Walnut Scale Mr Mulligan

[Dwain Dibley.]

Hello Chums,

There has been a distinct change of direction here at Dibley Manor,

I like Scale models, I like helicopters and I like petrol power, but I also like indoor free-flight.

I have, therefore,recently sold a 50 cc Zenoah powered Gilmore Racer, in favour of an 18" Walnut scale rubber powered Mr mulligan.

Inspired by some on here, and elsewhere, plus the enforced solitude, to pursue my rubber fetish, I got the Dumas laser cut kit.

My intention also, is to learn how to cover with tissue over Mylar. I have used tissue before but not Mylar. Would 2 micron be suitable or not ? There's the first Question, this model needs to be light, but resilient.

The other thing that intrigues me about rubber powered free flight is the trimming, and the ins and out of getting a good flight, so I'm looking forward to that part.

Here is the kit and plan laid out on my table, it made me chuckle when the whole thing went on in one.

D.D.

This is it, apart from decals and some plastic bits, cowl and spats.

[Jonathan M]

Nice one Dwain!

Beware though... once you start down the road of FF scale and enter the strange world of uncontrolled flight, there'll be no turning back!

[Dwain Dibley.]

I know...............I find myself drawn to the youtube videos of takeoff, 2 circuits and landings.

I watch tons of it, into the wee hours. Like the F1D boys and girls who control their models with balloons on ropes.

Can you get your hat on ??

D.D.

[Jonathan M]

No pressure then....

**LINK**

[Dwain Dibley.]

This proves the Model flys at least, whether my one will is another matter.

Jonathon, I'm sweatin already Man.....LOL

D.D.

[Jonathan M]

If you haven't already spent all the money from the sale of the Gilmore Racer, then **LINK** is a treasure-trove of core information.

Next thing you'll be investing in a 10:1 winder, building a stooge and - if you're really badly infected - you'll be scouring eBay for a rubber-stripper...!

[Dwain Dibley.]

You know what ??? I have already looked a a winder..... but not gone as far as a stripper.........Yet !!

I have been poring over the plan and instructions this morning, there is a lot left to the builder to figure out.

For example, bits have to be left un-cemented, until the dihedral is added Later. However the trailing edge is pinned first, but there is no instruction to make it in 3 pieces, which OK, you could say was common sense to do so ?? but if you don't you will have to cut it later, which is possible by the way, but harder.

All the free flight guys screaming, don't rush it Lad.......LOL

Having built a few kits and from plans, I have learnt to study things and work out a plan of action. Go through the build in my mind and that way you don't do things you have to undo...............hopefully anyway !!

I'm going to have a go later, so will post after that.

D.D.

[Dwain Dibley.]

So Chaps, I have been sticking rather small bits of wood together... I have used Thin CA, not balsa cement, dunno if that is trad, but it's definitely quicker. I use a very thin extension on the bottle, which is very accurate.

I dry fitted all the parts just in case, but the laser cut parts turned out to be very precise. I put a chamfer on the bits that are not glued, so when the wings are lifted to fix the dihedral there should be a good joint.

The wing is built as one whole thing but it is in fact in 3 pieces, a middle section and two outer panels.

The wing tips have to be raised, and a template is supplied for this purpose, once they are in position the 1/16th top spar is added, this seals the deal. It felt weird cutting through such a delicate structure.

I added the strut supports, and then the main top spar.

Once I have set the dihedral, with blocks under each wing, I will glue the spars at rib 2 (either end of the centre section) and that will be the wing completed, apart from shaping and sanding.

I enjoyed it immensely, makes a change from bigger models.

D.D.

The dry fit.

Closeup of the tip construction, and the strut support.

Here are the cuts in the TE and spars.Notice the centre LE is a laser cut part.

My trusty rib jig just fits.

Setting the tips.

Ta-Dah moment. Before you point it out, yes the two ribs (2) are cracked and bent at the spar. 

Tip angle set.

Showing that the top of the wing is flat, before the Dihedral is set in.

 

Edited By Dwain Dibley. on 23/05/2020 17:06:55

[Jonathan M]

Nice and quick!

I stick (pardon the pun!) to aliphatic for the main structures, but quite happy to use CA when there is a rapidly unfolding sequence of glue-and-let-dry steps to get through. It does add more weight than evaporating glues like PVA or aliphatic, but not so much to make any difference... unless (a) you go mad with the bottle and (b) are trying to win a competition. The only thing to watch out for is that it's harder to sand, so if it's being used with particularly soft balsa (e.g. 1/32" nose-cowl sheeting) things can get a bit worty!

Will come back to you shortly on the tissue-over-mylar question... when I've asked someone who actually knows that is!

[john stones 1 - Moderator]

Nice subject model D.D always fancied one, too dainty for me to build though.

[Dwain Dibley.]

Thanks Jonathon. I thought the build would be slower due to the size, but seems to go together well.

I will take your advice and go with aliphatic on the fuselage in certain areas I think.

Thanks John, yes....I had forgotten how delicate 1/16th square was.....

So I now have a wing, 2 struts, a Stabiliser and a fin, fuselage next.

Had a bit of trouble getting the stab off the board even with the plastic down, as it's so fragile, but no disasters.

Should I want to free the rudder, I will have to split down a 1/16th ............

I know some modellers use the rudder to trim, by using stiff hinges, but there are other methods, like tabs or warps, Am I right ?

D.D.

[Dwain Dibley.]

I have to build two sides, not identical, so be careful, then add the laser cut formers.

[Jonathan M]

I like to hinge the rudder using thin aluminium cut from food packaging and CA'd in place, stiff enough so you don't easily knock it out of place, as this properly enables adjustment when tuning - especially useful for tight indoor spaces! Other people use tabs (or gurneys - see below), while some even glue the whole single fin-rudder assembly as an offset angle to the fuselage. Once I've got my rudder deflection about right, I then measure its angle (keep a card template in the flight-box) or record how many mm it is from the corner of the elevator.

Rudder controls yaw - therefore turning circle. Most trim for left-hand circuits as its easier to tweak, but duration fliers often go right (for reasons I'm too knackered to think about right now!).

A down-tab, gurney-flap or wash-in on the left (inside) wing then helps hold it up during the turn. But as the rubber runs down and the airflow over the rudder reduces, this can mean the model straightens out under the continuing right-roll influence of the inside wing, or even start turning right... into a wall! So I often ration the amount of down-tab etc but then add some tip-weight on the outside wing, the latter not being subject to changes in airspeed.

These basic trim settings, as well as CG, are usually mostly established doing glide tests and perhaps some low-power test glides (10-20% of full winds).

Then thrust settings are established under more power. I initially wind to only 40-50% of normal max, so if things go wrong there won't be quite the drama as if testing under full winds. If all okay then gradually increase, but be aware that torque will be greatest during power burst from full winds! Expect to need some down- and some right-thrust, how much depends on how long or short the nose is, etc. By making nose-block removable and using 1/32" and/or 1/64" ply shims, this is eventually sorted out. If increasing or decreasing rubber thickness (i.e. power and therefore torque) these will probably need to be re-established. Duration is a function of loop length, I usually start with a test loop of at least 2x distance from hook to peg, then increase size from there.

How many winds is another subject, but breaking winds are easily calculated from the thickness and length of rubber, then never go above 80% of this breaking figure.

Here are three videos of a real master, Tom Hallman, gradually trimming his own scratch-built Seafire outdoors (he uses gurneys instead of tabs). Its sounds more complicated than it normally is, but low-wingers are of course harder to trim:

27" rubber-powered Seafire - Anatomy of a Trim Session #1

27" rubber-powered Seafire - Anatomy of a Trim Session #2

27" rubber-powered Seafire - Anatomy of a Trim Session #3

[Jonathan M]

Okay, see here for the gen on covering with tissue over mylar: Ralph's method

When I asked Ralph what thickness, he replied:

Try 5m, never really sure what that is but Mike Woodhouse (Freeflight Supplies) would know. All the models I have posted on HPA are covered in 5m clear or silver. For small models I wouldn't bother with the tissue as mylar takes acrylic paints very well. My KK Globe Swift, on HPA, is tissue over mylar - because I wanted the "tissue" look.
I find that I get a better looking finish with T over M than tissue on it's own and of cause it also lasts much better and doesn't age like doped tissue.

Hope that helps Dwain. I'm off now to install and set up the radio in my new Ahi... the wind is due to moderate and veer into the NW this afternoon - perfect for my nearest slope.

[Dwain Dibley.]

Brilliant !! Thanks again Jonathon, enjoy the slopes.. I will read that in a bit...

5m I assume to be 5 micron thick, which is probably the max for something this small.

I now have two fuselage sides, weighing in at 8 g all in with what I've built so far.

Next job is a tricky bit perhaps ? Joining the two sides, the method on the plan is to pin them upside down and add the top cross braces. I may pin the braces down, offer up the sides and see how that goes. You have to hold yer breath with this stuff, else yer parts disappear.

Pinning such thin section is easier if you make "saddle clamps" out of 1 /16 th sheet and two pins.

D.D.

[Dwain Dibley.]

OK so, I have now got a pile of sticks that look like a model plane. The stringy bits were a night mare to a point, some of the 1/16th was like cheese, so I had to be careful where I put what. I broke a couple on the way but I am guessing that's par for the course on these tiny models, there is probably a bit more room in the 20" + wingspan models.

The final result looks OK. There is the forming of the LE to do and then a sanding all over, then covering. So Mylar to buy and eze dope and spray glue................................................................

I have also made the undercarriage and fixed that in place.

D.D.

There is an ingenious locking mechanism for the cowl, that I have to make later.

I may add the optional diagonal braces, as the fuz looks very vulnerable on the top behind the wing

[Dad_flyer]

Very nice. I get nervous at the covering stage.

[Dwain Dibley.]

I think I will too, with this......what you see in the pics above, comes to a hefty 12 grams.

D.D.

[john stones 1 - Moderator]

Cute.

[paul d]

Looking great! personally I wouldn't double cover but would just us tissue and real dope, I love eze dope but in this case real dope would add strength, decoration is best done using enamels thinned with cellulose...

Take a look at "ffscale.co.uk" the guy than owns the site is a master when it comes to indoor scale flying.

[McG 6969]

Great job, Dwain.

I wouldn't even dare to touch your model, let alone working on it...

Looking forward to your covering...

Cheers

Chris

[Dwain Dibley.]

Thanks Paul, will do. Re the dope tho, the frame is frighteningly fragile, hence the Mylar.

Chris, I have to order materials, so covering won't be for a while, but there is more construction, including a mind blowingly tedious cowl to fabricate. An interesting change to those giant slabs of balsa we are used to EH??

D.D.

[Dwain Dibley.]

The Bits I have left................

D.D.

Even cuterer with some wheels on.

[Dwain Dibley.]

Ok Chaps, I did this earlier, but got side tracked looking at all kinds of stuff re free flight........ it's like Alice and the Rabbit hole, the deeper you go etc.......

Any way I made the cowl up, and the ingenious turn buckle arrangement, so it doesn't have to be glued on. Make sure to get it right so it's upright when locked in.

The tedious part was cutting and gluing all the blisters on the plastic cowl part.

Looks the part when done.

D.D,

Left a nice neat lip to slip over the fuz.

[Dwain Dibley.]

So........... I have made the first tentative moves at covering, I have started with the tail feathers. The reason being is, that I decided to separate the rudder from the fin, so it can be used for trimming. I had to therefore, insert another 1/16th stringer along the back of the fin.......I did not fancy trying to cut one in half....to take the hinges. I am taking the advice to make the hinges from tin, cut from a curry carry out tray, so they stay put in flight.

Adding side and down thrust is, say the instructions, achieved by inserting a small wedge behind the cowl.......Now, the cowl is a damned tight fit due to the ingenious twist on doobry, so that will be interesting.......unless the amounts are indeed very tiny, to achieve trimmed flight....Hence the rudder..?

I can make the fit looser by adding a shim I suppose......We will see.

I think I have decided to go with tissue alone, I think that the mylar would be more of an advantage on an out door model, 20" plus, I think someone did suggest that earlier. i want to try it on something, as the results look amazing.

D.D.

Rudder wetted, and pinned on slats, to dry flat.

Fin awaiting moisture. the bottom 30mm will be fixed to the stern post, I left it attached as it's so small. Everything is so flipping small....LOL

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