Taurus retro aerobatic build

[Mike Bell]

I really like the styling of the older generation of competition aerobatic models. It might be because I grew up with them but actually I think they are genuinely more stylish than many of the modern designs and with a resurgence of interest in retro designs, plans and kits are now fairly readily available.

Anyway, Belair kits had a stand at the retro meet at Buckminster a year or so ago and Leon had a built Taurus on display. It immediately caught my attention and one of his kits duly followed me home. Due to other commitments it remained untouched until recently but I'm now in a position to start assembly and I thought I'd share the experience.

As the box label below shows this is a 70 inch span plane but beware the erroneous reference to engine size. The original was fitted with a Veco 45 so a modern 46 would deliver much more power. I don't know where the reference to 70 to 90 size engines came from but it is clearly incorrect.

So, what is in the kit? You get a large (humongous) plan, three bags of laser cut balsa and ply parts and a vac formed canopy. There is a fair bit of sheet and strip etc that you will have to provide yourself and there is no accessory pack or wire parts for undercarriage. Despite this I reckon that the price is fair considering the work saved on all the tedious cutting out and the number of parts you get.

The cut quality is very good and the quality and grading of the balsa parts is excellent. As you can see from the rib detail below, the wing section is thick and blunt and semi symmetrical. This is typical of the designs of the day and promises benign handling. The ribs have support tabs to ease assembly and jigging parts to help fitting of the sheet around the front. There is no leading edge strip, the sheet wraps around the front of the ribs, so that should be interesting!

I have decided to start with the fuz which I'll begin in the next installment.

[Andy Blackburn]

Nice. Watching with interest.

I assume that the reference to 70-90 size engines is for four-strokes...?

[Mike Bell]

Hi Andy. That reference could be for 4 strokes but I doubt it. It was designed for a lightweight 2 stroke (no silencer) so getting it to balance with a large 4 stroke could be a challenge. I treated myself to a nice new OS 55 two stroke at the Nats. I'm sure this will be overkill on the power but I know what the throttle stick is for so should be fine.

[Mike Bell]

The plan is very busy with detail, especially for the fuz. It is pretty difficult to make sense of some of the assembly and it looks like Leon has made some changes and possibly mis-interpreted some of the detail. An example is the fuz side doubler. On the plan is seems that this was a diagonal grained balsa doubler (common in older designs) but in the kit this is substituted with a ply item that is curiously in 2 parts. I think that the outline of the doubler is incorrect at the front as it doesn't allow the engine bearer, font former or upper side doubler to sit correctly.

Not a big problem, I just added some filler pieces. Those ply doublers are a bit of an overkill in my opinion, the ply is 3/32 in or thereabouts; I would have made them 1/32 but weight shouldn't be a problem when you look at the size of the servos it was designed for.

Those servos are for reed radio and they are like bricks. The linkages are rather convoluted as well so the controls must have been soft to say the least. I was impressed that despite the crudeness of the radio gear the original was fitted with wheel brakes actuated by the elevator servo (down gives brakes on). I won't be trying to replicate that. Anyway, the point is that modern radio must be at least half a pound lighter so the beefy doublers shouldn't be an issue.

[kc]

I notice that a set of Taurus wing ribs and other parts are available from a different source, doesn't include the plan or canopy and perhaps not the fuselage sides etc but much cheaper at 47 pounds inc postage. Lots of other wing rib sets from iGull too

Bubble canopies are available from Vortex Vacform for about 9 pounds

Plan and original article are on Outerzone

also on that Outerzone site are some details of shortening ( !)  the fuselage for proportional RC and changes to the CG position which may be of more interest.

There is also a 60 inch span version for electric power on Outerzone

 

 

Edited By kc on 29/09/2019 17:39:56

[Peter Christy]

I built a Taurus many years ago, but cheated with foam core wings! It flew very well:

(I was a LOT younger, then!) Yes, that's my Bonner Digimite transmitter (still got it, still works!) and the engine was a Webra 61 (pre-Blackhead) that is currently flying my KingPin:

(The KingPin was a Dave Platt design, but clearly heavily influenced by the Taurus!)

My original Taurus was modified for conventional ailerons - I'm not fond of strips - and this was an easy mod with the foam cores.

A building tip: It can be difficult to wrap the leading edge sheeting around the LE without it splitting. To overcome this, use a wet piece of sponge so soak the OUTSIDE of the LE sheet. This will make the LE sheet curl, and it will be much easier to apply. Stick it in place before it has had chance to dry properly.

The Taurus was originally designed for a Veco 45, but most people fitted 49s or 61s. Bear in mind that this was in the pre-Schnuelre porting era, so an old school 61 is about the same power output as a modern 45, and probably lighter, too!

My KingPin came in 2lbs lighter than design. This had nothing to do with me being a light builder - I'm not! Modern radio gear is a LOT lighter than that from the mid 60s - indeed about 2lbs lighter!

Watching this with interest!

--

Pete

 

Edited By Peter Christy on 30/09/2019 11:09:23

[Mike Bell]

Thanks for the advice Peter. It will be a week or two before I face the leading edge sheet challenge. I'm sort of looking forward to it, it should be an interesting experience but it will result in a really nice leading edge contour if it's successful.

[Mike Bell]

Got a few more bits glued up this evening, nearly ready to join the two fuz sides

The ply pieces to the left of the pic are included but no indication of what they are for. I presume they are to beef up the engine bearers but there is no room in the slot cut in the firewall and don't look necessary. Maybe they are for anyone feeling like fitting a big 4 stroke as mentioned earlier. I'm leaving them off.

Main formers, doublers and triangular glued up. The front cheek doublers need to be cut to fit either side of the bearers. I think they have been cut in one piece to accommodate electric set ups that won't use the bearers.

[Mike Bell]

Fuz structure in the jig.

Engine and tank dry fit. Can't wait to fire up the new 55AX

Fin assy glued up.

The ply pieces at the bottom of the picture are doublers intended to fit on the fuz sides under the tail plane. I really can't see any need and they are quite heavy, so I'm not fitting them. The two pieces above are tailplane ribs. Problem is, these are the only two in the kit, should be loads more.

[Mike Bell]

Tailplane assembled today. I can see why only the centre ribs have been laser cut, there are no other views to trace for cutting and they are all of a different length. The construction design is a bit strange and probably more complicated than it needs to be but I have followed it anyway. You can see from the sectional views that, except for the centre ribs that are sheeted over none of the other ribs actually support the covering. I can only assume this is to preserve a smooth surface appearance.

Construction is done bar the shaping and sanding. The result feels light and strong but seemed like a lot of work for a tailplane.

[Mike Bell]

Just started the wing construction with the RH wing panel laid out and ribs in place.

Nearly made a big mistake at the first hurdle. I should have packed the lower spar up, without doing this the alignment tabs didn't sit flat to the board. Not sure if this would have made a big difference but I spotted it and corrected anyway.

A couple more kit error glitches cropped up during this stage. At the inboard end of the wing the spars are double thickness so the spar slots are deeper. However, two of the outboard ribs had one deep and one shallow spar slot cut.

One of these is wrong on the plan but the other is correct on paper. Not big problems but a little irritating anyway.

[Mike Bell]

It's been a while since the last installment, life, holiday and a bit of illness got in the way. Also I'm at the point I haven't really been looking forward to, the leading edge sheeting. This design calls for 3/32 sheet to be wrapped around the front of the ribs, there being no conventional leading edge strip. This is some fairly extreme wood bending but I discovered that our Vax steam cleaner has a separate nozzle ideal for applying steam to jobs like this. An experiment with a bit of scrap showed that a tight bend (around a broom handle) could be achieved fairly easily.

Some weeks ago I had already butt joined two lengths of 4 inch wide 3/32 sheet using waterproof wood glue. This was my first mistake as waterproof it turned out not to be. I should have known better really. So when I had soaked the sheet in water and started to bend it, the seam started to come apart and the job had to be stopped.

After doing some fairly ugly rework on the butt joint with cyano I tried again. I started by forming the tight nose radius around the broom handle using the steam hose on the pre-soaked sheet. by working up and down the length a bit at a time a decent radius was achieved and the sheet was loosely clamped around the broom for half an hour or so to take a set.

With this pre-form achieved I pinned the wing to my board over the sheet and started to wrap the sheet around the ribs, using the steam to help. This is not a one person job, Mrs Bell was pressed into service to work the steam cleaner while I did the bending. By the way if you wear Marigold gloves there is no danger of scalding yourself.

The picture above is some final steaming going on after the main forming was complete and the sheet was pinned to the wing. No gluing was used at this stage. At this point the assembly was left overnight to dry. In the morning the sheet was unpinned and it was found to be nicely moulded.

Now wood glue was applied to the ribs and the sheet cyanoed to the lower wing spar. The sheet was wrapped firmly against the ribs and then the upper edge was cyanoed to the upper spar, job done. More steam was applied to stress relieve the assembly and it is now sitting weighted down to dry.

After I had calmed down from the initial disaster I must admit this job was not as bad as I had feared. Can't see me incorporating this method into any of my own designs though.

[Dean Hunter]

Well done Mike. You made it sound quite straightforward ..... Originally I imagined damping/bending/glueing each of the 3 sheets individually, joining all three and then fixing the complete LE as a single unit seems to be the way to go? I will ask around for a VAX - it seems to have helped. Thanks for the post.

[Peter Christy]

Very nice job, and what an understanding missus!

I remember when I did mine - foam cores, but still the same bending issue for the LE - it was quite a struggle! I did manage it, once an "old hand" had taught me the water trick, but I didn't have the benefit of the steam cleaner - or an understanding assistant! I wonder how Ed Kazmirski did it with the original? Sadly, he passed away only a few years ago, so we're no longer able to ask him....

They do fly really well though, so well worth the effort! Should be more than "adequately" powered by a modern 55!!!

--

Pete

[Bob Cotsford]

As an alternative to steaming, I've had good results moulding balsa using ammonia solution. I'm sure that we used to get lovely flexible tangent cut wood that would roll easily without splitting, all I seem to see for the last 20 years or so is the stiffer random cut stuff.

[Mike Bell]

I did look into ammonia, Bob, but apart from being difficult to source and rather smelly I read that the properties of the wood can be permanently affected too. Anyway the steam wand did the trick so I'll stick with that.

I do have a rather understanding missus Pete. We met back in the '70s when I permanently smelled of diesel fuel from control line combat wings so she knew what she was letting herself in for .

I need to order some wood before I can do the other wing so there will be a bit of a pause again. Don't want to wait too long though, I'm hoping to have it ready for the Ponty retro do, or at least the Buckminster one.

[kc]

Putting masking tape or any tape or even Solarfilm on the outside surface of balsa, veneer etc will enable bending to a tighter radius without the balsa cracking. Easy to try a small sample and see what difference the tape makes. I am not saying it's better than the steam method Mike used but it's worth trying for some jobs. Better than using ammonia which is often considered too hazardous.

[Mike Bell]

Well it's been a while since my last post, in the meantime I got a wood pack for the TN Gnat for Christmas so I got distracted and knocked one of those up. Since then I've been slowed down by sciatica and other life stuff but eventually I got going again and built the other wing - much easier second time round, the wrap around leading edge was a doddle this time.

I have just got the servos for the wings, one in each side of course these days so made simple mounts as below.

Need to finish off the centre section sheeting then I'll be ready to join the wings.

Next job is to sort the upper turtle deck on the fuz. In common with practice at the time of the design the plan calls for carving the whole thing from 1 inch thick balsa sheet. I did think about changing this but what the heck I'm sticking with it. I must say it feels wrong to buy an expensive sheet of balsa then leave most of it on the floor as shavings but I'm getting over it.

[Dean Hunter]

Congratulations Mike

I have made progress with the fuselage - I too have a nice thick piece of balsa for the turtle deck...... I will sand that to shape outside.

I have just started laying up the tail, not looking forward to sanding all the little ribs - the whole model does seem over complicated?

The Taurus is very much a builders model.

Regards

Dean

[Mike Bell]

They were all builders models in those days Dean, but I agree about the tail. What a complicated way of doing it for no advantage I can see.

According to the weather forecast it's going to be another building weekend, hopefully I can make some more progress.

[Mike Bell]

Made up a pair of nut plates to fit to the underside of the engine bearers. These are 4mm steel with holes threaded M3. I was quite pleased when all the holes lined up nicely.

The third hole is for a self tapper to help keep the plate in place. It will be epoxied as well.

Here it is epoxied in place and the remaining side doubler glued in place. There is still space to add lock nuts as well if required. I was feeling quite please with this.......then I realized that the engine fouls the nose leg installation .

I can't move the engine forward now, and don't want to anyway, so I'll have to look at installing the nose leg on the other side of the firewall. Have to think about that one.

[Mike Bell]

Been busy planing and hollowing.

I don't suppose the hollowing out will make much difference weight wise but it is necessary at the front to allow the fuel tank to sit high enough. I'll tidy the hollowed bit out before fuel proofing and I won't glue the top deck on until the push rods are inserted.

I think the nose leg issue is sorted, more later.

[Mike Bell]

So, the nose leg was fairly simple. A bit of rearranging with the suspension spring position allowed the top mount to be moved down out of the way of the engine.

The leg is actually too long so I made another on the SLEC wire bender

I had a rethink about the push rods for rudder and elevator. The engine is going to be heavier than the original so the model is likely to be nose heavy. That being the case I'm going to mount mini servos in the back of the fuz. This allows me to glue the top deck in place and complete the front end doublers.

I got the wing joined too. There are no centre section braces shown on the plan but I decided to embed some carbon strip into the spars. They are half inch square at the centre section so there is plenty of meat to cut into.

The picture shows the carbon strip prior to cutting the slot. There is a similar but shorter one embedded into the upper side as well.

[Mike Bell]

Haven't posted for a while but I have done bits and bobs including loads of shaping and sanding. Every time I sand the front of the fuz I decide I should take a bit more off the corners and end up sanding some more.

I have also been pondering how to tackle the tail and fin assembly. Ideally I would like to cover separately the assemble but to get fairings and everything to blend in I really need to assemble and fettle which means a trickier covering job. So, in true tradition when faced with a decision, put it off and build another plane. I'm now most of the way through an Aero-Naut Pepper but I have a decision to make on that one as well so..... back to the Taurus.

Servo mounting sorted for the steerable nose leg. I should be able to cover most of the servo to be less conspicuous. The hatch it's mounted in will be screwed in place to allow access.

I cut the ailerons out of 3/8 balsa (they aren't included in the parts set for some reason) and when I started shaping them look what happened to one of them. There must have been a lot of internal stress in that tree. It started out flat and took the banana shape when I planed the section. I'll try the steamer before I bin it. Above the ailerons is the tail plane which is having fin fillets fitted before shaping. I'm still putting the decision off.

[Nigel R]

Looking good Mike.

That is some decking!

The aileron looks frustrating.