Small Comet Curtiss Robin build

[knapster]

This will be "quick & dirty"... it's a little model, not especially true to scale, so I'm not planning to take many pains in the detail department.  I bought this kit on EBay, and found that one side of the fuselage frame was already built.  Probably should have chucked it, but...

Here is a photo of the kit box, and beginning of the build.  I'm planning on building it pretty much per the plan...might make a few adjustments.

[Arnold S]

Nothing wrong with that approach, looking forward to seeing how it pans out…

Andrew

[Rekitus]

Iffin ya got the plans, you can get it built and on wing.
I, also, am looking to see how it rolls out.

I recall seeing the kit among the selections... many years back.
never got one. 

there are a lot of kits like that for me
cause I had a weakness for spitfires...

victor

[knapster]

As a kid, I always thought the Comet models were crude compared to the Guillows kits.  But in retrospect, they were (in many cases) lighter.  This Robin kit actually has die cut parts rather than printwood.  I found the die cutting to be pretty good-- parts were cut through for the most part, and not much crushing.  Of course, there isn't many parts, so...

Anyway, a bit more progress.  Despite my bid to not mess with the design, I made the nose removable, with a bigger opening for a more realistic rubber motor size.  I left the original motor peg location, but added another one a bit further forward (with a tad bit of bracing). I also added 1/16 balsa sheeting on each side at the front (y'know...just in case).  The convoluted landing gear and wing strut arrangement is the first thing that will either break or be shed when I make the first test glide, so I decided to add a thin piano wire LG and some related gussets. added weight was minimal.  I'll add all the struts after I get it to fly (or give up trying!).  Tail parts are per plan.

So far the frame is doing pretty good weight-wise.

[Arnold S]

Looks good.  Your Mods are all sensible.  I am a bit of an originality freak, but even so I would have done pretty much the same as you with this.  You have to be pragmatic sometimes don’t you?

Andrew

[knapster]

On to covering!  Nothing tricky here-- no compound curves except for the solid wingtips.  I used glue stick for most of this, but diluted white glue for those tips.  Glued the top edge, then snipped "fringes" up to that point, then schmoozed it all down and around to the bottom with the white glue.  Turned out OK...

[knapster]

Covering complete and clear Krylon applied.  Now on to all the "fiddly bits"... quick pre-assembly just for kicks.

[knapster]

Ready for assembly...weight is pretty good-- wing area is about 33 square inches.

Per plan, there appears to be zero decalage, so I added a shim under the wing LE, which should give me about 1 degree.  I have a little bit of room for adjustment of the stab, but not much.  Plus, it's a bit tricky with the vertical right there in the way.

[PB_guy]

I have been following your build. Very nostalgic. Good work.
ian

[knapster]

Thanks, Ian.  Couple of spots aren't so great (let's hope they don't show in the photos!), but this guy is a lot smaller than the stuff I usually build, so a challenge in places.  I'm curious to see how much nose weight I'll need, and if it will fly well.  I'll know the nose weight soon...flying might be a bit longer-- lots of wind here lately, and even 5-10 mph will be a challenge for this little guy.

Gonna start another Comet build soon-- their 18-inch "P-40 Tigershark."  A bit bigger, but also very light construction.

[knapster]

OK...a little more progress...

I decided to add at least the main wing struts before I try to test-glide.   So the wing and horizontal are glued in place, and stock for struts is painted.  I held off on attaching the vertical, since I'm sure I would bust it while trying to position the wing struts.

Tomorrow I will hopefully cut and glue the struts (may even add the jury struts!) in place, then add the vertical.

I figured the struts will add a smidge of wing strength (instead of relying only on the glue joint to the top of the fuselage) and shouldn't be directly in the line of impact during ungainly test-gliding.  I'm really hoping the small mass of the whole thing will minimize any damage.

I frequently explain to folks who haven't been exposed to my hobby that my planes come as a bunch of sticks and small parts in a small box.  Then I assemble them into a large airplane.  Then I attempt to fly it, and it crashes-- so now it fits back into the same original box! (I hate when that happens!)

[PB_guy]

Looking good! I always do my test glides over the bed to start with. Especially with peanuts.
ian

[knapster]

Thinking about the idea of test-gliding onto a bed... not sure I have a spot with enough room....but there wouldn't be any wind!  Might have to find a creative alternative.

So I got all the wing struts on, and the vertical.  Added a rubber motor and worked to get the balance right...the chunk of clay is very attractive, huh?  The scale shows I missed my half-a-gram-per-square inch target by just a little bit (target would have been 16.5 grams).  I'll find another (less ugly) way to add the ballast.

[PB_guy]

That is not a bad weight since you used the kit wood and didn't lighten any of the construction.
ian

[Prosper]

Neat build, knapster.

Stephen.

[knapster]

Thanks, guys!  Here's a few more photos of the almost-finished little Robin, a couple with its big brother (sister?) I scratch-built from my own plan several years ago.  Hopefully I'll get a chance to test-glide in the next week, and then maybe add the rest of the landing gear struts.  At that point I'll add more photos. (Unless the gliding goes horribly wrong...even then I might add a "final" photo!)

I have several "Honey-do's" coming up, then on to the Comet P-40 build.  I think I'll have several spots on that one where I'll want some opinions.

[Prosper]

knapster, I'm interested in what motivated you to build this little critter when your own-design NC76F shows you have high skills in this racket already? Have you moved away from adequate flying space for the big brother/sister?

Stephen.

[Arnold S]

That Looks cool Knapster!

Andrew

[knapster]

My motivations were several... First, I have WAY too many unbuilt kits sitting around and need to start burning through them.  The scratch-built Robin was a lot of work (and time), but the kits-- for the most part-- go together relatively quickly.  I still find myself starting a kit thinking I'll see how it flies before I add much detail...but then I start carving exhaust pipes, and changing the construction, and...  So I swore I would minimize that with this little guy.  And if it crashes and gets re-kitted, I won't care too much.

Second, I need to learn to trim my models to fly better.  I like building, and feel like I'm fairly good at it.  But getting them to fly well is a whole 'nother matter.  The big Robin has flown a few times and did OK.  But I want to get more trimming experience before I do much more flying with it.  So I'm sorting through my many, many kits to try and work out a sequence of building and flying that will further my trimming skills.  The high-wing examples (in theory) will be easier to trim than the low-wing Corsairs and Mustangs and such.  So the little Robin is part of that, although I think the smaller models will be a little trickier to trim.  I'm actually starting a Comet P-40, which doesn't quite follow my sequence, but it appears to be very light and I have several of those kits, so low risk.  After that, I'm thinking a laser-cut Herr "Scout" which is a bit bigger high-wing which should be quick to build and hopefully durable enough for lots of trimming experiments.

As far as space, I'm OK there-- I have 35 acres here, but I'm at almost 10,000 ft, so the air is thin and it is very often windy.  As I write this, it's blowing about 25 mph, gusting to over 40.  Calm days are not very frequent, although mornings and evenings can often be OK.  My other problem is that there's not much tall grass-- the acreage is natural, so only native grasses.  If we get good rain/snow, they will grow well and get tall, but the stalks are fairly stiff, and are champs at puncturing tissue! 

I'm finally 95% retired, so I want to master getting my models to fly (or at least get mediocre at it), and then I'll feel better about scratch building and adding details.  I have enough kits of all types that I'm willing to sacrifice a lot of them in the learning process.  If some of the necessary repairs look a bit crude, I'm OK with that.  Once I get things like the Comet P-40 sorted out, I can build another based on the lessons I (hopefully) learned and spend more time on the detailing.

Thanks to all for following my build-- P-40 should start soon!

Mike

[Prosper]

Wow - 10,000' - I didn't even know that human life was sustainable at such altitudes . Less than ideal for flying models, esp. if hot too. . . Me, I live at about 100' AMSL .

Trimming scale models can be demanding, and I agree that the smaller they are the trickier. I find that any kind of a wind or turbulence really limits what one can deduce about a model's behaviour, unless it has a good dose of inherent stability to start with. I remember being baffled by the inconsistent behaviour of my first scale model, which eventually I got to fly well. The little patch I was flying it on has a fold running across a part of it - a slightly raised ridge with a dip either side, each dip only a couple of feet deep, and maybe 8-10ft wide. There are no steep slopes, it's just like a gentle wave in the ground. Only several new models later did I realise beyond doubt that this was what had been causing the models to behave in unaccountable ways when the breeze blew across the undulations. It's so obvious now that I can predict that a model will rear up about there, and drop sharply there, or roll suddenly to the left just along there. . .but back then I never thought that such a minimal landscape feature would have any effect on the air ten feet above it. Silly me.

Stephen.