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Old Jan 08, 2003, 10:46 PM
Mark Triebes
MarcusT's Avatar
Elk Grove, CA
Joined Sep 2001
868 Posts
Enigma Questions

Hey guys . . .

There was a thread about the Enigma a while back, and a few questions were left unanswered . . . I've just picked up one and was hoping those with experience with this plane could speak up with some helpful pointers.

First off, is there a consensus on boom length? Is shortening the boom a couple of inches a good idea in helping with keeping the nose weight to a minimum?

What is the best way of attaching the vertical fin to the boom? Sal's instructions call for cutting a slot in the fin and gluing . . . anyone come up with a better way?

What is the best way to mount the horizontal stab? There was talk about locating the stab under the boom rather than on the small pylon . . . any thoughts?

Launching peg . . . instructions call for it to be located just behind the main spar and 1 3/4 inches in from the tip . . . seems a bit too far in to me . . . where is the best location for a dlg peg to be?

Thanks in advance, guys . . . any helpful comments are greatly appreciated.

Mark Triebes
Acme Flying Machines
www.acmeflying.com
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Old Jan 09, 2003, 11:29 AM
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United States, CA, Glendale
Joined Jun 2001
434 Posts
Hey Mark,

While I can't help you with your DLG, I just wanted to say that I was very impressed when I saw your Tempest at Visalia last year. It's very nice. Any idea when it will be available in a cruciform tail. How does the V tail plane handle? I was very happy with my Super V from way back but my Herra felt like it could use larger V tails which turned me off of V tailed gliders again. Anyway, just wanted to say great job.

Best Regards,

Marc Webster
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Old Jan 10, 2003, 02:24 PM
Mark Triebes
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Elk Grove, CA
Joined Sep 2001
868 Posts
Hey Marc . . .

Thanks for the kind words on the Tempest . . . I've been thrilled with the plane's performance so far . . . only had about 4 fllights on it before Visalia . . . since then have put a few hours on mine and just love it.

The cruciform version will be available in about a month . . . I'm hooked on the V, but there are still some people who just don't do the V thing!

I made the V-tail plenty large on this plane and it shows in the performance . . . great handling characteristics even at very slow landing speeds. Hopefully as more and more of the V's get out there, people will realize that they fly just fine.

Mark Triebes
Acme Flying Machines
www.acmeflying.com
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Old Jan 20, 2003, 09:26 PM
fragged you
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Los Angeles, CA
Joined Mar 2002
112 Posts
a new enigma is born, 10.8 oz

Just finished building my Enigma.. came out to be 10.8 oz. I am still scratching my head wondering how it shot past 10. I read over the [poor] instructions 10 times before I lifted a finger to build and thought everything over according to this philosophy: right, light, strong. But with all the components crammed into the front of the fuse the verdict still came out heavy. Here's what I used:

Wing:
  • 2 MPI MX-30 servos in the wing, with the provided clevises and pushrod
    - attached to the wing using 1/8" thick servo tape
  • 2 servo extensions, soldered onto the MX-30's above
  • 2 dubro nylon horns
    - attached with 5 min epoxy

Tail section:
  • 2 dubro nylon horns
    - attached with 5 min epoxy
  • assembled as instructed with 5 min epoxy (sparingly)

Fuse/Boom join:
  • sanded and joined with 5 min epoxy

Fuse nose (in order from nose going aft):
1: 4 cell 250 mAh battery
1: .75oz lead
2: Hitec 555 Rx (no cover)
3: 2 Cirrus CS-10 micro servos (comparable to the MX-30's)
- including two balsa pieces to set the servos, CA'ed in with instant ZAP glue

Afterthoughts:
  • I seriously don't think the wing was meant to hold two servos. 8" out from the fuse and they don't fit "well" inside the two balsa skins
  • The wing came pre-drilled.. which is convenient BUT with the dowel installed it didn't sit tight on the saddle and I had to put a little velcro to keep it from dancin' around
  • The provided manual gives conflicting instructions on where to drill the holes fo r the pushrods in the boom.. and where to install the control horns on the h/v stabs... be forewarned.. I think they were looking at a Martian clock or something. Forward looking aft, the "8 o'clock" should have been "2 o'clock" and the "3 o'clock" should have been "9 o'clock." -- this caused me MUCH anger when I discovered the instructions were wrong and I already had done the first cut.
  • The provided wooden-laser-cut control horns are total junk, throw them away. They broke on me when I was trying to install the provided Sullivan clevises. I replaced them with nylon Du-bro horns.. modified to be the same shape as the wood ones they replaced. Turned out to be much stronger.
  • The carbon pushrods were a good idea and I kept those, but the CS-10 servos barely have enough room to move the arms in the fuse without rubbing up against the side. I staggered them and threw both throws against the left and it worked out nicely.

That's it. I need to investigate ways to remove 1oz, any suggestions? Took it out for a trim today but forgot the Tx! Ha! I'll post a flight report when I can make it back out to the field (WITH the Tx).
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Old Jan 20, 2003, 09:31 PM
fragged you
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Los Angeles, CA
Joined Mar 2002
112 Posts
Here she is, all done! It came out clean.. took 3 days to build including life's usual interruptions and honey-do's.
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Old Jan 20, 2003, 09:34 PM
fragged you
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Los Angeles, CA
Joined Mar 2002
112 Posts
Here is that control horn I was telling you about.. while testing the aileron servos the darn thing just popped out. Glad that didn't happen in flight!!

I have more photos, will post later.
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Old Feb 02, 2003, 04:06 PM
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West Boylston, MA
Joined Feb 2003
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Re: Enigma Questions

Quote:
Originally posted by MarcusT
Hey guys . . .

There was a thread about the Enigma a while back, and a few questions were left unanswered . . . I've just picked up one and was hoping those with experience with this plane could speak up with some helpful pointers.

First off, is there a consensus on boom length? Is shortening the boom a couple of inches a good idea in helping with keeping the nose weight to a minimum?

What is the best way of attaching the vertical fin to the boom? Sal's instructions call for cutting a slot in the fin and gluing . . . anyone come up with a better way?

What is the best way to mount the horizontal stab? There was talk about locating the stab under the boom rather than on the small pylon . . . any thoughts?

Launching peg . . . instructions call for it to be located just behind the main spar and 1 3/4 inches in from the tip . . . seems a bit too far in to me . . . where is the best location for a dlg peg to be?

Thanks in advance, guys . . . any helpful comments are greatly appreciated.

Mark Triebes
Acme Flying Machines
www.acmeflying.com
Dear Mark,

I'm very happy with my Enigma. Only construction pointers I have are:

1) Might want to reinforce the portion of the fin below the boom.
2) Personally, I wouldn't shorten the boom. Even if you end up at 11 oz., it still flies great!
3) Do wrap 1 layer clear packing tape around the pod cover joint; ads a lot of crash-resistance.
4) Be sure to fillet the control horns with epoxy.
5) I slotted my boom for the fin, which worked out fine. Also attached the stabilizer above, using the supplied pylon. works great.
6) I thin CAed the pushrod tubes down either side of the boom, elevator nearest throwing hand, rudder opposite throwing hand. Gives you free rudder and elevator help at launch due to boom flex moving the surfaces appropriately. Can be flown without any preset for poor, non-computer-radio types like me, but you'll need the CG at 40% root chord to get enough pitchup on launch. (Computer radio and preset would get higher launches.)
7) I went against Sal's advice (no disrespect, Sal :-) and ran my antenna in the light wing to save tail weight. Reception is fine.
8) Stay away from HS55 servos. They're thermometers; the center changes a lot with temperature.
9) You'll need nose weight for the full length boom, but the launches are good!
10) Put the throwing peg 1/2" from the edge of the curved tip and 2 1/4" from the trailing edge (measured perpendicular from the trailing edge).

Then have a blast! I am.

Peace,

Marc
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Old Feb 03, 2003, 12:37 AM
fragged you
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Los Angeles, CA
Joined Mar 2002
112 Posts
Enigma damaged, need advice rebuilding the fin

Hey guys -- second flight today.. didn't go well again. First flight went straight up.. and straight down. Minimal damage to the plane, maximum damage to my pride. Today's flight was a trim test with a more experienced flier helping out (whose name just so happens to be Mark as well).. flight seemed to go ok but upon landing the vertical stab broke off when it hit the ground (and it didn't hit hard at all).

I have the feeling I attached it wrong. Sal's instructions weren't clear so I went off the few enigma pics I could find of this section. Here's what I did:[list=1][*]Cut a 1/8" slot in the upper and lower parts of the rod just barely big enough to fit the fin[*]Using an exacto knife, cut a very shallow slice into the fin (on one side only) to allow the ends of the rod to fit snug against the fin[*]Installed the fin onto the body with a minimal amount of 5 minute epoxy[/list=1]

This apparently made for a very weak bond. When the fin snapped off this afternoon, it cracked the boom with it about 1" ahead of the fin. Here's what I was planning on doing to fix it:
  1. Epoxy a 3/8" tall carbon fiber piece to both sides of the fin where the boom will be installed
  2. Epoxy a 1/2" carbon fiber piece to the boom completely covering the area that cracked.
  3. Glue the fin to the newly reinforced boom with Household Goop

OK.. so now tell me.. is this a good idea? How did you all affix the vertical fin to the boom? The instructions were SOOOOO vague.

Also, how did you affix the horizontal stab to the wood piece? I epoxied it but it seems to me a little weak too.

--r
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Old Feb 04, 2003, 02:26 PM
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West Boylston, MA
Joined Feb 2003
1,093 Posts
Trimming/Rebuilding Advice

Quote:
Originally posted by gamehaus
Hey guys -- second flight today.. didn't go well again. First flight went straight up.. and straight down. Minimal damage to the plane, maximum damage to my pride. Today's flight was a trim test with a more experienced flier helping out (whose name just so happens to be Mark as well).. flight seemed to go ok but upon landing the vertical stab broke off when it hit the ground (and it didn't hit hard at all).
Hi! Too bad about the vertical tail. This seems to be the weakest link in all these gliders, and I'll add my not well proven thoughts about how to rectify that below. As to trim flights, I did all my trimming in firm, straight-ahead glides. Once I got it trimmed that way, with a fairly forward CG of 40% root chord, my self-taught discus launches were pretty uneventful and satisfying. You may want to try flying with a more forward CG for a while.

Quote:
I have the feeling I attached it wrong. Sal's instructions weren't clear so I went off the few enigma pics I could find of this section. Here's what I did:[list=1][*]Cut a 1/8" slot in the upper and lower parts of the rod just barely big enough to fit the fin[*]Using an exacto knife, cut a very shallow slice into the fin (on one side only) to allow the ends of the rod to fit snug against the fin[*]Installed the fin onto the body with a minimal amount of 5 minute epoxy[/list=1]

This apparently made for a very weak bond. When the fin snapped off this afternoon, it cracked the boom with it about 1" ahead of the fin. Here's what I was planning on doing to fix it:
  1. Epoxy a 3/8" tall carbon fiber piece to both sides of the fin where the boom will be installed
  2. Epoxy a 1/2" carbon fiber piece to the boom completely covering the area that cracked.
  3. Glue the fin to the newly reinforced boom with Household Goop

OK.. so now tell me.. is this a good idea? How did you all affix the vertical fin to the boom? The instructions were SOOOOO vague.
Your plan sounds reasonable to me. I first tried fixing the vertical tail to the side of the boom with epoxy, and knocked it right off. I then slit the boom, as you did, and the first landing sideload (caught the wing peg in tall grass) broke the bottom of the tail. I then reinforced the tail below the boom with balsa (all I had at the time), which worked.

Unfortunately, the next hard sideoad, some months later, split the boom, like yours. I made a repair much as you've described above, and it seems to be holding. I've also read a suggestion, perhaps from Polecat Aero, to wrap and CA some kevlar thread just ahead of the vertical tail to preven the boom splitting there in a mishap.

Next glider, though, I'm slotting the fin instead of the boom, and reinforcing the fin below the boom with carbon. The slot in the boom just seems to weaken it unacceptably.

Quote:
Also, how did you affix the horizontal stab to the wood piece? I epoxied it but it seems to me a little weak too.

--r
I epoxied mine. It got knocked off once, so I now had a little epoxy platform atopt the pylon. I've since used thin CA to glue the stabilizer back onto that epoxy platform with good results. The stabilizer isn't very vulnerable, except to hangar rash, and as Sal at Nesail rightly pointed out, the best way to attach all these parts is such that they can be knocked off clean, rather than shattered in a crash. The joint seems flimsy, but I've found it completely functional.

Hope this helps.

Sincerely,

Marc
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Old Feb 04, 2003, 04:06 PM
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Albuq N.M.
Joined Dec 2001
21 Posts
I would like to thank you guys for the info that has been provided in regards to the enigma,,,,,,received mine today,,,was having a hard time deciding which one to get,,,,but nsp ran a special on the enigma ,,,,,,after the initial shock,, due to the color of mine,,,yellow with electric, pinkish red stripes,,,,,i calmed down and thought,,wow,,,,this is going to be neat,,,,,
Now,,,if there was just a few more threads of how to,,,Marc,,you mentioned slotting the rudder,,,,do you mean cutting it in half and having a top and bottom section,,,,,so that maybe only the lower half gets torn off?? also mentioned was ca,,ing the rods to the carbon shaft,,,,dont they usually break loose from the carbon rod,,,seems like goop might work


Bill
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Old Feb 04, 2003, 08:23 PM
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West Boylston, MA
Joined Feb 2003
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Enigma Answers?

Quote:
Originally posted by soarin3
I would like to thank you guys for the info that has been provided in regards to the enigma,,,,,,received mine today,,,was having a hard time deciding which one to get,,,,but nsp ran a special on the enigma ,,,,,,after the initial shock,, due to the color of mine,,,yellow with electric, pinkish red stripes,,,,,i calmed down and thought,,wow,,,,this is going to be neat,,,,,
Now,,,if there was just a few more threads of how to,,,Marc,,you mentioned slotting the rudder,,,,do you mean cutting it in half and having a top and bottom section,,,,,so that maybe only the lower half gets torn off?? also mentioned was ca,,ing the rods to the carbon shaft,,,,dont they usually break loose from the carbon rod,,,seems like goop might work


Bill
Dear Bill,

Congratulations on your purchase!

I suffered color shock, too, then buggered up my own graphics to make my Enigma truly ugly. I figure this wing will never take any damage; if it had been beautiful, I'd have smashed it for sure!

I have to tell you, it doesn't matter. Flying DLG is such a pleasure.

Firstly, the pushrod housings. Thin CA worked for me, perhaps too well. These are NEVER coming off that boom. I installed the tail surfaces forst, and drilled holes in the back of the pod 3/4" aft of the wing bolt and 1/2" apart, just above the boom. I inserted the pushrod housings to where their aft ends were positioned appropriately, then had a friend hold a 4" section of housing to the boom and put a drop of thin CA on it. After it dried, we moved to the next 4" section. (I recommend placing them 180 degrees apart, down the left and right sides, with the rudder rod away from the throwing peg.) You'll need to leave the aftmost part of the elevator pushrod housing free of the boom, and put a little balsa pylon on the elevator pylon to route the last bit of housing. (I will try to put a picture of this in a subsequent post; camera batteries are dead right now.)

That did work, but tail weight on the Enigma is an issue. You might want to 1) cut sections out of the housing and glue pieces to each side of the boom every 1.5(?) inches, or 2) buy a pair of much lighter carbon-spectra pushrods from PolecatAero.com for $3.25 each. I would do the latter next time around.

As to the fin, I've got to be honest with you and say, I don't have a design completely fleshed out. I'm convinced it's a bad idea to slot the boom. I think maybe cutting a slot for the boom in the fin, through two carbon strips and butting up to the third. Epoxy this slot over the boom and lightly fillet the joint (perhaps with epoxy and microballons; I'm so new to composites! I'm a balsa guy. Lastly, I'm tempted to make tapered patches of Aerospace Composite Products' Graphite/Kevlar or Graphite/S-Glass (easier to cut) and bond them in place on the fin, from just above the boom, over the curve of the boom and down to the bottom tip of the fin, one on each side. I suggest tapering them to avoid creating a stress concentration in any one place. If tapered, the fin will be stiffest near the stiff boom, and gradually more flexible toward the tip. Again, I'm just trying to resist landing side loads that result from catching a wing tip and whipping the tail to one side or the other.

Bottom line is, your engineering sense is as valid as mine here. Let me know what you end up doing.

Good luck, and enjoy your Enigma!

Peace,

Marc
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Old Feb 04, 2003, 09:34 PM
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Albuq N.M.
Joined Dec 2001
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Marc,,,,,,,

enjoyed your post,,,,looked around and found 2 setups on avenger post by ferradas,,,,,didnt like either,,,seems as tho the one about olegs is like a meat cleaver,,,wanting to cut the stab into,,upon landing,,,,the first one simular to your suggestion,,,if im right,,,,maybe its the best as it shouldnt damage the boom,,,and will tear off,,,,just a quick ca job at the field if it does come off....

i,m not an engineer either but,,,,,,I had an idea or two i,d like to bounce off of ya,,,,weight of the tail,,,,ratio 1 to 3 to nose,,,therefore I think I,ll go with a pull pull system using kevlar lines or something simular,,,,,,rudder/fin,,,,,have you seen the strakes on jets,,,why not cut fin into,,,,use upper half as control,,,per regular aircraft,,,and have bottom half as a yaw preventer on launch,,,,,mount it on bottom of boom,,,,180 degrees from upper fin,,,,maybe fillet it for strength.....

mounted servos in wing,,,used the fiberglass as cover for servos,,mounted wing,,,fits snug,,,tails next,,,,lord help us all....oh,,,i used the small green metal hydride battries for pack,,,approx inch and 1/2 long,,,cool,,,and the 55,s as servos....awaiting your reply,,,before i cut the fin into,,,,,the chicken i,am


Bill
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Old Feb 05, 2003, 08:46 AM
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Albuquerque, NM
Joined Aug 2002
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On mounting the tail surfaces:

On my Xp3, which uses balsa rather than foam tail surfaces, I cut a slot in the rudder about 1 1/4" long. That slot is a tight fit on the boom. Used CA to glue in place, then added 1" square fiberglass patches over the boom/rudder joint on both sides.

For the stabilizer, I'd use a piece of fiberglass long enough to go from the stabilizer, around the bottom of the boom, and back to the stabilizer. It should lap onto the stab for about an inch or so on each side of the boom.

As far a pull-pull, I wouldn't. I used pull-pull for my rudder, and its a real pain. If the cables are tight enough to prevent flutter, they've got so much tension on then its very easy to breack off the control surface with a slight bump. I'm always fiddling with the darn things to get the correct tension. Next time I'll eat the extra few gram in the tail and the nose and use a pushrod.

You need very tight, slop free controls for a good discus launch, and a pushrod is your best bet. Just make sure the rudder pushrod "pulls" the rudder in the direction to counter the launch.

I would not recommend actuating only the top of the rudder, this will cause a very undesirable rolling moment on launch.

John
Abq, NM
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Old Feb 05, 2003, 12:15 PM
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West Boylston, MA
Joined Feb 2003
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Enigma Replies and Photos

Quote:
Originally posted by jihlein
On mounting the tail surfaces:

On my Xp3, which uses balsa rather than foam tail surfaces, I cut a slot in the rudder about 1 1/4" long. That slot is a tight fit on the boom. Used CA to glue in place, then added 1" square fiberglass patches over the boom/rudder joint on both sides.

For the stabilizer, I'd use a piece of fiberglass long enough to go from the stabilizer, around the bottom of the boom, and back to the stabilizer. It should lap onto the stab for about an inch or so on each side of the boom.

As far a pull-pull, I wouldn't. I used pull-pull for my rudder, and its a real pain. If the cables are tight enough to prevent flutter, they've got so much tension on then its very easy to breack off the control surface with a slight bump. I'm always fiddling with the darn things to get the correct tension. Next time I'll eat the extra few gram in the tail and the nose and use a pushrod.

You need very tight, slop free controls for a good discus launch, and a pushrod is your best bet. Just make sure the rudder pushrod "pulls" the rudder in the direction to counter the launch.

I would not recommend actuating only the top of the rudder, this will cause a very undesirable rolling moment on launch.

John
Abq, NM
Dear Bill,

I tend to concur with all John's input (Thanks, John!) except for reinforcing the stab with glass. The stab just never gets hit, and if you take it off putting the glider in the car, a little thin CA puts it right back on.

John's input on pull-pull makes sense. PolecatAero.com's carbon-spectra rods are very light and should be durable. I wouldn't worry too much about all up weight. Mine's 11.5 oz. and flies fine. I don't see any way to get below 10 oz. with a servicable Enigma.

Be well,

Marc
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Old Feb 05, 2003, 12:55 PM
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Albuquerque, NM
Joined Aug 2002
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Marc, Bill,

On the XP3, the stab is actually removeable with two screws. The fiberglass reinforcing is seen on the Taboo and Avenger 2, probably others as well. With the foam stab on the Enigma, you're right, the fiberglass reinforcement is probably overkill.

These little birds are a lot of fun for $$$ invested!

John
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