Help needed with 1/6 scale Wildcat Plans

[Reno Racer]

Dear all traditional warbird plan builders, I need your help to interpret a set of plans for a 1/6 Scale F4F Wildcat. At 73" wingspan, with a tuby fuselage is a nice size and should be well suited to my OS 22GT petrol swinging a nice size 3 bladed prop

Known on US based forums as a complicated and unorthodox build, there seems to be little coverage on this plan and the build, less the original success Bob Karlsson had at US Scale events a good 30 years or so ago. Unlike many others, I won't let this one gather dust and am determined to build it.

The plan seems to suggest the formers have no method of joining them to each other, less the balsa sheeting. I can see no stringers, internal structures etc to hold in to shape prior to skinning. To me this looks like a recipe for a banana shaped plane, but it must have worked for Bob all those years ago. I have attached pictures of the plan below, in the hope that other can either shed light of how the fuse is constructed, or offer suggestions on alternative, but close to the plan alterations.

Edited By Reno Racer on 01/04/2015 13:29:57

[Jon H]

personally I would get the parts laser cut and have them cut each former in half vertically. You could then build the two halves of the fuselage flat on the board and fully sheet (apart from 2 inches either side of the centreline to allow for a 4in wide sheet over the joint) before gluing them together. You could even build one flat on the board and then build the other onto the first half.

You could also split the formers horizontally so you build a top and bottom. Pica did their kits like that and it works well.

I think it would be less worry than trying to build it floating in mid air. And also why is the former for the fin not shown in the centreline like all the other formers? :\

[Reno Racer]

Thanks Jon, confirmed my initial thoughts along the same lines. My gut feeling is to build two fuselage sides, but a top and bottom might prove easier to fit the wings and undercarriage mountings? - I'll see what the undercarriage plan looks like when it arrives, I think that has more detail on the former its mounted to, which seems to be where the centre of strength is.

Dylan, I wonder if you fancy a laser cutting project? Parts look quite simple, so it should be fairly quick and easy, even if you cut all the fuselage formers in two.

[Bob Cotsford]

As Jon says, treat it as two halves. I think I'd split it horizontally for the best chance of keeping it straight,

Another way would be to get hold of a piece of 1"+ square section tube, cut square holes in the centre of the formers to match and build it using the tube as a jig.

As for the fin former, maybe it's drawn that way to make it stand out as a separate part and not be mistaken for a cutout in the formers that it's drawn over?

[onetenor]

I think it is intended as a crutch construction having looked closely a the formers Either that or a single square longeron laid on the board and a cutout to match in the formers at he sides of them OOOR 2 Square longerons flay on plan and formers cut in half horizontally and notched for the longerons. If using the crutch method the cut to accomodate the crutch would mean taking out the centre horizontal cut of 3/8 or 1/4 thick to keep formers outline right Method one and 3 will give a more certain trueness.

[Reno Racer]

Just had a thought, I could use blue foam as spacers- cut them, number them, then build the fuselage sandwich of foam and formers.

Just as I started typed I had a chat with Falcon about laser cutting and the best way to do it. Cost seemed quite reasonable, so I now just need to decide to either spit horizontal, vertically, or get square section or round hole cuts into the centre of each former to build on a jig.?????

[Jon H]

personally I would got for the horizontal split. get the top built first and then add the bottom afterwards

[kc]

That plan seems to have some really distorted former shapes especially the one marked 9 is not symetrical.

It looks to me as though many of the formers have the centres cut out and then replaced ( note grain direction changes) and this suggests the centres are part of a removeable support which is just used during construction. If the centres are not for that what are they?

Horizontal split ensures that a bananna shape is avoided, however both wing and tailplane need to be on the same part to avoid incidence problems.

As there is another similar size Wildcat avail from myHobbyStores it might be worth reconsidering.

Edited By kc on 01/04/2015 19:58:13

[Reno Racer]

The photo of the plan is probably quite deceiving, many of those changes in grain direction shown are actually a different former, drawn off centre from the one is drawn on top off.

That said, clearly the formers cannot be solid and must have centres cut out to allow control runs, cockpit, servo tray and fuel tanks etc. considering everyone's suggestions and having a good look over the plan I thing the easiest would be to get the parts laser cut with a split horizontally through the centre datum line. That way I can build to top section first over the plan and fit the bottom have directly to this when removed from the board after skinning. It should also allow the wing and tailplane to remain square ( in the top half) and should allow easier fitting of the servo tray and more importantly that complex section around F3 where the complex retract mechanism bolts too and the wings are secured and aligned to the fuse. Still needs some fettling, for example the former F3a doesn't make sense. It's drawn solid and full fuselage shape, yet must be clipped at the top for the cockpit and much of the centre cut out to facilitate the servo tray. I suspect I will end up getting the parts laser cut, then having to modify as I go. If I get change I will probably modify the plan as I go and redraw a new plan.

Just after a logic check to make sure my crazy idea above makes sense and I've not made a rash decision, before I shell out £170 quid for all the parts laser cut.

Also seems I can get the canopy and cowl form the U.S., but with shipping is about £100! Might have to make plugs and make my own, or at least try and if that fails.......

Edited By Reno Racer on 01/04/2015 20:07:53

[Reno Racer]

KC, I've looked at that plan, although clearly I know have the plans for this one, and I don't think the MHS plan has the retracting undercarriage done sale- a critical feature of the Wildcat. I might be wrong, but I ordered a 1985 copy of RCM&E which has the build of this MHS plan as a feature, so I'll know in a few days.

[Reno Racer]

Also just managed to find, and order, back issues of Model Aiplane News from Feb (main build) and Mar ( undercarriage) from 1983 so hopefully the articles shed some light on how the designer built the Wildcat.

[Tony Bennett]

i too would split the fuselage into two halves vertically.

maybe get the cutters to cut a single notch in each former so you car run a bit of 6x6 balsa along the outside and under the sheeting, might help keep the formers vertical.

[onetenor]

Any one remember the way Kiel Kraft scale were built. ( rubber power ) Formers vertical split and open centre ro allow motor installation. A flat balsa outline was laid on plan and pinned down. The formers were notched at top and bottom to fit over this keel then stringers added to one side then when set unpinned and other side stringered. Straightness not guaranteed.. If done horizontalty with a crutch .i.e. a horizontal outline instead /straightness guaranteed This can be done with a flat plate i.e solid cut to the outline and formers cut across removing the thickness of the flat plate.It needs only be a thin plate and could have the centre of it cut out. All sorts of options

[Reno Racer]

With great expectation the two (very) back issues of Model Airplane News arrived, Feb and March 1983 to be precise, it all looks very dated, but in a nice way.

The build articles by Bob Karlsson shed some light on the construction requirements, particularly the undercarriage, which will be my first job to master. Without the undercarriage, it's pointless building the Wildcat, since it's such an integral part of the essence of the fighter. I could buy the undercarriage from Century Jet in the UK for $719 plus shipping and taxes, errr no! That's excessive for a 90 size warbird.

Funnily enough, even Bob suggests builders might consider splitting the fuselage and using the crutch method. So I think it makes sense the get the parts laser cut vertically. As I've said, I'll start the undercarriage first and see what happens!

I just wonder if buying Hangar 9's new 20cc Corsair and reprinting her in Royal Navy colours ( like the 50 size one I did- my avatar). It would certainly be cheaper. Mmmmm decisions!