Basing a home desgn on the famousWOT 4

[Myron Beaumont]

Kc

Thanks -Never thought of using foam   Will go for the 1st idea . Will solartex stick to foam without melting it ?- It's all new to me  I'll stick to the 52 I think .I can always change things later as I have drawn it up to take a mount already . The cowl will be a GRP jobby -but that is the last bit to do .

[kc]

SolarFILM will stick to some foam and 'Tex might.  Try a sample.

The first idea  doesn't have foam exposed,  the balsa sheeting  (normally added to the last wing bay even if the middle is open ) comes right out the tip and is rounded in one direction just like the centre section sheeting.  The underside is flat and should have a balsa sheet covering.   Try a rough piece of foam and see if the shape pleases you when chamfered.  I Bet it surprises you at the nice shape it forms!

The 2nd idea could not be balsa covered because its curved in 2 directions 

 

Carbon Copy do a 'glass cowl for Wot4 and others.  Also carbon u/c.

Edited By kc on 31/08/2009 12:38:43

[Myron Beaumont]

Kc

Thanks again . Now have the computer on a side table -My work bench/ drawing board in front of me . I intend to make my own "plug" & mould to fashion my cowl --That'll be in a few days time . I'm really enjoying this .The only thing I don't have "in stock" so to speak,is 1/4 " ply . Off to the skip !

[Myron Beaumont]

PS -- And you probably won't believe this -But my 1/4 " spars will be made from rocket sticks I collected  off the roads  last year . Incidentally -The CG is exactly on the measurement of max wing section depth SO I know where my main spars will be

[kc]

I built a foam wing with this section and chamfered it off ( undercut ) at 40 degrees. 

The actual tip needs to be 2.75 inches to chamfer off at this angle.  The flat underside then is maximum 3.25 inches and tapers to almost zero at LE and TE.

So you need tips of at least 2.75 inches.

 

I cannot wait for November 6th to get some free spars.   But it might be duff timber with faults or grain not parallel etc!   Otherwise I will use Ramin from the DIY store if they still sell it.

 

 

[Myron Beaumont]

Kc

 I' ve decided to make ailerons 18" long each (1/2 a normal length of TE stuff of which I have 2 lengths ) I shall stick the two lengths together flat to flat 'cos it is then the perfect section contour  for the section I've sort of invented . Funny you should say 2.75 " 'cos that is just about perfect for my rib spacing  .I can get 6 ribs out of a 4" wide sheet & I need 24 in all .The centre sheeting will be 4 pieces of  4" wide X 9" long sheet which equals one 36" X 4" sheet .

As they say " back to the drawing board " When I eventually make this model I will make a materials list based on what is available easily with little scrap left over . By the way -It is not a copy of the Wot4  but it is the inspiration -It looks right & as they say "if it looks right it is right".

Even 'er  indoors likes my version already !! 

[kc]

I have just consulted someone who has an orignal Wot4 Mark1 plan.

 

The wing is at zero incidence and  the engine has no side or downthrust. 

[Myron Beaumont]

Second attempt at a reply Kc

Great - That's what I've done Except-

 I've put a smiggin' of downthrust (LE at negative incidence on the tail feathers from everything else being dead level with the datum & the thrust line .I received about 15 basic measurements from y'all and having drawn it out have altered the fuselage cross section to a more aerodynamic shape .It actually resembles an aerofoil from any angle with the underneath looking like camber. 'I've taken a leaf out or Peter Millers book And am going to plank & skin the fuselage top & bottom to give the more rounded cross section (5 formers in balsa from the wing TE to the tailplane LE ) & the engine is to be at a 45 degree angle as well . I've noticed how many parts have been derived from 4 inch wide available sheet balsa !

Decided not to use my "rocket sticks" & buy some proper 1/4" square spruce for the main spars & also put webbing between them .Don't 'alf increase rigidity!  Not quite sure whether to use 1 cm square for the LE at 45 degrees angle or use 1/2 " thick stuff and shape accordingly after sheeting the front with1/16" sheet .

Anymore info welcome of course . Getting to terms with my (her) new camera & 'er indoors reckons she can put the design & build onto the forum .

[kc]

I reckon the LE system advocated by Phillip Kent and others is best.   A 1/8 sheet LE is put on before wing sheeting, therefore wing sheeting goes over this.  Then the  LE proper  another piece 1/8 ) is put on after sheeting.  Much better as the sheeting goes into a 'rebate'  and more glue area at the joint.  Also saves balsa as the front LE is narrower!

Edited By kc on 05/09/2009 11:45:14

Edited By kc on 05/09/2009 11:46:18

[Myron Beaumont]

Kc

What a good idea ! -I was going to use some 1 cm square stuff at an angle 45 degrees if you see what I mean as I said,  but your ( & others ) idea is much better for the very reasons you've explained for an aerofoil like this one . Having a bit of a rethink about the fuselage front -I've scaled up the half size diagram of the electric conversion (the only picture I can find) Trouble with the OS Fst is the length needed in the cowl section & I don't know obviously how it will affect the eventually balancing to get the CG correct.

 Another quicky ! Why is the bulkhead at the wing LE made of two overlapping pieces near where the wing locating dowels enter or is that part of the 'lekky conversion ..I shall stick the "fairing " extension of the top 1/2" block that blends into the wing shape behind said bulkhead ONTO  the wing .Another quicky; Is the the U/C ply mounting parallel with the datum line or at  about a 15 to 20 degree angle  as  shown on a few pics I've seen in adverts and articles about the ARTF version .It appears to be in a different position ie with its rear in line with the CG point .This would give about a 30 degree angle from the CG position on the wing which I reckon is about right ( I think)

g-umpy 2

Dave bear/Phil rules OK

[kc]

This LE method needs aliphatic glue or even balsa cement according to P Kent so the glue does not pull out when sanding.

The Wot4 has a very short nose and for light .40 plain bearing engines I would extend it 3/4 inch because mine had an OS40FP and needed a chunk of lead up front.  Maybe the longer heavier 4 stroke would be Ok as standard or maybe 3/4 inch longer would be safer. Depends how heavy the tail is ! This extra length would still  just come out of a 36 inch sheet.

The u/c plate rear edge is fixed 6 3/4 from engine bulkhead at an angle of 100 degrees from bulkhead, so it is not parallel to datum by 10 degrees.   U/C has wheels just ahead of LE. This angled front fus gives the rather pert & delicate appearance together with the curved rear underside.  If you are using piano wire torque rod U/C  ( Boddington style ) then the u/c can be tweaked to get wheels in right place.  If using alloy or carbon /glass U/c then its a matter of checking if the wheels are at right angles and central on the alloy and adjusting where ply plate needs to be drilled.  Probably a standard  alloy or glass u/c will be raked forward like the Wot4  wire u/c so the standard ply position will work.  Fus has little strength near u/c plate so U/C needs to flex.

 

The bulkheads front and rear are made from 1/4 square balsa with 1/8 cross pieces lapped jointed.  Top cross piece is balsa but ply if dowels are used.   All this is to save material & weight i suppose.  Quite a good method of construction and avoids the cross grain problem if cut from solid balsa.  Cheap too!

Edited By kc on 05/09/2009 18:50:33