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Dec 06, 2008, 01:41 PM
Übung macht den Meister..
Deuce's Avatar
Build Log

Back to the Drawing Board-Off I: Fletcher FL-23


I've wanted to build this one for some years now, and the contest just may be the impetus to start!

The Fletcher FL-23 was designed to the late '40's Army spec for light liaison duty. It was the only aircraft entered designed specifically for the competition, the other entries being mods to commercial designs. During one of the test flights, the horizontal stab parted company, the FL-23 crashing. It was not able to be rebuilt in time to finish the competition, so the Army ended up with what became the L-19 Bird Dog. Not that that was a bad thing, of course! It simply makes documentation of the FL-23 difficult at best to find...

Quick specs:

Span of 33' 4"
Length of 28' 4"
Power 235 hp Continental
Vmax of 133 mph
Vstall of 38 mph
Crew of 2

As near as I can tell, the current holder of the type certificate is Pacific Aerospace Corp of New Zealand, and the only photo I can find (attached, via Aerofiles.com ) has their copyright. I s'pose I could contact them for to see if there is any more info available...

Obviously, models have been built of this aircraft, evidenced by the pics attached of the Air Trails publication of Oct '58. As well, I've seen a peanut scale kit listed on the SAMS Models website. I also recall Model Builder magazine having published peanut plans of the FL-23. Still, it seems to be an obscure subject, seldom modeled.

As for my attempt, I figured I'd use Carl G. Ahremark's plans in AT (scan attached) as a starting point, with the needed mods to allow for RC as well as compliance with the contest rules.

At 1/10 scale, the span would be spot on 40", and the wing area just about 400sq". I'd also considered going with a 44" span & about 484sq", but as I plan to use an Axi 2212/34 w/3s LiPo (because I already have it!), I may stick with the 40" span... unless someone more expert than I believes the Axi could handle the larger of the two!

It is my goal to go full-house with controls (t,e,r,a,f), but I may need to simplify the elevator/stabilator for the model, as the original used an "articulated" setup. According to Ahremark's text, "The airplane had a special stailizer-elevator combination developed to insure perfect control. The stabilizer was hinged at the rear spar and so linked that when the stabilizer moved down the elevator also moved down and vice versa." Despite his explanation, I can't seem to picture the action in my head. Maybe the action shouldn't be in my head! Also, if the photo is looked at closely enough, there is an external linkage (or two?) at the wing root that is called "aileron control" by Ahremark, who added the detail to his model. It almost seems to be two such external controls, perhaps one aileron & one flap?

Anyone with more info on the FL-23, please do speak up!

I prefer to use good ol' wood construction, and sheeting the model seems a foregone conclusion. I am open to suggestions on finishing materials to simulate to a reasonable degree the bare aluminum, yet keeping things light. I need also to deal with the corrugated wing skin, but I have some ideas in mind that may or may not work, depending on finish technique (is there no "Swedish" technique? ).

Well, that's a start, now to warm up that CAD system! Hehe!

James
Last edited by Deuce; May 22, 2009 at 03:40 PM. Reason: History revision!
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Dec 06, 2008, 01:48 PM
Two left thumbs
Excellent selection! Glad to see you taking the plunge!

I'm pretty sure Bob Banka would have a three view, etc, but why not call our friend in Illinois, Roland Friestad? You saw all those planes he had on his database when he was out here.
Geoff
Last edited by GeoffinIN; Dec 06, 2008 at 02:01 PM.
Dec 06, 2008, 02:13 PM
Übung macht den Meister..
Deuce's Avatar
Quote:
Originally Posted by Geoffinpdx
Excellent selection! Glad to see you taking the plunge!

I'm pretty sure Bob Banka would have a three view, etc, but why not call our friend in Illinois, Roland Friestad? You saw all those planes he had on his database when he was out here.
Geoff
Ooh! Good call! I believe Roland did mention he has copies of all(?) the AT mags, or something like that. Wonder if he has the actual Ahremark FL-23 plans...? I'll shoot him an email and ask what he might have.

Just checked Banka's catalog (pdf), and the only Fletcher listed is the FU-24. I might send an email or call him as well.

James
Dec 06, 2008, 02:44 PM
Übung macht den Meister..
Deuce's Avatar
Okay, I just dug up my August '77 copy of Model Builder with the peanut-scale FL-23 plans, by Charles Schaaf, and I'm not sure there will be much help from them. The fuse cross section differs markedly from Ahremark's design, so I suspect some interpretation from photos. It is not a bad-looking model, however, and likely flies rather well the big wing! I've always fancied the "split" ribs for extra lightness on small rubber-motored models...

James
Dec 06, 2008, 04:13 PM
Registered User
lake flyer's Avatar
Of course you know , for true scale effect , your horizontal stabiliser must fall off during your maiden !!

Seriously , good luck , looks like a pretty plane .
Dec 06, 2008, 04:24 PM
Übung macht den Meister..
Deuce's Avatar
Quote:
Originally Posted by lake flyer
Of course you know , for true scale effect , your horizontal stabiliser must fall off during your maiden !!

Seriously , good luck , looks like a pretty plane .
Haha! Actually, from what I've been able to dig up, it was not the first flight the stabilizer was lost. That may be the tricky part, finding out on which flight I need to lose the stab!

James
Dec 06, 2008, 04:30 PM
Registered User
lake flyer's Avatar
"T" tails are dificult to make strong enough without getting too heavy , but they sure look nice !!
Dec 06, 2008, 04:45 PM
Two left thumbs
If fall off it must, do it on the flight AFTER taking the photos of a successful takeoff and landing so you won't be disqualified in the contest.
Dec 06, 2008, 04:49 PM
Registered User
lake flyer's Avatar
Maybe you should include a parachute , for when the tail falls off , that would win the contest hands down !!
Dec 06, 2008, 04:58 PM
Übung macht den Meister..
Deuce's Avatar
Quote:
Originally Posted by lake flyer
"T" tails are dificult to make strong enough without getting too heavy , but they sure look nice !!
Yes, it puts the stab on a thin lever! Pa has a video about the F-104, and during testing of tail configs, one t-tail setup just disappears somewhere after mach one! It begins to oscillate, then just... disappears!

I doubt I'll try to model the prototypical articulated setup, mostly because I simply don't know the actual execution of it! I'll likely settle for a stabilator, and work out as much a balance between structure and lightness as I can. If I take the AT plans as accurate, scaling up the thickness of the fin to 1/10 scale, the fin will be about 7/8" at the root, and just over 1/2" at the tip. If I go for the 44" span (roughly 1/9 scale), I will obviously have a bit more meat to play with.

I've sent out some "feelers" for some more info on the FL-23, so pending such, I hope to make a few more concrete decisions about structure before too long!

James
Dec 06, 2008, 05:07 PM
Übung macht den Meister..
Deuce's Avatar
Quote:
Originally Posted by Geoffinpdx
If fall off it must, do it on the flight AFTER taking the photos of a successful takeoff and landing so you won't be disqualified in the contest.
What would be really cool, if somewhat tragic, would be to try to find some original footage of the real FL-23 losing the stab, then documenting the model flight duplicating the catastrophe! Okay, maybe not so cool...

Quite frankly, I, too, am hoping for success!

James
Dec 06, 2008, 05:15 PM
Registered User
lake flyer's Avatar
Everything will be ok , just keep her below Mach 1 .
Dec 06, 2008, 05:48 PM
Übung macht den Meister..
Deuce's Avatar
Quote:
Originally Posted by lake flyer
Everything will be ok , just keep her below Mach 1 .
Awww, gee! You're no fun!


James
Dec 07, 2008, 12:48 AM
Dog is my co-pilot.
mrdj's Avatar
If you want, I have the Jane's entry for the FL-23, complete with (very bad) 3-view.

djm

edit: here they are, sorry the on page is inverted.
Last edited by mrdj; Dec 07, 2008 at 01:12 AM.
Dec 07, 2008, 11:10 AM
Übung macht den Meister..
Deuce's Avatar
Quote:
Originally Posted by mrdj
If you want, I have the Jane's entry for the FL-23, complete with (very bad) 3-view.

djm

edit: here they are, sorry the on page is inverted.
Despite your opinion of the 3-view, it does hold some interest for me! Ahremark used a series of flat sections for his greenhouse, and the 3-view at least shows a plausible profile for the curves, especially the aft part, obscured by the wing in the pic. As well, the 3-v shows a different fin tip profile that may show a more likely shape than Ahremark's design.

The photo I posted is the same as the one in Jane's, but it is a very low-res pic. I have been trying to interpret as much as possible from the pic, but the poor resolution has left much ambiguity in spots. The pic and the 3-v agree with each other to a greater degree than does Ahremark's design.

The Jane's I have is WWII specific, and the info in yours is indeed helpful! If it would be possible, could you scan the relevant FL-23 bits from Jane's at a higher resolution and email those to me (I can PM my email address to you if you are able to do that.)?

Thanks!
James


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