New design by Lindsay Todd
win a set of parts for the Lockheed Vega
in the shops 4th July!
|Lindsay Todd||08/12/2013 23:07:40|
1739 forum posts
Well more than one project going on of late and this one has been in the planning for some time but in need of a little break from the Blenheim i decided to crack on. The drawings have actually been complete for a couple of months so a quick call to Slec provided a rapid turn around of super quality parts that arrived quickly and allowed some really rapid progress over the last couple of weeks.
The little diecast and film Amelia have been useful inspiration, I intend to replica the red colour scheme of Amilia Earharts aircraft and as the blog goes on will fill in some background to the aircraft itself.
I'll start the blog construction notes off properley in a few days but for now here is a couple of shots as she stood before and after the weekends progress.
She stands at 57" wing span and has been designed around using my 3cell lipo packs and 300 watt 1100kv motor, not sure of a final weight but circa 3-3.5lb should be realistic I hope. Anyway hope this wets the appetite and will kick the build off properely soon. Linds
1240 forum posts
That looks good.... I do like a good build blog, so I'll be watching with interest!
Edited By GrahamC on 09/12/2013 07:45:11
|Dave Miller||09/12/2013 08:14:40|
341 forum posts
An excellent project, as indeed was the film.
|Peter Miller||09/12/2013 08:42:36|
11093 forum posts
For years I have considered the fact that a kit manufacturer could make one GRP fuselage and one foam wing and make the whole rance of Lockheeds, just needs a variation in U/C and tail surfaces and some different wing fairing.
Thinks of it, The Vega, Orion, Sirius, Air Express and then float planes as well..
I look at the Wylam (or is it Nye) set of drawings and think about it. But then I am too lazy to do anything about it!
|Tony Bennett||09/12/2013 10:01:43|
5082 forum posts
now that does look nice.
grrrrrrrrrrrrrrrrrrrrrr see what i mean about sanity warnings. cos i fancy this one as well.
|Biggles' Elder Brother - Moderator||09/12/2013 12:14:29|
15748 forum posts
Amazing aeroplane the Vega - held a lot of distance and endurance records at one time. Nice start Linds
|Tim Hooper||09/12/2013 22:00:16|
2899 forum posts
NIce one, Linds.
You don't mess about, do you?
|Lindsay Todd||09/12/2013 22:56:50|
1739 forum posts
I think we have much in common Tim
Thanks for all the comments, much appreciated, time to start of the build I guess starting with something nice and simple with the tail plane and elevators. The elevator is entirely made up from pieces of medium grade 6mm balsa cut into various widths to form leading edge, trailing edge and cross bracing. The only issue here is to make sure the grain always runs parallel to the span and that the joints are nice and tight. The only tricky bit to cut is the leading edge profile. The little fillets at the front are actually a bit of a problem later and we will need to trim one away when we slide the tail into the fuselage but leave it all intact for now.
The elevators are made up of laminates of 2mm medium balsa, a centre core the exact size and then 6mm wide strips glued top and bottom to increase the thickness to 6mm and simulate the ribs. We then add some 2mm ply to the centre region aft of the leading edge, again top and bottom to give support for the wire joiner and horn fixing. Finally the elevators are sanded from the rear of the leading edge strip to the trailing edge to feather the profile and a 45 chamfer given to the leading edge and job is basically done. simples.
The rudder and fin follow exactly the same mode of construction as the tail and elevators, again note the ply doublers added for the tail wheel wire and horn location to add strength. The fin will slot into the fuselage and sit down onto the surface of the tail. A couple of triangular fillets for strength and rounding off of the leading edge is all that's required.
So with some easy bits out the way its time to get started on the fuselage. I took advantage of Slec's cnc cutting service to provide me with a super set of parts, basically the fuselage formers, wing seats and ribs for the wings plus a few other items.
It certainly saves an awful lot of time, providing your drawings were correct to start with. I have to admit I have made a couple of amendments as I progressed, these have been addressed for future but I'll try to highlight them as I progress. Most were actually associated with the formers around the cockpit area as the shape was difficult to visualize initially so I went with an option that would allow me to 'figure it out' as I went along and it has so far proved to have been a sensible option and was in fact far less complex than I had first thought.
I don't own a building jig, but I have to admit it would be helpful sometimes. The fuselage is built around a series of formers supported by 6mm square longerons and a 6mm sheet wing seat so stays fairly flexible initially so some careful marking out and a little patience is required to keep checking all stays square.
To start however we need to laminate the fire wall former and former number 3. The firewall simply increases thickness and strength, former 3 will have part of the undercarriage fixed to it so it also needs some strengthening plus the front doubler also forms the cut out for the battery compartment that runs from former 3 through to the firewall. When dry a quick sand and we can start the fuselage assembly process.
Two longeron's run parallel the length of the fuselage from 6mm square balsa start by pinning these down over the plan from the firewall forward face and clearly mark the position of each former. When marked up remove and pin down a second set and repeat the process. The build starts by gluing former 3 and 4 square to these longeron's. A wing support is cut from 6mm balsa sheet and is glued flush to the front of former 3 and runs square back through a slot in former 4. Position and glue this in place ensuring the formers stay square, when dry we can now add the second set of longeron's to the opposite side of the fuselage making sure the former positions are aligned. When dry add the second 6mm wing seat between former 3 and 4 check for square and glue in place. When dry we can add former 5 which locates onto the rear of the wing seat and should be set square. Glue to the wing seat first and when dry the longeron's can be pulled into the former and also glued, tape and cyno is probably easiest for this.
Once this assembly is dry we have a bit more strength and subsequent aft formers 6,7,8 and 9 can be added one at a time aligning with the marks we made on the longeron's and check for square as we go. At this point we can also add the top centre longeron that extends flush to the front of former 5 and back to the rear face of former 9.
well I recon that's a good start for now. More soon. Linds
|6514 forum posts|
|A 57 inch span scale model with a chunky fuselage & radial cowl to weigh 3 to 3.5 pounds? Sounds as if Lindsay has got some pre production samples of the new helium filled balsa!|
Normal builders would expect 4 to 4.5 pounds with lots of lead up front wouldn't they?
|Lindsay Todd||10/12/2013 13:00:39|
1739 forum posts
Kc, I think at this stage it is fair to say the final weight of the model is unknown, I see no harm in having a goal to aim at as chunky means there is a lot of fresh air which last time I looked didn't weigh very much. We'll have to 'weight' (get it) and see who's closest when she is ready to fly. If it's 4.5lb that's still sounds pretty good to me. Linds
|6514 forum posts|
|The idea of a 57 inch scale model for 300watt and 3S seems a great idea. However I based my assumptions on the nearest model I have seen which is Peter Millers 57 inch Cessna C37 Airmaster ( Flying Scale Models Feb 2009)for .32 glow which PM said weighed 4 pound 12 ounces. The Cessna had sheet balsa tailplane & fin rather than built up. Even allowing for less vibration in electric and therefore less in the way of ply doublers fuel proofing etc 3.5 pounds seems optimistic. However one has to be optimistic and aim low (weight) |
I hope you manage it and it becomes a pull out plan for RCME.
|Vecchio Austriaco||11/12/2013 19:02:02|
1498 forum posts
looks good, looking forward to see it finished!
|Colin Leighfield||11/12/2013 19:45:31|
5996 forum posts
What a great choice Lindsay, a true all time classic. Hard to see how it can't fly anything but really well.
|Lindsay Todd||11/12/2013 22:42:01|
1739 forum posts
Time for a further catch up
Repeating our process for the rear formers, the cockpit front panel and firewall can now be aligned with our marks and pulled together to meet up with the longeron's. The firewall sits parallel to former 3 and this is helpful to take measurements from to ensure it is sitting square as of course it dictates the thrust line and is therefore critical in the build so take your time making sure before gluing permanently in place.
The additional longeron's around the fuselage can now be added and glued, this adds significant stiffness to the structure and once they are all in place the fuselage is quite robust. Next job is to glue the 3mm balsa sheeting to the base and sides of the battery compartment that runs from the former 3 doubler through to the firewall. This has been sized against my own 3cell lipo packs 2500mah, there is a bit of slack but if you have different sized or larger packs now is a good time to open this area up a little if necessary to fit your own packs, just ensure you don't go so deep that you impact on the motor mount position central to the firewall.
Back to the rear of the fuselage and time to fit the lite-ply tail plane support and triangular brace, the support locates into a cut out in former 9 that fixes the position and the support sets the correct angle. The last former 10 is then glued onto the back of the support and a little triangular stock added for strength. The lower centre longeron is then flexed up and glued into former 10, I added a few cut slots to remove pressure on the bend and when in place added a few drops of cyno to fix.
more soon. Linds
|Richard Harris||11/12/2013 22:51:30|
2168 forum posts
An excellent choice!. I really do like the 1920's/30's aircraft . I am sure I read somewhere that the fuselage was moulded in two halves over a concrete plug?
I will be watching with great interest.
|Lindsay Todd||11/12/2013 22:58:04|
1739 forum posts
Well very soon actually.
The fuselage shape at the rear of the wing seat has to conform to the fuselage shape so to do this, and it is a bit of a compromise from scale, but then this is very much sport scale so that's ok, we build up the inside face aft of former 4 with laminates of 6mm sheet , slowly reducing in length as we get towards the centre line rear of the open area that the wing sits on. Eventually what we are aiming for is a minimum 6mm land for the wing seat once we shave and sand the excess away.
The black line shows the shape and line we now need to trim and sand back too. I found this a relatively easy task with a razor plane and final sand to shape blending nicely with former 5.
A couple of more laminates and I will then also trim the inside edge to approx. 6-8mm thickness. I have kept all these laminates to the same depth and will use the underside as a fixing height later when I come to fix the wing bolt plate into position.
more updates soon. Linds
|Simon Chaddock||12/12/2013 13:46:34|
5716 forum posts
The remarkable feature of the Vega was how the fuselage was made.
It had a normal former and stringer structure but the skin was added as a pre moulded half shell in one piece!
Each half shell was built up in a female concrete mould and before the glue set a rubber bladder was lowered in and air pressure used to force the complete skin accurately into shape.
It created an exact profile with a good surface finish but was expensive to do.
The De Havilland method using a thick self supporting ply/balsa/ply sandwich skin built over a male mould was probably more practical for mass production.
Edited By Simon Chaddock on 12/12/2013 13:47:00
11749 forum posts
I am not sure that the Lockheed system is any poorer than the Dehavilland method.
The Lockheed system is essentially the same as has been used for large GRP vessels (boats and yachts), then many glass/CF/Kevlar composite models are produced, in addition to some racing motor vehicle body components. Its advantage is that the accuracy and high surface finish are achieved of the moulds.
In the case of Lockheed, using concrete for the moulds, meant that they were extremely heavy and not easily moved.
I do like the idea of Peters for a manufacturer, in that for a relatively small outlay a whole range of scale models can be economically kitted.
As for the model under construction. Well I stand in awe, not having the skill or patience to build such a model.
It looks good now, I am certain it will look even better when constructed. Perhaps I am wrong there, as much of the craftsmanship will not be evident, particularly to the casual observer, on the other hand, the superb shape and of course the finish will compensate.
I increasingly see that electric propulsion has become ever more popular in the larger size models. I guess it is the ease of accommodating the drive train. Rather than have to juggle the cooling and exhaust requirements of IC engines. I am also guessing that the model can be built lighter, with all the benefits that come with weight reduction.
|6514 forum posts|
|It looks like there is only space for 1 wing bolt and yet there looks like only 1 dowel Would be strong enough for a light model but will it seat the wing firmly?|
|Lindsay Todd||12/12/2013 21:01:01|
1739 forum posts
1 wing bolt, 1 dowel, yes quite adequate for this design, of course you could always add more to yours if so desired. The wing seat is actually quite wide so well supported. I'm not planning any high G manoeuvres so no need to go for anything more on this design, however it will use a heavy weight nylon bolt just in case.
Very interesting re construction of the full size, lots in common with composite technology today. Linds
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