Simples Max

[Martin McIntosh]

Now getting really, really bored but I pondered for a while over yet another quirky free plan. I saw the original fly last year at Buckminster and was fairly impressed with the way it flew so I rummaged around in the boxes of balsa, gear and motors to see what I had. Needless to say out of the tons of wood there was nothing really suitable but maybe I could laminate some to the thicknesses required. Just about enough.

I have a spare Axi 2820-14 and an esc to go with it but also an OS 25FX, so I stripped the motor to find the expected very rusty bearings and a dodgy cylinder which may be useable, so am awaiting the new bearings before I decide. There is also available an SC 32 and a West 36 but perhaps at bit OTT.

Anyway, I made a start with the fus sides, (laminated), LE and TE, also laminated, and the ribs. I was rather less than impressed by the suggested assembly sequence so have done it my easier way. The LE is straightforward and simple to put the slight bend in the spruce, ( which, by the way, I had to saw from a larger piece, having no 1/4x1/8 left). I did not fancy that bend in the TE strip so cut it in half and glued to the TE which has had the ailerons pre cut off, making that part much easier. Quite easy to then cut a spruce infill at the centre to join.

The ribs were a pain. The little bits at the back kept breaking during assembly so I chopped them off and added 1/16x1/8 balsa strips to the TE to replace them. These can then be sanded to a taper.

So that is it for now other than some pics.

[Mike Bell]

Hi Martin

Always good to see different takes on assembly methods, I know what you mean about the ribs at the trailing edge, these used to drive me mad when building combat wings this way, but once glued and filleted they are up to the job.

I think it may be wise to add some kind of brace across the trailing edge spruce strip where you cut it in the middle. This is effectively one of the spars so it's integrity could be quite important..

Mike

[Martin McIntosh]

Hi Mike,

Spruce infill added as planned, rib fillets sanded and LE shaped ready for the other bits to be glued on.

The motor bearings arrived today and have been fitted so since all the neighbours are at home it will be a good opportunity to annoy them when I test run it.

[Mike Bell]

Surely the noise of an engine can only bring them happiness and joy into another lock down day

[Martin McIntosh]

Coming along rather well now. On my i/c version the hatch is better placed underneath. At the moment it has been cut to full length but this can be changed once I know where everything is going to go in after checking where the cg is likely to turn out.

It will be orange on top and black underneath. Why is it that black film of any type or make is so much more difficult to make a good job of? It is the only dark colour I have left anyway.

No 1/4" suitable balsa left so the hatch and wing tips are from 3/16".

I can only get a 4oz SLEC tank in but this should give up to 5min. flight time similar to an electric set up. If i/c does not work out OK for any reason I can easily fit an AXI 2820-14 which is equivalent to the OS 25FX.

[Martin McIntosh]

Well, here it is ready to go (this year?).

This is how I got a neat covering edge on the underside.

I firstly applied a strip of orange then two layers of masking tape on top so that the knife would not cut through to the black when the top orange was folded round and cut.

AUW is 2lb 6oz which is rather more than suggested but still peanuts for the OS 25FX which normally powers a 4lb model ballistically. The cg is a little forward but at least on the safe side. I may add some lead at the rear before trying it. I could also substitute an OS 20 which is considerably lighter. A lot of the fus material is thinner than planned because the whole thing has had to be made from what I had; I even reverted to a toggle switch since all my slide ones have been used up

I am surprised by the control surface movements stipulated because they seem huge and were none too easy to achieve with the mini servo arm lengths.

I had a problem with the recently re-bearinged motor because when I finally tightened the prop. nut the driver bound on the crankcase, but stripping it and re-seating the bearings cured this. The model can very easily be converted to electric should the need arise.

[David Ashby - Moderator]

Cor, you don't hang about Martin, nice.

[Martin McIntosh]

Thanks David. I seem to be knocking them out faster than the mag flies through the door.

Now I need something to take up a year or so.

[Mike Bell]

Nice quick work Martin. How far forward is the cg? Too far forward and you might run out of elevator. To move cg back you might consider shortening the nose because it is so short coupled that you might need a lot of lead to make any difference.

Regarding movements it depends on how you like your responses but I would keep the elevator movements fairly large until you get the cg right, especially with it being a bit forward.

Good luck with the maiden, hope you can still remember how to fly by then.

[Martin McIntosh]

Hi Mike,

It is about 8mm too far forward but only needs a little lead with a dry tank to correct. The problem is that although the motor weighs about the same as electric plus battery, all of the weight is right at the front, something I did not think about. No chance of shortening the nose since I had to shoehorn even a 4oz tank in. I have also used a 5 cell NiMh pack split into 3+1+1 around the fin base instead of my preferred LiFe one. I have some extra elevator available on high rate should I need it and bicycle clips at the ready.

It will certainly not be the first of my new fleet up when the field eventually reopens, more like my old Dalotel or Stampe.