Thread Tools
Dec 27, 2019, 08:26 AM
Registered User
Tim Cullip's Avatar
Thread OP
Build Log

Peanut F4U Corsair


Now that I've cut my teeth on the Peanut Ki-43, La-7, and Yak-3:
https://www.rcgroups.com/forums/show...3-Peanut-Ki-43
https://www.rcgroups.com/forums/show...Lavochkin-La-7
https://www.rcgroups.com/forums/show...7-Peanut-Yak-3


I've decided to move onto a potentially more difficult project: F4U Corsair with its inverted gull wing.
The real challenge will be to get ailerons working on this small plane with a single central servo and routing the torque rods through that gull wing section.

I'm using plans for a 1/24th scale (originally 20" wingspan) version out of the book "Flying Scale Models from WWII" which I've shrunk down to Peanut size.

Wish me luck on that inverted gull wing and the ailerons


Tim
Sign up now
to remove ads between posts
Dec 27, 2019, 10:27 AM
Registered User
Oh. An allied fighter now?
Fun aside. How bout actuators? You could even make the wings swing up then, for easier moving and storage...
Also, cool plan.
Last edited by JustAHuman; Dec 27, 2019 at 11:18 AM.
Dec 27, 2019, 09:21 PM
Registered User
Tim Cullip's Avatar
Thread OP
The wing's central inverted gull portion will be the first thing to tackle. I temporarily glue-sticked the patterns for the LE and main spar to help get accurate cutouts. This will be my first wing that I can't build pinned flat to the working surface, hope it comes out unwarped and symmetric.


Tim
Dec 28, 2019, 01:12 PM
Go small or go home
ruzam's Avatar
Nice! Can't wait to see how you handle the aileron linkage. Do you have any ideas rolling around yet?
Dec 28, 2019, 03:58 PM
Registered User
Tim Cullip's Avatar
Thread OP
Here is the progress so far (wing center section, then left wing panel, right panel will be next). I probably should have left out half the ribs, but that inverted gull wing design has so many different planes (not just: slope down, slope up again; rather : horizontal inside the fuselage, slope down, short horizontal section, then slope up to the tip) that just removing half the ribs would have been impractical. Instead I would have had to reposition many of the ribs and was too lazy to figure out the new shapes/sizes for the repositioned ribs.

I linked two torque rods together with a small section of flexible insulation from of a small diameter wire.
You can see the setup in the photos. Seems to work okay on the bench. My major concern is if either torque rod slips/rotates inside the insulation which would cause the aileron to get out of sync with the servo position. I put a very small amount of thin CA on each end but I'm not convinced it wicked in any to get a slip proof bond.


Tim
Dec 29, 2019, 09:12 AM
Senior to who? Member
crossup's Avatar
Yet another great plane build Tim, you are a building machine.

I dont know how I missed how nice the Flying Models plans are, its a real struggle finding plans that are laser cut friendly. Some where along the line I figured out a way to remove the balsa grain lines in one of my graphics programs, but alas that was going on 2 years ago so now I have to figure it out again.
I get so tired of trying to extract parts from plans that are low resolution scans with all the parts touching so thanks for bring attention back to this great book.
Dec 29, 2019, 10:23 AM
Registered User
Tim Cullip's Avatar
Thread OP
The wing is now framed up, sanded, and almost ready to cover. The second photo shows one of the intake inlet cut-outs. I used a drill bit, round file, and sandpaper to do it. Hopefully the second one will go as well and they end up looking semi-identical.

Currently at 2.4 grams (kind of heavy, but at least with the large cord it will have the greatest total wing area of my Peanut WWII fighters so far).


Tim
Dec 29, 2019, 10:34 AM
Registered User
Tim Cullip's Avatar
Thread OP
Quote:
Originally Posted by crossup
Yet another great plane build Tim, you are a building machine.

I dont know how I missed how nice the Flying Models plans are, its a real struggle finding plans that are laser cut friendly.book.
Glad to repoint you to that source.

I used to think about getting a laser, but over the past couple of years I've actually grown to like cutting the parts out by hand with an X-acto (but maybe that is just the dark masochist side of me). Then again, when I get to the point of cutting all the notches in the fuselage formers I tend to question my choice of tools.


Tim
Dec 29, 2019, 04:07 PM
Registered User
Yes... notches.
Your build-quality is amazing. I think your tails might very well have more love in them than my whole planes.

Concerning your aileron problem:
Since it is already over weight, 2 servos? You could do flaperons then. That could even overcompensate for the additional weight, if you plan to fly slowly.

Alternatives: routed cables (pull pull), hydrolics, pneumatics and magic of course.
Last edited by JustAHuman; Dec 29, 2019 at 04:12 PM.
Dec 29, 2019, 09:16 PM
Registered User
AntiArf's Avatar
I enjoy cutting parts also. Seems if you invest time in printing a plan and then hand cutting parts, then models are actually built. Plenty of modelers with a stash of unbuilt kits, including LC kits. Used 0.015" music wire for single servo ailerons on the gull wing 500 series Stuka which worked well. A bit of pre curving the wire to shape got the friction down to an acceptable level. With a bit of rudder mix it's tough to tell how well they actually work stand alone, as the gulls can turn reasonably well with rudder only.

I wouldn't say he's overweight, more trying to conform to the conservative standards of a good micro builder. Basically just his own terms. A 16" Corsair with the generous wing area could be 80 grams with BL power and still be a good flyer, although not exactly indoor material. Tim will come in a good bit under that I imagine. Had a guy once suggest possibly abusing gear with HV batteries for more power, since according to him I was "toward the heavy end" of my personal set goal, based on extensive experience with micro EDF. Never saw him build or fly micros. Ended up at 15% under my max target, (which was a conservative max and would have flown well at) where 15% less is a considerable difference anyway. The 30mm EDF AR234 ended up being an excellent flyer and as expected with ballistic speed. Not even a thought of needing more power.
Dec 30, 2019, 10:49 AM
Registered User
Tim Cullip's Avatar
Thread OP
Started working on the fuselage.

This one is different than any I've done before in that keel separates the top half from the bottom half rather than left and right sides, but so far I kind of like this approach. Also I normally run stringers from the full front to back and then plank the front half or so, but this time I decided I'd sheet the front while it is still pinned to the plan (and it only had the two keels and one stringer under the sheeted part. The sheeting is about 1/64th inch thick (started out as 1/32nd and sanded it down to a reasonably uniform 1/64th before gluing it to the fuselage). Also all the formers start out as two sheets of 1/32 glued cross grain and then once dried, sanded down to a little less than 1/32 total thickness. Having a 2-ply cross grain former make it very strong, very light, and easy to cut the notches without pieces breaking off (just took twice as long and twice as much balsa [but over half of it then sanded away] to make them).

The gap between the two sheeted sections is meant to simulate the cowl gap of the real F4U. The back of the front sheet is bevel sanded from the inside, the front of the back sheet is bevel sanded from the outside.


What you see is 1.7 gms.


Tim
Dec 30, 2019, 05:33 PM
Registered User
Tim Cullip's Avatar
Thread OP
It's slowly starting to look a little like an F4U. Currently sitting at 4.7 gms.
Still to go on the frame: more bottom stringers, some sheeting or planking on the bottom front, the front cowling, and tail feathers.


Tim
Dec 30, 2019, 07:42 PM
Registered User
jumo004's Avatar
Delete
Last edited by jumo004; Dec 31, 2019 at 08:45 AM. Reason: don't want to start a pissing contest with antiarf
Dec 31, 2019, 04:12 PM
Registered User
Tim Cullip's Avatar
Thread OP
Tail feathers are done, also did a little more sheeting on the front bottom. Cowl will be next. Currently 5.3gms.


Tim
Jan 18, 2020, 07:26 PM
Registered User
Tim Cullip's Avatar
Thread OP
The F4U is now 95% done and has survived its maiden flight.

I still have to finish:
canopy
belly pan under the wing
decals and any other decorating
paint the battery hatch


I didn't use Esaki tissue this time and kind of regret that decision. Even though I painted it a dark blue I wanted to start with a dark blue tissue to reduce the number and thickness of coats needed to get a decent finish and I didn't have any blue Esaki, but I did have some blue Easy Built tissue so decided to go with that. First off, it doesn't have the wet strength of Esaki, and more importantly second off I have very little experience with it, and finally third off the F4U's wing has lots of convex and concave curves with its inverted gull wing shape. End result - I wasn't real happy with the results, they are passable but not up to my usual standards. Don't get me wrong, I'm not blaming the Easy Built tissue, I'm blaming my lack of experience with it.

The plane ended up at 22 gms with a 150 mah battery, a few grams heavier than the three previous WWII Peanuts I've done, but it also has the largest wing area due to its low aspect ratio wing.

As for the maiden, the first attempt required a fair amount of right aileron trim. After the flight I noticed the wing did have a bit of a warp to it - a little harder to notice with all those angles in the inverted gull. So I went home and wet the wing (fortunately I was able to do that through the paint surface) and let it dry while twisting out the warp best as I could. Second flight resulted in dead neutral ailerons so I was happy with that. Once trimmed out it flew quiet well though it needs a larger diameter prop without increasing the pitch so I need to search for a new prop. But even with this one I was able to loop it from a very shallow dive. The aileron response is more than adequate for turns but barely adequate for rolls. It rolls about as fast as a real full sized F4U - about 90 degrees/second which means it covers about a 100 yards during an entire 4 second roll (at least it felt like it took about that long and covered about the full size of my neighborhood soccer "flying field". A four second roll in a full sized plane would probably feel pretty fast, but it felt agonizingly slow for a Peanut flying over a soccer field.

Anyways, I'm calling it a moderate success and a good learning experience. In the first post I mentioned this would be "a potentially more difficult project" and it lived up to that prediction.

It may be awhile before I post a final picture of the fully finished and decorated plane but eventually will (I'm already working on my "insanely difficult" next project: Peanut P-38).


PS: So far the aileron torque rod linkage is holding up.



Tim


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Parkzone f4u corsair VS Airfield f4u corsair Hoopsta17_99 Electric Warbirds 55 Jun 22, 2017 01:36 PM
Question AR636 F4U Corsair SAFE huff6 Radios 1 Sep 21, 2015 12:45 PM
Discussion Cute Little Corsair <<< "Cartoon Corsair">>> Slow flying model of the F4u Corsair D DaDesign Foamies (Scratchbuilt) 37 Jan 03, 2015 02:27 PM
GWS F4U vs. Alfa F4U Corsair DWA Parkflyers 10 Jan 08, 2005 09:56 PM