Clive Weller's Concept

[Martyn K]

The Magic saga is coming to an end so I have been looking for the next one to build. I have settled on the the 'Concept' designed by Clive Weller and published in RM in December 1984 - so this just fits in nicely with the UKCAA classic guidelines.

This is a very different model to the Magic - 2 piece mid wing, tail dragger and IMHO, a very sleek looking aircraft with lots of LE taper (read that as I will crash it when it tip stalls on landing)

Engine will be a OS61RE with pipe.

A couple of plan shots

and tailplane

I transferred most of the ply parts from a scan into Draftsight and exported them as DXF. These were passed to Dylan at Lasercraft who commented that they were the worst scanned items he had ever seen - curves on formers were a series of straight edges etc - although the wing ribs were OK. I was aware of this and had allowed for a little additional sanding. So - if you fancy this as a build - Dylan has the files but don't blame him for what you get. His side of the bargain by the way was a beautifully cut set of parts..

So... here is my mini kit. I probably wont make a start on this until I get back from my holidays but feel free to discuss

More to come..

Martyn

[kc]

I remember several other Clive Weller aerobatic designs from RM or RCME that would seem worthwhile - each rather different from the average aero design of the era.

I have to say the very thin ply top sections look vulnerable during construction - possibly worth gluing a temporary balsa cross member to the parts?

I presume you have the magazine article Martyn? If not, ask me to find my copy.

[Martyn K]

Hi kc

I don't have the original RM article. I have been looking for a copy of the magazine for a while. If you could scan the relevant pages for me, I would be very grateful. I will happily reimburse any costs.

Thanks

Martyn

[David Foley]

Good to see one of Mr Weller's designs been built. Always liked his

Titan and Mercura T.E.T.A. Will be watching with interest.

Dave

[kc]

Titan is from RM May 78.

The Mercura article was in RM August 82 and the Mercura T.E.T.A. in RM Sept 87. 

There are copies of RM for May78 and Sept 87 on sale if anybody needs them.

 

 

Edited By kc on 10/08/2014 11:38:46

[Martyn K]

Back from my hols so I have made a start on this:

As I seem to do, I started on the tailplane. The ribs were scanned and printed and then pin pricked through into some rather nice 1/16" balsa. A couple of hours with a scalpel and its quite a simple job laying out the ribs, spars and LE.

I have added 2 large gussets in the centre - probably not required but they add a bit of strength at the joint

This was just over an evenings work so I started on the wing. Both panels are made over the same half drawing - the only tricky bit is to make sure you make a left and a right - determined by the joining tube.

There are 4 main spruce spars converging about half way down the wing with the tube supported on lite ply ribs with 1/8 lite ply doublers. The inner sections also have balsa doublers in the inner part of the wing.

The joining tube is rather large - too large IMHO, but this is as specified..

Close up of rib and doubler

After a few hours work, we have 2 wing panels and 1 tailplane ready for the next stage. Quite an easy build so far - just make sure you dont build a twist into the wing - they are very stiff already..

More to come

 

Martyn

Edited By Martyn K on 15/09/2014 16:04:17

[Jack Banner]

Looks good Martyn,

Subscribed.

[Martyn K]

A bit more progress:

I have added the shear webs - these are full length and of course, the grain goes vertical...

One mistake that I made was I had placed the root rib upside down. Its a symmetrical wing section, but the joiner tube hole is not central - 1mm out - makes big difference to the cap rib though.. Removed and reinserted the right way up..

As usual now, I am using Kevlar cloth for my hinges. Sandwiched between 2 1/4" square strips and then glued to the rear spar pair. Note that all the rear triangles behind the spars are now cut off. I am not really sure why Clive did it this way/ I'll probably find out when I build the ailerons..

The wing tip blocks are laminated from 3 pieces of very soft 1/2" sheet and roughly hacked down before the sheeting goes on.

Finally I have made a start on the sheeting. I will only cover the upper surface at the moment. I still need to make the aileron servo mountings that sit in the second bay out.

More to come

Martyn

[Martyn K]

I have made a bit more progress. I am actually working on both wing halves at the same time to keep the build in step so..

I have created the aileron servo boxes. The plan show the servos mounted sideways and buried in the wing with an access hatch. It looked a bot cumbersome - there was no real detail so I have chosen to mount my servos vertically but recessed, so there is only a minimal protrusion (the servo arm) into the airflow.

The bearers are two different sizes to make sure I can get good glue contact, the smaller bearer sits against the liteply rib and the other bearer is supported by a 3mm balsa box

Finally - I completed the sheeting and subsequently been planing and sanding to shape.

More to come.

Martyn

[Tony Bennett]

nice one martyn

[Martyn K]

Thanks Tony

This is going together really easily (so far). Just started cutting parts out for the fus this morning - that bit is definitely more complex..

Martyn

[Martyn K]

I have continued with the tailplane and the fuselage.

The tailplane - I have simply started sheeting the top and bottom with 1/16" sheet after adding the soft tip blocks

 

again - using Kevlar sheet for hinge material

The fuselage is fairly straightforward - so far.

1/32" ply doublers - I needed to get some 1m x 300mm wide ply for this - they are rather long.. The fuselage sides are 3/16" sheet - I have gone for some nice medium density straight grained wood for these - using the pin prick technique for marking the boundaries after scarf joining the sides..

The plan is a bit confusing as it shows the 1/32 ply doublers as sitting outside the balsa sides on the lower edge by about 2 or 3 mm. Longerons added on top - then removed again as a diamond shaped trebler needed to be added as well... This is where the wing joining tube goes.

So.. last night, the formers were inserted and all left to dry. I also added part of the floor area to give some support when the other side was added today..

Which is what I did at 07:30 this morning...

Those batteries get everywhere

Finally - I went round with a square to make sure that sides were parallel and importantly, the wing joining hole lines up on both sides. I expect that a small adjustment may be required - but hopefully, it will be small..

Not sure why this photo is on the side - its the right way up on my home machine!

More to come...

Martyn

Edited By Martyn K on 26/09/2014 11:19:45

Edited By Martyn K on 26/09/2014 11:21:06

[Martyn K]

A bit of progress.

I have also got my camera working again so I don't have to mess about with the mobile phone..

We are having an extension built as well. The associated clearance activities are impacting on my quality wood time and also flying time

I have planked the upper decking at the rear fuselage. The trick (IMHO) is to keep matching up the sides, start from one side and then do a matching plank on the other. This model is planked in 3/16" sheet, which means that each plank has to be bevelled slightly to match up the the plank below it. The problem is that as I fit a plank, I glue (PVA) then pin and let the glue dry before the next plank goes on - this makes it quite a slow process

A bit hairy

The rear of the fuselage was completed first as this had a very tight curve which was totally lost - until I sanded it.

You can see how I pin it as I fit it..

Finally the top piece was fitted and then bound down while the glue set.

While this was going on, I finished the tailplane and elevators. I used solid sheet elevators cut from very soft sheet.

And the top decking finally sanded down.. No filler

Time to start work on the cowl. The cowl is integrated with the lower pipe tunnel. However, I need to get this completed separately as all the intricate carving and fitting needs to be done first.

So. Engine back in and all orifices sealed.

Fit a spinner and use this to centre the front former. Note I have added 2 internal soft balsa cheeks as the fuselage is very slightly wider here than that shown on the plan - because I used a nylon mount.

Another shot..

A basic frame cut from 1/2" sheet and lined on the inside with 1/32" ply. At this stage, its cut well over size as I dont know where this is going yet. The plan instructions aren't clear ("Cowl from 1/2" sheet". I also wanted to upsweep the front of the cowl as well so I can get at the plug easier.

I have decided to go for 3mm lite ply bottom and sides - so the top - the hole is cut using a cheap powered hole cutter. The secret to use these is to cut half way through then flip over and cut back from the other side

The sides are carefully cut to the profile of the fuselage side then damped and glued with lots of PVA and left to dry/set overnight

The joint will be the lower deck will insert into the slot at the top, the sides will butt up to the sides of the cowl with 1/16" ply side plates.

While this was drying, I added the rear block - with a slot cut out for the ply mounted tail skid

First pass at sanding the cowl - still a bit hairy.

More to come

Martyn

[Martyn K]

mmm Still on Page 1 and the model is almost built..

Things have been a bit slow - we are in the middle of a house extension which has slowed things down a lot. But I have managed to sneak into the shed on occasions and progress this further.

Carrying on with the lower fuselage and tunnel. Basically, this comprises of a 3/16" planked tunnel on an almost square frame. The frame is cut just before the last plank is fitted to release the cowl and tunnel

I chose to use thick - full width planks - which - with hindsight was a mistake

Adding the base and left overnight.

I needed a little bit of padding on the frame..

I then boxed in the other side with the 3/16" sheet and cut away the frame (on both sides) with a saw before adding the second side

Which was then added, bound and clamped into place and allowed to dry. When I released it the next day, the tension in the wood caused the sides to bow out alarmingly. The only way I could recover this was to get my balsa stripper and partially cut through the sides in 1/2" wide stripes. This allowed the ply frame to pull it back in again. A little cyano and PVA into the seams and all was OK.

I am planning to glass this model, so I have glassed the inside of the tunnel with 60g/sq m glass cloth. I wasn't aware that this would shrink and it has now pulled the sides inwards - which makes the tunnel a very tight fit.

Which brings me onto the Canopy. The plan says 'use a suitable canopy cut down to size'. This canopy is huge..

This is a 2L pop bottle which was plan B - Plan A failed when I was unable to find a suitable commercial canopy to cut down. The usual commercial vac formers were unable to help - the Canopy is bigger than their machines can cope with..

Plan C is to make one out of balsa, glass it and paint it - black or metallic blue.

A frame was constructed.

The canopy curves were all sanded by eye starting from the rear and aligning with the rear fuselage and then moving forward. It took a while but seems to be OK.

The canopy was then planked with 1/4 x 1/6" balsa. Adding one plank at a time and then letting it dry. This meant that I was adding four planks per day - morning, lunch, tea then bedtime... a slow process

Each plank was clamped to the one below it and pinned to the frame.. Note that I completed (almost) one side before starting the other in case my eyeball method of alignment was miles out. I also made no attempt to taper the planks as they were fitted. the tapering process would have been far too complex to work out around the composite curves.,

Eventually... (and before final sanding).

The top of the canopy was a bit of a pig.. I eventually got to the state where I couldn't bend and twist the balsa planks any further, so the top "plank" on each side was a cut to size piece of balsa sheet.

Quite pleased with the canopy - which is also the radio access hatch.. Note I have also added the ply facing ribs for the wings..

Just one spot I am unhappy with, a bit of a lump on the top left hand side but not really noticeable by eye.

So next to the fin and one huge mistake on the plan - so huge I am amazed it got through. Basically the base rib for the fin is about 20 mm too wide. so this had to be re cut with the other ribs in situ and referenced against the top of the fuselage.

That took a few hours to sort out...

Finally, the front fairing into the cowl has been added. the gap you can see will be sanded out and a 1/32" ply facing piece added. The rear of the canopy will be pegged to the fuselage - not sure how I am going to secure the front though. I may just settle for magnets..

More to come.

Martyn

[Jack Banner]

I am enjoying this thread Martyn, good to see a classic going together. I have designs on a scratch built classic someday, maybe a slik - fly (sp?). Just bought a Crescent Bullet on ebay, ready to go, so will likely fly that over the winter and build something more exotic for the summer. Keep the pictures coming

[Martyn K]

Hi Jack

the late ntsmith did a build blog of the Slik-Fli (not sure of the spelling either). Its here

Its a lovely aeroplane. I started work scaling it down to 25 sized but never finished it (yet)...

Thanks for the feedback as well. The Bullet is a cracking little aeroplane - I have seen quite a few in the past year - it flies very well.

Martyn

[Jack Banner]

Good to hear the bullet flies well, I have been after one for ages but thought the PB kit a little expensive. I nearly bought an 'original' ( read Very Old) 70's one at wings and wheels but ended up taking home a nicely scale Ryan STA (built from the classic SIG kit) instead.

Thanks for the slik-fli link, good thread. Shame to hear the fella died on the flight line though.

[Martyn K]

Moving along with this..

Work on the fin continued. I didn't quite get the angles right first time so I scrapped it and started again...

Added the sheeting. Note I have inlaid the sheet rather than overlaid around the perimeter as shown on the plan

Additional thick gussets added. The rudder horn was cut from thick formica. Decent sized pieces are available as samples from places like Wickes. It is flexible and tough and easy to work with. This is pinned and epoxied to a thick balsa gusset which was then lightly crushed by the retaining clamp.

One additional rib added - there are only 2 shown on the plan and the crushed gusset replaced. Note the pins that have been left in place..

And glued in place. A little micro balloon epoxy mix is required to fair the join in..

And the horn..

The tail skid from 'proper' black piano wire, bound and glued to a 1/16 ply plate as shown on the plan

I wasn't happy with the base of the canopy which looked rather dented and tatty. 2 1/4 x1/16 spruce rails have been added. The slots were cut using a balsa stripper - it cut a perfect recess..

The fixing for the tuned pipe. Screwed to a 1/8 birch ply x 2 - one inside the fuselage, and one in the tunnel as shown here - all sandwiched together. However, I don't know how to calculate the header length - any suggestions please?

And some dry assembly shots

This has the filler fairing around the fin - needs just a touch more on this side

Front fus...

View down the sharp end. Still a bit more fitting to do here as well.

More to come.

Martyn

[Sam Wragg]

Concept looking good Martyn, she looks similar to Ken Binks 'Stylus'. I like the idea of plug in wings and starting to wish I'd done the same with Arrow.

Sam

[Martyn K]

Hi Sam

Been a bit nervous about the plug in wings. My eyes don't line up properly - I suffer from double vision - so when I look down the fus from the tail they look like they are about 5 degrees out which is nerve-racking. When I measure the trailing edges from the datum they are spot on though. When I fly it, I will find out just how accurate I have been.

I have made up the undercarriage legs this week using the Martin McIntosh School of metal bending method. Hit it with a large hammer. I wish that I was using wing mounted retracts though as the mid mounted legs look very spindly despite being 6G.

Hopefully, I will start glassing this week, all the catches and mounting bolts have been completed and its getting the final sand down and filler. Hardpoints for the elevator and ailerons were done last night and a little extra filler was added around the fin and the exits for the closed loop rudder. They will get sanded tomorrow when absolutely hard - start the glassing on Thursday probably

M

[Martyn K]

I am embarrassed to say that it is almost 5 months since I lost updated this blog. Excuses are long and boring and possibly justified but nevertheless, work has continued - albeit slowly.

At the last post, the airframe was basically completed and I was pretty happy with it. Once again I decided to ruin it applying glass and paint but I do need to master this technique. I restarted the build in anger about 4 weeks ago (glassed it last year) and all I seem to have done for most of this time is sand, prime, sand, prime, sand, fill, sand, paint etc. I must be doing something wrong (although I have now been advised about Peel Ply (thanks Danny).

Anyway, it looks like this at the moment.

and

It's more or less the same underneath except it is red instead of yellow.

Just don't look too closely..

Time for fitting out.

I have acquired a brand new unrun OS Max 61V engine for this.

Its got two big holes which implies that it should be quite powerful and also quite thirsty..

There is very little info on this engine on the OS archive, in fact I cant find any reference to it. I have a choice of a number of tuned pipes I can use now - one came with it, but it looks rather small compared with the other 60 sized pipes I have so may be wrong. The supplied header looks like it has been used as a hammer - its very badly creased so I order a new one from Just Engines. They also had no info on the engine

Now, forgive me if I am teaching you to suck eggs here, but I need to set the pipe length and this can be calculated using the following formula

Pipe length (in inches) = Exhaust Timing (in degrees) * 1650 / Desired RPM.

I am hoping to get 12000 rpm on a 12x8 prop (in the absence of any other information).

The exhaust timing is calculated by placing the engine at TDC, turn the crank (in the direction of rotation) and look for the piston crown just appearing through the exhaust port (at the top). Note the angle on the timing disc. Continue to rotate through BDC until the piston crown disappears again on the compression stroke - ie you have timed the exhaust open window.

I made up a simple timing disk and attached a pointer using a jubilee clip as shown.

and

Using this technique, I measured this engine to have an exhaust open timing of 145 degrees.

Substituting the numbers above,

Pipe length = 145 * 1650 /12000 = 19.9375". I believe that the pipe length is measured from the centre of the piston crown to the baffle in the pipe where the diverging and converging cones join.

Can anyone confirm that is right before I take a hacksaw to my currently very long header pipe?

More to come (and in less than 5 months) - I want this completed and maidened before the UKCAA SLEAP do next month.

Martyn

[Martyn K]

One thing I forgot to mention is that the current weight is just under 3kg - expecting just over 4kg complete but dry.

M

[Paul Jefferies]

Martyn, this all sounds very scientific....... It is a long time since I have tuned a pipe but I seem to remember using a rather more empirical approach. I started with a pipe that was obviously too long and measured the revs on the ground (obviously!). Then I chopped the header pipe about 6mm at a time and tried it again until there was no increase or even a slight drop in the revs. Bearing in mind that the engine unloads in the air and the revs will be higher, a pipe that is slightly too short on the ground will probably be about right in the air. You want it to come on the pipe as you load it up when you fly upwards so inevitably you want the pipe a bit too long in level flight and then as you pull up and the revs reduce a bit, it comes on the pipe....... At least that was my theory so tune it on the ground and then fly it. If needs be you can then "fine tune" it by chopping the header pipe a further 3mm at a time. If you think you have gone too far you can always increase the length again by putting the little rings you have cut off back into the silicone joiner between the header and the pipe. It may seem a bit hit and miss but it worked for me back in the day!

Best,

Paul

[alec james]

I used to use the info on tuned pipes from Bolly (an Australian Company). Type in Bolly Tuned Pipes in your search engine and you will see down a bit the left hand side a chart on tuned pipes V rpm.

Hope this helps

[Martyn K]

Thanks Paul

I was following the guidance on a post on RC Groups for this. I hadn't seen it expressed this way before so I thought that I would try it. As we are talking about standing pressure waves, it should be feasible to calculate the correct value.. but.. I really wanted a start position then cut it about 25mm too long then try your idea of cut to fit until its right.

The 20" pipe length looks about right - so to be safe I'll probably start at about 22" and work down from there.

I'll need to run the engine in (a bit) before I get too far with it though.

BW

Martyn