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DB 60" Sopwith Pup

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Geoff Sleath22/10/2019 20:26:29
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3434 forum posts
297 photos

Sorry no updates recently. I had to put it on one side for a week because of house maintenance duties which were somewhat boring but necessary. I am back building but it's wings and as there are 4 almost identical panels, there's not much of interest to report.

One thing that does seem somewhat daunting is the anount of rib stitching I'm going to have to face. On my last build (the DB Gypsy Moth) I just went for the tape without bothering with the underlying stitches. It looks OK but I would like to include them on the Pup. I tried doing my own on my DB Tiger Moth with limited success. I made a board with nails at the side which allowed me to zig-zag thread across with paper underneath. I glued the thread to the paper but when I sliced it into strips, some of the 'stitches' came off so I ended up with some missing under the tape. Is there an easier way?

Geoff

J D 822/10/2019 21:17:59
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1312 forum posts
78 photos

Mick Reeves stitching tape or try the Richard Crapp tape tutorial.    John.

Edited By J D 8 on 22/10/2019 21:18:36

Geoff Sleath22/10/2019 23:06:50
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3434 forum posts
297 photos

Thanks, Jphn. I'll try the carpet tape method and perhaps cotton thread rather than synthetic.

The problem with Mick Reeves is the weird way he expects you to order and pay. It seems he expects you to send your card number via email which isn't something I'm comfortable with.

Geoff

cymaz23/10/2019 05:15:07
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8765 forum posts
1190 photos

I’ve rung Mick up and paid by card over the phone.

McG 696923/10/2019 08:46:52
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2644 forum posts
997 photos

Hello Geoff,

Regarding your stitching, it might be useful to visit this thread of a Fokker Dr1 built by Mightypeesh. Please look at page 3 and following.

He used some water slide transfer sheet and lacker to produce his stitches.

You're right to use cotton instead of polyester as it isn't affected by temperature and doesn't deform by the warm iron.

Hope this helps.

Cheers

Chris

Alan Gorham_23/10/2019 10:39:39
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1026 forum posts
123 photos
Posted by Geoff Sleath on 22/10/2019 23:06:50:

Thanks, Jphn. I'll try the carpet tape method and perhaps cotton thread rather than synthetic.

The problem with Mick Reeves is the weird way he expects you to order and pay. It seems he expects you to send your card number via email which isn't something I'm comfortable with.

Geoff

Geoff

Mick had to modify his advice on ordering this way after several of his customers had their card details intercepted. He changed his advice on the front page of his website. It's pay by Paypal now plus a small surcharge or place the order by email and ring up to give card details.

Interestingly, I've tried to get on his site just now on PC and mobile and I can't get on....

ceejay23/10/2019 11:08:30
426 forum posts
322 photos

hi geoff

I use the above method from Mcg 6969 I have jigs made specifically for 1/4 and 1/3 scale stitching all my 1/3 stuff uses it

here on a wing 1/3 scale paneldh covering 2013-04-10 012.jpg

Geoff Sleath23/10/2019 12:44:17
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3434 forum posts
297 photos
Posted by Alan Gorham_ on 23/10/2019 10:39:39:ff

Mick had to modify his advice on ordering this way after several of his customers had their card details intercepted. He changed his advice on the front page of his website. It's pay by Paypal now plus a small surcharge or place the order by email and ring up to give card details.

Interestingly, I've tried to get on his site just now on PC and mobile and I can't get on....

I googled Mick Reeves Models last evening and when I clicked on the link I had a problem as the site was considered dubious. I suspect the term 'model' can be suspect sometimes However there was another link to his Accessories page which worked perfectly.

Thanks for the tips and advice gents. I'm nowhere near covering yet but building the wings with all the sub ribs along the leading edge has put the fear of rib stitches into me!

Chris, pity you don't have a 6th scale jig that I could borrow. The Pup is actually 1:5.5 approx for some reason but it's a good size for an every day club model that won't sit in the 'hangar' (ie loft) rather than flying. Should be very easy to rig as well.

Geoff

Danny Fenton23/10/2019 14:19:18
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9213 forum posts
4063 photos

Glad to see rib tapes are still so popular

Cotton does seem to work better. For larger thread try crochet thread it is a bit more substantial

The double sided tape method I outlined was originally from Richard Crapp, so cannot claim it as my own.

Cheers

Danny

Geoff Sleath23/10/2019 16:42:53
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3434 forum posts
297 photos

Danny, the rib tapes on my Gypsy Moth are just that - tapes. There's no 'stitching' underneath. I suppose at 1/6th scale it's not so obvious but the tape alone does add a little interest. I confess there's no tape under the wing or tailplane where a casual viewer, when the model's on the ground, won't see it anyway. blush

There will be stitching on the Pup, however, mostly because the wings are bigger, not so much in length but the span is greater.

Geoff

Geoff Sleath24/10/2019 20:35:02
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3434 forum posts
297 photos

A bit more progress to report. I've made the top wing centre section as well as having a minor panic.

The centre section in 11" wide and each wing panel is 24.5" which added up equals a wing span of 60" as required. So far so good until I looked at the drawing for the bottom wing centre section which is only 4.75". I thought at first that all the wing panels were the same but the lower wing has an extra bay and each panel is 27 11/16" (I hate Imperial units!!) which brings the lower wing span to 60.125". Allowing for my measurement and ultimate building errors then that's OK. It had me worried for a minute though. So if anyone here is building (or has the kit ready to build) be aware that the upper and lower wing panels are different.

I made a couple of minor alterations to this part. Here's the centre section:

wing 9.jpg

The first mod was to extend the 0.5" x 1/4" plywood parts at the leading edge through the adjacent ribs by making new ones and add triangular stock to increse the glueing area. For anyone familiar with DB biplanes the top wing sits on a platform at the top of the cabane. At the L/E there are plywood hooks which engage with the plywood parts I've extended. I just felt happier with a bit more security in an area that holds the wing on.

The T/E is held on with 3mm bolts through the 2 holes you can see in the photograph. When the model is completed there will be solid balsa filling to the top of the ribs and a brass tub inserted for the bolt to pass through. I'm leaving the infill until I've drilled through for the 'T' nuts on the wing platform. I think it'll be easier to be accurate.

The shaped balsa below the holding down bolts is made from 3 laminated layers of shaped 5mm soft balsa to make a solid piece which needs to be carved to suit the profile. The supplied parts ended short of the rib end and I added a bit at the end to fair it smoothly to the T/E. I thought the sharp edge would show through the covering and this will be neater and weigh very little.

Now on to the the 2 lower wing panels and centre section. They'll be more complicated as they carry the aileron servos (probably Corona CS239mg). I must remember to put in a paper tube to feed the servo leads from the bays to the centre.

Just wondered if anyone here has already bought the kit to build over the winter. The last time looked DB were out of stock, so some must have been sold in addition to mine. I think this kit is a better proposition than the similarly sized Flair Puppeteer, which seem to command high prices, even if only because there's DB support and, in addition it's near scale.

That's all for now.

Geoff Sleath31/10/2019 00:32:47
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3434 forum posts
297 photos

Despite the shortage of posts I've been soldiering on with the build. It's just that building wings isn't very interesting for those following my build. Anyway I've had a few minor issues surrounding the bottom wing centre section and its attachment to the fuselage that may be of interest to anyone else constructing thiis Pup.

Here's the centre section in question. It's much narrower than the top wing centre and the 2 wing panels for the bottom wing are longer than the top so both wings are 60" wide.

wing 10.jpg

 

The wing mounting bolts are 3mm cap heads as is common for DB biplanes (and perhaps other models). The first thing that springs to mind when studying the drawing is that they're shown as 5mm bolts - that's an error and they're definitely 3mm and are provided in the kit along with 3mm T nuts.

There's extra confusion in that the 2 plywood plates (1x 3mm and the top one 1.5mm) have 6mm holes and sandwich a soft balsa infill. DB do this to give some latitude as to hole positioning and drill 4mm holes through the balsa and epoxy in brass tubing with o/d = 4mm with 3 mm hole. This will certainly work, however, I decided to make new pieces with 4mm holes. The 3mm one at the bottom is the same size as the original (except for the hole size) but the top one is slightly bigger so that it butts up against the t/e spar. This to be sure of its position exactly above the lower plate.

I glued them in position with the soft balsa infill between. I was then able to drill an accurate hole from the top with my bench drill by taking advantage of the flat bottomed aerofoil. It worked perfectly.

The next part that concerned me (unnnecessarily as it turns out) was the fusleage plate which will carry the 3mm T nuts. It has 4mm holes ready drilled but none of them matched the bolt holes in the wing centre section. It's seen at the side. So I made another plate (seen above it). I then discovered the holes in the original part are purely for weight reduction and there's plenty of room behind them to take the T nuts, so my work was unnecessary.

As an exercise, I shaped the outline of my new part to be the same as the original without the smaller holes but with the 2 bigger ones in the corners and they weigh exactly the same. I'm going to use my part, mainly because I've already made it!

The instructions specify that the the wing dowels are glued in with epoxy once the position is verified after the fuselage is built. When I queried it with Richard at DB he restated that just epoxy is fine and has given no problems at all. I believe him but I'm still not comfortable with it so I've added some support at the back and front.

wing 11.jpg

I've added soft balsa support at the l/e, 6mm x 6mm strip under the wing dowels to give more glue area and a plywood support at the spar.  As it is the dowels stay in place without glue and I'll glue them once I'm sure it'll fit the fuselage properly.

The plywood plates 219  are for undercarriage support.

Be careful about using the spruce strip for the rear wing spar.  Be sure to leave sufficient for the cemtre section rear spars.  I messed up slightly and ended up with 2 lengths of spruce about 50mm too short for the wing.  I've allocated on short spar to each wing and scarphed another piece to the end.  The rear spar is filled with balsa so the joint is well supported and in any case is right at the tip where the loads are the least.  I've got away with it but it's better not to be forced into such a measure.

Nearly finished the 3rd wing panel - one more to go.

Geoff

 

Edited By Geoff Sleath on 31/10/2019 00:51:43

Danny Fenton31/10/2019 00:42:30
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9213 forum posts
4063 photos

Looking good Geoff, looks a well thought out kit

Cheers

Danny

Geoff Sleath31/10/2019 21:56:14
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3434 forum posts
297 photos

As I'm building the bottom wing halves the time has come to decide what wing servos I'm going to use as they need to be accommodated in the correct sized housing.

My first thought is to use CoronaCS238MG from HK. The on-line spec is here but briefly they have 4 kg cm torque (more than a Futaba 148 @ 3 kg cm IIRC), metal gears and ball bearings on the output shaft. They're analogue. Each servo would be driving 2 ailerons (top and bottom).

I've fitted them in the Ryan ST I've built but not flown. That's a model I'm not too worried about. If it survives the test flight successfully that will be a major achievement So, apart from testing them for an hour or so on my servo tester, I don't know how good they are.

Has anyone used them? What other choices might I make? Should I go for more expensive servos like (say) Hitec?

Geoff

Trevor Crook31/10/2019 22:33:54
868 forum posts
65 photos

I'm using some cheap Hobbyking wing servos in my Ballerina and they've been performing faultlessly for a year or so, but unfortunately have been discontinued. I would think the Coronas will be fine, especially after a session on the tester.

Andrew Calcutt31/10/2019 22:34:53
14 forum posts

Nice model like that,get some proper servos,not worth the risk.

Martyn K31/10/2019 22:59:04
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4983 forum posts
3624 photos

I have used those Corona Servos on my 1/4 scale glider for aerons and spoilers and also 2 other slope soarers. I have used both standard and hv types and have got them fitted in my Fury as well.

No problems at all Geoff.

Martyn

Geoff Sleath01/11/2019 11:06:05
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3434 forum posts
297 photos

Thanks for the advice gents. I know choice is supposed to be a good thing but there are so many servos (and other things) you tend to get overwhelmed. When I was in Portugal where my wife was working we went into the small non-tourist town where we were staying to buy a an electric kettle to brew up in our hotel room - every shop had the same kettle at the same price. It was so much easier

I think I'll go for the Coronas. one each for the ailerons and one for each elevator half in view of Martyn's experience and my own tests.

Geoff

Geoff Sleath06/11/2019 12:11:07
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3434 forum posts
297 photos

Building wings is a bit repetitive so I haven't bothered updating for a while but that doesn't mean it's been idle time in the workshop - after all it's been really idle on the flying front so I've had the time.

I've been extolling the virtues of magnetic building aids so here's a picture of the last wing panel being built a few days ago. You can see how easy it is to ensure vertical ribs. That doesn't mean I don't make mistakes - I make a lot but it's down to my inherent clumsiness rather than the technique. There's a few bodges I'm keeping quiet about.

wing 13.jpg

 

One mistake I did make I'll admit to, just to help future builders of this model. There's a mantion of a 0.8mm ply reinforcment for the end rib of the ailerons; I failed to find it. Instead I stuck a piece of 6x3mm edge on to stiffen the rib against being distorted by the covering. That works fine. The horns for the ailerons are 0.8mm ply and cover the whole of an aileron rib on one side with a backing piece on the other. They work really well. Then I realised there were what I thought were backing pieces intended to reinforce the end rib. See? Careless on my part.

I find one of the most stressful parts of a build is wing joining - very important for flying success and very difficult to correct if you make a mistake. The wings are joined with 60 minute epoxy to give me lots of time to get things right. I used about every clamp I own for each wing. I got out my big building board for the job but used the steel board on top to fix the win centres firmly.

wing 16.jpg

This is the top wing joining. While that was setting I installed the wing servo mounts in the bottom wing.

 

wing 17.jpg

The ribs need to be cut to accept the the 2x3mm ply end supports so that the cover (which carries the servos) is flush with the top. I also added some 3x3mm strip between then to support the sides. The top cover is only 1mm ply which I thought seemed very thin but in practice it seems to be OK. I was puzzled by the 1mm parts that are the same outline as the 3mm supports. See above. Then I realised they need to be cut away so that the whole installation ends up flush with the top of the ribs.

The actual servo supports glue onto the underside of the cover and there are options for differently sized servos. I'll show that once I get my servos and fit them. It's very well thought out.

Note the paper tube made from a sheet of A3 printer paper which is only just long enough to reach from the centre to the servo bay. Making paper tubes is harder than you think. I rolled mine round some 0.5" alloy tube, holding it with Sellotape, and pushing it through the existing holes before cutting the tape (it was just at each end) and withdrawing the alloy.

Here are my 2 wings more or less complete.

wing 18.jpg

 

Now the fuselage. Here it is fitted in my SLEC jig with the first former glued and clamped. It's a lot bigger and chunkier than I expected. It's wider than any of my clamps which made it tricky to clamp well - hence the variety of clamps and rubber band. I'd hate to do this without the jig which has seen service for some years and been used for several fuselages as well as my Thames sailing barge hull.

fuselage 3.jpg

 

fuselage 4.jpg

 

That's as far as I've got. Lots to do on the fuselage including decisions on motor mounting and battery placement. It does look as if there's ample room to get 2 x 4500 mah 4S LiPos vertically immediately behind the firewall with access via the top hatch as long as the top wing doesn't get in the way.

Geoff

Edited By Geoff Sleath on 06/11/2019 12:14:10

Alan Hilton06/11/2019 18:04:42
102 forum posts

Hi Geoff

please could you post details of your magnetic building board .It sounds a great idea

Alan

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