Ok ... I have started to scan and modify the parts for this build.
The original model is built on a lite ply / balsa frame and then clad with foam blocks. The blocks then shaped / carved / sanded to form.
Wings are foam hot wire cut and then covered in brown paper and PVA.
My idea is to convert to similar frame but then sheet in depron.
The wings to be conventional ribs (depron) and spars (pine strips).
My questions are :
4 E-Motors ... Original model has 4 x 25 Glow with 8x4 props. So I am thinking of 2830 or 2836 1200 - 1400KV motors with 8x6 props.
LiPo ... Some vids show conversion to 4S and massive batterys ... why ? With 283x motors and 8x6 ... they live happily with 3S. So I think 2200 3S packs if 4, or go for two large 3S packs.
ESC's ... 283x motors are happy with 30A ESC's ... so that's fine.
BEC ... obviously I am going to have to look at servos and power drain. I'm thinking to add a separate LiPo via voltage regulator (YEP 20A Dual outlet seems good bet) to g'tee radio lock regardless of motor side.
Retracts ... will power of the second output of the YEP regulator.
I see AUW runs from about 7kg up to 8.5kg depending on who converts. I'm hoping to come in at about 7kg and then it allows me to add the rest of "fancy bits" ...
One avenue I want too explore is wing ... original is single piece wing. My thoughts are to divide into two and bolt to fuselage side like my 3D machines ... have a spar through fuselage into wing tubes and then bolts to captive nuts to lock it all together ...
Guys and Gals .... I need your help !
Suggestions on suitable motors, retracts etc. (please keep to Hobby King as that's only real place I can get the gear at prices I can do the job with !!)
Oh ... nearly forgot. I have one Art Tech Sound System coming ... and my Pal has another he doesn't use and he will give to me. That is now 2x Art Tech sounds ... should be enough !
Question related to this. is there any small light audio booster board I can connect in .. so the sound boards can be amplified ? The AT Sound boards will need a bit more oomph to the sound I reckon and I hear that pushing them to max volume as stock overheats.
My club has got into big discussions about this model. With some questioning motors and power requirement.
My 2836 motors have been thrown out as not enough, with one proposal to have 1kw capable motors EACH !
Ecalc indicates motors in the 35xx range with 3 blade props would do it. Eg 3536 1450kv with 8x5 3 blade on 3s.
One of the problems actually is determing weight. Some have been as light as 12lb, others at 20lb. YouTube is no help as the range there is significant as well with few actual examples of this particular model.
I think I will be buying the Magazine with the build article !
So c'mon guys and girls ---- Help !
I'm hoping to keep the model in the 13 to 15lb range. Wing span is 90", root chord 15", tip chord 8", giving about 8 sq ft.... = about 27 oz/sq.ft.
I'm out of my comfort zone with a model like this, I don't have much experience of multis.. however..
if the original version flew on 25 glow motors then going by the 'equivalent power' rule you would be looking at a e-motors capable of around 450W each when spinning the same (8x4) prop. looking at APC's prop performance data you would need to spin a 8x4 APC prop at about 15000RPM to generate that much power. This ties in very well with how fast a good .25 glow motor would rev.
So if running a 3s battery that would point toward a pretty high Kv motor, I work it out at 1700Kv. That would be an unusual spec of motor. I think you might have to go 4s or even double up the batteries for 6s to get enough RPM on those small props?
You could maybe use 3 or 4 blade props and drop the Kv a bit
It does sound like a very interesting project.. will you give it working bomb release?
But back to the motors.. I think my calcs are in the right ballpark because if you come at it another way... You are using the same size props as the original 25 glow engines used. So it seems obvious that you need an electric motor that will spin the props at about the same RPM as the glow engine spins at.
It's been a while but I recall that a .25 revved at least 15000RPM, so that's around where you need to be aiming at.
That page says that a APC 8x4e prop spinning at 15000RPM absorbs 0.485Hp (about 375W). allowing for motor efficiency that's about 470W from the battery.
The table also says that each prop will produce static thrust of 3.6lb which seems about right for a plane of this size and weight (considering 4 motors).. possibly a fair bit of thrust to spare to be honest but bettermore than you need rather than less than you need. You can always throttle back!
That ends up around 1700Kv on 3s or 1450Kv on 4s or 850Kv on 6s and 450-500W
Nigel,a leccy version would come out much lighter than a glow job,wouldn't it?
I doubt that you would need to go to such big motors,especially if you can lose some of the foam pieces.I would go for a set of bell motors,like the DT series.They seem to offer a lot of power for little weight.
I'm using 2 DT800's in my Focke Wulf Ente,and the 2 3000-3-cell packs are there only for balance purposes.I could use only 1 pack,and still get 10 mins. flying out of it.It weighs around 4lbs.
I know the Lanc. is a lot bigger,but I think you could probably cut a lot of weight out of the wing too.Build in some lightness,somebody once said
The plan calls also for packing case foam blocks to be carved / sanded to shape for fuselage. I think I will pass on that !! The mess will be amazing.
Depron skins and folding to shape is my plan.
To give all strength will be synthetic silk, (very thin plain Net Curtain) and PVA covering. Original uses packing paper ... which I hope using the silk will save more weight.
I'm just annoyed that the Plastic Moulding set is so expensive to get shipped. I don't mind the £28 for the set ... 4 cowls, turrets, bomb-aimers and canopy ... but £60 shipping ? That's not funny.
The wing seat / top ... I am adding a 2mm Lite Ply doubler to the depron to strengthen this area. Stretches from F3 back to F7 along bottom and then an insert to the removable top section between F4 and F6.
The wing seat area on the Lanc is notoriously weak in models.
Sorry about so much text and no photo's ... still putting together materials and ideas to get this monster sorted.
I think I am going to have to either build a Gravity foam cutter or resign to making traditional wing.
OK ... I cut the fuselage depron sides in 3 sections ... and joined at less stressed points. The 6x6mm pine longerons will provide the real strength required with an extra longeron at wing saddle level.
Just getting an idea of size and dry run of the 4mm ply formers (propped up by lipos etc) ...
Boy this baby is BIG !!
There will of course be extra sheet / strips to the fuselage sides to build in strength as the depron alone will not be enough.
So she's moving along slowly, but I think in terms of sq.ins of model when compare to my usual scratchbuilds .... fast !!
The 6mm basic depron sides joined at two places to create the one piece per side are now slotted inbetween the longerons ...
My concern at moment is the pine longerons are really stiff - I'm not going to have a weak structure especially across that wing section. This means that the planned slight curve UP of the lower fuselage line may not be as much as necessary. This of course will affect the incidence of the tailplane in relation to the main wing. It will only be a small amount - but I will have to build a jig to match the wing and tailplane .... altering tailplane of course to suit.
I think I could have reduced the size of longerons ... she's very stiff now but at least I'll know she's strong !
Before I get complaints .... the purists will not be happy with my project. I will not be building a scale model.
As Chris said himself - its 'cartoon Scale' or as we used to call them years ago ... Semi-Scale !
The characteristic wing break and outer dihedral will be there, the general fuselage will be there, but some of the curves will be simplified out to allow a lighter and more easy build.
Engine nacelles will not be all rounded of as some would like - but basically flat sided with curved top / bottom ...
The model is intended for Club Shows and not for any competition status. It will have 619 sqdn markings to honour my Mother. Research underway at this time.
Chris Golds plan states 12.5lb weight ... (5.5kg) .... and I reckon I can shave a bit of that.... aiming at 10.5 - 11lb.
Motors on way from China .... RCTimer ... 3536 1450KV .... to turn 8x4.5 contra props .... eCalc gives me 0.84:1 Power to weight .... and I have 8x6 props available if necessary. All on four 3S 2200 Lipos spread on the model to balance her out.
Still trying to sort Retracts ... One of the aspects of retracts is the direction of operation. Generally they are designed with a side to side movement. This means that model does not push against the servo's ability to keep legs extended. But on the Lanc - the legs will be folding with the direction of model, putting load on the servo drive. Some people I know have legs fold with this .....
Tail wheel steering ... that will be Stinger all in one nose wheel unit parallel with twin rudder servos. No need for rods across tailplane etc.
Cheers RK 97 ... beginning to think I was all alone out here !!
Data so far :
The Fuselage in 1/2 finished state weighs 516gr at present ... so its working out better than I expected.
I reckon by time its finished ready for radio / batterys etc. - it will be about 800gr.
4 x 3S packs ... 155gr each .. 620gr + wiring of about 10 gr ... so 630gr ...
Radio gear ...
Rx : 10gr
4 ESC's of 50A of 15gr : 60gr
2 rudder servos of 9gr : 18gr
2 elevator servos of 24gr : 48gr
tail wheel assembly about 20gr : 20gr
2 aileron servos of 24gr : 48gr
2 flap servos of 12gr : 24gr
2 retracts and wheels ~ 50gr : 100gr
4 Motor / Props at ~ 70gr : 280gr
So total fuselage RTG without wing ...
800+630+10+60+18+48+20+48+24+100+280 = 2038gr ..... leaving me with approx. 3400gr to play with for the wing .... note above weights already include motors / ESC's / retracts ...
90" wing should come in well under such figure ... in fact I reckon more like half that if I play it right.
So potentially I am looking at a model of about 3.5 to 4.0kgs if I get it right ...
No Nigel iam always watching from the weeds on any multi motor build ,multi motor planes is the reason i switched from nitro to electric . I belong to the fourm in the UK but dont post there much at all . good forum and great people there flying off some of the worst flying fields i have ever seen tho. You have to build a tight ship and be a good flyer on their fields . joe
There are some good sites in UK - Beaulieu is one. Lord Mountbatten supported application to leave the aircraft apron for model flying exclusively when the RAF withdraw after the war. Today it is still exclusive to models, even though the Horse Fraternity try to break it. Its slap bang in the New Forest.
Various ex Fleet Air Arm / RAF sites now open for models.
Slope sites - Buster Hill .... gives near 360deg slope capability. Mendip Hills ....
But yes - there are lots of rough field sites that its all hand launch / belly landing.
With the advent of computers and apps as simple as 'Paint' ... I have found a solution to my tapered wing construction.
I used to use the clamp blanks together and carve system with Balsa ... but of course that was with 1/16th and the whole was manageable ... but with 6mm Depron blanks - its huge !!
Root rib is just under 16" long ... and then you have ~ anything up to 15 ribs out to the tip which is much smaller. I tried to carve ... but it was wasted time.
Paint ! why didn't I think of it before. When I was sorting the scaled up Ultrawatt model ... I used the scaling feature of paint to fashion the intermediates.
I measured the root and tip ribs and found they were close to being same aerofoil. So close in fact that ignoring the difference would not be noticed in the model.
You need TWO Paint apps running simultaneously. One has the large template to have all intermediate ribs pasted between the root and tip ribs from plan. Call it A
You cut and paste the Root rib to the second Paint template - lets call it B ... then apply a scale DOWN factor ... in this instance is 98% ... copy result to A ..
Now apply 98% to the scaled down rib on B and copy to A.
The trick is to NOT revert B to original size but keep applying the scaling factor to each successive scaled rib. You then get a graded reduction ... the slight non-linear factor is not significant in such a small scaling factor.
The factor you use is really a trial and error thing ... but easy to arrive at.
I will try and upload the various pic's so you can see the results ...
First are the two scans I did for the laser cutter to fashion the root and tip ribs. I had to laser the root in two sections and the V you see in the rib - is the alignment to ensure when joined are straight etc.
Next two pdf's are the original root and tip ribs with the Paint scaled intermediates pasted in ...