Warbirdkits.com F7U-3M CUTLASS Proto #2 66mm/505 - RC Groups
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Oct 24, 2009, 01:51 PM
Big gov never Works
St. Martin's Avatar
Build Log

Warbirdkits.com F7U-3M CUTLASS Proto #2 66mm/505


I'm finally getting around to building the second(and final) prototype, of the Cutlass. The first one was a huge success and is still tearing up the sky.

Two problems, with the original, were the canopy not matching the width of the fuselage. And, not being able to move the minifan back far enough to balance, with a short can mtr, such as the HET 3W or Mega 16/15/3. So a Astro 805K (3700Kv) was used on a 2200-4S. This made it a skyrocket! You could cruise at 25% power.

So this version will use the WeMoTec 505 66mm fan. This can be moved further aft and use a lighter short can mtr. For those still wanting to use the minifan or HET 6904, parts will be supplied for both size fans. As another surprize, I plan on developing two other Cutlass's for twin WeMo microfans. This will be a joint project between Sam B. (Megowcoupe) and myself.

Tom at Warbirdkits, already said he would make parts avail for this conversion. Should only be two bulkhead changes. I will be making the molds for glass intake ducting and giving the molds to Sam. He can farm them out, to those interested in the twinn micro.

Well...back to this version. Here is the link to the first Cutlass. Vid at the end. https://www.rcgroups.com/forums/showthread.php?t=849128

The first thing I did, was join the supplied bottom wing sheeting, using the tape method. (BTW, this is a short kit. You supply the fuselage planking and top wing sheeting. There will be a supply list I am making)

While the sheeting is curing, I elected to make my own 66mm 505 shroud. Tom may supply a polycarb shroud. I'll let him clarify this. But Oliver at WeMo now supplies a shroud with the 505. My shroud is made of two lams of 1/64ply. I made a jig from 1/8" ply to form it on. The finished product is VERY stiff and strong. The mtr in pics is a HET 2W used to set it up. Haven't decided on mtr yet. This will be long or short as CG requires.

Now to start on the fuselage..

Stats: WS 30.75, WA 256sq",LOA 28.125. (AUW of proto #1, I forgot..err very light! Glides forever..Check original thread)

Fuzz
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Oct 24, 2009, 05:14 PM
To drive or to fly......BOTH!!
FresnoJay's Avatar
Fuzz, she is looking good. Nice work on the shroud. Another option for a shroud to use the 505 in could be a Wattage fan housing if you could locate one.

Jason
Oct 24, 2009, 05:51 PM
Big gov never Works
St. Martin's Avatar
Hi Jason
I have several Wattage Shrouds. The rotor here is actually a 505 from WeMo. They are slightly larger. I grabed one cut to fit the Wattage and it fits loose. Same with a few KY rotors, that fit the Wattage. Speaking of which.. At power levels below 500W the KY rotor pulls better in the Wattage shroud VS the cut minifan. The cut minifan has to be absorbing more than 500W before it is faster than the KY. I attribute this to blade area or possibly the stators in the Wattage(3) 505(4)

I think there is a lot of lost efficiency with the Wattage/cut-minifan combo. The 505 rotor really works much better with the WeMo stator. On another downside, You cannot use full ducting and enclose the "bell" on the Wattage.

But I do have two jets that use the Wattage/KY combo. And they perform great at 425W.


I'll post pics tomorrow. I have both verticals done, fuse nose section framed, and the wing sheeting ready for use. It takes me a little while on builds like this. This proto requires the edited construction pics and build manual. This takes time. For this reason, I'm not going to get into too much detail, here on the thread. It will all be covered in the kit. And seeing I type with one finger....

Fuzz
Oct 24, 2009, 07:52 PM
To drive or to fly......BOTH!!
FresnoJay's Avatar
When I ran the 505 in my Wattage shroud I really had no comparison to judge differences. At the time I had the 505/Wattage combo was really my first big time EDF. I learned alot from it and knowning what I do now your testing and info sounds right. You did a great job on the shroud and if I did it again would try the same. The Wattage shroud would just be a on hand suggestion but then again if you had a Ky rotor would be better . Cant wait to see the outcome Fuzz.

Jason
Oct 25, 2009, 06:46 AM
Big gov never Works
St. Martin's Avatar
Hi Jason, A good point I learned from the guru's: If you have an odd number of rotor blades, you need a even number of stator vanes. So the Wattage rotor has 6 blades/3 stators. It was explaned to me once by Eric Barnett(AirX), but I forgot the reasoning, but not the lesson.

Fuzz
Oct 26, 2009, 11:42 AM
Manzano Laser Works
TomJacoby's Avatar
Quote:
Originally Posted by St. Martin
For those still wanting to use the minifan or HET 6904, parts will be supplied for both size fans.
Quote:
Originally Posted by St. Martin
As another surprize, I plan on developing two other Cutlass's for twin WeMo microfans. Tom at Warbirdkits, already said he would make parts avail for this conversion.
The minifan/6904 and twin microfan parts probably will be extra cost options.

Quote:
Originally Posted by St. Martin
Tom may supply a polycarb shroud. I'll let him clarify this. But Oliver at WeMo now supplies a shroud with the 505.
I will supply the polycarbonate shroud for the first dozen or so kits - depends on demand after that.

Tom
www.warbirdkits.com
Oct 26, 2009, 05:13 PM
Big gov never Works
St. Martin's Avatar
Thank you for clarifying, Tom. Sorry I did not post pics yesterday. I just kept working on the Cutlass. The fuse is framed, fan mounted, hatch functional. Now ready to make the ducting. Also have one wing panel, minus the top sheeting. I'll try posting pics in the next few day's.

Fuzz
Oct 26, 2009, 05:56 PM
Manzano Laser Works
TomJacoby's Avatar
Glad to see that you're back on the Cutlass! I am looking forward to building one for myself, or maybe I should hire you to build one

Don't forget to send me a list of the items you need to complete this model.

Tom
Oct 27, 2009, 06:29 PM
Big gov never Works
St. Martin's Avatar
Quote:
Originally Posted by TomJacoby
Glad to see that you're back on the Cutlass! I am looking forward to building one for myself, or maybe I should hire you to build one

Don't forget to send me a list of the items you need to complete this model.

Tom
Email me, Tom. I would be glad to build you one. Searching for a good mtr, I'm thinking HET 2w-18 or 20.

Fuzz
Oct 28, 2009, 02:24 AM
Registered User
hommel's Avatar
signing in... one of my all-time favourite jets!
Nov 01, 2009, 08:13 AM
Big gov never Works
St. Martin's Avatar
Welcome, Hommel

Finally got some time to work on the Cutlass and post pics. As I said before, this is more of a generalization of the Cutlass, than specific construction details. This due to the fact that there is no sequence estabished, for the kit. I have to do this from my notes and construction pics. So bear with me as I "hop around" on different assemblies. This does not relate to the actual construction sequence.


So.. I have the wing panels completed, sans cutting the ailerons free. The wings are very strong. The proto used supplied carbon tube and dowel for joiners to the fuselage. These were supplied, by Tom. As he was having a hard time locating these items, I did have slightly larger 1/8" carbon dowel on hand, and 1/8"id alum tube. This required a slight enlarging of the pilot holes in the wing ribs. The proto had the tubes retained as far as the second rib bay (W2). I extended these to W3. For really no reason than other than "piece-of mind". The proto has had a few mishaps with terra-firma with no damage, other than a few paint nicks.

I will cut loose the ailerons and install the servos today, then move on to the ducting. The jig for the ducting is complete. I could have made molds and made glass ducting for this. But, this would have increased the cost of the kit by approx 60$. And the ducting worked great in the proto. It's not hard to do, I used the same type/construction in a 1/2doz jets. While I have only put 650W through this type, I see no need to use any higher watt system. The airframe is designed to utilize it's light weight/power ratio for outstanding performance.

The proto was 34oz. This version should be lighter, approx 30oz. due to the use of contest grade balsa, lighter fan. Even at 34oz, it was lightly loaded. The low frontal area required learning how to land it. It would glide forever. 50% power enabled it for anything I would want it to do. Full power and it had unlimited verticals. If the full scale version flew like this, we would still have it in inventory.
BTW, Tom, I found a set of plans. I think you sent two copies for the first build.

Fuzz

Here's some pics:
Nov 01, 2009, 12:10 PM
Manzano Laser Works
TomJacoby's Avatar
Quote:
Originally Posted by St. Martin
The jig for the ducting is complete. I could have made molds and made glass ducting for this. But, this would have increased the cost of the kit by approx 60$. And the ducting worked great in the proto. It's not hard to do, I used the same type/construction in a 1/2doz jets.
This looks like the same technique you used on the Skyhawk ducts. Very cheap and very effective!

Quote:
Originally Posted by St. Martin
BTW, Tom, I found a set of plans. I think you sent two copies for the first build.
Good!

I'm painting the new Mustang (never thought I'd build one) and framing up the new Defiant today. It's gorgeous fall weather, there's snow on the mountain, and I've got nothing to fly

-tom
www.warbirdkits.com
Nov 01, 2009, 03:54 PM
Big gov never Works
St. Martin's Avatar
Hi Tom, yes, the ducting is simple, cheap, and light. and performs well in these applications. Im looking forward to the Mustang. Ofcourse, I want to do one of the Allison Mustangs. Maybe the Apache. Nice 3 blade prop.
My cam batt need charging. So I could not get pics of the ducting. But the ailerons are done. Servos are HS-55. Out of curiosity, I tried a HS-80. Too big for the wing depth. But the HB-56 or similar would work well, also. 55's are just fine.

I used the supplied 1/16"ply control horns. These work fine and look better than nylon jobs. But I do glass both sides w .75oz cloth and thin CA. Never had one fail. And they have been used on planes much larger than this. Servos are attached to the ply servo hatch with flex-zap, after roughing the servo side.

Linkage is .032 wire with .032 threaded sleeve, nylon clevis. The linkage is very short, flexing never happened on the first Cutlass.

Belly is full of sunday dinner, time to relax with a couple of brewskies and watch Brett throw the pigskin..

Fuzz
Nov 01, 2009, 05:46 PM
To drive or to fly......BOTH!!
FresnoJay's Avatar
Looking good Fuzz.

Jason
Nov 01, 2009, 06:12 PM
Suspended Account
Quote:
Originally Posted by St. Martin
Hi Jason
I have several Wattage Shrouds. The rotor here is actually a 505 from WeMo. They are slightly larger. I grabed one cut to fit the Wattage and it fits loose. Same with a few KY rotors, that fit the Wattage. Speaking of which.. At power levels below 500W the KY rotor pulls better in the Wattage shroud VS the cut minifan. The cut minifan has to be absorbing more than 500W before it is faster than the KY. I attribute this to blade area or possibly the stators in the Wattage(3) 505(4)
I think there is a lot of lost efficiency with the Wattage/cut-minifan combo. The 505 rotor really works much better with the WeMo stator. On another downside, You cannot use full ducting and enclose the "bell" on the Wattage.

But I do have two jets that use the Wattage/KY combo. And they perform great at 425W.


I'll post pics tomorrow. I have both verticals done, fuse nose section framed, and the wing sheeting ready for use. It takes me a little while on builds like this. This proto requires the edited construction pics and build manual. This takes time. For this reason, I'm not going to get into too much detail, here on the thread. It will all be covered in the kit. And seeing I type with one finger....

Fuzz


Sorry The stators in the Wattage fan is 4 not 3, see photo.


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