some of the lateral formers so this says that the glue is grabbing but it is grabbing before the stretch has occured. You could try starting at the rudder leading edge, get a good bond there and then work gently backwards, that way the glue will grab only in one direction of application, maybe the pinches are witness marks to it trying to bond in more that one direction?

 

..that, or maybe see if you can get some solartex - it is much more forgiving than this stuff looks to be?

 

..anyways - I know you will crack it & can't wait to see the next update

 

Peter

[brahman104]

 

 

I don't believe any of us doing this for the first time could do much better.

 

Thanks for the encourage mate! I'm not too worried at this stage..... I've very rarely got anything first go on this build!

 

 

 

Good work on the experiments there. I have some covering of the Bearcat control surfaces I have not worked out yet so watching you closely.

 

Thanks Jim, hopefully I'll have some good news for you soon. Thank you for sharing the story about the B-17 too.

 

 

hmm - sorry to see it's still proving a challenge Craig.. I guess keep at it and try different approaches

 

 

Thanks for the pointers Peter, I appreciate your input very much. I believe this material is somewhat thinner than solartex, hence it will show up almost every little mistake I do. I do agree with you, I feel I need to start on one side first, then work back, laying it down and keeping tension on it at the same time. When I applied heat to what I'd already done, it tensioned up nicely for a while then sagged off again, so I think I do need to get it as close as I can first. I'm far from frustrated yet, there's plenty of trial and error to be had here, and hopefully I'll find all the wrong ways to do it so I'll never repeat them in future!

 

Cheers,

 

Craig

 

[brahman104]

Wow! so my last post was over 3 months ago....... I haven't disappeared off the face of the earth (not entirely anyway) and the old girl is still very much on the bench, well in fact, a new bench!!!

 

I've also been away a lot with work, so not the greatest of progress to show, but it still is progress

 

First of all, the bench....

 

Got this one for a really good price (wink wink  ) and I've been taking the time to customize and set it up as to how I want it. I've also designed a set of retractable caster wheels so if I need to move or clean around it, I can just jack it up and away I go!  I still have a lot more to go on it, but at least it's in a useable state and the show can continue.......

 

 

I'm also getting my contortion/yoga practice in drilling holes and fitting various brackets to it  I made custom lighting using two LED downlights from Bunnings and 3D printing brackets to hold them. The lights are completely repositionable to where I need direct light, and can switch between cool white, warm white and natural light, whihc is very handy when it comes to mixing and painting colours! 

 

 

Anyway, what's going on with the Fort?

 

Well I've set aside the control surfaces for a little while yet and have been making some progress on the "bathtub." This, like getting the lines of the cockpit right, will be a critical focal point if I'm going to pull off this conversion convincingly. I did make one a while ago using the 3D printer, but I was never happy with the shape. I redesigned it and went down the vac-forming path following the success I had with the nose cone....

 

As usual, it took a few goes to get right and keep the bubbling to a minimum. This also meant I did not have to retrospectively make a clear panel for the rear of the tub later on....

 

 

 

Why is it in two parts? Only because of the limited size of my little vac former......

 

Like all things to do with this project, trying to work out the actual size of the window panel proved nearly impossible, so I deferred once again to the trusty eyeball

 

 

The bathtub can only be added once the two fuselage halves are together permanently, so it's a bit of a chicken and egg situation. I joined all the pieces together and reinforced them using araldite and styrene. This will be hidden by the cushion and side walls so I'm not too concerned with neatness at this point....

 

 

Now it came down to a fair amount of whittling to get a nice corresponding contour to the top of the tub where it will meet the fuselage.

 

 

 

I also noted that the new tub over lapped the wing root fairing on the existing kit. This isn't right, so I carefully reshaped the fairing to give a new contour....... this is before:

 

 

You can see the current vs the new lines in this photo:

 

 

And after.... Still needs some refinement, but I feel I'm on the right track, and the change is subtle enough not to ruin the clean lines of the B-17..

 

 

So that's kinda where it's at right now....I'm going to start fitting out the inside and making the gun mount brackets. There quite a bit of metal work in here, so I need to make sure the walls are nice and rigid to give me a solid and true surface to work off....

 

More updates soon!

 

Craig

 

 

[LSP_Kevin]

Welcome back, Craig! Fantastic work as always.

 

Kev

[tomprobert]

I’ve missed this build - it’s great to see some more progress. 

 

You’ve made an excellent start on the tub and no doubt it’ll really start to come to life as you add the internal details. 

 

Tom

[chrish]

I would love to make a comment... but I’m speechless !

[Geddyme]

Welcome back and congratulations on the new bench, Craig, very nice indeed!

 

Your B-17 project is looking fantastic! I think you nailed the bathtub and that wing root area is excellent work as well. Keep it coming.

 

Cheers, David

[LSP_Ron]

A very interesting build.

 

Well done