Li`l Cub

[Martin McIntosh]

Anyone else out there attempting this? I like the odd offbeat thing, and having built a couple of Peter`s designs in the past I have every faith in it.

Looks like just another simple Cub on the face of it but not quite so.

I had no 1/4" hard balsa dowel and the LMS only had loads of soft stuff. I did, however, have just enough 4 and 5mm carbon tube for the longerons. This made construction a little more difficult but I got there in the end. Aligning the fus sides was not easy, and mine is not quite right but it will do. It is very rigid.

Don`t make two left hand sides will you since that would be daft!

The wing looks to be pretty normal but I changed the order of assembly a bit then wished that I had not done so.

The servo wire holes need to be a little further aft, otherwise the centre section ribs become rather delicate where the dihedral brace slots are cut.

I have top hinged the ailerons to give a little built in differential.

Servos will be Corona DS939HV since I shall be using a LiFe pack. No electrickery in this one. I had an OS 26FS and 52FS available but neither looked to be suitable so have obtained an SC30FS to try.

I did not intend to start a thread on this until it was finished and tested but here it is anyway so far.

[Dwain Dibley.]

This is something I want to build too Martin, so a build thread is just the ticket. Mine would be electric.

Looks the Mutts just now Mate, keep up the Stirling effort.

D.D.

[Martin McIntosh]

I have not done a blow by blow build thread on this but will keep you posted as it progresses. If the i/c option does not work out then it is easily converted to leccy. I shall not bother with a dummy engine as yet for that reason.

[Levanter]

Very nice Martin

Sorely tempted to have a go myself. Do keep us posted.

Levanter

[Steven S]

I have started on one also. Just have the fuselage sides made and am fitting the doweling to them now. I have gone with hardwood dowels as I couldn't find any balsa ones here. I will be using electric power for mine.

[Tim C]

Martin,

You can see my build on Peter Millers original Valdez thread, its a similar state to your, just fitting out the completed airframe and final covering to do. Its leccy, and like you a few mods to the plans, top hinged Ailerons, slotted hinge flaps. I used 5mm Dowel and 3mm Bamboo for the frame, its turned out very light and strong., I got my 5mm dowel from SLEC, but note that the local Hobbycraft have plenty, B&Q have plenty 6mm dowel if people want to follow the plan, I think balsa dowel would be a bit weak.

[Martin McIntosh]

Thanks, I did not know that it existed but have now read it. Lots of useful info.

[Martin McIntosh]

Lots done now, with the fus. covered and painted bar the fuel proofer, tail done and ready to fit and the wing 3/4 covered. I have had to put the rudder and elevator servos at the back because of the heavy motor.

If I never see another slat again it will be too soon. I have found these to be very difficult so far and they still need to be shaped. I am toying with the idea of tissue covering and painting the inside then glueing them on and shaping later, but we shall see.

[Piers Bowlan]

Martin, which adhesive are you using to glue the dowels together? I was wondering if it might be possible to tie them together with carbon tows for extra strength without unsightly lumps around each joint?

Be interesting to hear how she goes on the SC 30FS.

[Peter Miller]

Hi Glad tosee another Li'l Cub on its way.

Yes, it does lend its self to variations on the construction.

Yes, slats are a pain to do. I made three because I loused one up.

I too will be interested to hear how itgoes on the SC30FS

[Martin McIntosh]

Hi Piers,

To glue carbon to carbon or balsa I first sprayed the joints with 3M Polyolefin Primer, item No. 05917. By far the cheapest way to buy it. This allows the use of c.a. (I used thick). Brilliant stuff. No need for reinforcement (I hope, because I have not as yet even run that motor, let alone in the model).

I first came across this when I was at work and needed to make some awkward joins on prototype items. I tested it on a polythene bottle similar to a fuel tank and glued another polythene item to it with c.a. I still have this and after 15 years still cannot separate them. The primer I used then was super expensive and bought from RS or Farnell. About £12 for a 5g brush bottle! The 3M was around £3.50 for 200ml.

My power set up is a guess so I too shall be very interested to see how it performs but as I said earlier it can easily be converted back to electric.

[Piers Bowlan]

Thanks for that Martin, here is the product from Amazon with free delivery.

Good luck with the maiden flight.

Edited By Piers Bowlan on 26/06/2019 06:18:34

[Martin McIntosh]

A bit more expensive than I seemed to remember but still very good value.

[Martin McIntosh]

Nearly there now with just the tissue covered slats to paint and glue on. I cannot guarantee that these are exactly to the shape shown on the plan but they should be OK despite one end of one of them having lost its section somewhat. This will be placed at the wing centre so it should not have too much of a detrimental effect.

I was originally intending to try a FrSky module in a JR Tx but I bought a virtually unused DSX9, identical to my favoured set which has all memories full, at W&W, so it will be a test flight for that too.

Quite a challenging build but that is what the hobby is all about. It got called a Li`l something a few times and it certainly was not Cub.

[Peter Miller]

The shape of the slats is what I call TLAR and they seem to work OK.

I willlook forward to seeing the finished model

[Martin McIntosh]

Just waiting for the 30 min epoxy to set on the wing struts and it is finished. Finally found a use for those Robart hinge points other than as fuel tank bungs.

The AUW has turned out at 63oz, 1.78kg which is very close to the original; cg is spot on.

Too dark now to take pics in the garden but hope to take it to the field tomorrow pending a successful motor run up. Will try to remember to take the camera with me.

[Martin McIntosh]

Ran up the motor prior to a field visit. It was bought on ebay as supposedly bench run only and as new. Not so.

Everything which could possibly be tightened had been done with pliers, leaving lots of marks including each side of the carb. needle assembly, even the prop. driver. Crash damage to the carb. intake and mounting lugs. The prop. washer and nut were missing and it was covered in grass seed!

I ran it on Laser 5 fuel which should be OK. Not possible to lean out the mid range enough because the screw has bottomed out, but after fitting a new plug it is acceptable. Probably just a design fault on a budget motor.

Up at the field I range checked the untried gear and all was OK, so here we go. Take off was fine with less than full power but it violently veered off in a right roll and I only just had enough aileron authority to get it straight so carried on and landed at the far end of the field which luckily had the hay crop removed. It also tended to climb a lot and felt very stally.

On inspection the ailerons and flaps seemed to be drooping, despite careful setting up on the bench so I corrected this and added more throw with differential. I could see no warps so tried again, landing after a straight line flight. It was the wind sock which was telling porkies and wind under the left wing that caused the initial problems.

Went back up and flew round normally for a while, trying out the flaps at height. A few clicks of down were added. I felt that I was running out of up on the landing but too late to flick the rate switch.

Will increase the elevator throw for next time out. I use lots of expo so too much throw will not be a problem.

Power seems about right too.

I always like to take model home and check over everything after an initial flight so called it a day. Nothing else that I can think of to change so this should now be fine.

Question for Peter.

I have not fitted strut braces as yet. What are they for please?

[Steven S]

Beautiful plane Martin, I hope mine turns out as nice. Was it very tough to do the covering around the leading edge with the slat mounts glued on?

[Denis Watkins]

Magnificent model Martin

The motor by the way is not cheap and cheerful, and run beautifully when set up right

It sounds like the low end needle is wound right in

Inspect both, by winding both out

If they are straight and undamaged, the return both using the " blow down fuel pipe " method

This will get you within one of two clicks of optimum

Sneak some 10% in the tank if you have any, and test fly 9 x 6 and 10 x 5 prop as well as you 10 x 6

Have found myself that this motor prefers the brakes off with a 9 x 6

Edited By Denis Watkins on 11/07/2019 18:02:52

[Peter Miller]

Glad you got it flying OK.

The strut braces are just scale. Mine does not have them (I am lazy) On the full size they will stop the struts flexing

The SC 30 is a lovely engine. I always use 10% nitro and fly on a 9X6.You can go down to a10X5 but I prefer the 9" props.

I have used several SC 30s on many models, never had a problem. A friend is still flying my Peret Mauboussin which is about 78" span and he floats it around and half throttle or less.

[Martin McIntosh]

Hi both and thanks.

Steven, the wing was covered as normal first. I then attached the slats with tape with the mounts fitted to them and drew round on the LE with a felt tip. Slats removed and thin strips of masking tape applied round the ink marks. The covering was then cut off between these strips which were then removed. Slats then re taped on ensuring that they were level with the underside of the wing. A little thin Zap top and bottom to tack them in place then some r/c modeller`s glue to ensure a secure joint. Did not take as long to do as it may seem.

Denis,

I used the 5% because that was what was in my bottle at the time but would normally use 10% on these small four strokes. The SC instructions say a 10x5 but since my 26`s are happy with 10x6`s I tested it with one. Will probably change this for the next flight since it did not seem very happy. The top end needle was sensitive which 10% will sort out. My OS motors have been fitted with an extra head shim to allow the use of up to a 12x5 on 20%. I shall strip down the carb to find out just what the previous idiotic owner has done to it. 10% fuel would need a richer mixture all round anyway so this may sort it without further attention.

[Martin McIntosh]

Don`t know what has happened here but I just replied to Steven and Denis. It has not appeared. OK, I shall do it again!

Steven,

The wing was covered as normal then the slats, with their mounts fitted, were taped in place. I then drew round the mounts with a felt tip, removed the slats and put thin strips of masking tape round the marks. Covering then removed between the tape which was then also removed, slats re taped in place and thin Zap applied. R/C modeller`s glue to make sure. Not as bad as it may sound.

Denis,

I would normally run these small four strokes on 10% but the 5 was in my box. My OS 26`s are happy on a 10x6 but I have added an extra head shim to them so that I can use up to a 12x5 on 20%. Next time out it will be a 9x5. The top end was sensitive on 5%. Rather than strip the carb. to see what the previous idiotic owner has done to it I shall wait and see since the 10% will require a richer mix anyway.

Peter,

Glad I did not bother with them.

[John Bisset]

Hi.

Does anyone know where I might be able to buy a copy of the June issue of RCME to get the 'L'il Cub' plan? I missed it, by being away on holiday - bother.

It looks as though the print version is not available as a back issue here - I presume it has run out.

The idea of building a machine with both slats and flaps for seriously slow flying is great fun. I'd really like to work out a way to duplicate the automatic slats which the Rallye aircraft, though in small scale friction may be too high for air loads to overcome. First though, to build a simpler fixed slat aircraft !

Regards,

John Bisset

Edited By John Bisset on 02/08/2019 12:49:22

[Steven S]

My local hobby shop usually has the last three month in the racks, maybe check yours out. I'm building this plane and when I went in for wheels last week they still had 3 copies of the June issue.

[John Bisset]

Thanks Steve. Unfortunately my nearest hobby shop is ~120 miles away. Only A WH Smiths here,a ndthey have long since returned any spare stock.