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Top Flite F8F-2 Bearcat Red Box Build

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Old 01-22-2012, 11:56 AM
  #51  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

These forums haven't been very stable - just lost my retract post. Try again.

As mentioned earlier I'll be using Lado RS333 85 degree retracts with 180mm oleo struts they should be arriving any day now. In the meantime I'm using the Corsair's Lados (90 degree rotating, but same dimensions) to design the mounts. Sketch of the traced W5 side view and a scale markup on my full-size scan attached. It's a tight fit but if I do it right should be very clean.

Please let me know if 1/2" x 1/2" basswood rails aren't going to be strong enough.



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Old 01-22-2012, 01:09 PM
  #52  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

I would also put some tristock reinforcement from across the basswood gear rail to the wing ribs and somehow tie them into the spar as well. You want as much glue contact as you can put in those rails to prevent it from pulling out on a hard touchdown. Tristock doesn't weigh all that much and it'll really help spread the load.

When I put retracts in my Royal B'Cat, I really over engineered it with a 3/16" gear plate and glued to the leading edge and all connected ribs with tristock. It up the weight about 6 ounces but no way will the gear be pulling out of there.

Your way looks fine but it needs more glue area, IMHO.

Just a thought.

Don
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Old 01-22-2012, 09:17 PM
  #53  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

The LG plate is a good idea, I'll keep it in mind for future builds, but for now I went with what seems to be a low-weight option. I'll look adding some bracing once I have the final structure but there don't seem to be many options with the structure up against the LE and away from the spars.

Imodified W5 and W6 to hold the 1/2" x 1/2" basswood gear rails and scanned them for later cleanup in Autocad. I was careful to have a perfect horizontal alignment with the ribs resting on their jig tabs - hopefully this is correct.

Then I went ahead and glued the remaining ribs to the bottom spar, forgetting that I need to cut slots for the struts, and it appears the wheel well also. Should be simple enough but I hate it when I rush ahead of the plan. I'm learning more lessons than just model building.

I added shear webs between the ribs with the grain running perpendicular to the spars to mitigate up/down wing flexing. Top spar fits in place quite well but isn't glued yet. The other wing half comes next. I'm surprised how much smaller the Bearcat is than the Corsair, yet the difference in span is only 2" (62 vs 60). Am hoping to come in around 8lbs, 2lbs lighter than the Corsair yet with the same motor/esc/battery. Should be fun.

[4.5h / 64h]
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Old 01-23-2012, 05:59 AM
  #54  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

Hope you don't mind a suggestion but here's what I was going to work for my WarZone Models blue foam Bearcat: [link]http://www.largescaleplanes.com/reviews/review.php?rid=619[/link]

I can get these scanned and done-up in vinyl in Singapore for a song (similar to motorcycle decals). Here are some examples:
[link]http://www.daddyhobby.com/forum/showthread.php?t=51165[/link]
[link]http://www.daddyhobby.com/forum/showthread.php?t=51042&page=2[/link]

Happy to get them worked for you if you get the dimensions sorted against the plan.

Good luck with the rest of the build. Will be keeping tabs.

Dave
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Old 01-23-2012, 06:29 PM
  #55  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

Hi Dave, I really appreciate the offer - I actually have that picture in my collection of Bearcat photos and was planning on using the red bull Thai scheme on a future build. If you don't mind, I'll probably get in touch with you on the second build a few months from now. I worked in Thailand for 9 months a few years ago and it would be a cool memento.

Seems like I'm putting off a lot of things for the 'future build', but I'm looking forward to incorporating ideas people are sharing. At the moment I just want to get the kit together and see how well it flies!


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Old 01-23-2012, 07:27 PM
  #56  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

The Lado retracts arrived and apart from one of them being 80 degrees instead of the 85 degrees I ordered, they look pretty good. They've made the set screws on the pinion and the struts much larger which is a needed improvement over the older version. The 180mm struts are a perfect match to the plan and are much longer than the Corsair's struts (which also arrived today after having the set screws tapped larger under warranty). So I'll send one retract back to France and keep the other to continue building the wing and wheel wells. I have no idea how or if I'll build working gear doors - will start researching.

Also on the supply side, the LHS has ordered in some Ultracote Corsair Blue (boring, but familiar) and I'm trying to place an order for some matching Oracolor paint and hardener from a shop in the UK. The German factory won't ship it overseas. If that fails there's a supplier on eBay who'll probably ship it. I'll wait as long as possible to order a couple more 6S Lipos from HK - the technology is changing so fast it's best to wait.

The AXI motor mount and a prop radial mount have been ordered from a shop in Quebec. I need to start looking at props.

I'll also start working on the cowl modification so that if it doesn't work I have time to get a new one ordered in.

Shipping from Europe to Canada takes a week, within Canada about 10 days, and from the US or Hong Kong it's 3-4 weeks.

I replied to an older post talking about washout on the Bearcat and the jury is still out some people say it tip stalls too easily, others say it's not a problem. In any case I don't know how to modify the ribs/airfoil to do it properly so I'll continue building the wing per the plan. When it crashes I know what to blame

[youtube]http://www.youtube.com/watch?v=I01sv4nLsfA[/youtube]


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Old 01-23-2012, 09:30 PM
  #57  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

After gluing the top spar with Titebond I ended the day with some creative destruction. I marked an angle with a 1/2 inch arc at the front of the cowl on each side, cut the wide piece out and then cut down the center of the angle with the razor saw. Will sand it to fit and glue it up tomorrow. Not sure if I should use CA or epoxy to do this - getting a flat finish will be important.

[2h / 66h]

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Old 01-24-2012, 05:45 AM
  #58  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

I want to cut my Bearcat cowl as you have to create a more scale appearance. I read somewhere that a 1" (at the front) wedge should be cut. Curious how you arrived at 1/2"?
I'd experiment with the adhesives on the scrap piece. I assume CA would work better than epoxy, but either way, I'd re-inforce the inside with fiberglass tape and additional adhesive.
The good news is, if you screw it up, it's the same as the current Corsair kit cowl and replacements are about $10.

Anxious to see how yours turns out.
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Old 01-24-2012, 05:52 AM
  #59  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

The cowl modification link above refers to a conversation someone had with Hal Parenti, who designed this kit, mentioning a 1/2 inch wedge. I've never used fibreglass tape - could you provide a link to a sample?

And yes.. the only reason I went ahead with this was because the stock TF Corsair cowl is exactly the same (if not a bit more solid, less flexible it seems), available, and cheap! Will post the results.
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Old 01-24-2012, 06:16 AM
  #60  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

Your probably right on the 1/2". I'm relying on my ever failing memory. []

Fiberglass tape is nothing more than fiberglass cloth cut into strips. The only advantage it has versus cutting your own strips from cloth is that the edges are straight so it doesn't have as much of a tendency to un-ravel like a piece of cut cloth can.
[link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXK255&P=0]Fiberglass Tape[/link]
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Old 01-24-2012, 09:31 PM
  #61  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

I'm getting a little tired of getting errors and losing my posts.. in short.. sanded the edges and they match up well but the medium CA I used on the scrap didn't seem to hold was still gummy after 45 minutes. Looking around the net it seems that epoxy is a better choice so I'll pick up some 5 minute epoxy and some fibreglass cloth or tape (for inside reinforcement) tomorrow. I won't be able to hold it steady for much longer than 5 minutes, the odd shape and flex means it has to be held manually. The gap at the front ended up at 9/16".
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Old 01-25-2012, 05:47 AM
  #62  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

Have you thought about tacking the halves together with thin CA just enough to hold it together, then adding the epoxy and glass to the inside? Just so you don't have to hold it while it cures. You'll have to work pretty quick to get everything lined up, the glass in place, epoxy smeared and verify alignment. I wouldn't trust myself to do all that with 5 min epoxy. I've overmixed it too many times and had it cure in the mixing cup before I put any to use.
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Old 01-25-2012, 08:51 AM
  #63  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

There is glue available for ABS that sort of welds the plastic together. I think it is mostly acetone. You could also try PVC glue for gluing PVC pipe together.
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Old 01-25-2012, 09:03 PM
  #64  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

The shop didn't have the $10 epoxy I usually use and I didn't want to pay $20 for 5min epoxy that Irarely use, so I got some JB Weld for $6 that says it works on fibreglass. Ugly black stuff but it seems to work on the scrap. Will try sanding it tomorrow and if it works will go ahead. Got some fibreglass tape to epoxy over the seam on the back but am hoping I won't need to use it.
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Old 01-26-2012, 09:28 AM
  #65  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

You will/need to re-inforce with fiberglass tape on the inside. FYI, the epoxy at Lowe's & Home Depot will work just as good as the stuff from the hobby shop.
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Old 01-26-2012, 09:45 AM
  #66  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

They make ABS glue for gluing ABS drain pipe together. I have used regular PVC cement on ABS cowls and it works quite well. The cloth can be pushed down into the plastic as it melts.
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Old 01-26-2012, 09:52 PM
  #67  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

I did some research and the cowl is fibreglass, not plastic and so I went with the trusted 30 minute epoxy. I taped up one side so I could crack it open and put a thin bead of epoxy on one seam and it seemed to work so I immediately did the opposite seam as well, without the full tape covering and using a tissue to clean up the excess. After sitting for two hours it seems to be quite strong. I'll take the advice and epoxy fibreglass tape on the inside of the seams.

I think the jury is out on the resulting geometry. I suspected things wouldn't look right (you can't cut a slice out of a tennis ball and expect it to be a sphere after gluing it together) but the side profile seems ok, which was the goal. Whether it's worth having an out-of-round opening and other strangeness will have to wait till it's completed. I'll add the dummy radial radial engine, and I'm looking for a way to do good cowl flaps, so that might take attention away from a deformed nose. We'll see.
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Old 01-26-2012, 10:08 PM
  #68  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

Continued with the left wing, cutting out space in the ribs for the strut and the wheels. They just barely fit within the height of the ribs and I'll have to adjust the axles so they don't protrude. I cut and glued some thin ply doublers to reinforce the very thin remaining upper portions of the ribs - I might need to tack temporary bottom rib pieces when I skin the wing to keep the shape. Will be counting on the skin to provide strength.

Lado have already shipped another pair of retracts to resolve the 80/85 degree problem, which they were flummoxed by. At least there were no hassles, and they shipped them immediately without waiting for a return receipt from me. In the meantime I'm using the Corsair rotating retracts for fitting.

I cut some existing control rod rib holes a bit larger to pass the servo and lg wires through. Will be using y-harnesses for the aileron, flap and lg pairs.

[71h]
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Old 01-28-2012, 06:47 AM
  #69  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

The epoxy on the cowl was hardened and I sanded the bottom flat. The joints took quite a lot of abuse during the sanding and subsequent stretch to fit over the cowl ring so I suspect the fibreglass tape won't be necessary after all. I'm wondering if cutting two more wedges 90 degrees from the first two might not be a good idea.

I'm thinking about modifying the cowl ring to add hinged flaps connected to a small servo that is linked to the wing flaps via two y-harnesses (one for the two flap servos, one for the cowl flap servo). That could cause problem limiting the cowl flap servo throw (plan to use the DX8's 3-position switch for the wing flaps). Or I could just use a separate channel for the cowl flaps and limit the throw with the radio.

Building the right wing structure was straightforward. I glued the shaped leading edge on but will have to replace one of the trailing edge sticks as it's badly out of shape. The dihedral jig is confusing because there's a line cut into it part way through and I'm not sure if I should cut it off or not. Will wait till I get some replacement TE sticks before putting the two wing halves together.

Am going to have a problem with the forward retract mounting screws sticking up through the skin. I switched the front hex bolts to a lower profile machine screw but will have to wait and see how it goes.

Started preparing the flaps and ailerons in the meantime.

[8h / 79h]

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Old 01-28-2012, 11:26 PM
  #70  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

I was wrong about the epoxied seams on the cowl being sufficient - after a night sitting on the cowl ring, which is a tight fit after the modification, one of the seams popped open most of its length. So I soaked two strips of heavy fibreglass tape in 30 minute epoxy and stuck them to the inside of the seams. If this doesn't hold, nothing will.

Picked up new wood for the trailing edge, planed it down to size and CA'd it to the back of the ribs. I put epoxy fillets on the rib and LE/TE junctions and on the LG mounts. Need to think of ways to add more bracing for the mounts. There just isn't a lot of wood in the wing.

It took a long time to put together the ailerons and flaps with all their little ribs but I'm happy with the end result. I like the way the instructions kept it all in two long pieces the sanded down shape is nice and consistent. I was thinking to add the 90 or so ribs to the much delayed Autocad plans (not sure what other kits do with this) but I suspect that sanding is needed to get the right shape. I wonder if the cost of lasercutting would go up with that many small triangles.

Marked the hinge locations. I think I'll go with CA hinges on these surfaces as well - I wasn't too happy with my workmanship on the Corsair using Robart point hinges. They were necessary for the 3-part flaps along the bent wing, but the Bearcat is much simpler.

[8h / 87h]
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Old 01-30-2012, 05:16 PM
  #71  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

I was so intent on sanding the aileron leading edges to a nice V that I went and did the flap LEs too before realizing I shouldn't have done that. Something about sanding that makes me zone out and stop paying attention until it's too late. Not sure if I'll build up half of the V or if I'll put a thin strip on the wing to cover the gap. I picked up a slot cutting machine and it made quick work of cutting the CA hinge slots. They fit nice and tight and I save a few hours of frustration and bloodied fingers. They'll be glued after covering.

I CAd some balsa reinforcing blocks around the LG mounts. I'll put a wedge in between the front mount and the LE for good measure.

Sanded off the rough edges of the fibreglass tape on the cowl seams.

I glued the ply aileron horn blocks in a different position than the plan to line up with the wing-mounted servos.

[3h / 90h]

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Old 01-30-2012, 08:28 PM
  #72  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

Nice work ChinookRC looking good! No big thing on that flap, I'd just ca some tri stock on the wrong bevel and sand back to shape.
I have both this kit and a Royal Bearcat kit so your build thread will be very helpful when I get going on them.
Thanks for posting your work.
Scott
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Old 01-30-2012, 09:35 PM
  #73  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build



Thanks for the boost Scott. If nothing else, this thread will be a good list of what not to do when building your TF Bearcat! I'm looking forward to the second iteration I plan to build. I have some Royal Maratuka and Jerry Bates Bearcat plans coming soon and I'm curious to see different design and construction techniques. One of the biggest shortcomings I have (apart from being impatient and mirror-image deficient) is a lack of experience building and seeing how other planes are put together. Joining the wings tonight was a pain...



I had misgivings about the dihedral jig from the moment I saw it. I cut the questionable part of it off, measured the angle at 6 degrees (versus an apparent dihedral of 3 degrees on the full size plans) and despite the misgivings, folllowing the instructions, marked off and cut the top and bottom spars, LE and TE according to the jig. The end result was a mess with none of the four sticks lining up such that the tip of the raised half was 4 inches above the table top - more like 6.5". BTW, setting the W6 jig tabs level of a 4.5cm high block will give the required 4in height at the bottom of the outer rib.



The halves are joined at the spars by two W-13s which I measured at 3 degrees on each side. A better approach to trimming the sticks would have been to draw a line bisecting W-13 and mark the sticks at that point with the bisector vertical. I don't remember having such a hard time joining the Corsair wings will have to improve this in the next build.



Since the main joining mechanism is the W-13s, I decided not to worry about the gap between the sticks and to shim and glue them after the epoxy has set. Doesn't look very good right now but I took care to ensure the two wing halves were laterally aligned along the top spar with a straight edge, and it does seem that the W-13 geometry is accurate.

[2h / 92h]
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Old 01-31-2012, 12:41 PM
  #74  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

Wow your really doing a great job. I bet you appreciate that gold edition corsair now compared to the old red box kits. If I may suggest why don't you use the bell cranks as designed? They have been used for years by Topflite and even in full scale aircraft, and work really well. Any decent std servo will handle the load considering the size of the ailerons and you will save some weight and avoid those servo arms sticking of the bottom of the wing. I use a nylock nut on the bolt to make sure they don't come loose. Here is my setup on my P-47 build
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Old 01-31-2012, 12:53 PM
  #75  
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Default RE: Top Flite F8F-2 Bearcat Red Box Build

here is where you can get a new cowl if needed http://www.fiberglassspecialtiesinc.com/catalog.htm
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