Boot Hill STOL

[David Davis]

Having built a Webbit for the first Greenacres, a Super Sixty for the second and a Mini Barnstormer for the last, (didn't fancy the Tucano,) I am going to build Peter Russell's Mk 2 STOL for the 2015 Fly-In. I feel that I ought to have a stab at it as it was me who suggested the model for the Mass Build in the first place!

However, I never seem to have enough time to finish and test fly the models so of the three completed models which I took to Greenacres, only one, the Super Sixty, had been test flown prior to the event, its maiden flight having taken place the previous day! At the event I managed half a circuit with it (in the monsoon!) before the engine cut.

I had not tuned it correctly.

So this time I am determined to build and test-fly the model before the actual event. However, if things work out as I hope, (and they never do of course), I will be retiring to France in 2015. Indeed, I had expected to be there already but I have not managed to sell my house due to buyers dropping out, chains breaking, estate agents overpricing the drum etc. All this may well get in the way of building time but I have a cunning plan!

Talking of plans I looked at it this morning. Mine, RC/1445, is not the most clearly printed plan in my possession and some things are far from clear.The fuselage and tail plane seem to be very conventional but the wing is a little more intricate. It is made up from two 3/8"x1/8" spruce main spars, two 1/4"x1/8" balsa spars for the trailing edge, 1/2"x1/4" leading edge and 16 ribs at about 8cms between centres, these being interspersed with riblets. I have studied the plan most assiduously but cannot see any reference to the thickness of the wing ribs. As they are so far apart I'm going to go with 1/8" balsa but perhaps they should be 3/32". Similarly the dimensions of the slats require a bit of working out.

My plan is RC/1445. I believe that the Mark 1 STOL (plan code RC/1190) was a three-channel model but as I don't have this plan I can't be certain. There have been a number of questions concerning the STOL on another thread.I'm happy to answer them as well as I can in this paragraph. The Mark 2 STOL has a wingspan of 55 inches, an overall length of 39 inches including the rudder but not including the spinner. The push-rods to the ailerons and flaps appear to be the correct way round but I will be using micro servos. The Mark 1 STOL (plan code RC/1190) may well be a smaller model; it's advertised as having a 48" wingspan, mind you so is R/C1445! Only the Mark 2 STOL plan is currently discounted.

I do not have a 19-25 two-stroke but ASPs appear to be quite cheap from HK. I have a number of electric motors which would do the job so might electrify it, and a nice little HP VT 25 fourstroke. As this engine has flown a Junior 60, it should be able to fly the STOL. The STOL's fuselage is only made from 3/16" sq strip; it should come out as a very light model.

Do you think that 9 gramme servos will be suitable for the ailerons and flaps?

[Martian]

I shall be waiting and watching

[kc]

Well everything I can find says the STOL Mark 2 was 48 inch span and so is the original mark 1. All the Plans Handbboks and adverts for the plan say 48 inch as does the original mark 2 plan itself.

After reading through numerous RCME articles by Peter Russel where he discusses the STOL there is nothing to suggest there ever was any error or change in the span. RCME for Dec 83 says about the errors in the flaps/aileron bellcranks on Mark 2 plan but does not mention span. The May 83 RCME article by Peter Russel himself says about the Mark 2 " the fuselage and tail are just about the same as the Mk1 but the wing whilst retaining the same plan form and dimensions......."

So unless someone can measure the span on the original mark 2 plan or the mark 1 we cannot really know whether the currently sold 55 inch plan is correct or not. My belief is 48 inch is correct or the very meticulous Peter Russel would have said so in his many writings about the STOL. Also the specified .19 engine is rather small for a 55 inch short take off plane (PR flew it from his back garden! )

The original STOL was published in RCME May 73 and also in Model Airplane News in USA ( perhaps later) The Mark 2 STOL was published in RCME October 83.

However even if it's been enlarged to 55 inch span, with a suitable engine it should fly well as long as the wing is strong enough. . It's noted on the original tiny plan in RCME that the mainspar is spruce and has 1/16 balsa webbing between the two 1/8 by 3/8 spruce.spars. also the TE spar is 1/8 by 1/4 balsa with 1/16 balsa webbing. Ailerons & flaps also have webbing. Does it show all this on the latest plan?

Note that Dec 83 RCME says about the bellcrank errors and also that the cabin window should be moved forward 3/4 inch so the wing dowel can be lower to clear the flaps. i wonder if that has been corrected too?

[David Davis]

There must be someone out there with RC1190 who can tell us the size of the wingspan on his plan.

I have had my plan for at least ten years, it's a Nexus plan. There is text on the plan next to the title box which reads, "A 55" span Short Take Off and Landing R/C Model for 19cu.in. motors." Near the outline of the engine on the plan there is some more text which reads "OS 19-25 shown."

There is indeed balsa webbing between the spars, ailerons and flaps. I will probably simplify the construction of the aileron and flaps. I can't comment on the dowels.

[kc]

We await someone with an original plan......

In addition to the wing dowel needing moving down the Dec 83 article says "a couple of thinner dowels projecting rearwards from the extremities of the trailing edge of the centre section will prevent the wing retaining bands from slipping into the flap area" and "the dihedral braces of 1/16 ply go in front of and behind the centre section spar flanges so you need four of them"

The four dihedral braces ( rather than the quantity "2 off" specified on the original plan ) seems a rather important point!

I suppose wing bolts would cure the rubber bands interference with flaps problem.

Nobody has yet commented on 9g servos yet. I found they worked OK on ailerons for a 48 inch aerobatic model ( Swamp Rat) but I have not had enough flights yet to be certainif they will last Metal gear types would seem desirable.

[kc]

A bit more research has revealed that Mark 2 plan with ailerons & flaps published in Oct 83 has RC1190 printed on it ( bottom right corner) while the top left corner has 48 inch span printed on. This is the article reproduced here on Modelflying but I used the original magazine and studied it with a magnifier! It is clearly a flat bottom wing section unlike the Mark 1. So RC 1190 was the number for a mark2 plan at one time - at least in 1983. Why the number became anything else is unknown and it's certainly not mentioned in any of Peter Russel's columns even though he mentions other peoples STOL mark 2's often during 1984.

So if anybody buys RC1190 now it might be a Mark 2 ( flat bottom wing ) or it might turn out to be a Mark 1 with undercambered wing. Perhaps MyHobbyStores could look at the plan and let us know?

[David Davis]

I think it less likely that STOL builders will opt for the Mark 1 plan, RC1190, at £17.50 a pop when the Mark 2 version, RC1442 is available discounted at £7.50.

Perhaps someone with some clout within the organisation could get MyHobbyStores to reduce the price of a Mark 1 STOL plan to bring it into line with that of the later version so that builders may have a choice.

[kc]

David, you missed my point! RC1190 is ( or was) a Mark 2 according to the original article and many subsequent adverts in RCME.

[David Davis]

1190 is still expensive compared with 1445.

[kc]

I believe you pay a premium -5 pounds or more- to have them find an old plan from the X list and prepare it for modern printing. That's why these old plans are dearer.

We have spent a week or more discussing this and nobody from MHS has noticed and replied!

[David Davis]

Gentlemen I regret to say that my STOL will probably not be built in time for Greenacres. Life has got in the way, I'm selling my house and I hope to be living in retirement in rural France long before July. It's a pity as I was the first forumite to suggest it as a model for the Mass Build.

I will build it one day and will post my progress.

I was going to cheat anyway.

I've got a complete fuselage and tailplane which had been left behind in the Boot Hill Corner of our club hut!