Guillows kit 505 Messerschmitt Bf-109

[RolandD6]

Please ignore this post. I began it before I had my brain in proper gear and before I had read relevant parts of Martin Simons, Model Aircraft Aerodynamics. 

[Don McLellan]

Hi Paul,

Curious:  does the white acrylic ink that you use to seal the Tengujo tissue allow the tissue to (water) shrink after installation?  I know nothing about Tengujo tissue; have only ever used Esaki.  Also is the acrylic ink applied to the underside of the tissue, or do you print over the acrylic ink?

Don

[RolandD6]

Hi Don

I prepared a lengthy reply for you on my iPad over breakfast but the technology failed somewhere between me and the HPA server so about an hours work was lost. I will try again later on my computer and prepare the response as a text file outside of the browser.

A short answer is I print over the white acrylic sealer but there is more to it than that which I had written about but lost.

Should have know better because it has happened before in similar circumstances.

More later

Paul

[korale]

Hi Paul,

  Hows the progress on the build? I'm sure it will be to your usual high standards, looking forward to seeing it in flight.

[RolandD6]

Hi Paul,

  Hows the progress on the build? I'm sure it will be to your usual high standards, looking forward to seeing it in flight.

You will see it, even sooner if you come for a visit.

Made a little bit of progress this afternoon but more of that later.

Paul

[RolandD6]

Don, another go at answering your question this time from prepared notes.

Tengujo is normally used by conservators for repairing old books and manuscripts. The fibres are very strong for their thickness and there may be other properties that suit the intended application. I first became aware of Tengujo by taking note of the modelling forum on this site:

http://minimakety.cz

I am not absolutely certain now but I think it was a thread about one of the models by Robert Pajas. Here is a link to another Sopwith Pup project by Jiří Doležel that is absolutely amazing:

http://minimakety.cz/forum/viewtopic.php?f=5&t=862

Further down you will find a thread about a model by Robert Pajas

Both Robert and Jiří mention Kashmir as the covering material which may be this:

https://www.talasonline.com/Kozo-Kashmir-Paper

Kozo is the fibre and Tengujo is the type of tissue and is also made from Kozo fibre.

If you study the conservation papers on the Talas web site you will see there are many papers that may suit model airplanes.

You will also notice that many of these papers have a much more open weave than Esaki, particularly the lighter weight grades.

Doing a Google translation of some of the posts on the Czech modelling forum may give you a clue as to how those people seal the tissue covering. I think at one time Robert was using a type of polyurethane lacquer but I am not aware of his current technique.

In my case I cannot use polyurethane extensively for health reasons so I need to use water based acrylics. I say water based because there are solvent based acrylics in the market place. Pigment particles in water based acrylics need to be much larger and heavier than what they can be in a solvent based acrylic or other solvent based resin which is why the solvent based paints that plastic modellers use have very good coverage. There are dye based acrylic inks and inks that contain shellac and so on but they tend to be transparent (with the exception of black india ink) which may or may not be desirable.

It appears that the Czech modellers are using 11 gsm Kashmir but they may also be using solvent based paints or inks which are lighter for a given coverage. Because I am limited to water based paints or inks I have chosen to use lighter grades of tissue. I have Tengujo and other Kozo based tissues ranging from 3.5 gsm to just under 8 gsm.

In the case of my Sopwith Pup project, I wanted to print the markings and I chose to use 6 gsm Tengujo. That meant I needed to fill the pores in the tissue so that there was a surface to accept the printer ink (Epson Durabrite). I used a white concoction of various acrylic materials for the wing covering which may not ultimately be the best technique. I have other materials waiting for further experimentation that may produce a better result at a lighter weight.

Unlike Esaki, there is no front of back side of these tissues from our perspective. Conservators may have a different opinion but my technique for filling the tissue pores does create a front and back side.

I lay the tissue on a smooth clear backing that has low surface energy and apply the coating by brush. The side adjacent to the smooth backing will be smooth and the other surface will show the texture of the tissue fibres. I will not go on about the technique I use because it is still evolving unless more information is requested in which case I will continue in another post.

Paul

[RolandD6]

Hi Don

Further to your question.

Tengujo does not water shrink or very little if it does. It does expand when wet with water which may allow wet covering of compound curves even when sealed with acrylic ink, paint, or what ever.

IT WILL SHRINK DRAMATICALLY IF DOPED WITH CELLULOSE LACQUER. It is the dope film doing the shrinking dragging the tissue with it.

So far I have not tried wet covering. The Bf 109 may be the first instance. All covering to date has been dry and I have been able to get it sufficiently tight to not require further shrinking.

Paul

[Don McLellan]

Hi Paul,

Thank you for Tengujo tissue info.  As mentioned, I've only ever used Esaki, so this is all new to me.  And have to say, am amazed by the detail of the Sopwith Pup project by Jiří Doležel. 

Cheers,

Don

[RolandD6]

A little bit more work done today.

I have sanded all of the wing ribs with the exception of the root ribs down to 0.6 mm thickness. I have been scratch building wings with 0.5 mm ribs so 0.6 mm is conservative.

I have ground and sanded as much wood as I dared from the inside of the fuselage formers to reduce weight. I have also added small sticks of very hard Solarbo 1/32" balsa as cross grain reinforcement. I have had that piece of balsa for about 60 years and it is handy for this type of application. The sticks that go past the vertical crutch members will help me align the other half formers and also provide cross grain reinforcement for them.

The half fuselage frame is about 1.87 gm which I think should be acceptable. I suspect I could have got less than that if the frame was scratch built from lighter wood.

Paul

[TimWescott]

A little bit more work done today.

I have sanded all of the wing ribs with the exception of the root ribs down to 0.6 mm thickness. I have been scratch building wings with 0.5 mm ribs so 0.6 mm is conservative.

I have ground and sanded as much wood as I dared from the inside of the fuselage formers to reduce weight. I have also added small sticks of very hard Solarbo 1/32" balsa as cross grain reinforcement. I have had that piece of balsa for about 60 years and it is handy for this type of application. The sticks that go past the vertical crutch members will help me align the other half formers and also provide cross grain reinforcement for them.

The half fuselage frame is about 1.87 gm which I think should be acceptable. I suspect I could have got less than that if the frame was scratch built from lighter wood.

Paul

This all mystifies me.  Wouldn't it be easier, and result in a lighter product, to just scratch-build the thing, re-engineering as you go, using the plans, and maybe some of the die-cut pieces as guides?

(It's still a nice build, and I'm not dissing your effort, here -- I really am curious).

[RolandD6]

A little bit more work done today.

I have sanded all of the wing ribs with the exception of the root ribs down to 0.6 mm thickness. I have been scratch building wings with 0.5 mm ribs so 0.6 mm is conservative.

I have ground and sanded as much wood as I dared from the inside of the fuselage formers to reduce weight. I have also added small sticks of very hard Solarbo 1/32" balsa as cross grain reinforcement. I have had that piece of balsa for about 60 years and it is handy for this type of application. The sticks that go past the vertical crutch members will help me align the other half formers and also provide cross grain reinforcement for them.

The half fuselage frame is about 1.87 gm which I think should be acceptable. I suspect I could have got less than that if the frame was scratch built from lighter wood.

Paul

This all mystifies me.  Wouldn't it be easier, and result in a lighter product, to just scratch-build the thing, re-engineering as you go, using the plans, and maybe some of the die-cut pieces as guides?

(It's still a nice build, and I'm not dissing your effort, here -- I really am curious).

The simple answer is yes but it would take much longer and I am trying to meet a deadline. I get very tired very quickly because of the concentration needed to build small models so I can only put in an hour or so at a time.

I have some Dumas kits and I will be doing exactly what you suggest with them because I hope to not have any deadlines to meet. Namely:

Waco YMF-5
Stearman
Piper J-4

The first two are nominally 1/22 full size which is my preferred scale. My own designs are 4.6% scale which is close to 1/22. I have been working on and off on a Waco 9 and a RANS S-7 Courier but that has stopped because my workstation computer died and the service people are still having trouble getting it to work properly again.

All of these models will fit into my standard 450 x 450 x 150 millimeter storage boxes.

Paul

[RolandD6]

The first two are nominally 1/22 full size which is my preferred scale. NOT TRUE. THEY ARE CLOSER TO 1/20. Oh well they will still fit into my standard 450 x 450 x 150 millimeter storage boxes.

I little more progress today. I am sanding and fitting the other side fuselage formers in turn, allowing the glue to dry properly before moving on to the next one.

The second image shows how much wood was in the kit parts.

The third image shows the handy gadget I use to hold small parts while sanding them. Clamping and holding the balsa at an appropriate angle reduces the risk of splitting it.

Paul

[RolandD6]

The basic fuselage is now just about finished as in the first image. It weighs 4.37 gm as shown by the second image. The small squares with holes in them are 0.6 mm birch ply to reinforce the inside of the rubber peg part of the fuselage. I have moved the rubber peg forward and reduced the amount of wood around it.

The fuselage frame has had one coat of clear acrylic ink applied to raise and toughen the fuzz which was sanded off with 400 grit open-coat paper. The infill bits are 4 lb/cub. ft. balsa which is rather pithy but does the job.

I attempted the sand the kit tail tailplane and fin parts to make forms but that was a disaster because I had the shakes and the disk sander was too aggressive. I inserted a scan of the plans into TurboCad and redrew the tail parts, printed them onto a large adhesive label and stuck them onto 1.2 mm birch plywood. This was much easier for me to control on the disk sander.

The next image shows the laminated outlines waiting to be removed and placed in the assembly jig shown by the fourth image.

This is the second go at making the laminations. The first time I wrapped plumbers PTFE tape around the edge of the forms but that was also a disaster. Surprisingly the glue stuck to the PTFE causing little bits to adhere to the lamination. Because the tape goes clear when stretched, I could not be certain there was none at an internal joint hence the need to make the laminations again. This time I wrapped shiny packaging tape around the form but have yet to try and remove the laminations from the form. Should work.

I guess nobody is surprised when I found the kit supplied plastic nose does not fit the fuselage. It is supposed to overlap the balsa frame.

More later.

Paul

[RolandD6]

I had hoped to be able to slide the plastic nose over a balsa frame but it is now clear I will need to scratch build it. So much for trying to save time by building a Guillows kit.

I guess some of you are thinking "I could have told you so" but remained quiet and polite.

With luck I may be able to use the plastic radiator air scoop which would be helpful because that its the bit that will strike the floor first. I do not plan to fly this model with a dangling undercarriage.

Paul

Edit: I had a thought after posting this that I may be able to sand the rear of the plastic cowl so that it is a good butt fit to the balsa frame. A problem with the molding is the rear face does not appear to be parallel to the front so it would be easy to ruin the whole thing trying to get them parallel.

[RolandD6]

As I suspected, the cowl molding is not parallel.

The first image shows the bench top to be level.

The second image shows the tilt of the front of the cowl is out of range of the spirit level. Significant upthrust if used as is.

This will require some careful consideration.

Paul

[Don McLellan]

Hi Paul,

Had a bit of a chuckle when I read of your PTFE tape adventure.  I have done the same thing, many times.  For whatever reason, the tape likes to bond to diluted Duco, and as you say, it is difficult to determine where the tape stops and the Duco begins.  I have tried wax as a parting agent on the periphery of forms used to make laminated wing tips etc, and have had marginally better success. 

Very nice work, and am following along with interest.

Don

[OZPAF]

Hi Paul. I have only just come across your build and enjoyed reading it. I particularly liked your coverage of Tengujo tissue and your approach to the use of the half formers - using the stiffening sticks as alignment aids for the second half of the former is simple and elegant. I enjoy your careful approach to solving the little challenges.
Nice work. It should fly well.
happy building.
John

[Crabby]

Hi Paul Great looking build you have going on there! Paul, have you considered filling the plastic cowl molding with plaster then reforming it? Once the plug is removed you can sand the bottom back to parallel and re-form. Somebody on here has done this and it worked pretty well. Maybe check out Chris Boehm on you tube for the procedure.

[ZK-AUD]

Or just ditch it and make a wooden one that you can adjust thrust lines and get proper access to the rubber for winding perhaps?

[RolandD6]

... I have tried wax as a parting agent on the periphery of forms used to make laminated wing tips etc, and have had marginally better success.  

Very nice work, and am following along with interest.

Don

Hi Don

I have used wax before myself but this time I was concerned about the possibility of wax remaining on the laminate. The plastic strips that appear in the photos are polypropylene. The clear ones come from DVD cases, the blue ones from Blue Ray cases and the red ones from a picnic dinner plate. Aliphatic glue does not stick to polypropylene very well and there is no risk of contaminating the laminate surface. I machined them on my mill and they are either 5 or 6 mm wide, various thicknesses and lengths.

For future models that I may make more than once I will try using polypropylene for the templates.

[RolandD6]

Hi Paul Great looking build you have going on there! Paul, have you considered filling the plastic cowl molding with plaster then reforming it? Once the plug is removed you can sand the bottom back to parallel and re-form. Somebody on here has done this and it worked pretty well. Maybe check out Chris Boehm on you tube for the procedure.

Hi Crabby.

No the thought of using plaster like you suggest had not occurred to me. I have yet to build a vacuum forming device but sanding the whole assembly would provide much better control of the removal of plastic from the flimsy molding if the dried plaster is left inside it. The plaster would take far too long to fully dry so that idea is not practical for this project.

[RolandD6]

Or just ditch it and make a wooden one that you can adjust thrust lines and get proper access to the rubber for winding perhaps?

That is somewhat like my current thinking. I am considering drawing and making thin sheet balsa keels that define the side and plan views of the airplane’s nose and using them to support the nose plug assembly in the correct position. The keels would remain as part of the airframe. Then I can see if the plastic molding can be manipulated, modified or what ever to be useable. If not then simply complete the nose in balsa as you suggest. I have plenty of 4 and 6 lb balsa block so it should be possible to create satisfactory light weight thin balsa shells.

Thank you all for your suggestions

Paul

[tross]

Hello Paul I hope all is well there.
It's coming along well and very enjoyable thank you.

Removing the nose plug as a whole to install the motor and blast tube is probably already part of your plan.
You might consider some structure inside the cowl to support it, removing the entire cowl for winding.
If so you could go ahead and install the structure into the cowl, set in a sixteenth or so from the top side.

Then temporarily placing a duplicate of B2 (is it?) for a guide to trim and straighten the back of the cowl to the structure.
In the end leaving a lip of cowl to fit over the tissue.
Not as elegant as your plan of course.

Tony

[RolandD6]

...
Removing the nose plug as a whole to install the motor and blast tube is probably already part of your plan.
You might consider some structure inside the cowl to support it, removing the entire cowl for winding.
If so you could go ahead and install the structure into the cowl, set in a sixteenth or so from the top side.
...

Yes something like your proposal Tony.

[RolandD6]

I spent more time looking through my references and on the internet after making an observation about the Guillows Bf-109 compared to the clearly more accurate VMC Bf-109E build described by Steve Neil in his thread (see https://www.hippocketaeronautics.com/hpa_forum/index.php?topic=24482.0 Reply 13). It appears the profile drawing of the Bf-109D in “Famous Fighters of the Second World War by William Green” is either inaccurate or depicts a slightly different version of the Bf-109D compared to the D-1 purchased by the Swiss shortly before WW2. Other information and photos show the Guillows kit to be a reasonable facsimile to the D-1 operated by the Swiss.

See:
http://hyperscale.com/2007/features/bf109dswissph_1.htm
https://acesflyinghigh.wordpress.com/2016/10/22/swiss-air-force-centre-messerschmitt-bf-109e-3/
https://modelingmadness.com/review/axis/luft/109/rey109d.htm
http://richard.ferriere.free.fr/3vues/bf_109d0_3v.jpg

The kit radiator cowl is not quite right. The Swiss Bf-109D-1 did not have exhaust shrouds and the lower rear fuselage and the rudder need small alterations. All are easily incorporated at this stage of the build.

Paul