Hennings Top-Flite GS Corsair build with quite a few mods
 

OK. Here goes with my first build thread. The build itself started a few weeks ago and the fuse is well underway. I will though back track in steps to show the modifications. First off though is the construction of my recently received specially designed tail feathers. The design is Chad Veich's very realistic work, and he also did the parts cutting for me. I must say that I am terribly impressed by the accuracy of his work - the parts slotting together like nothing I've built before.

The tail feathers is just one of the mods I have planned. When receiving the kit I was almost shocked to see that Top-Flite have designed the Corsair with absolutely flat stabs. This just couldn't go unchanged. Other changes planned (and underway) are:

• Scale wing and stab incidence
• Tail gear and doors - using Earl Aune's scale gear with working tailhook
• Robart electric mains with functional gear doors and gear door sequencing
• Functional cowl flaps with Oregon Scale Aviation's ThermaCowl heat sensor and flap controller
• Sliding canopy (I think)
• Nav lights
• Scale detailing (door bays, panel lines, rivets, ++)
• .... your suggestions here ....;)

My last project was the 1/8 Thunderbolt, which I also modified quite a bit. To date that is my biggest bird, using a Saito 100. So moving up to the giant scale class with my first gas engine (Zenoah 62) is a big step up. This is something I have looked forward to a long time, and as a lot of the parts I am planning to use is with me already I can really dig in.

Hoping for help and comments along the way. :D

Part one of stab assembly slotted and glued. Absolutely perfect fit! Also impressed by the material that Chad's chosen for the different parts. Extremely light balsa for many of the parts, but stiff and rigid where needed, for example for the ribs. Great work Chad! For anyone else not impressed by Top Flites pancake flat tailfeathers, I can highly recommend getting in touch with Chad. I bet he'll comment in here in due time.

http://www.rcuniverse.com/forum/atta...mentid=1954968

Central stab build up and first elevator nearing completion. No doubt this will give the correct look and feel to the tail once covered. Bought some extra 1/16'' (1,5 mm) sheeting and leading edge balsa today. These items aren't included in Chad's kit, and I opted not to use the thicker stab skins originally supplied by Top-Flite as these would be more difficult to get around the curved profile of the new stab. Once glassed the structure is also more than tough enough with 1,5 mm skin sheeting.

Henning

I'm subscribed, I have this kit on my radar for my next sports scale build. Chad does great work, are you having him do your cockpit too? looking forward to your build.

TB

Hi Tony. Didn't know about Chad's cockpit. Any links or pics?

Here are some pics of my TFGS P-47 cockpit Chad made for me.



TB

Unsurprisingly great looking cockpit! What's it made of?

The tub is laser cut light ply, the sides are styrene, and the components are plastic.

TB

It is a full size cockpit too. All the parts came painted and assembled.



TB

Tony

Thanks for loads of great pics! Now I have to decide if I want to do some detailed cockpit work myself or if I contact Chad once again.

Henning

Finally got the stab sheeted and nearing completion on the elevators. Nice to see that my stab seat mated near perfect to the stab! :D

Henning

The stab seat needs to be adjusted to allow for the correct incidence. For now it's around +2 degrees - just a tad too much. As far as I've found out the wing is supposed to be at 2 degrees while the stab should be a bit less. I haven't though seen any definite definition of this and I'm still searching for documentation on what the real Corsair had. Any help on this is greatly welcomed.

Here I'm using my Robart incidence meter to first level off the fuse before measuring the stab.

Henning

I think you want to stay with what the plans say, I would guess it is +1 degree!. It usually will be on the plans telling you what the stab incidence is. The kit is a proven flyer and changing it to a more scale might make it fly different then the design. Just my thoughts.

TB

The plans have 0 degrees incidence for both stab and wing. One of the main design characteristics of the full size Corsair is the 2 degrees of positive wing incidence. This is important for getting it to look right. Together with the stab incidence, this also gives it it's slightly nose down attitude in flight. The theory is thus that if I change both the wing and the stab then the flight characteristics of the model won't be altered negatively. Usually a plane will have slightly more positive incidence on the main wing, so this is also something I want to get right. I am working on +2 degrees for the wing and around +1.5 degrees for the stab, but I am still looking for the correct specs of the full size.

Henning

I'm pretty sure the full size Corsair has +2 and +1.25 degrees on the wing and stab respectully so you are smack in the ball park Henning. I would definitely make the change were I building a TF Corsair in order to emulate the nose down flight attitude which is so characteristic of the full size. My .02 cents of course.

Chad,

Are you still making Corsair parts and vinyl rivets?

Rivets are no problem 550. The Corsair parts I can do but only on a time available basis as their is little profit in them. Shoot me an email if you want to discuss it further.

[email protected]

Thanks for input on the incidence angles, Chad. Looks like you are spot on. I found a great source of technical drawings at http://www.f4ucorsair.com/. Among them is this blueprint of the aft fuse. From a printout I drew up lines to measure out the angle of attack for the stab. From this it was easy :confused: , using all my vast childhood math skills :rolleyes:, to calculate the difference between the horizontal lines and the line through the stab. The result came out very close to 1.25 degrees.

To measure angles it's useful to think in circles and find the height of one degree from horizontal. First I needed to find the circumference of the theoretical circle for which the width of my blueprint horizontal line is it's radius. The radius being 37,85 cm. Using formula 37,85 x 2 x 3,14 (pi) I get 237,7. Dividing this by 360 I get the height (or length) of one degree of the circle: 0,66 cm.

In the drawing I found that the height difference of the stab line is 0,8 cm . Seeing as how one degree is 0,66 cm then 1,25 degrees is 0,825 cm. Taking into account all kinds of inaccuracies of my drawn lines, then these two figures are close enough for me to say that my new target is 1,25 degrees for the stab.

This concludes today's math class. Class dismissed. :D

Henning

currently working on the same aircraft with the same set of plans. thanks again Chad. has several mods myself that I'm considering for this build. Will be watching. What info do you have on the tail wheel. looking for something better myself.

Received cowl from Fiberglass Specialities
 

Just had a great week in Las Vegas at the SharePoint Conference. While there I ordered lots of R/C-stuff to my hotel. One of the things I got was what looks to be a fine fiberglass cowl from http://www.fiberglassspecialtiesinc.com/ . Since I am going to add the working cowl flaps I am happy to see that these seem to be well suited to be cut off from the main cowl. Only thing left to see is if the size of the cowl is near enough scale for me to be completely happy.

Things are going a bit slow with the Corsair now as I am also building a .40 size RV-4 to replace a recently crashed sunday flyer of the same size. I need to finish this before getting back to the Corsair.

Tail wheel unit from Earl Aune
 

The tail wheel unit is from Earl Aune. Been doing a few modifications to get the mounting and placement of the unit correct. By design Top-Flite have located the gear support system to far forward so this needs to be redesigned. Will get back with details of my approach here. For now, here are a couple of pix of the Aune unit.

See also this review in Model Airplane news

Henning

OK. Long time, no update. The RV-4 is done and is happily doing it's thing around the sky regularly. Now I'm finally back to the Corsair and my incidence angles. Pictures and updates will follow shortly.

Very happy with todays results. Finally got the wing crutches right, and also the stab seat, and most importantly - got some lame twist in the fuse sorted out. The work started some days ago when I really couldn't figure out if my stab seat was way off or not. It seemed that there were some differences in that either the wing crutches or the stab seat weren't quite parallell. At least one of them had a tilt in that either the left or right side was too low (or high).

I tried measuring just the fuse, trying first to be sure that the fuse actually was level before measuring. This in itself proved difficult, and the only real solution I found was to start building the centre part of the wing so that I had this to mate the fuselage to when levelling the stab. The plane of course has to have level wings and stab. Actually having the wing built at this time would help me a lot.

As described earlier, I have cut away quite a bit from the wing crutches to allow for the positive incidence. The building of the wing section would also allow me to finally test that this had been done right, both regarding the angle of incidence and that the wing was level. The two crutches were certainly the same when they were dremeled and sanded before installing them, but that is no guarantee that everything would be perfect when in the fuse.

The building of the wing section was an easy task although be careful to check that all rib parts align when glued to the main spar. I temporarily covered the top of the section in PRO-SKIN to really see if the profile would match the crutches. Of course it didn't! I had used the original profile of the crutches and simply used one of the crutches laid over the other when drawing up where to Dremel away. Even so there was quite a bit to correct. In some places the wing didn't touch the crutches at all. Also, when measuring the height from my table top to the underside of the main fuselage stringers/rails left vs. right, I found a noticable difference. Clearly one of the crutches needed to be sanded more than the other.

To be sure that the wing profile and the crutch would match perfectly, I taped sticky sandpaper to the top of the wing to use as a sanding block.

Being careful not to sand too much between new checks, I used my square many times to measure the height from the table to the main stringers on both sides, both fore and aft of the wing, to find when I'd done enough. To be sure not to sand away more than I had to on the low side, I used masking tape on that crutch.

After getting the crutches right, the next problem that arose was that I found the stab end of the fuselage not to be level when the front end was. Clearly a twist that was built in when planking the upper fuse. I was never really happy with what I'd done here, finding the sheets to not fit as well as I wanted, and I'd obviously not been careful enough to awoid twists. So what to do?

Thinking that the warp had not been there before planking, I guessed I could correct the fault by really soaking the balsa sides aft of the rear cockpit wall in water and rigging up the fuse with an opposite twist until dry. I used a lot of warm water until I saw the balsa being wet through, and then using my wall mounts where I usually store my finished planes (see at back of picture of crutches clampet together), I used clamps to hold the front end of the fuse level, while using more clamps to induse the reverse twist. Turning up the heat in my 'hangar', I then waited for hours. As the fuse surely would spring back some from the forced twist I had induced, I was very happy to see that I had guessed this just right. The fuse was now straight and level.

I could thus get back to the job of getting the stab seat adjusted. Originally I had sanded in 2 degrees of positive incidence. To get to the correct 1.25 I used the same method as for the wing seats. Sticking sandpaper to the underside of the stab I carefully sanded until the stab was both level and at the correct incidence, again masking parts of the seat with masking tape when needed.

I regularly used string to check alignment between fuse and stab, as well as between wing and stab, checking that string length was the same both sides.

More tailfeather work
 

So, up next was securing the fin. Before ordering the parts from Chad I'd done som measuring and found that the rear main spar of the original kit would be too short. Chad fixed this before cutting the parts, so that I received one more than long enough. I cut it just long enough for the fin to be at the correct height and so that it would rest on the plate right below the fin where the rudder torque rod assembly is to be fastened.

Doing some careful measuring and aligning to get the fin vertical, I first marked lines and then cut and sanded the rear former to get the spar to fit snuggly.

One thing that needed correcting was that I'd cut the skins too short. The turtledeck would cover most of the gap, but not all. I thus added a skin double that protruded below the skin for the extra balsa to be glued to. When done, I sanded the skin so that it now rests on top of the upper stringer.

When doing these modifications to the original kit new things appear all the time. As the new fin is way wider than the flat original then the fin was close to being wider than the width of the fuse. To correct this I loosened and moved the upper stringers some 2 mm further out before glueing them back in. This will allow for the fuselage skin to sit correctly in relation to the fin sides. More on this later.

definietly interested to see how the incidence changes both the flight attitude and flight characteristics. Doesnt the verticle stab have some offset built into the full size?