Dang, Can I cut an inch off the engine mount? [Archive]

Brian Jackson

10-07-2004, 05:11 PM

Yeah, I might do that. But it only cost $6.50 for 4 ft of the angle, so I'll just order some more. I'll probably work on the fuel tank mount before I go to work tommorrow.

What have you done with yours so far?
Hmmm... well the neighbors think I'm nuts for hacksawing aluminum out on my rear deck at midnight; it's the only place I have enough space to deal with the raw tube & angle stock lengths. My wife (whom also thinks I'm nuts but puts up with me for reasons unknown) took the attached photo. I superimposed it to show how I'm labeling each item pre- and post-cut for orientation, including the cut-lines (oversized for blade kerf).

Determining which tube would be what gyro part was kind of fun. As I'm sure you've witnessed, raw materials, when shipped, generally arrive with varying degrees of minor scratches and/or divots. They're typically so miniscule as to vanish when buffed. But occasionally one would require a bit more buffing to eliminate completely, if at all. As nit-picky as this sounds, I mapped out the locations of every divot & scratch that I could "feel" with my fingers onto the 3D model of my GyroBee airframe. This allowed me to play with my cut locations such that any imperfections in the stock would either be in low-stressed or non-visible areas.

That's why I cleaned, measured & labeled every piece of raw stock before I made the first cut... which began at 10:10 PM last night. As of 10:20 PM I'm now the proud father of a 48.05" baby keel tube! But as I suppose most fathers will attest, the real work is just beginning. At least I don't have to put her through college.

Keep pluggin' away, Kevin. Perhaps eventually our gyros will meet and become friends. Who knows... we might even be flyer-in-laws someday with little balsa wood models running around to look after :D

Cheers,
Brian Jackson

KDOG

10-08-2004, 04:35 AM

I labeled mine as well, but I just used a sharpie to write on the inside at one of the ends of each tube so it was not visible. I will probably work on my fuel tank mount today.
I'm going to look into a hacksaw like you have...looks pretty tough.

scottessex

10-08-2004, 05:27 AM

I label with a sharpie, I'd be lost without it!

And KDOG, sometimes you will spend a whole day making a really nice looking piece of scrap! I did it last weekend!
that is just the nature of homebuilding.
Just measure, measure and then re measure before drilling or cutting.
and some time you will cut it twice and it's STILL too short!

Jim

10-08-2004, 06:07 AM

Don't feel to bad about mistakes. Years ago I went to a workshop on the Sonex by John Monnett. (Renouned designer of the Sonerai, Monerai, Moni and others.) Even he once cut on a line that was intended for bending. :eek: :eek: The aluminum had to be discarded.

After that I use two sharpies - one for cutting lines and another colour for the rest. :rolleyes: :rolleyes:

And yet, even with that I have made my fair share of mistakes. :D :D

Jim Gordon

KDOG

10-08-2004, 08:46 AM

Heh, heh. Yeah, I suppose it won't be my last mistake either. Using the 2 different color sharpies isn't a bad idea...

Brian Jackson

10-08-2004, 03:17 PM

I label with a sharpie, I'd be lost without it!
Scott,
I originally wrote right on the material with a black Sharpie "Permanent" marker and it wiped right off... So much for being permanent. This was even after I'd washed and dried the stock. What gives? I'd rather write directly on the material, but if an inadvertent hand swipe renders the info unintelligible I could be in for some frustration. How do you avoid accidently wiping off your writing when working/tooling the stock?

Thanks,
Brian Jackson

KDOG

10-09-2004, 08:07 AM

Be careful. Thats why I write on the inside end of the pieces. I also put little arrows to indicate front and top.

banaari

10-09-2004, 03:33 PM

Hmmm... well the neighbors think I'm nuts for hacksawing aluminum out on my rear deck at midnight

That's one of the most encouraging posts/photos I've seen so far... the sight of someone actually cutting airframe metal is EXTREMELY inspiring, especially seeing as I'm still in that horrible limbo phase waiting for the first tubing to arrive. Can't wait to get started on that psychologically all-important first piece. :)

John

PW_Plack

10-10-2004, 12:13 AM

Put a small piece of Scotch Magik translucent tape inside the end of the tube, and write on that. It won't wipe off. Just don't get carried away if you're going Part 103. :)

scottessex

10-10-2004, 04:59 AM

I haven't had any problem with the sharpie coming off. But I don't clean any of the material, I wipe it off, but don't use alumaprep untill the holes are drilled and all shaping is done. then the sharpie comes off.

Brian Jackson

10-10-2004, 12:41 PM

That's one of the most encouraging posts/photos I've seen so far... the sight of someone actually cutting airframe metal is EXTREMELY inspiring, especially seeing as I'm still in that horrible limbo phase waiting for the first tubing to arrive. Can't wait to get started on that psychologically all-important first piece. :)
Thanks, John. Sounds like you and I are a mere days apart in construction. I understand how important it is to maintain psychological enthusiasm for a project so detailed as building an aircraft. It's easy to get overwhelmed when one tries to contemplate the totality of the daunting task ahead all at once. That's why I focus on minor tasks... Rough cutting lengths, etc.

Thank you to Scott, Paul and others for the input regarding proper Sharpie usage. :D It's amazing how much support exists here, even over the dumbest details. What a blessing this forum is and has been.

Today I cut the raw lengths of my diagonal seat braces, which I'm oversizing slightly in length. The reason is that, to my eye, it always bothered me that the lengths of those items were cut perpendicular with the material rather than planar with the keel. I'm cutting my seat braces such that they terminate on a plane parallel with the keel instead of square-cut. To my eye it just looks a little better, and adds only negligible weight; a few grams at best.

I decided to proceed with development of a composite empennage (tail feathers) instead of buying one. Ralph Taggart's plans offer a wealth of proportion information, which I'm strictly adhering to. The attached image shows the T-tail I'm doing for my GyroBee. It has a 3-degree dihedral and its H-Stab is pitched down negative 2.5 degrees.

I modeled this arrangement loosely on the geometry of the Boeing 727, which I've always loved. This design places the horizontal Stabilizer further back than the tailboom allows, which increases its moment arm and effectiveness.

John, there's me, KDOG, and a few others that are current GyroBee builders. We exchange phone numbers and touch base regularly. DO NOT email me because I don't even check my email anymore; Long story for another time. But I'd like to speak with you in real time. Let me know. Thanks.

Respectfully,
Brian Jackson

Victor Duarte

10-10-2004, 12:46 PM

nice brian !
just a comment, why dont you exploit a larger rudder surface ? if you build it, post pics please, it s of interest
cheers

PW_Plack

10-10-2004, 01:02 PM

Brian,

Looks cool, but will the rotor still clear in in back?

Brian Jackson

10-10-2004, 01:53 PM

Looks cool, but will the rotor still clear in in back?
Yes, by several inches. Originally I scaled the form such that the center camber of the H-stab was coplanar with the prop centerline. This made for a huge-ass tail, so it was scaled back such that the flat plate areas and main rotor clearances were in check.

Besides surface area, my biggest concern was pitch angle of the stab. I used 2.5 degrees negative pitch with a symmetrical airfoil. In fact I'm using the same airfoil sections as the Blackhawk. Modeling is a real bitch, but once done the foam core can be CNC machined to spec, then 2X kevlar wrapped.

Curran3

10-10-2004, 05:26 PM

I'd add 6" of clearance over what you compute you need at rest. Sooner or later you may make a hard landing or have a mild blade flap. Both will cause the rear blade to slam down with some downward momentum. That will carry it significantly lower than just the angle at the rotor head stop. At that moment your beautiful foam/glass tail may take on a new shape.
Curran in Jacksonville
Gyrobee, Soma, PA22

Brian Jackson

10-10-2004, 06:05 PM

I used a "worse case scenario" to design around. Rotor cyclic = -25 degrees. If we cant generate a useable scenario from this, we're in real trouble

animal

10-10-2004, 06:53 PM

Thanks, John. Sounds like you and I are a mere days apart in construction. I understand how important it is to maintain psychological enthusiasm for a project so detailed as building an aircraft. It's easy to get overwhelmed when one tries to contemplate the totality of the daunting task ahead all at once. That's why I focus on minor tasks... Rough cutting lengths, etc.

Thank you to Scott, Paul and others for the input regarding proper Sharpie usage. :D It's amazing how much support exists here, even over the dumbest details. What a blessing this forum is and has been.

Today I cut the raw lengths of my diagonal seat braces, which I'm oversizing slightly in length. The reason is that, to my eye, it always bothered me that the lengths of those items were cut perpendicular with the material rather than planar with the keel. I'm cutting my seat braces such that they terminate on a plane parallel with the keel instead of square-cut. To my eye it just looks a little better, and adds only negligible weight; a few grams at best.

I decided to proceed with development of a composite empennage (tail feathers) instead of buying one. Ralph Taggart's plans offer a wealth of proportion information, which I'm strictly adhering to. The attached image shows the T-tail I'm doing for my GyroBee. It has a 3-degree dihedral and its H-Stab is pitched down negative 2.5 degrees.

I modeled this arrangement loosely on the geometry of the Boeing 727, which I've always loved. This design places the horizontal Stabilizer further back than the tailboom allows, which increases its moment arm and effectiveness.

John, there's me, KDOG, and a few others that are current GyroBee builders. We exchange phone numbers and touch base regularly. DO NOT email me because I don't even check my email anymore; Long story for another time. But I'd like to speak with you in real time. Let me know. Thanks.

Respectfully,
Brian Jackson

nice pic what program do you use to draw those? I had turbocad and never could get it to do the 3-d drawings.

banaari

10-11-2004, 12:27 AM

KDOG

10-11-2004, 05:41 AM

banaari: Nice Bee you have in your garage there!

Brian: Nice tail!! Looks like its right off an airliner!!

Update for mine: Fuel tank mount is complete!!! Took me a while, there was some frustrations. It took me 4 tries to get the diagonal pcs cut and drilled right, but now its done. I just have a lot of 1"x1" angle scrap lying around. I think I can use some of those pcs for the rudder pedal though, I'll have to check...

Brian Jackson

10-11-2004, 07:18 AM

nice pic what program do you use to draw those? I had turbocad and never could get it to do the 3-d drawings.
I'm using Rhino 3.0 for the surface modeling of the tail and matching instrument pod. I'm still kinda new to the program, but for complex surfacing it's kick-butt! I wouldn't even attempt to ask AutoCad to handle this.

Victor Duarte

10-11-2004, 07:22 AM

brian, try solidworks if you can, i pacticed a little rhino, fine for nurbs, not really cad.
if you can, really test SW2005, it s kicking ass.
cheers

animal

10-11-2004, 07:42 AM

I'm using Rhino 3.0 for the surface modeling of the tail and matching instrument pod. I'm still kinda new to the program, but for complex surfacing it's kick-butt! I wouldn't even attempt to ask AutoCad to handle this.

Where do I get that at? and what's it cost?
thanks.

Brian Jackson

10-11-2004, 07:56 AM

Where do I get that at? and what's it cost?
thanks.
You can get it at rhino3d.com (http://www.rhino3d.com/). I believe you can D/L a trial copy, but I'm not sure of the cost. I know it's cheaper than AutoCad (and free if you work at the right place! :D ).

Cheers,
Brian Jackson

Doug Riley

10-11-2004, 08:44 AM

Brian: Have you considered the nonexistent bracing of the stock Gyrobee tail tube? It's held on by just two 1/4" bolts, both way forward. How much cantilever load can the tube stand? How about the fact that the mass of your HS is well away from the centerline of the tube (because it's at the top of the vertical fin)? You have torsional loading to consider, too. You want the tail not only to stay attached to the aircraft, but also to be rigid enough not to move about or vibrate.

Finally, a cantilevered structure is always heavier than a triangulated one, unless strength is sacrificed.

The placement of the Starbee and Watson HS's fairly low on the vertical fin was driven by these considerations.

Ralph

10-11-2004, 11:26 AM

Brian,

Still another way to make Doug's point is that your T-tail configuration develops a significant lever-arm right out on the end of the tail boom. Unless you add some additional bracing beneath the stab you will also be transferring the stab loads to the attachment structure for the vertical fin through the lever-arm represented by the entire height of the fin assembly.

Also, while the swept-back stab is very sexy, that configuration has two distinct problems:

(1) More complex twisting loads are transferred to the attachment points for the vertical fin and stab.

(2) The swept-back portion increases your vulnerrability with respect to a rotor strike. Once you have seen blades flap, your entire consept of rotor geometry will be forever changed! Someone noted 6-inches as a clearance factor between the blades and the vertical fin. On page 103 of the documentation, you will note that the suggested clearance is 6-12 inches. Based on personal experience, I would prefer to be at the high end of that range.

Ralph

gyropilot

10-11-2004, 02:54 PM

I have a Rotax 503 on my GyroBee.

Following Bensen's and Doug Riley's lead, I tilted the engine support nose down by 3% to more closely align the prop thrust with the VCG, but I otherwise fabricated everything to Ralph's stock dimensions during initial construction back in 1999. When I finally got around to test fitting the engine on the support angles, I quickly discovered that the 503 model is longer than the 447 model. Angling the engine nose down only made the situation worse... turned out the support angles were way too short! In the end I think I wound up making 3 sets of engine support angles before I got everything just right.

Now I'm adding oil injection to my 503. Unfortunately the oil injection pump adds almost 2" to the front of the engine, making it yet longer still and requiring it to move rearward! So once again... new support angles!

Because of shifting the engine back so far, I've become concerned about the leverage on the rear of the engine support structure. Besides being longer, the 503 is also heavier than the 447. As a result, I've decided it's time to add a single vertical brace (a strut) from the rear of the engine support angles down to the top of the tail boom. Rear engine support struts are found on many gyro airframes. Of course I hate the thought of adding more weight to the airframe, but it's necessary for safety. This is the sort of vicious cycle one gets trapped in when making "upgrades."

I finished the new longer engine support angles last week and have been working on the vertical support strut for the last week or so. As soon as it's finished I'll post some pictures.

After the support strut it's onto figuring out where/how to mount the oil tank and then painting everything.

Regards,

John L.

Brian Jackson

10-11-2004, 06:03 PM

Thank you Doug & Ralph. Your input is greatly appreciated and respected. Part of what I love about this forum is the high level of design expertise among its more learned members such as yourselves. I love experimenting with new ideas knowing full well they'll be shot full of holes once knowledgeable builders & designers here examine them. But I always end up learning a lot more than I did before, which is why this forum exists. To that end the design time is never wasted.

By the way, in my post on page 2 where I said "The attached image shows the T-tail I'm doing for my GyroBee" I was referring to the 3D model only, for conceptual visualization; I would never blindly and ignorantly commit to building something of this nature without critically scrutinizing its design with the aid of talented builders & engineers. Too many "ifs" in the equation, as you've noted above.

I'd like to volunteer something for consideration with respect to the "twisting load" and "nonexistent bracing of the tail tube" issue that you guys mentioned in your posts above. Could not the tailboom be coupled with the keel by simply not cutting off the keel near the mast? In the attached image the keel is extended by about 16" and cheek-plated with the tailboom ahead of the propeller. The extended coupling of these two items might create a more rigid structure where a much more modest T-tail could mount without the averse consquences.

I'm going for "near ultralight" Experimental. I'm getting my license and registering it... so ounces aren't a hueg deal. I'm getting my license.

Thanks for any input.

Respectfully,
Brian Jackson

Doug Riley

10-12-2004, 09:06 AM

Brian: I don't see why not. Ralph may have more input for you.

HOWEVER: How about applying the "if it ain't broke" principle (closely related to Occam's Razor)? I'm not just being a wise guy here. The trouble with modifying before you've flown is that it's impossible to spot the real defects that actually NEED fixing. Most "modifications" by first-time builder-pilots are based on an outsider's aesthetic judgment. Very often, the funny- and/or awkward-looking aspect that you seek to change is a precisely-designed feature, put there for a good reason. What's more, one change begets three more (as you can already see) and slows you down. Finally, you REALLY need to learn on a craft that's a known quantity. A stock Gyrobee is just about as benign and predictable as a gyro can get.

Trust me: the tail setups and structures currently in use on flying Gyrobees (including mine, which is the original Doc Watson machine) don't need fixing. The only way, in my opinion, that they could be improved is to go to a Dominator-style "tall tail." This wouldn't change their pitch stability noticeably (they already fly quite similarly to a Dominator in pitch). It would, however, eliminate most of the yaw and roll effects caused by prop torque... something that no variation of the half-height vertical surfaces can do.

KDOG

10-12-2004, 10:12 AM

Brian. Do you need to lengthen it that much? It seems that 10-12 inches longer would give you the support you are looking for. Also, that will put more weight to the rear and the bee must tilt forward 9-11 degrees on your hang test!!!

As for me, I am going along with what Doug is saying. I'll be flying a Starbee tail or a nice tube and fabric tail of similar design. UPDATE on my bee: rudder pedal braces cut and shaped. Next will be ordering the alum sheet stock for the pedal webs and seat plates!! WooHoo!!!

Brian Jackson

10-12-2004, 02:21 PM

As for me, I am going along with what Doug is saying. I'll be flying a Starbee tail or a nice tube and fabric tail of similar design.
Me too, Kevin. Don't get me wrong, I'm not making any changes from the stock design or StarBee tail on my first build. I'm merely brainstorming ideas for a future project... "pondering the possibilities." Sometimes it helps me to have a 3D graphic of an idea. As for the tail, I really would like to try my hand at composites, but I'm going with a conventional tail design to start with. As I learn more about what works and what doesn't, I'd like to experiment with some of these ideas, but that's a couple years away at least.

Cheers,
Brian Jackson

Brian Jackson

10-12-2004, 02:30 PM

...also, the only additions from the stock design will be strobes, prerotator, a SportCopter rotorhead, and perhaps brakes. That will probably put me slightly over the Part 103 UL limit, which is why I'm going to register the ship.

Dean_Dolph

10-12-2004, 02:32 PM

.......Trust me: the tail setups and structures currently in use on flying Gyrobees (including mine, which is the original Doc Watson machine) don't need fixing. The only way, in my opinion, that they could be improved is to go to a Dominator-style "tall tail." This wouldn't change their pitch stability noticeably (they already fly quite similarly to a Dominator in pitch). It would, however, eliminate most of the yaw and roll effects caused by prop torque... something that no variation of the half-height vertical surfaces can do.Doug, I thought you, and others, had stated that a horizontal stab in the prop flow serves the same purpose as the tall tail in eliminating the roll from engine torque. If that is correct, then assuming that structural concerns could be satisfied, why couldn't the Watson tail be modified enough to serve that purpose? If so, then this would solve the roll problem which sounds like it is harder for a newbie to handle than yaw.

Brian Jackson

10-14-2004, 02:49 PM

Brian,
great stuff - flick me an email or message with your phone#, and a reasonable contact time during the weekend; you're currently 6 hours ahead of us and 1 day behind.

cheers,
John

ps. Nice piece of tail!
Hi John.
Call me at 269-687-8927 (home phone). I'm usually available from 6:00 PM to midnight on weekdays, and 8:00 AM to midnight (or later) on weekends. I live in Michigan, but to double-check the time translation you can look at this post time and compare it to 5:50 PM. (my post time). Subtract that and you'll get my precise time zone differences in hours.

Hope to hear from you. Thanks.
Brian Jackson