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Mar 17, 2008, 11:58 AM
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Profile F7U cutlass


Even thought I swore I wouldn't work on any airplanes this weekend, I found some free time and finally got to the cutlass. It is very simple, single fuse, with a doubler on each side for the engine intakes, single piece wing with 1/8" round carbon spar, elevons, and two tail pieces. To be a little different, I did the leading edges as if the leading edges were extended showing the "navy" red undersides, I like it this way, if you didn't like that you could just slice the leading edge straight. I used a spektrum 6100, grayson C-20 1500kv with apc 6x4, dynam 18 amp controller, and a 1320 3S pack, nothing added for CG, motor pulls 8 amps, and has hover power at around 70% throttle, at the RTF weight of 11 oz. 28" wingspan.

Every once in a while, I have a maiden that is just perfect, this was one of those. Where I had placed my velcro before painting was just a bit ahead of the glide test CG, so I left it there, increased throws to 150% on the xmitter.
This morning had a pretty good gusty breeze. Due to the forward CG I dialed in about 8 clicks of up trim. I throttled up to about 70% throttle, gave it a toss and away it went, took out all but two clicks of up and two clicks right, and that was it. Loops were very nice, pitch control was excellent, roll rate was perfect, glide is very very good, I was doing about a 20 degree nose up hover into the wind, both right side up AND inverted, inverted took almost no down elevator, outside loops are very tight if you want, slow speed flight was excellent. CG is a bit forward so snaps are more of barrel rolls, but I like it that way. Power off glide into the wind from around 75' up took about 30 seconds to touch down, at almost zero ground speed. In fact, the test flight was so good, I had it completely wrung out, and I didn't even bother to fly the second battery before heading to work

Oh, happy day

I'll scan in the plans this morning if I get time.

Frank
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Mar 17, 2008, 12:12 PM
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Very nice! Are you putting a carbon spar inside the fuse? Or just relying on the laminates for strenth?

Jasta
Mar 17, 2008, 12:50 PM
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Jasta, on planes where I have a long chord wing, I do not use a longeron in the fuse, except for the non-doubled nose section, I slice and inlay a flat 1/8" carbon strip on it's side and CA, I run it from the nose to about 3" into where the doubler would overlap. This has worked perfect for supporting the battery load, minor impacts, etc. The only planes I've needed to put a full longeron in were my Starfighter, and the buzzbomb. Normally for a wide chord wing, with the doubled fuse and the glue joint you just don't need it.

It might be different if you were doing a kit that was optimized for putting into a small shipping box where you have to segment the pieces more and splice them together, I'm not designing these with that in mind.

Sometimes I'll do the same slice and insert of the 1/8" by 0.032 carbon in the vertical tail if it is long and has a narrow chord, maybe about 50% of the time it needs it, usually one will suffice.

You'll need to tell me more about the KF wing, sounds interesting.

Frank


Quote:
Originally Posted by Jasta_66
Very nice! Are you putting a carbon spar inside the fuse? Or just relying on the laminates for strenth?

Jasta
Mar 17, 2008, 02:03 PM
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Jasta_66's Avatar
Ah, you knew why I was asking about the longerons....

Ive been influenced by some of your fuse doubling laminations and are trying to incorporate them into some "combat"-style tractor planes for future sale on my site.
When making profiles, I have usually gone with the cuciform method vs. the fuse doubler method.
One advantage of the doublers is I like is being able to hide the cf spars inside the laminations.
And speaking of KF, Im able to hide spars (or do away with them completly- B-2) on the underside of the wing, between the step lamination and the main wing.

Another advantage (for me) is that I can mix black and white depron in the laminations to get good effect.

The KF....Im just a user of it...a junkie the "heads" know all about the scientific properties of why it seems to improve flight performance. Wait...I take that back...They dont know either...just think they do... Heres the best thread on it: https://www.rcgroups.com/forums/showthread.php?t=558321

jasta
Mar 17, 2008, 05:00 PM
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Jasta, those look nice. For my Cutlass, it actually is a cruciform design, with the fuse interlocking into tabs in the wing, and probably would have been fine as is, but I wanted the doubers not for strength but for the intake details, and it didn't add too much weight. Actually, I don't always like the looks of the cruciform bodies, I think a lot of profile jets have nose art or markings at the nose and the cruciform at the nose detracts from the look, of a pointy fast jet. I like the clean looks of a pure profile at the nose. Another downside of a cruciform is that it adds lift up front and that means the CG has to be more forward, and requires moving the battery even more forward to compensate. Only a couple of planes I think look good with the cruciform rather than the pure profile, one of those is the X-15, since the top view shape is so much a part of that plane. However, it is so long compared with the wing placement you can get the CG without too much trouble. I think that would make a good kit, you probably would only need to splice the two fuse pieces near the wing center and it wouldn't take away from the strength, only one carbon piece for the taileron, no painting to add weight if you do it in black, very simple.

Where are you getting your colored depron, and what colors does it come in?

Frank
Mar 17, 2008, 07:11 PM
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J Morgan's Avatar
Man Frank, it looks like work is getting in the way of your building! Nice job.

J
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Mar 18, 2008, 01:08 AM
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flight video


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Mar 19, 2008, 05:55 PM
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Jan 14, 2009, 07:40 PM
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burkefj,

What paint did you use to paint your Cutlass?

Thanks, Kurt
Jan 14, 2009, 08:22 PM
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Kurt, that was testors Chrome. I like the shine, but decals don't stick super well to it if there is any compound curve. IN this case things were pretty flat and I haven't seen any problems, I used the same for my B-58 hustler.

Frank
Jan 15, 2009, 04:35 AM
Registered User
Thanks Frank, I'll try to find a UK distributor of Testors paint. Did you do any surface prep on the depron before airbrushing/rattle canning it? Sorry for the simple questions, I'm new to electric foamies!

Cheers,
Kurt
Jan 15, 2009, 12:32 PM
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Kurt, I did not do any surface prep, a lot of guys like wbpu(water based poly urethane?) to seal foam before painting, but for my planes i haven't done this.

Frank
Jan 16, 2009, 12:52 AM
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Rudi's Avatar
Quote:
Originally Posted by burkefj
...Oh, happy day

I'll scan in the plans this morning if I get time.

Frank
Hello Frank,

very nice model The F7U is my all time fav. and I am sure I will build it one day from depron.
Is threre a plan to download aviable ?

Rudi
Jan 16, 2009, 03:02 AM
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burkefj's Avatar
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Yes, just scroll up a few comments in this thread and it is there.

Quote:
Originally Posted by Rudi
Hello Frank,

very nice model The F7U is my all time fav. and I am sure I will build it one day from depron.
Is threre a plan to download aviable ?

Rudi
Oct 16, 2010, 08:07 AM
Registered User
Hi Frank - Just came across this thread, as a friend of mine copied your plans and shrunk them down and made a full fuse for flying in a small park. What a great plane. I was wondering, did you put your B-58 Hustler plans on here somewhere, and if so, can I ask where.

Thankyou
-Pete-
[email protected]


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