8178

My Feedback: (17)

Your build thread and work is really great!

Is it an optical illusion that Helms' canopy placement looks correct and Naruke's looks like it is way too far back from the nose?

Bootalini

8178, I never looked at the 2 photos that close but I think you're right! And significant differences at that. Not only does Naruke's canopy start further back, it seems smaller both in length and height, and the high point looks further back along the fuse as well.

Anyone out there know if Naruke had several prototypes of the Aurora? Perhaps the design underwent a bit of tweaking along the way. I'm assuming that MK would make a point of being accurate when kitting a design....?? To be honest though, I much prefer the front end looks of Helms' Aurora. A point to ponder is that Steve had his 2 airplanes built for him by craftsmen in Japan I believe. We can't necessarily assume that they built them from MK kits.

stiletto660

You're right! I've seen both of those photos before, and never noticed the difference up until now. That's a good 4" difference. If we could somehow get our hands on these "Radio Technique" plans, it might contain some revelations.

chronos333

Jeff,
First, on the weight issue... you can save a lot by using a UBEC. Medusaresearch is providing some hi current/5A continuous/6 volt Ubec... that's the one you need.
Second, it is unfair to compare your setup to a 60-2 stroke.
Your power plant with a 14X14 is closer to a 120-4S powerwise ... except that it is a lot lighter
I did a power/weight comparison in our club's journal... but it is in french. Here is the link:
(look at page 8)
http://www.c2vm.org/buse/C2VM%20-%20...ril%202006.pdf

Best regards,

Alex

8178

My Feedback: (17)

Jeff. I like the Helms canopy placement best too.

chronos333

for the ones who likes vids:
http://www.rcgroups.com/forums/show...717#post6277005

Bootalini

Alex, I was under the impression that a BEC was not yet available for the higher volt/power application that we're discussing here. I'll check into that as you're right...I could save the weight of the airborne radio pack. I wonder if adding a BEC to an ESC increases it's weight?

Ref the newsletter, that's a very informative E vs Glow comparison that should open a few eyes among the 60 size pattern crowd. For those of you that are French impaired, I think you can easily interpolate all the page 8 info except the last para "en termes de prix" which means "in terms of price" - Alex states that the price of the 2 setups is roughly the same except for the fact that because of the present charging rate limitation of lipos, you have to go out and purchase at least 1 spare lipo pack unless you want to bring a shaving kit with you to the flying field.

An extra 8S pack (3700 mAh) will run at least $300 but if you consider that a properly maintained pack should last 200 flights, that translates into a fair bit of flying. Compare that to the price of 15% glow fuel X 12-14oz/flight, expensive glow plugs etc, it's not so bad. I'm also told that if you don't over-amp these electric motors, they have a lonnnnnggggg life. When I was flying seriously, I never got much more than a season out of a piston/liner including the shadel ones, and I changed both bearings at least twice a year as well........I think you get the idea. For the glow guys (including me) the pain up front is buying the charger, discharger etc......and we're getting older and becoming resistant to change.......wink, wink.

My cores arrived late yesterday. Mike Hester (of Black Magic fame) custom cut them for me including boring the holes for the wing and stab tubes. Mike did a great job and I owe him big thanks and my strongest endorsement for any of you that may deal with him in the future. Keep in mind that I'm picky and my last 4 airplanes were kitted by Henry Piorun and Greg Marsden, both of which are know for their excellent craftsmanship. Thanks Mike!

chronos333

Wow Jeff, you were eating more bearings than I was! Maybe because nitro was cheaper in north-america. When I was flying seriously I set of bearing per season was OK... but they were quite noisy at the end of the season! (I was runing 5 to 10% nitro).

Now about the BEC, you have 2 kinds of BEC's:
- Linear Becs (like the ones on low voltage esc & some voltage regulators): avoid them if using more than 3S lipo and 2 servos! They are not efficient as they dissipate the excess energy in heat. Thus their power handling capacity is limited by their heat dissipation capacity. I almost lost my hotliner by overeating the ESC's bec.
- Switching BECs (UBEC/SBECS/etc...) they are the way to go. However, most are limited to 5 or 6S lipo input and 3amps continuous 5amps peak. Which is OK for 6/7 std servos (=3-4 digis or 3-4 high torques) but I like to have some headroom that's why a 5 amps continuous is great. Why 6V? Because I use micro servos! For this season my Ubec is out as I need weight (rx pack) in the tail to fine tune my cog (I can't put the 8S anymore in the back)

For the charger, go buy yourself an Astro 109D and some good lipo balancer... the cheapest Watt/$. The current market price for a 109D in good shape shipped conus is around 90$
For the connectors, at these power levels don't trust sermos/asto/deans and the likes go for gold bullet 4 or 5mm, if you have troubles finding some, let me know... I buy them in bulk.

Last but not least about the Glow Vs E planes.
In terms of weight, a glow plane tends to get heavier as the glow fuel soaks & roten the wood!
In terms of airplane's life expectancy, glow engines causes a lot of vibration (on top of being unreliable) which affects reliability of both the airframe and its electrical components.
In terms of power and flight times, the e-engine will give the same amount of power no matter what the weather is, no on the field tuning necessary...just plug/play/unplug/go home!
e-hp are real hp, not paper hp in ideal conditions at 17K rpm.

Bootalini

I managed a few hours in the basement today with the NFL playoffs in the background. The photos show my progression from laying things out on the bottom of each core to building the false ribs which will support both the wing tube and the main gear mounts. I'll cover this phase in detail for the benefit of those out there who have never built plug-in wings. For those experienced in this area, it's likely old hat. If you look closely, you'll notice that the tube holes on the false ribs are off center quite a bit. That's because Mike Hester purposely offset the tube hole vertically in the cores to obtain acceptable tube depth (8") in the thinner than stock wing panels. By the way, the chosen airfoil is a NACA 63 012A (12% with high point at 35% of the chord) which is a notably thinner airfoil than the original.

Each wing panel will use 2 ribs of 3mm lite ply in the area of the landing gear. In addition, the inner root of the wing will also be capped with a lite ply rib (full length of the chord) which will support wing tube where it first enters the wing panel. The wing panel pins will also be glued to the inner ribs. I've used this set-up on my last 4 airplanes and I've never had anything come loose or get "soft". As a gear attachment point, it's also a very robust setup for those of you that have ever torn a main gear(s) assembly right out of the foam during a rough landing.

It's important that when you cut the wing tube holes in the ribs that the holes fit the tube with zero play otherwise you'll have to use excess glue when installing the rib assembly to ensure that there are no gaps between the tube and supporting ribs. Last thing you want is for the tube assembly to have play within the wing core.......that would be a minor nightmare trying to repair later. I still have to drill holes at the back of each false rib to accomodate the aileron servo lead hole/tube which runs from the wing root to the servo boxes. I'll also fabricate the main gear mounts and glue them to the false ribs. Once all that's done, it will be time to glue the wing tube outer sheath and the entire false rib assembly into the cores. I normally use epoxy for the wing tube and silicon for the false ribs.

Steve25

If the 35 or 40 Mhz band is free for use for rc airplanes, acteurope.de is offering a nice alternative. No bec needed.
You can switch the receiver and servo's directly to two lipo cells.
Now, part of the ACT receivers have a seperate bus for plugging them onto the current, and this bus can handle up to 15A.
The big servo is offering :
Stellkraft 305NCM bei 7,5V = 30,5Kg power
Haltekraft bei 7,5V -> 385Ncm = 38,5Kg Holding power

They have a smaller version as well, and they do work on lower tension as well.

I guess an option

Hope some of us guys can use this info

Bootalini

I was a bit short of building time this week but I did manage to get some pre-sheeting prep done on the wing cores.

First, I cut and fit the hardwood gear mounts to the false ribs. I cut the false rib rectangular slots carefully so as to attain a nice snug fit which when combined with a bit of glasswork will make for a strong
setup. You'll notice that the forward mounting gear beam is sitting a bit deeper in the false rib in order to maintain the gear hanging vetically with the gear down. Let me explain......the main gear positioning on this Aurora is further back than on the original plans due to the fact that I now have to account for a wing tube. The thinner than normal wing is not helping either. The net result is that the mains are mounted "non-level" behing the high point of the wing camber.

Next on the "to do" list was cutting a path for each wing servo lead. Central was all out of Gator tubes for this so I defaulted to plan B. The photos illustrate better than I can explain but this method worked well. Simply start by cutting a vertical slot of approx 1/8" X 1/2" deep with a sharp X-Acto and then let the Dremel do the rest. This method actually leaves a relatively clean setup.

Next up is glassing the beam mounts to the false ribs, installing the whole assembly into the wing including the wing tube, and then gluing/sanding the balsa skins. I hope to have the wings sheeted by mid-week.

Bootalini

The last steps prior to the installing the false rib/gear mount assemblies was the reeinforcing of the gear mounts with a bit of glass cloth and the capping of the tube sleeve ends. I didn't have to use much light cloth and Zap to solidly anchor the mounts and that's good because I didn't want to increase the width of the ribs by a substantial amount. After capping the carbon fibre sleeve ends with lite ply, I was then ready to glue the whole mess into place.

I layed pieces of Saran wrap in the foam 'saddles' as there would inevitably be some epoxy and/or silicon leakage in the gluing/setup process. I started by coating both sides of the false ribs with RTV silicon and then press fitting the entire assemblies into the cores. After cleaning up the excess silicon that oozed out, I then mixed a small batch of 3 hour epoxy, coated the tubes and inserted them into the cores to the desired depth. Speaking of tube depth, the tubes/sleeves are embedded 8.5" into each core which equates to each tube running 1/8" past the outer rib in each wing panel.

The last step was ensuring the alignment and squareness of the cores relative to each other and the tube. Everything looks to be bang-on but I should mention that I tried numerous dry-fits before going ahead with the glue and silicon. WRT alignment, it didn't have to break a sweat really as Mike Hester did a first class job of cutting the cores and boring the holes accurately....and that's the key!!

Almost forgot.... the PBG carbon sleeves are very thin and while the glass work on them did not appear to be porous, I waxed the wing tube as a precaution in case the epoxy seeped thru the sleeves. Having the tube weld itself to a sleeve(s) would be disastrous!!

rainedave

My Feedback: (1)

Remarkable work, Bootalini. Thanks for documenting your method. I certainly would be nervous holding the metal straightedge with one hand and "freehand" routing with the other.

Bootalini

Thanks Raindave. That method is actually easier than you think. The key is to have the smooth section of the axle running up against the side of the metal ruler. You can either freehand the depth or in my case, the chuck was riding up against the top of the ruler which provided the constant depth. You get a bit of chatter that way but if you keep that hand relaxed while you move the Dremel, it works well.

MHester

My Feedback: (1)

Great to see those cores are working out for you. Those just about kicked my tail before I figured them out. I hope the tube position is ok.

With any luck, we'll have a belly pan mold soon.

-Mike

Bootalini

The wings are now covered. The following how-to comments are for the inexperienced builder so I apologize if the following detail is painful.

After gluing the 1/16" wing sheets together, I make a point of sanding smooth both the wood surface that will be glued to the foam and the cores themselves. A smooth wood surface uses a lot less epoxy when you're spreading it on and smooth core surfaces maximize the surface area available for adherance. For sanding the cores, I use fine sandpaper (320-400ish) and I proceed slowly and lightly until the foam is very smooth. And be sure to remove all the dust from both the cores and the wood prior to gluing. I even vaccum the cores after sanding. The left photo shows 'before and after' sanding the cores.

For glue, I use 3 hour epoxy. I pre-heat the tubes in the microwave before mixing (clear part A=15 secs on high, gold color part B=30 secs) which makes the glue spread better. I use approx 12cc of glue for each skin (therefore 4 X 12cc for the entire wing). Spead the glue on the skins (using an old credit card) not the foam and spread until the glue on the balsa skins has a flat or at most semi-gloss sheen to it. If the glue appears glossy, then you've used too much glue in that area.....not a huge deal, just extra weight. After the glue is applied to the skins, sandwich the whole mess in the original core blocks and apply weight.

For those readers using contact cement to glue their skins to cores, I highly recommend the epoxy method described above if you're concerned about preserving accurate wing panels when building. As long as your work surface is perfectly flat, the cores will remain as accurate as when they were initially cut by the kit manufacturer. I don't mean to trash the contact cement method but it's a riskier and unforgiving method. A warp of even 1/16th" in a wing panel will cause notable trimming problems.

Trisquire

The sailplane guys swear by vacuum bagging at this point in the wing construction. Is that ever done with pattern ships? If the epoxy is applied only to the skin and not the core, there is potential for lack of solid contact in isolated areas.

By the way, the level of detail was perfect.

Tom

Bootalini

Trisquire, I'm guessing that a high percentage of the pattern folks use a method close to what I described for skinning foam wings. I've never had a skin lift or bubble on me.

Ref vaccum bagging, I'm aware of the benefits and I'm sure some of the pattern kit designers/builders are bagging. Generally speaking though, it's my impression that the competitive gliders and thin-winged pylon racers etc benefit a lot more from the vaccum bag process. Might be viewed as overkill by most pattern types??..............Anyone else?.........I'm certainly not the best person to answer that question.

Trisquire

Thanks Jeff. It's a great build thread. I haven't read about skinning pattern ship wing cores since the '70s. I had assumed that contact cement was still the preferred glue. I can see the benefit of epoxy however.

Yeah, overkill is my middle name.

Tom

nxtdoor

My Feedback: (10)

I am a sailplane flier/builder and pattern flier/builder. If you are asking about fiberglass bagging a wing core I am quite versed in the method. It is not difficult, just different. I also bag balsa skins to white foam cores for my pattern planes. This is an excellent method for pattern wings.

If you are interested in fiberglass skinned foam cores such as sailplanes, we typically use pink/blue or spyder(surf board) foam for cores. This is generally heavier than the 1 pound white styrofoam used in pattern plane construction. Fiberglass bagging sailplane wings requires a higher density foam because we are skinning much thinner airfoils in the 6-8% range. I intend to try a fiberglass skinned pattern wing soon. The finish on this type of wing is applied to the mylars prior to bagging the core and when the core is done, the paint is already on the wing. The only downside is that the mylar cannot wrap around the leading edge fully or the tips and leaves an area that must be sanded and finished, albeit a small area.

The use of vacuum bagging a styrofoam core with balsa cores is beneficial since you apply a much higher pressure evenly across the core than you can with weights. You would need many times the weight you typically use to sheet a core than if you bag it even at 7-10 pounds of vacuum. This allows you to use less glue to skin a wing by bagging saving weight. Typically you scrap as much glue off as you can once you wet the skin and still you have very good adhesion due to the higher pressure applied.

Only downside of bagging is you have to buy the equipment to do it. However, once you own it, you can use it forever.

I would be happy to answer additional questions if you have them.

Jeff

Trisquire

Thanks Jeff. We can learn from other areas of model aviation. There's a lot of overlap in what we do. I've also noticed that the control line guys build nice light balsa airframes.

Tom

mmattockx

Tom,

For a great manual on how to do balsa/foam with polyurethane glue, check out Terry Brox's page:

http://www.mackrc.net/patternwings2/index.htm

Epoxy is not much different, in that the prep work is all the same and you simply use different adhesive in the end.

Mark

Trisquire

Thanks Mark. That's a great link.

Tom

Bootalini

Next task was mounting/aligning the wings to the fuselage. As I thought this process thru prior to getting to work, I quickly gained an appreciation for those fiberglass fuselages/plug-in wing kits we buy that have the wing fillets integrated and parallel to each other when looking from above the fuselage. The issue here was that exactly as per the plan, the width of the fuselage was not the same at the front of the wing as compared to the rear. Over the length of the wing chord, the was a difference in fuselage width of approx 3/4".

Alignment
The way I proceeded was to mount and secure the fuselage in the middle of my pool table (a great reference flat surface) and use a large square to make sure the vertical stab was absolutely vertical. In conjunction with this, I ensured the fuselage itself was at a "0" incidence angle by using the plans as a reference. In the MK plans, both the wing and stab are set at "0" degrees incidence and both are parallel with the bottom of the plans which made the math easy. Bottom line here was that if you use the center of the wing tube as the datum, the stab datum needed to be 36mm higher for the fuselage to be level/horizontal. I had carefully plotted the stab position previously. I double and triple checked all my calcs as I didn't want to make any critical errors. Once satisfied that the fuse was level and vertical, I inserted the wing tube, the 2 3mm lite ply spacers and the panels themselves which left the fuselage suspended with the wings attached but the incidence of each panel yet to be set. I then shimmed each wing panel from underneath so that the incidences of each panel was zero while ensuring each wing tip was equidistant from the table using a measuring square. The last step was to ensure the entire wing assembly was square to the fuselage when looking from the top. I used a tape measure to measure from wing tip to vertical fin on both sides and I was within a couple of millimeters first try. I just had to nudge the rear of the fuselage a bit to get it right on.

I should mention that this alignment process as described took me at least a full hour as I had to proceed slowly with many small adjustments affecting previously made ones. Essentially, I'd describe it as "slowly zeroing in" the alignment. Next was epoxying the plywood wing tube guides inside the fuselage to permanently fix the center tube guide in place. This of course would lock-in the wing alignment.

Important note: You'll notice I did not yet add leading or trailing edges, or tips to the wing. This is by design until I've completed all the alignment. I don't use incidence meters as I find they give slightly different readings each time. And the problem with leading edges is that you lose your center-wing datum inevitably as a result of errors induced during carving/sanding. Same with trailing edges or tips. I place thin marker lines on the foam to denote the center of the chord line etc. In this case if you're trying to find a "0" degree of incidence for a wing, that equates to the datum lines at either end of the wing chord being an equal distance from the table again using a square to ensure vertical integrity of the measurement. I know that I'm easily able to distinguish within a 1/32" (maybe 1/64") using my reference lines and when you consider a chord length of 14" in this case (no LE or TE).......do the math, that's more accurate than those incidence meters IMHO.

So now the wing positioning is set but I still have to account for the large gaps between the rear of each wing panel and the fuselage when the wings are butted up to the fuselage. I was left with 2 choices:
1) build a fillet/false rib to bridge the gaps between the fuselage and rear portion of each wing panel or;
2) trim each wing panel so that the full length of each wing panel fit flush with the fuselage.

I chose option 2 as it would be easiest to execute. The fuselage sides in the area where the wings butt-up against it had virtually no curvature so is was easy to make the required linear cut to each panel. After each panel was cut, there was now excess wing tube socket material (an extra 1/4") hanging from each wing panel that had to be trimmed. The carbon wing wing tube also had to be trimmed a corresponding amount or the wings would not fit flush to the fuselage because the wing tube would be too long. As the photos show, I was able to achieve a nice fit.

Yowsa...I'm tired of typing. Next time I'll cover installing the wing adjusters and gluing the lite-ply inner ribs to each panel.

Atlanta 60

My Feedback: (18)

Wow!! I just came across this thread....Awesome!! I've been out of things for a while...The bug is back now...

I Really want an Aurora60!! I'd been hoping I could come across a kit...It seems they aren't avaliable??

I came across an old post of a fellow who had made a set of molds off the Phillips Aircraft PA2 drawings...I flipped...I've contacted him and he has graciously offered to check and see if he still has them!! How cool of a fellow...And How cool that would be if they were still around!! I also came across another website that has the Aurora60 kit on their list...Awating a Reply from them?? The website seems inactive...Hopefully they are still around..

OK...Sorry to ramble...You have offered me another option I had never considered!! Scratch building!! Awesome!!

One Thing I wanna Say: I was a bit too excited and I really breezed through all the posts...But I picked up on the fellow who suggested making some molds of the Belly pan ect....Please!!!

I would be more than happy to help out there if you havn't had anyone offer yet...I have a Composite tooling back round...

Only problem I see is judging from your pics your moving right along...You may be too the point you wouldn't wanna let go of the "master models" at this stage..he he...I'm a little late in the program...Sorry

Maybe you or someone else has already made some molds off them and I missed it?? But if not...Please Feel Free to contact me!!

I read where the canopys are still avaliable from Singapore Hobbies...I think I'll contact them tomorrow and order one or two...We could build a vacuum form for them which would be no real big deal...I'd like to get one before they are all gone!!

Drawings: I wonder if they are still avaliable?? I'd like a set also...I have a Aurora45 kit...I wonder if I could scale those drawings?? If anyone has any suggestions...

Could I bother someone to have a copy of their drawing's re-produced?? Not sure how much that would cost but I'd love to check out that avenue if someone were willing...

Also..I saw reference to "Dan at Carolina Custom Aircraft"...Does someone have a link or a phone number?? (Google wasn't my friend on this one..he he)

Thanks Allot for this thread!! She's beautiful!!

I have to go read through it again now...(Sorry if I asked some questions that were already covered...)

Have Fun...