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Author Topic: DPCM Sopwith Pup  (Read 3508 times)
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RolandD6
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« on: June 18, 2019, 10:20:36 PM »

Hi All

I have got back to this model during my break from the Kinner engine project. It is a DPCM Sopwith Pup that I purchased from Dave in August 2012. I cannot remember when I started building it but I do remember I built the wings first and used Deluxe Matrials Super 'Phatic! for the first time probably not long after I heard about that glue. It did not impress me much at the time compared to the alphatic glue I had been using, an Aussie product called Triton (brand name) now no longer available. After the loss of Triton I tried all sorts in addition to Deluxe including all three varieties of Tite-Bond and currently am working with Gorrilla Wood Glue.

The first three images show the fuselage frame in one variation of my universal jig. It is built from kit wood but sanded down to 1.3mm thickness. The sheet bits where sanded before assembly and the strip wood was sanded after assembly so they are typically 1/16" X 1.3 mm although some of the kit strip wood is closer to 1.7mm square. All joints were pre-glued with Gorrilla thinned with 1/3 water, left to soak in and then when sufficiently gelled the joints were completed with a tiny dob of full strength Gorrilla.

The white piece in the jig is scan and print of the fuselage plan top view printed on full page adhesive label stock and the stuck to a piece of light card. The top surface had a layer of shiny adhesive tape to prevent the glue sticking to the pattern and then all was cut to shape. The right angle jig pieces touch the edge of the pattern to ensure the outer profile of the fuselage frame is the correct size and shape. The kit supplied cross pieces are now too small so that have been replaced with 1.4 mm square strip on the fuselage bottom and 1.2 mm square on the fuselage top, (the frame is upside down in the jig). The smaller strip was used on the top because the kit supplied formers will add the necessary extra strength. They have been sanded down to 1.3 mm but I am thinking of reducing them further to 0.8 or 1 mm.

Continued in the next post.
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RolandD6
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« Reply #1 on: June 18, 2019, 10:22:04 PM »

The next four images show the wings, empennage and engine cowling in their current state. I have used laminated outlines to the wing tips, fin and rudder but I cannot remember if that is to plan or not because I have managed to lose that particular part of the kit. The covering is 6 gsm (nominal) tengujo Japanese tissue sealed with various acrylic ink and paint concoctions. The markings were printed on the coated tissue by an Epson XP400 printer using DuraBrite ink. The tissue was laid on a fresh and clean polypropylene sheet and the white coating applied with a 1/2" red sable brush. The tissue is very delicate and the drag of a larger brush tends to tear the wet tissue.

I am modelling the Sopwith Pup replica located at the RAAF Museum, Point Cook in Australia, hence the white finish. The Pup is powered by an Armstrong Sidderley Genet Major 1A hence the longer than usual cowling. I will just use a print of the engine inside the cowl because I suspect the model may be nose heavy with the extended cowl and because I have moved the rubber motor peg position forward by one bay.

More later

Paul
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RolandD6
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« Reply #2 on: June 19, 2019, 02:25:13 AM »

Fuselage out of jig and engine cowling loosely positioned. Not going to glue the cowl to the frame until much later (if possible) to protect the fine rear edge which is already a bit damaged.
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RolandD6
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« Reply #3 on: July 13, 2019, 09:45:48 PM »

A little bit more progress.
Rear turtle deck stringers added but they are not the original 1/32" x 1/16" kit supplied strip wood. They are triangles cut from 0.7mm wood like those described by Bill Dennis on his Bristol Scout/Bullet shown on page 48 of the April 2019 issue of Aeromodeller. The original kit stringers were only supported at each end whereas the triangles are supported by the box frame cross members at 5 points.

The forward top decking is attached; kit wood sanded down to 0.6mm a while back that has sprung back to about 0.7 mm due to the winter humidity. Next up are the 'cheek' panel pieces, also nominal 0.6mm wood.
The photo below shows a current weight of 2.48 gm. It was 2.68 gm before I cut the four lightening holes, the edges of which have a light coating of thinned alphatic glue to hopefully prevent splitting.

The paper tabs are for reinforcing the cabane strut to fuselage attachment points. They are not ordinary paper. They were cut from an old Microsoft 5.25 diskette sleeve. It looks and feels like Tyvek as recommended by Don Ross. The paper has embedded reinforcing fibers that make it very difficult yo tear.

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OZPAF
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« Reply #4 on: July 14, 2019, 05:39:22 AM »

Interesting approach Roland. I like the idea of locating the squares in the channels of your jig with wedged in pieces of rubber tubing. Neat.

John

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RolandD6
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« Reply #5 on: September 11, 2019, 03:52:59 AM »

I finally bit the bullet and tried to apply a chrome finish to the cowling areas.

An easy but expensive approach is to purchase a 30ml refill bottle of Molotow liquid chrome. Some plastic modellers have tried this and there are a few videos on U-tube demonstrating successful airbrushing of plastic models. The local price for this is $50 which is a bit much for a single model. I tried a 4mm pen and the results were not encouraging.

I had hoped to get a satisfactory result using Heidiswapp reactive foil. The local price for this is $16 for a 12.25" wide by 120" long roll. See first image.

The first step was to decide on a grain filler the would work on 0.6mm balsa and would not aggravate my asthma. Years ago I happily used a lacquer based sanding sealer on C/L models  but that is a no-no now. The strongest fumes I can tolerate in a ventilated workshop is small amounts of denatured alcohol. Nominally 95% ethyl alcohol and 5% methyl alcohol. It is mainly the methyl alcohol that upsets my chest.

I tried all sorts of materials mixed in water or denatured alcohol but in the end only one easily obtainable material was satisfactory as a sealer/filler, de-waxed shellac. I applied two coats of the recommend strength for french polishing to the balsa, sanding after each coat. The wood was sealed but the grain was not filling quickly so I applied a coat of black india ink. The pigment is carbon black which sanded nicely. I next applied a coat of yellow india ink which did not cover the black very well but helped to identify unfilled areas.

Next was a layer of Vallejo acrylic-polyurethane grey surface primer sanded back and then a coat of Vallejo acrylic-polyurethane Desert Tan surface primer sanded back to get the result show in the second image.

Other experiments on test samples suggested that gold size is superior to thinned acrylic contact cement for sticking the reactive foil but disappointingly the gold size I had purchased would not self level very well. Never-the-less I decided to push on, perhaps foolishly, and the result can be seen in the third image. Coverage was not good in parts so I applied a second layer of reactive foil which only went part way to the fixing the problem. Little patches of exposed filler still existed so I tried patching by brushing little areas of ink from the Molotow pen. As you can see from the photo, the outcome was not good.

I don't want this to beat me because I have the rest of the engine cowl to do and other airplanes are waiting in the wings that also have polished cowls and other parts, WACO's with ring cowls in particular.

Looks like I will be purchasing a Liquid Chrome refill bottle, attempting the sand down the unsatisfactory work and airbrushing everything.

Paul

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Jack Plane
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« Reply #6 on: September 18, 2019, 04:33:00 AM »

Nice one Paul

I've got the same kit lined up for building in the near future... so look forward to following your job.

Jon
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Russ Lister
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« Reply #7 on: September 18, 2019, 06:45:46 AM »

I do like a Pup .... look forward to further progress... from both of you!

I like the jigging, Paul.  Smiley

By coincidence, I had a look at my OD Pup "jar of bits" this morning.  Roll Eyes
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Squirrelnet
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« Reply #8 on: October 05, 2019, 01:22:17 PM »

Hope you don't mind me joining/crashing the party Paul  Huh

 Like Jon I have the kit too but I have mine lined up as my 2020 Indoor Kit Scale entry, I plan to paint though so it may end up in the open class for the craic

I was thinking of converting it to CO2 but I think I will stick with rubber power for this one

I wasn't sure if I should move the motor peg forward, but looking at photo's of other DPC Pups and RolandD6's build I don't think I will. It's such a short nose anyway it probably wouldn't give much of an advantage as it still wouldn't be possible to distribute the motor across the CG, unless the motor was 2" long

I'm building mine as a Standard Motor Company Pup built as a night fighter but later used privately as G-EAVX. The colourful scheme is from when it entered the 1921  Aerial Derby at Hendon. It failed to make it around course and crashed on landing. The pilot Lester Forestier-Walker was reportedly drunk …. well that may make trimming it to fly in scale manner easier ?  Grin.

EDIT - I should add that Lester  survived the incident. The aircraft was stored by the Graham White factory but no payment was received for storage or repair so the wings were sold off. Amazingly the fuselage survived and is now being restored at RNAS Yeovilton

So far I have a fuselage side
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Mark Braunlich
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« Reply #9 on: October 05, 2019, 04:32:13 PM »

All photos of EAVX
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RolandD6
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« Reply #10 on: October 05, 2019, 04:40:12 PM »

Hope you don't mind me joining/crashing the party Paul  Huh

...


I am OK about it. Mine is unlikely to be done before 2020 also. I have the bottle of Liquid Chrome now but will not be returning to the Pup before the Bf 109 is finished. I will soon post more about that project soon.

My fancy computer workstation is still in the hands of the service people. The repaired parts have come back from the manufacturer but they say there is still an unresolved problem with the graphics. The whole reason for spending the money on it in the first place was to get superior and fast graphics, vital if you don’t want to go insane waiting for 3D renders to finish.

I am also OK about sharing this thread with your DPCM Pup project if that is what you would like to do.

Paul
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Squirrelnet
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« Reply #11 on: October 06, 2019, 12:31:30 PM »

Thanks Paul.

I look forward to seeing yours come together when you do come back to it.

I managed a bit more on the fuselage today. I was puzzling over how to build it square as the top formers are curved so building it flat upside down on a board, which would be my preferred method, is not going to work. I did consider building it as a simple square box fuselage over the plan and adding the formers later... then I read the instructions on the plan  Roll Eyes

Dave Cowell has designed the fuselage to self square itself, and with a bit of care and this time following the instructions I have a square Pup fuselage.

Rather than quitting while I was ahead I also made up some formers for the tips and fin and after blasting them with the wallpaper stripper, laminated up some 1/32" x 1/16" balsa

 
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RolandD6
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« Reply #12 on: October 06, 2019, 07:33:01 PM »

Your Pup is looking good.

Clearly you will finish yours well before I finish mine. Still getting a bit of progress on the Bf 109 but not ready to post anything in that thread yet.

Paul
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Squirrelnet
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« Reply #13 on: October 13, 2019, 01:03:30 PM »

Thanks Paul , I'm following your Bf 109 thread with interest.

It was a wet day again here but at least it gave me a chance to get on with the Pup.

I now have a basic airframe. The only mod I have made so far is alter the wing tip shape to make it more Pup like with its straight edges, I've added some 1/16' sq to help give some strength to the tip as well as per the fullsize.

The cowling will need some mods too as the version I'm building had the slightly larger Monosaupape cowling. I'm thinking I could roll the sides from 1/64 Ply

Chris
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RolandD6
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« Reply #14 on: October 14, 2019, 02:28:02 AM »

Chris

You had me worried about the wing tips until I checked photos of the RAAF pup. It has wing tips similar to the kit so all is good.

Paul
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Squirrelnet
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« Reply #15 on: October 14, 2019, 03:04:27 AM »

Sorry about that Paul.. I should have said to make the tips more like the example I'm modelling
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Squirrelnet
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« Reply #16 on: October 19, 2019, 02:00:16 PM »

The Pup has progressed a bit. I now have the basic structure completed, though the top wings still need sanding.

The wheels have had tyres added from 4mm neoprene sponge cord, total weight for both wheels is slightly more than balsa only wheels at 2.5g but not only does it look better to my eye, its saved a bit of time balsa carving time too. The spoke impressions on the wheel covers are made by drawing the lines on the back of the covers with a pencil to score the thin card

The cowling is the larger Monosaupape type so I made up a former and rolled a strip of steamed 1/64" ply round it to form the outside the front face will also be 1/64" ply too.

There's still a few things to add, undercarriage, struts etc but all the bits including a Dave Banks pilot come to 15.5g, hopefully that's in the right ballpark?



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Russ Lister
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« Reply #17 on: October 19, 2019, 02:09:11 PM »

Looking good, Chris  Smiley

Just to feed my wheel obsession ... what diameter are the wheels?

Don't forget to hollow out the Bank's pilot .... it saves .... er ... loads. Well ok not loads, but it is worth doing.
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billdennis747
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« Reply #18 on: October 19, 2019, 02:22:48 PM »

Chaps
About 1/4 of the way down this page you will find the Sopwith logos in FF scales. I don't think either of you are using the fin decal but if you want the strut logos I have spares I can send
Bill

sorry - forgot the vital bit
https://www.mickreevesmodels.co.uk/~mickreev/Bipes/p2bipe.html
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« Reply #19 on: October 19, 2019, 02:25:19 PM »

Very nice Chris.  Could be worth having a look at that rather small opening in the firewall in relation to where the hook will  be once all the downthrust is built in.  Likely to be anything up to 5 degrees if my Camel and triplane are any gauge
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« Reply #20 on: October 19, 2019, 02:54:05 PM »

Russ - you have wheel obsession ? OK  my vernier calliper gives 1.496". 16" span model, does that sound right ? My attempt at wheels is no where near your spoked wheel prowess but hopefully I will get away with it

Great offer Bill but I think the struts had been painted over in red on the example I'm modelling so I don't need any.

Mike - very good thought, and actually looking at it with the predicted downthrust it will need more room at the top. Thanks  Grin

Chris
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Russ Lister
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« Reply #21 on: October 19, 2019, 03:02:44 PM »

Bill,
Great link .... I didn't think that Mick Reeves did anything in FF sizes.

Chris,
That sounds a good weight at that size. Sounds like the Pup is about the same scale as the DPC Triplane I have built.
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billdennis747
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« Reply #22 on: October 19, 2019, 03:08:40 PM »

Bill,
Great link .... I didn't think that Mick Reeves did anything in FF sizes.
Russ, I just suggested it to him and he did it. The very smallest (KK Camel size) lose a little definition but they are very useful. When I do a Sopwith I prefer the early ones with unpainted cowls and these usually have the fin marking.
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billdennis747
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« Reply #23 on: October 19, 2019, 05:24:37 PM »

double post in error
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RolandD6
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« Reply #24 on: October 19, 2019, 05:52:02 PM »

It’s coming along nicely Chris. The suggestion of needing 5 degrees down thrust is a bit of a worry. You will have yours flying before mine so waiting a bit may be an advantage for me. I intend to build a new cowl for mine so I can crib a bit of  down angle in that. My home made grub screw thrust line adjustment jigger is only good for about 3 degrees maximum In any direction.

Got my work station computer back this week, after two months in the repair shop. Turns out the unresolvable graphics fault was caused by the new 2K screen module. The original had developed a line of dead pixels. They generously replaced it with a 4K unit at no extra cost. Seems to work fine but the downside is the command icons in TurboCad are now tiny. There may be some adjustment for that.

On the bf109 front. A lot of research into the ‘D’ model flown by the Swiss has revealed a lot of conflicting information even  though there is very little info about the C and D models anyway. Most of the ‘fake news’ is in the terminology. The D is a development of the C model of which very few were built. Some C and D models were sent to Spain for trial in that war. All of the C models were powered by a Jumo 210 ( it seems) and some D models were similarly powered and some were powered by an early DB 601 (or DB 600). Out of that mish mash of info it is clear the Swiss Bf109 D aircraft were powered by the Jumo 210. There appears to be little information about the Jumo 210 but quite a bit about the Jumo 211. The 211 IS NOT A VARIANT OF THE 210. The Jumo 211 looks the same as the 210 but it is actually physically larger. It was used to power the JU87 and other bomber types.

Currently drawing new fin, rudder and tailplane for my bf109 because the kit is completely wrong. The engine end looks a bit like a B, C or D But the tail end does not.

More later in the Bf109 thread.

Paul
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