Tweedy Bird (Small Dirty Bird)

[Wasaforumite]

I enjoy flying planes that I can fit in the boot of my car, the E Flite Advance 25 being a favourite. About half my planes are self build and I was looking for something possibly with a bit more speed and came accross the plans for the Great Planes Tweedy Bird. This is a 49 inch span version of the Joe Bridi Dirty Bird for .19 size ic. It seems ideal for conversion to electric (sorry!).

I have a JP Enrgy C3520/10 1100kv motor and on 4s it should be a good match for plane that will hopefully weigh around 3-3.5lbs.

The Great Planes plan shows enough detail for the build except that only the root rib is shown. I am indebted to David (posts as Doxilia on various web forae) for sending me a couple of pdf's of the ribs. He has produced laser kits of various F3A planes. Unfortunately, as he is located in Montreal, the cost of bringing these over to UK would be prohibitive.

I will be using a Mk26 Swann Morton laser aided by an Epson printer that does produce good plans at 100%.

Hopefully, some members of the this forum will be interested although of course I realise the size and the fact that its electric will put quite a few off!

Over the next few days I'll put up some pictures of progress.

Edited By Wasaforumite on 22/02/2016 20:47:28

Edited By Wasaforumite on 22/02/2016 20:48:42

[kevin b]

What's wrong with electric ?

Actually I thought this thread was some reference to a Geordie pop star.

Sorry mods, but I couldn't resist it.

[Martyn K]

I am certainly interested and will be following closely. I also agree that these smaller pattern aircraft are incredible fun, great value for money and IMHO massively under rated

[Robin Colbourne]

Hi Wasaforumite,

The Tweedy Bird, Birdie Ten and Baby Birdie are all very attractive designs. I'm another who will be looking forward to your progress.

Here's the plan for anyone unfamiliar with the design:

[Wasaforumite]

**LINK**

(hope I'm allowed to show links to pictures on web)

There aren't many images of the Tweedy bird on the net. Here's one I found. The Dirty Bird heritage is pretty obvious.

Looking over the plans I was pleased to find that the undercarriage is almost the same as that of my E Flite Advance 25 and to save a lot of work I found a 'spares' kit in my local model shop. This had the three legs, mounting hardware and some collets. The legs are about 2 cm longer but with our bumpy strip it will help save a prop.

I'll post pictures tomorrow of work on the fuselage.

[Robin Colbourne]

Wasaforunite, if you go with the recommended prop for your motor you will probably want that extra leg length, as the original would have used a 7" prop on a .10 sized motor, whereas your motor appears to be aimed at a 9" prop on 4S.

[Jim Purcha]

What is nice, is that Bridi designs are straight along the top of the fuselage, making it a quick build upside down on the building board. If you can cut a foam wing, it would speed up the build I think.

Jim

[Martyn K]

Here you are

[MaxG]

I have a Birby 40 hanging in the garage that I keep considering what to do with. Has only just escaped the dustbin although the airframe is OK. Just needs a clean and recover. Had an Irvine 40 in it.

Maxg

[Wasaforumite]

Many thanks for the constructive replies received so far. I've got a few photos of the construction which I'll post below.

Jim your point about how the fuz is built is very relevant. I initially thought I would use my SLEC jig in the usual way but found on the net that the Dirty Bird fuselage is built over its own top 'plank'. So I unpicked what I had already done and started again. I dislike liteply, especially for formers, as it always seem to warp as soon as it is cut so the front two formers are 1/8 birch ply and the next two are laminated 1/8 balsa with the corner joints overlapped.

I did end up using the Slec jig to help hold the curves. The position of the slot for the tail plane was marked but not cut as at this stage the fuz still has a flat top and it’s easy to mark out. Apart from substituting 1/8 for 1/4 ply and not using lite ply these are the only changes so far.

The first picture shows the fuselage that was scrapped. The second shows it reassembled in the correct way.

[Wasaforumite]

The fuselage consists of four box sides but they are all joined at the 'seam' by tri stock. Ttri stock is really quite expensive but I haven't found an easy way of making it. The commercial stuff is quite hard which is good for this purpose. The fuselage corners are planed/sanded to make a rounded section.

One problem I found was that the front undercarriage mount screws more or less have to coincide with the motor mount. As the motor has to stand off the front bulkhead I made a sandwich of ply. The motor is attached to the first layer, the second layer is a filler and the final layer is the bulkhead itself with the u/c mounted on the back not the front as shown on the plan.

[Wasaforumite]

I'll just catch up this evening on responding to those forum members who have taken the trouble to contribute to this thread.

Robin: As you say the longer u/c will be useful for the bigger prop required by the electric motor. I'm going to use 4s to keep the prop size as small as possible. The hatch will be on the underside in front of the wing. Not the most convenient place but I would like to keep the top 'plank' in one piece for strength.

Jim; Your comment came too late, sorry - I'd started the build a couple of weeks before deciding to run this blog. You are quite right - build the fuz on the underside of the top 'plank' and get a straight fuselage. Later, I found an article on building the full size DB and it explains it. Set up the formers on the plank and glue them into position.

I'm not experienced in building foam wings (only repairing them!). They are a time save and are pretty strong. I'm trying to build light, helped by modern servos etc. so I don't end up with a missile. My reactions are going to be tested by this plane for sure.

Max; I hope you can revive your DB. Good Irvine 40's might be expensive to find though, if you haven't kept yours.

I'm well on the way to finishing the right wing and i've discovered how to print out mirror images on my Epson Workforce printer so the left wing should be started this weekend. I'll post a few more pictures tomorrow.

Edited By Wasaforumite on 24/02/2016 20:44:25

[Wasaforumite]

Here's a view of the rear of the fuselage. I'm using DuBro snakes. The rudder and front wheel are operated by a Hitech HS225-MG and the elevator by an HS81MG.

The rear of the fuselage will be covered by 1/8 balsa sheeting with the grain running lengthways. The plan calls for 1/16 sideways. I'm hoping that the cross pieces and formers will overcome any weakness in the grain orientation. I really don't get on trying to get a good finish when sanding acroos the grain. There's a lot of sanding and shaping to be done yet.

Now onto the wing. I cut out all the ribs only to waste 4 of the 20 by deciding to up the thickness of the two ribs in each wing that carry the undercarriage. Mr Bridi obviously never saw our strip or my landings when he designed the wing! I also cut out some heftier reinforcements that carry the load right into the wing spars.

There isn't much else to report at the moment. One problem looms - the plan calls for 3/8 by 1 inch ailerons and they are solid wood. There's no way I can cut or plane such sections accurately and this size doesn't exist in any of the shops I can get to. I couldn't find smaller t/e stock that I could laminate either. Looks as if I'm going to have fabricate them which will be time consuming.

[Jimbo565]

WFM

Slec do a t/e section that is 3/8" x !.25"

Just have to trim off 1/4"

link**LINK**

[Jimbo565]

I have just seen this thread, I am building a Birdie 10 at the moment,slow progress to date.

will be powered by Enya SS15 BB.

Jim

[kc]

Balsa Cabin list 3/8 by 1 inch tapered elevator/aileron section.

The Birdie Ten seems to have a higher aspect ratio wing to the Tweedy Bird although both are 49 inch span. Both plans are on Outerzone together with supplements for wing ribs. The larger Dirty Birdy plan is also on Outerzone fpr anyone who wants to compare them. ( note that you have to spell 10 as Ten and correctly spell Birdie or Birdy to find these! )

[leccyflyer]

The Global Models Birdie Ten was my favourite model, before being lost in the River Mersey. After years of searching I finally managed to source a kit (and plan) and she's on the list to be built when I retire. Smashing little model that flew like she was on rails, initially o an OS.10 FP and latterly on a Mega 16/25-4 and 8xCP1300mah Nimhs.

[leccyflyer]

Here's a piccie - whilst glow powered..

[Wasaforumite]

Thanks to you all for suggestions re the trailing edge stock. Before pressing the 'buy' button at balsa cabin i thought I'd give Al's hobbies a ring and it turns out they have this stock after all. I won't be able to get there until later this week.

I've made more progress with the wings. I'm fretting the tips out of 1/2 inch balsa sheet and there's still a lot of capstrips to do. As with the Birdie Ten trailing edge pictured above, I've sheeted the it with a half inch strip. I think the trivial weight penalty is worth it for the extra strength. I'll post some pictures tomorrow.

As soon as the wings are finished they will have to be joined together.

Slightly off topic, I was reminded by the picture of the ic Birdie Ten that once I got used to flying this machine, it might be interesting to compare it with one powered by a 25. However, it's pretty boring to build two planes the same in succession. I looked at the Mantua kit for the Mini Kosmo, which is much the same size but I was rather put off by comments on Italian forums that said it was heavy and flew like a missile. The full size Kosmo 3 looks a beauty and  I am surprised there hasn't been any mention of it in the group.

Edited By Wasaforumite on 01/03/2016 23:15:53

[Wasaforumite]

Jim - I notice you are going to use an Enya 10 SS BB in yours. Should be a terrific performer - the ballbearing Enyas are superb engines.

[Jimbo565]

WFM

Enya 15,I ran it up for the first time yesterday,started first time and it's a little screamer.

I'm finding there is not a lot of space in the fuz for the servos.might put two mini servos at the tail end and one in each wing for the ailerons.

[Wasaforumite]

I went into Al's at Wolverton today to pick up the trailing edge stock. I was amazed to see that there was old kit for sale for the Birdie Ten! This is picture above see leccy flyer's post.

There was no price on it but it's worth a call if you are interested. It's at the back of the shop on the left at knee level in case you want to help the assistant find it.

[Wasaforumite]

I've loaded another photo. The fuselage is nearly finished and the wings have now been joined, althought the join still needs glassing.

I have been trying to source a canopy but neither Sarik or Vortex have one suitable. I've started work on making one using blue foam which I will cover with fibreglass cloth. This will be new to me so I'm keeping my fingers crossed.

I was really scratching my head about how to get a template for the teardrop shape, particularly the overhead view. It finally dawned on me that the wing aerofoil shape was as good as any - staring at me from the plan! I just scaled it up by 12% in my printer and then widened it by about 1mm on each side. The side view is shown on the plan and that's enough to get me going.

I have been quite taken by the logic of this design and how it evolved through Kaos, Super Kaos, Dirty Birdy and UFO. As I mentioned earlier I was toying with idea of the Kosmo 3 for my next project but I have come to the conclusion that it will be too fast for me. I've now got a pdf plan for the Super Kaos which might be a bit more suitable. It will mean that I'll have to get my hands dirty with glow fuel and I'll be the butt of a million remarks at my Club, where I'm known as a staunch leccy flyer. I'll have to go in disguise.

The image is upside down. It isn't on my computer!

[Wasaforumite]

After a few days some more progress. I seem to get to stages in construction when the 'chicken and egg' problem arises. Here it's the case that the wing can't be finished until it's been fitted to the fuselage and fitting to the fuselage is difficult because the wing isn't finished, if you follow me. Also there are steps that are critical to the performance of the plane like the alignment of the wings that are best done slowly. Anyway these are my excuses for apparently not getting on!

The procedure for mounting the wing is outlined in the original kit instructions for the full size Dirty Birdy.

With the fuselage upside down, the wing was first roughly fitted by sanding the saddle. The wing bolt is then fitted and the alignment checked many times with more adjustments to the saddle. The measurement from the wing tip to the tail was equalised using a steel rule. More adjustments were made to the saddle.

The position of the wing dowels was then marked through the holes in the former in front of the wing and the wing leading edge was drilled to accept the dowels.The inner ends of dowels are anchored by holes in lite ply spar webbing . I predrilled the webs and made them slightly undersize so I could adjust the position of the dowels. I wanted the dowels to position the wing without any unnecessary stress, so after positioning the wing the webs were just glued with epoxy where they ended up. I haven't at this stage glued the dowels in place as I want to put a fibreglass band around the wing joining area and it will be much easier without them being in the way. (chicken and egg again).

I hope this explanation is clearer from the picture.

Having mounted the wing, I can now get on with installing the servos and remaining sheeting.

[Jimbo565]

WFM

check this out

**LINK**