Blue Pants

ian1954 Fri Aug 30, 2019 6:12 pm

This is one of my favourite planes - Blue Pants - 37in span CL stunter, designed by Henri Stouffs. Winning stunt model at the 1954 World Championships - I first built one in 1968 but it was a disaster. I built it too heavy and powered it with an Enya 15 glow. Unfortunately, at the flying site the silencer rule was introduced and it ended up even heavier, underpowered and didn't survive a single lap.

It was always mu intention to build another one - I suppose the 1954 has something to do with it and childhood/teenage memories.

I built this before the Radian+, Peacemaker and the Dominators (still not finished).

The first thing to build on this is the wing - the fuselage is built around it.

I decided to tissue it but this became problematic. The tissue I chose seemed fine - very strong but ........... it had little wet strength and I had several attempts at covering without tearing it.

Finally it was covered but as the tissue shrank it tore badly. I then applied it dry and doped it - again it tore.

Removing tissuse is a pain but a judicious amount of thinner works wonders but is very time consuming.

i then used a heat shrink covering and, although it wasn't the classic finish I was aiming for - it looked OK.

A couple of days later - yuk!!!!!

The whole thing had developed tight wrinkles - even over the open bays!

I was not happy with this at all and removing it was even harder tham tissue. I threw away the roll that I had used - not sure of the make or origin - and redid the wing with Solartex in the same colour.

I have to say that I am not a fan of these heat shrink coverings as they seem to add little strength to the wings of vintage models but it is much quicker and this is a strong wing structure.

To be continued

ian1954 Sat Aug 31, 2019 5:46 am

This may seem like a saga but it is meant to illustrate the trials and tribulations we all experience at some time.

There i was, a wing constructed in 4 hours - one afternoon. Next day, a couple of hours sanding followed by 4 days of frustration.

I understand why a few of our members prefer the slab and plank models that can be built and flown the next day. (weather permitting!)

I then faced another delay in the choice of engine. The original engine per plan was the ED Racer 2.5 diesel. No problem, me thinks - I have two of these and I have run them both up.

Luckily, I decided to bench run them both again but this time I was a tad disappointed with the results.

My first choice was primed and started first flick, I ran it for 6 minutes and then it wouldn't restart .

Cooled down and first flick start. Back to the workshop and the head removed - i could see that the contra pistion was worn and needed replacing.

Second choice - a buskelised ED Racer

This one was not an easy starter but once warmed up - it ran fine but the gaskets around the exhust collector needed replacong and so back to the workshop. New gaskets made and fitted and back to the bench.

Starting was no easier but it ran fine. Didn't fancy the endless flicking while fitted to a model so time for a full strip,

Con rod needs replacing and a new bearing.

Two more engines consigned to my repair/restore box and the Blue Pants build put to one side.

As some of the longer serving forum members know, I am not short on engines but when a project becomes frustrating - I put it to one side. I don't like to rush builds and I don't aim for a concours finish but when something I had planned on a couple of days has spread over three weeks .................

to be continued

rsv1cox Sat Aug 31, 2019 7:19 am

Looking forward to it Ian.

I always had good luck with almost everybody's favorite covering - Monokote. But Dirk Gently can really lay down some tissue. Maybe he can chime in with some pointers.

Give me an engine that will start easy and run well over any hard starting hopped up engine any day.

fredvon4 Sat Aug 31, 2019 10:28 am

Ian have you ever worked with Silk?

Process nearly exact was wet tissue but without the tearing and I think takes a compound curve better..

You could use 5MM the lightest in white and first dye it the blue you desire...or Use pre colored 8MM from Dharma

If new to this I would recommend a few clicks all over the Dharma site on dying care and prep of the fabrics and other neat to know things

MM is how silk is graded 3MM is very sheer and as the number goes up the weave tightness is denser and the individual filament are larger in diameter..In aircraft model world we mostly use the 5MM and 8MM stuff...differing opinions about final weight ...most of us think it is a wash...5MM is lighter but takes several more coats of Dope too fill the weave vs the slightly heavier 8MM but less dope

shrinkage

Fabric Details
- 100% Habotai Silk
- 8mm, 45" wide
- You can dye the white ones with Acid Dyes, iDye or other dyes for silk, and you can also over-dye the colored ones, except for black.
- We found that this shrinks 10% in Length and 2% in Width disclaimer
- Suggested usage; scarves, pillows, linings for jackets, banners, etc.
- Available in cut yardage and bolts.

Here is a beautiful, Blue you might consider....BTW cost per Yard is relatively inexpensive IMO...from a Hobby outlet you pay 3 to 5 times the per yard cost from Dharma

https://www.dharmatrading.com/fabric/silk/royal-blue-silk-habotai-8mm.html

Link above is a beautiful Blue 8MM "China' ( Habotai) silk

Cost per yard is cheap

Hint if width is 36 inches buy more than one yard..-------Logic.... 36 wide by 36 long is a square that you can NOT tell Length and width as it is mailed folded in a square for an envelope...

YOU NEED to know long length off of the bolt... READ the shrinkage speck above...Long length is span wise on a wing the 2% width shrinkage goes on chord wise

ian1954 Sat Aug 31, 2019 11:12 am

Never had those problems before but you should be aware that our materials are different. Monokote is not sold in the UK and our Americn brethren use butyrate dope. Our dope is cellulose dope - I believe you call it nitrate. Hence we need to apply fuel proofer when it has gassed off.

While I am on the subject of dope - almost all UK dope is produced by HMG and repackages for various distributors. It is difficult to find in sizes over 1/2 litre now and is expensive.

However, it also dries very quickly and even with thinner leaves brush marks.

Recently I found an importer of Randolph dope who sells it by the gallon (not a real gallon but a US gallon!) - it works out cheaper and delivered next day! Randolph also produce a retarder to slow drying and eliminate brush marks.

I think Randolph produce the dope for Brodak and SIG.

By the way - we call tautening dope shrinking dope and non-tautening dope just dope.

I have just posted details of the Wizard, ACE + and Roby completed while the Blue Pants was put aside.

Blue Pants to be continued

Mike1484 Sat Aug 31, 2019 12:14 pm

I like the non tightening dope . It does not bridge as bad in the corners like the tightening dope does . That is good stuff , I use it on my free flight models .

Mike1484

ian1954 Sat Aug 31, 2019 12:32 pm

fredvon4 wrote:Ian have you ever worked with Silk?

Process nearly exact was wet tissue but without the tearing and I think takes a compound curve better..

You could use 5MM the lightest in white and first dye it the blue you desire...or Use pre colored 8MM from Dharma

If new to this I would recommend a few clicks all over the Dharma site on dying care and prep of the fabrics and other neat to know things

MM is how silk is graded 3MM is very sheer and as the number goes up the weave tightness is denser and the individual filament are larger in diameter..In aircraft model world we mostly use the 5MM and 8MM stuff...differing opinions about final weight ...most of us think it is a wash...5MM is lighter but takes several more coats of Dope too fill the weave vs the slightly heavier 8MM but less dope

shrinkage

Fabric Details
- 100% Habotai Silk
- 8mm, 45" wide
- You can dye the white ones with Acid Dyes, iDye or other dyes for silk, and you can also over-dye the colored ones, except for black.
- We found that this shrinks 10% in Length and 2% in Width disclaimer
- Suggested usage; scarves, pillows, linings for jackets, banners, etc.
- Available in cut yardage and bolts.

Here is a beautiful, Blue you might consider....BTW cost per Yard is relatively inexpensive IMO...from a Hobby outlet you pay 3 to 5 times the per yard cost from Dharma

https://www.dharmatrading.com/fabric/silk/royal-blue-silk-habotai-8mm.html

Link above is a beautiful Blue 8MM "China' ( Habotai) silk

Cost per yard is cheap

Hint if width is 36 inches buy more than one yard..-------Logic.... 36 wide by 36 long is a square that you can NOT tell Length and width as it is mailed folded in a square for an envelope...

YOU NEED to know long length off of the bolt... READ the shrinkage speck above...Long length is span wise on a wing the 2% width shrinkage goes on chord wise

Yes I have worked with silk and dyed it. It is fortunate that you mention silk as this was raised with me by one of my Spanish friends - vintage aeroplane builder. engine builder and collector, Spanish model engine expert - and he has supplied me with some very high quality silk that I have washed ready for use.

I have tested a few squares of it and it shrinks about 3% all round.

I love the finish produced using dope on tissue, silk and nylon. I have just finished doping the nylon covered wings on the Dominators I am building but the wing has to be strong to avoid warping and although a doped finish adds strength it discovers weaknesses.

Here is one of my magnificent disasters. See balsa crushed and distorted!

https://www.coxengineforum.com/t7424-rsm-p51d-build

I have more caution these days and tend to 50/50 shrinking and non-shrinking dope for the first couple of coats and then just use dope.

However, understand my caution with silk. The P51d was a very expensive contest balsa kit and I was not happy with what I did to it.

The Blue Pants wing is very strong and it was the tissue that tore (over and over again). Haven't a clue what happened with the heat shrink covering. The Dominator wings are straight as straight can be but I couldndn't twist them before the nylon went on and now they are rock solid after 3 weeks.

I have evry intention of using silk again but have to have the confidence that the wing can take it.

ian1954 Sat Aug 31, 2019 4:12 pm

Back to Blue Pants - well sort of!

The thing holding me up was engine choice but during the lay up - my Spanish friend had located sveral ZOM negines to complete my collection of ZOM diesels. I now have every ZOM diesel variant except the very early short nose combat engine.

As an aside, I always knew them to be Oliver Tiger clones of sorts but he told me that the Spanish refer to them as Olivetas. Oliver-ETA.

He said he would like to see a ZOM installed in a control line plane and so I had a candidate for the Blue Pants.

In my restore box was a ZOM Mk1. It had obviously been in a prang as the NVA had been replaced with an Enya assembly..

Not happy with this but I ran it up and only got 8.500 rpm on an 8x6 prop. I was not that familiar with ZOMS but knew that they were renowned for being good Olly equivalants.

I asked my friend if he could locate a NVA for me and I sent him this picture

By reply, he had spotted the obvious - the cylinder liner was 45deg out of line nad the venturi had been drilled out for the Ennya NVA. The orignal NVA was only 3mm diameter not 3.9mm.

So, luckily, there were original assembly marks on the con rod, piston and liner - a simple twist and the liner was repostioned.

A gentle run up and 12,600 rpm.

The NVA arrived ready to be fitted - next job to make the bushings.

ian1954 Sat Aug 31, 2019 4:40 pm

As well as the diameter of the NVA being important - centering it is also ideal with a tight sliding fit. The venturi had been drilled out for the Enya NVA very accurately and was precisely 3.96mm diameter. A brass rod 3.97mm was turned and bored to 3mm..

Parted off to the correct length - each side different

Then placed in a freezer for an hour while the engine is warmed up under a halogen lamp

A very tight fit as the bushes are pressed into place.

A 14,500 rpm run followed by a clean and installing in the Blue Pants crutch.

ian1954 Sat Aug 31, 2019 5:22 pm

and

This was flown through the stunt pattern by a fellow club member. now I have a camera. I will film it. He was orinally concerned over the size of the elevator but everything went smoothly.

smooth_bill Sun Sep 01, 2019 12:38 am

Ian,

Great thread!

I've always enjoyed reading your posts, and the great building details that you cover so well, along with very nice photography!

What I don't understand is how your lathe works?

Doesn't your lathe create swarf, and/or chips? I've never seen a working lathe, so spotlessly clean, and rust free! Outstanding if you do all that yourself.

Not to mention that your work areas are also spotlessly clean. Kudos to you!

Your Blue Pants looks beautifully built, and very nicely finished, but apparently it flew as well as it looks!

Looking forward to more of this story.

Best regards,

Bill

getback Sun Sep 01, 2019 5:58 am

Looks Great Ian , that was more than a airplane build with the engine troubles . but it did work out to make a beautiful plane and the diesel looks good in there . So the Zoms are a variant of The Oliver Tiger know as Olivetas in spanish ? Good build !! and repair of the NVA !! Very Happy

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