ChinookRC

I've just completed my first kit, a Top Flite Corsair Gold Edition electric conversion and am getting started on aTop Flite F8F-2 Bearcat red box kit (1979) with the goal of having it ready to fly when the season starts up in April/May 2012. I'm a new builder and would appreciate advice and pointers as I make my way through construction over the next few months (assuming all goes well). This is a discontinued kit so I'm not sure I'll get much advice specific to this Bearcat, but given my recent experience with the Corsair, I'm painfully aware that any advice is helpful.

I'm also a new flyer and even with help from members of my local club I'm pretty sure the plane won't make it through the upcoming season unscathed. Since the kit is rare and discontinued (and the few that do come up for sale aren't cheap!) I have a secondary goal of being able to rebuild the plane in whole or in part from components laser cut from drawings that I'd like to produce in AutoCAD 2012 during the build process. I'm assuming that I can make copies for personal use without running into copyright issues with the good folks at Top Flite.

I won't be going for ultra-scale detail - if I develop an interest in that aspect of building I'll pursue it in future builds of the kit - and I don't expect any significant modifications (like turning it into a Rare Bear) this time around. Goals are to:

1. develop good building skills and practices
2. learn enough AutoCAD to generate drawings that can be sent to a laser cut shop
3. put no more than 4 months (say 300h) of time into the kit
4. document potential improvements or modifications to future builds of the kit

I'm not sure if anyone but myself will find the thread useful. I've found one other build thread dating back to 2003. And I'm not sure if I'll have the patience to keep it up! I have problems keeping up with emails, much less stopping to take photos and writing while I'm in the "zone" during the build. But I'll give it a go.

tailskid

My Feedback: (34)

I built one of those many years ago and sold it at the Toledo Auction.....I loved the 'instructions' - 4 pages if I remember correctly.....you do build "in" the fuel tank so make certain it is 100% correctly set up!

ChinookRC

Here's the loose wood that came in the kit. Am missing a 1/4 x 3/8 inch stick that's needed for the tail feathers so it's already off to the LHS.

The die-cut parts have already been removed from the sheets and sorted. Some warping on the 1/16 balsa pieces but I don't expect that'll be a problem.

The quality of the wood is pretty good considering it could be up to 30 years old (2011 minus 1979 is 32, wow) but I am finding that sanding the tail ribs to shape is resulting in some burring of the wood that I didn't experience on the shiny new Corsair.

Five pages of instructions actually. It's going to be a stretch for me coming after the TF GE construction book that I learned to follow meticulously!

ChinookRC

Kits comes with pre-shaped parts for the fuselage - "Superform Shells". One has a crack in it, others look good.

Canopy is in surprisingly good shape. I've read elsewhere that they tend to turn yellow with age and it can be a pain to find replacements.

I've started work on the rudder and elevators.

ChinookRC

Here's the Bearcat manual and some typewritten post-production notes.

The "Revolutionary New! Super Monokote" manual is dated 1969 which predates me. Gotta love the iron the guy is using.

Roary m

My Feedback: (67)

I would be interested to see what type of retract struts you will be using, if you go retract. Those struts are long.

ChinookRC

I was planning to use Lado retracts similar to what I put in the Corsair - RS333s, but hadn't put much thought into what I'd use on the Bearcat until now.

The plan is showing 7-1/4" from center of the axle to the bottom of the wing with an inside angle of 85deg as shown in the plans.

This brings up a few questions:

1. is it necessary to get 85deg retracts? I had an awful time getting the right angle on the Corsair (looking face on and checking that the struts are perpendicular to the ground). Maybe the bent wing made it difficult, but I couldn't seem to get the hardwood mounting blocks positioned exactly right. Had to shim it and still not satisfied.
   MagnumRChas a set of85deg retracts that look right so I could get theRS333-85L.
   I do like the Lado product - it feels solid, has nice smooth motion, and there's no way I'm going pneumatic. They also have oleo struts up to 8.3" I'd probably go for the 7"ERT170s.
2. the length of the struts will mean stress on the mounting will be even greater when landings don't come in straight. Not much to do about it but look at the mounting design when that comes, but a shorter strut will mean less moment around the mount.
3. the length of the struts means the wheel wells will extend deep into the fuse (see photo of another cat below). I think that's probably what you were getting at... hopefully it doesn't compromise any load bearing structures. It's hard to tell from the plans (attached). The wheels on this beautiful Ziroli Rare Bear don't extend that far into the belly pan.
4. are folding retracts available in a 60 size like the real bear? That reduces the retracted length significantly.
5. is using shorter, say 6" struts an option? A 16" prop would get pretty close to the ground.

It's a bit early to get into this detail but I'll be better off with a plan rather than hacking at ribs and spars with half the sheeting on like I did with the Corsair retracts.

ChinookRC

What is the best way to build trim tabs? I'm wondering if I should cut off the tabs I put on the elevators and rudder, cover them separately, and then reattach them. They'd probably look more realistic, but of course I'd have to make sure they were attached straight.

ChinookRC

No disrespect to Mr Paneti, but the design of the leading edge of the stabilizers is a bit strange. I remember on the Corsair that these were pretty chunky sticks that took a lot of sanding to get down to shape, but the Bearcat comes with shaped sticks that are supposed to be glued onto the tips of the ribs, with the planking glued to form around them (and then sanded to shape). It seems like a lot of trouble for the same result, and can potentially cause the leading edges to not be arrow straight. Fortunately it seems that my trusty book weights straightened it out.

[Where do you buy lead shot in Canada? I've asked at two hunting shops and they seem to think you can't buy lead anymore. Steel shot costs a ridiculous $30/lb or so so I'm still without bagged weights.]

It's also a hit or miss whether of not all of the rib ends will actually reach the shaped LE. And then the entire leading edge skin needs to be clamped down the whole length very tight to hold it there while the glue (Titebond, so it can be sanded easily) sets.

I'll do without the shaped leading edges next time around. (Note to self: add a 1/2" x 3/8" x 36" stick to the inventory to cover this change)

It also seemed strange that FIN8 is shown being outside the skin on the plans, but it isn't wide enough to reach the edges of the skin. So I shortened FIN8 to accommodate the LE, and glued it inside the skin. There's a big tip block on the end that can make up for the missing 3/32" width of the rib.

The instructions say to glue both skins to the ribs (up the the curve only) and then to glue the LE to the rib tips. I did that for the vertical stab, but on the horizontal, I had an easier time glueing the LE before glueing the second skin.

And finally, for the Corsair I bought Forstner bits to cut lightening holes in the rudder and elevators, but didn't on the Bearcat. I'm wondering if, since the nose is shorter, I should be paying more attention to the rear weight of the Bearcat.

JeffH

My Feedback: (43)

I have one of these built and glassed. I didn't do the basic construction, but I did remove the hard wood engine rails and used a conventional firewall. I set it up for an OS 61 pump, but I am thinking of going electric. I bought the a fiberglass cowl from Fiberglass Specialites. The Royal Corsair aluminum cowl will fit as well.
Mine is setup for RhomAir retracts with LONG 3/16" struts. I made the strust extra long so that it has the correct stance on the ground. The wheels retract well into the belly pan, so that part is not exactly scale.
I do have a unbuilt Ziroli kit with Barton scale retracts that shorten as they retract....very cool!!

ChinookRC

I've never seen an aluminum cowl before - very cool. The TF Bearcat cowl is identical to the TF Corsair cowl so there's an endless supply of cheap ($13.49) cowls for future builds.

There's an earlier comment on the site that notes:

I'm planning on giving it a try - if the pieces don't fit up properly after taking out the slices (, I can always get a replacement. The stock cowl is straight and doesn't match the real thing.

What would be the best way to cut that much fibreglass accurately?

Here's one of my favorite Bearcat photos - shows the angle of the cowl and and some good detail on the landing gear and oil cooler. I guess I'll be putting in an order for the Lado retracts soon.

ChinookRC

Starting on the top half of the fuselage. Seems a bit strange that the firewall is built in two halves, maybe it's to accomodate the hardwood engine mounts (that I won't be installing). Future improvement might be a single piece of ply.

Ply was warped pretty bad but I'm hoping the epoxied sandwich will hold it flat. Got the jigsaw pieces ready for tomorrow, at least the balsa isn't warped.

JeffH

My Feedback: (43)

The issue with the cowl always bothered me about my Bearcat. I never thought to do what was suggested. I might have to pull mine out of the back corners of the shelf and give it a once over again...

ChinookRC

Got to work on the fuse:

1. Instructions seem to indicate that the 1/4" x 1/2" "notched crutch strips" are already notched, but they weren't so I cut them out too large as it turns out so I used epoxy for the spacers. Really need to get some proper weights.
2. The formers come in two halves in the redesign I'll make them single pieces more like modern laser-cut formers

And continued the tail:

1. While the epoxy set, I returned to the elevators and rudder. Wasn't very happy with the way the shaped LE turned out. Maybe it's the age of the wood, but I wasn't able to sand down the skin to a smooth join with the LE out came the wood filler. Sanded them down nice trying to break a habit of leaving that kind of cleanup work to the end, and then having the final build stages stretch on for weeks while I catch up on the to-do's.
2. I sanded down the ribs in a straight line, again noticing some fuzzing of the wood. I put more time into this as I wasn't happy with the way the Corsair turned out - I left some outward curve in the ribs and I think the Ultracote emphasizes it too much. Should have followed CorsairJock's advice on that point. Didn't add any carbon reinforcements on the rudder since it doesn't extend above the fin like the Corsair, so it shouldn't be prone to break on tip-over.
3. Thought long and hard about cutting off the trim tabs, covereing them separately, and re-attaching them, but in the end decided not to. Feels like something that's just going to break off in the air. Maybe next time.
4. Also considered drilling lightening holes, but after weighing the pieces (8g for two elevators, less than 1g for the rudder) realized that I wasn't going to gain much except a weakened structure, even accounting for the longer rear moment around the CG.

[4h, 10h total]

ChinookRC

Continued top fuse:

1. Added to length of the center 'crutch strips'. Note inventory length should be 36", not 30"
2. Started having problems with the former widths:
   1. F-7A remove 4mm
   2. F-9A add 7mm
   3. F-10A remove 2mm from inside of each lower notch
   4. F-11A short 1mm, no change but it broke. The formers in future should be done in thin ply I think.
   5. F-12A ok
   6. F-13A appeared to be from a different kit, or numbered incorrectly. I made my own former from the plans.
   7. Another former broke while I was fitting the stringers. Really need to look at these again.

What I expected to be a straightforward snap and glue turned into a few hours of frustration, but it's straight and looking ok. Need to add some epoxy after it's unpinned to reinforce some loose notches, also the rear ply stab supports.

[3.5h / 13.5h]

optech

My Feedback: (9)

Maybe its just me but it looks like you glued the wrong ends of 13A together which is why it looks so off???

I've got one of these kits squirreled away but the place it was in had a roof leak. The kit didn't "Look" damaged but now that I think about it I should have opened it and looked. I'm afraid it may have moisture damage from being in the same room and I hope the preformed shells are okay.

Mike

ChinookRC

You're absolutely right.. how embarrassing. I'm very good at missing the obvious, and at finding problems where there are none it seems.

There's a comic on the plans that shows a guy who ends up building a boat... mine is looking remarkably similar to a boat right now.

More on the shells to follow.

Picked up some neat 2lb lead weights that were poured into a cupcake pan. Still looking for lead shot though.

ChinookRC

Sandwiched the bottom half of the firewall with epoxy and started the top fuse shell. Weight without the shell wass 5.1oz, weight with the shell is 8.0oz.

1. Lower pieces are cut but not shaped, some damage out of the box that I fixed, using CA accelerator for the first time to harden the medium CA in a bit of a gap. Nasty stuff but seemed to work ok.
2. The shell pieces were too large to scan so I traced them onto the back of the plans. I won't have shaped skins for the next iteration, and given the difficulty I had skinning the Corsair (a low point after which I had to walk away for a few days to calm down) I was looking forward to some easy building.
3. Instructions were a bit vague so I followed the Corsair recommendation:
   1. Wet the piece with water using a spray bottle. The piece curled up perfectly, great.
   2. Glue the bottom edge to the center stringer
   3. Starting from the nose, working a few formers at a time, glue the shell to the formers and to the stringer. Make sure not to do more than two hands can firmly hold down.
4. The upper pieces are the shaped shells and it was a treat not to have to bend them to shape and hold them down. It did take a bit of trimming to get the edges to line up at the top center.
5. I have some gaps at the center stringer that a bit of filler will hide easily enough - skin is firmly attached.
6. I wasn't able to get the skin attached to all of the formers. I was pretty frustrated by the poor sizing of the formers and this is where it bites. Not sure what the effect on the finished product will (maybe vibration will cause problems?) be but the gap is too large to fill with epoxy. I suppose I could cut some scrap and glue it in the gaps.

The shaped shell was nice to work with but I don't think it saved a lot of time in the end. Next time around I'll be using regular old planking.

To do:

1. I forgot to drill lightening holes in the cockpit floor before installing it. Will do that after I cut and shape the cockpit opening in the skin.
2. There are notches in the formed shells that I assume were used in the manufacturing process. I'll have to fill them and cut the excess off the tail end.
3. Sand and fill the gaps
4. Trim the canopy to shape
5. The fuse seems short compared to the Corsair, I'll do some sanity check measurements.

All in all things are moving quickly. Kind of surprised that the next step involves attaching the tail feathers already.

[4h / 17.5h]

Toysareforkids

My Feedback: (4)

Instruction booklet, 5 pages!
Your lucky, my red box TF P-51A came with some steps (instructions) on the lower right of the plans, and you had to tape a piece to the end, to have it all on one sheet.! LOL

Pat

ChinookRC

Not much done today:

1. trimmed the canopy
2. there wasn't a lot of guidance on what shape/size to cut the cockpit, the hole made by the shell pieces was just a starter. So I trimmed out the cockpit instrument panel decal and found that at 5 inches wide there's no way it could fit at the top of the fuse. Strange.
3. Didn't find much online as far as what other modellers did so I made up a shape and cut it out. I won't be putting in a pilot (hey, I'm the pilot) so I'm not too worried about it.
4. Decided not to risk cutting lightening holes in the cockpit floor. Without a firm base below the wood I wasn't sure there would be a clean cut. Will catch that next time.
5. Realized (too late of course) that I should have trimmed those strange notches off both ends of the shaped shells before gluing them on.
6. Realized (again too late, I'm good at this) that I did the tail end of the fuse incorrectly. Forgot at F-15. Some cutting and gluing fixed that.
7. Fill the gaps and gave it a light sanding. The shape feels pretty good to the touch. Pic is before sanding.

Started work on the shopping list - need to put in orders so that things arrive on time and don't hold up construction.

[2h / 19.5h]

ChinookRC

Started work on the stab and fin, realizing right away that I made a mistake with F-15: it goes on the bottom half, not the top. Had a eureka moment when I realized that my work in that area the day before was classic Daniel Kahneman whose book Thinking, Fast and Slow I'm reading. Off with the F-15.

ChinookRC

Shopping List

1. AXI 4130/16 motor
   already have one as I bought two when I got one for the Corsair. Seems to be a popular choice for 60-size warbirds.
2. AXI motor mount
3. AXI radial mount set
4. Castle Creations Phoenix ICE 100 ESC
   same as what I have in the Corsair. Surprised how heavy it is, but figured I'd get 100A instead of 75A. Who knows what will happen with battery technology in a few years and necessitate more amperage. I like the data logging feature but am confused why the watts measured by the ESCwere so different from the reading I got from the Watt's Up meter when I tested the Corsair.
5. Lado retracts and oleo struts
   same models mentioned in an earlier post
6. Futaba S3004 servos
   I have five left over, will need one more: ailerons x2, rudder/tailwheel x1, elevators x1, flaps x2. I did the rudder and tail wheel separately on the Corsair (7 total) and kind of regret that decision. Haven't checked if they'll fit in the Bearcat wing.
7. Thrust shims
   Still thinking about this one. The Bearcat firewall doesn't have the thrust angle built-in like the Corsair. Might shim the motor mount instead.
8. Cowl mount hardware
   Would like to find a more elegant way of attaching the cowl to the cowl ring than 4-40 hex screws and epoxied nuts on the other side. I haven't been able to securely glue the washers to the fibreglass cowl.
9. 3-blade props
   Need to do more research. I bought a 3x16x8 Master Airscrew for the Corsair that pulled 1200W (on the Watt's Up meter, 1050W on the ESC log) at 8000rpm which seemed good (AUW10.0lbs). Should get a few different ones from Hobbyking.
10. Zippy 6S 5000mAh batteries from HK (x2, to add to two already owned)
11. Multi-Lipo charger (use the current single Lipo charger for field use). I converted a PC power supply that puts out 18A at 12VDC.
12. UltraCote
    Guess I'll do the plain old Insignia Blue and save the yellow, or maybe a Thai metallic scheme, for a later build. I used 3 rolls of Corsair Blue on the Corsair and have most of an orange roll left over. I'll save fibreglassing for a future in which I have a build area outside the house.
13. Paint
    Hanger 9 doesn't sell spray cans that match UltraCote anymore so for the Corsair cowl I bought some Behr exterior semi-gloss that was a pretty good match. Unfortunately I haven't invested in a airbrush, so the final brushed on result isn't very good. The better half doesn't like the idea of an airbrush in the basement.... maybe later.
    I'm hoping that with Insignia Blue I can use the Monokote-matched spray paint.
14. Small Hardware
    Need to replace all the control rods, etc as they're rusted up. The local shops will be sufficient.
15. Wood
    I might replace the 3" balsa planking for the wings.

So there's stuff from the Czech Republic, USA, France, Germany, Japan/Taiwan, China and Ecuador.

ChinookRC

Epoxied the fin onto the stab. This should be looked at in the future for ways to get more strength built in through design. I can imagine a nose-over easily breaking off the fin with some sideways force. The Corsair had a high turtle deck with a slot cut into it that held the fin securely.

Applied the epoxy, tacked two right angles to hold it in place and balanced a lead weight on top to hold it down. Stopped for the day to let it set.

Thinking I should buy a set of Ziroli Bearcat plans to get some ideas.

Also wondering how to build the metallic exhaust panels on the front sides of the fuse. That's a detail that shouldn't be missed. Maybe I should add some Flite Metal to the shopping list - they offer a 12"x6" sample that would do the trick. Done!

[0.5h / 21.5h]

ChinookRC

Longeron or stringer? Not entirely clear how to transfer the definition to models where the number of components is far fewer. I'm leaning toward longeron as they bear forces between formers and ribs. Stringers support the skin only it seems.

ChinookRC

Found a picture of a 'cooling duct floor' from a Jerry Bates Bearcat build threadfor reference.