DB 60" Sopwith Pup

[Alan Gorham_]

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....

[ceejay]

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 panel

[Geoff S]

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 Fenton]

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 S]

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.

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 S]

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:

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 S]

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.

 

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.

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 Fenton]

Looking good Geoff, looks a well thought out kit

Cheers

Danny

[Geoff S]

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 Crook]

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 Calcutt]

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

[Martyn K]

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 S]

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 S]

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.

 

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.

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

 

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.

 

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.

 

 

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 Hilton]

Hi Geoff

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

Alan

[Geoff S]

Hi Alan

It's just a sheet of 1mm (approx) steel about 450mm x 1000mm in area, hough, it can be any size to suit the user. The magnetic blocks are very accurate triangular wooden blocks with a 6mm magnet embedded in one face. I think the wood is beech but I'm no expert - it is quite hard.

Someone was selling the blocks at Cosford last year as well as sheets of steel (though, of course, you could get the steel anywhere). I bought 20 blocks which is just about enough but I'd like another 10. Unfortunately the guy selling them wasn't there this year. I'm fairly sure he was an LMA member. I suppose I could make my own but I don't think I could match the accuracy of the ones I bought. There's always the opportunity to make other blocks for special purposes because the magnets are readily available - I use them for holding catches on models.

Much better than pins (though I sometimes use pins to hold parts together - eg holding the ribs down onto the leading edge) because, after a build, the drawings are as good as when you started as no adhesive seeps through the pin holes in whatever you use to protect the plan (I use cling film).

HTH

Geoff

 

Edited By Geoff Sleath on 06/11/2019 20:15:50

[Alan Hilton]

Thanks Geoff

Alan

[Geoff S]

You're welcome, Alan.

Now a bit more progress on the fuselage. I completed the front section but before I glued it all together I did a dry run and found a couple of components that were easier to glue together before full assembly. So to help other builders (if there are any here).

These fit right at the back of the wing seat and are tricky to fit in when it all looks like this in the jig.

Then I ended up with a complete forward section except for the firewall, which I opted to leave until later because it will be fixed with 60 minute epoxy (it tkes longer than 60 minutes to set completely so best left overnight.

and here

The rear section of the fuselage is frame structure rather like a vintage model. Each side is built flat on the plan from 1/4" x 1/4" strip. It's fairly straight forward except for the diagonals which I find a great pain to get right. The joints are reinforced with 1mm ply semi circles. I built the second side over the first, separated with cling film, in order to be sure of 2 identical parts

After some thought I decided the easiest way to join front to back accurately was with the front inverted because the top is dead flat. The top longeron goes right from the back to the firewall, and the slanting bottom longeron ends at the back of the front structure.

... and here it is. Looking almost like an aeroplane fuselage for the first time.

I couldn't resist trying the bottom wing to see if it fitted. It's perfect! I checked and it's absolutely square with the fuselage. The only tiny problem was that it was a bit too tight at the t/e and a couple of strokes with a Permagrit file and that went away. I think I may need to ease the fit a bit more to allow for covering but I'm pleased with it so far.

Geoff

[Danny Fenton]

Excellent Geoff the model is coming along well

Cheers

Danny

[Geoff S]

I seem to spend hours doing very little - or perhaps seeming to achieve very little but the model does actually grow

Last night I epoxied the firewall in place. I opted to use the 60 minute version to avoid panic as I tried with some success to clamp it securely - I even used an elastic wing band! I modified one part to allow me to add some extra glueing area by adding some 0.5" triangular stock outside the main central box.

The balsa sheet is there to provide a location for the stringers that support the 0.4mm ply which forms part of the tapered cylindrical shape characteristic of the Pup's fuselage. I cut away enough to allow the triangular parts to glue both to the firewall and the outside of the box sides. Probably not necessary but I like my firewalls well attached and the extra weight, especially so far forward, is irrelevant.

The first job this morning was to fit the bottom wing 3mm T nuts so that it was properly fitted in its final position before I tackled the cabane for the top wing. So I clamped it in place and checked for square by my usual method of a bit of string attached to very rear of the fuselage and checking to each wing tip. It was pretty well spot-on so I bit the bullet and drilled a 3mm hole through the brass tubes of the wing and into the attachment plate. After drilling the first hole I dropped a bolt in to ensure nothing moved as I drilled the second.

I opened the holes to 4mm and contersunk the back to accept the T nuts. Glueing was once more 60 minute epoxy (taking care to apply Vaseline to the threads.) The wing fits perfectly and the 3mm bolts drop straight into the T nut threads.

I deviated slightly from the instructions and plans when fitting the 2 parts of the fuselage together.

The top longeron has a big support triangle shown on the drawing. I couldn't find it so made my own. Subsequently I came across them but instead of part # 128 it looked like 123 and moreover was much smaller - so future builders be aware. I prefer mine

The other change I made is at the bottom where I added a long triangular support piece to spread the load. The balsa here is very soft - ideal for the wing seat but, IMO, not quite so much for a critical support component. I've effectivly added a 0.8mm ply doubler to the inside. You can see it clearly here on the port side. If I were building another, I'd leave the blanks in the lightening holes and actually glue them in. The balsa here is so light the weight increase would be difficult to measure. Just my feelings. No reflection on DB - I don't think I've ever slavishly followed instructions or plans on kits I've built. Going a little off piste is part of the fun IMO.

Geoff

Edited By Geoff Sleath on 10/11/2019 21:07:23

[Geoff S]

Today part 2.

Cabane fitting, next. The part that supports the front cabane mount is held back from the firewall by the extra 3mm ply which allows for the glow engine mount. As mine is electric I don't have that and that means the fixing point is further forward than shown on the drawings. To get the structure to agree with the drawing I've inserted a piece of 3mm balsa and taken about 6mm off the plywood itself. Because I'm intending to use the top hatch to fit my batteries I want it to be as big as possible. I also added some exta support underneath. I used aliphatic.

The drawing has a diagram showing the angle for the front cabane support. I made a pair of jigs from the glow firewall 3mm ply supplied and fitted them on the fuselage with tie wraps. Where the piano wire is stitched and glued (epoxy) the instructions suggest wrapping with masking tape. I've used that method before and it works surprisingly well. I did the same with the rear supports - again tie wraps help a lot.

It's important to get the incidence of the top wing exactly right so I got out my trustly parallel rules, blew off the dust (well they got me across the North Sea before such luxuries as GPS navigation aids!) and made the measurement.

There was me thinking they'd be parallel and all the measurement aid I'd need was a spirit level. I know it's only 1 degree but that comes at 5mm over a 250mm length. So it looks like myRobart incidence meter will be in use sometime soon.

I've also been thinking deeply about battery installation/changing but that's for later.

Geoff

Edited By Geoff Sleath on 10/11/2019 21:27:45

[Dove from above]

Hi Geoff, really enjoying this build, i am a newb so loads of great stuff here to learn from.

I would like to comment on the Slec jig, I got one of those and find it not that great. The plastic uprights are not vertical! at first I thought I was tightening the bottom to tight to the board but ruled that out. Have no idea why the tops flair out

[Geoff S]

Dave: Glad you're enjoying it. So am I

Just checked my uprights and they are quite square. However, the main advantage of the jig is in keeping the fuselage under construction, straight. The uprights can be held in place using the SLEC plastic clamps which fit exactly in the grooves and using a normal square to check vertical. I've had mine for 20 years. It's on a piece of MDF board with battens screwed on the bottom to keep it flat.

Geoff

[Geoff S]

I've got some Oratex covering but I'll need some matching paint for the cowl. Do you know if anyone supplies such a thing or am I goingto have to try B&Q for a special mix or a local art shop to try acrylics?

Geoff

[Geoff S]

I fitted the cabanes and top wing platform (I even put the top wing roughly in place just to see it looking like a biplane for the first time).

Checking that the front cabane is square before stitching and glueing with slow epoxy.

I stole a needle form my wife's sewing box (one with the biggest eye), cut off the point and used it to thread the super strong thread I use for jobs like this. It comes from a cone of thread that my wife rescued when she was working in a factory that manufactured clean room clothing when it was thrown out. No idea what it is but it's incredibly strong and I have literally miles of it I think. It'll last me out! DB supply a bobbin of thread for the purpose but I opted for my own which is a bit thicker, I think. My technique is to 'sew' 3 times for each hole and then fix it with a drop of cyano. My jig held everything firmly in place.

Binding and soldering the top was very easy and nothing shifted. There are often queries about what soldering iron to buy so I thought I'd show what the one I use for heavy soldering looks like.

I've had it for 60 years. I think my dad gave it me - either that or I stole it from him. It's 125 watts and has a wooden handle, though I'm sure newer ones will have plastic It's 125 watts and has a big enough thermal capacity once heated to make soldering piano wire a piece of cake. Not ideal for soldering integrated circuits, of course, but I have a smaller one for that!

The incidence of the platform is 1 degree +ve relative to the top of the fuselage (and the bottom wing).

Here it's very slightly over 1 degree but the rear cabane is still held with tie wraps and a slight adjustment will be made before sewing and glueing.

Geoff