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RE: Twin Otter 125inch wingspan
I'll take any compliment I can get...especially one from a citizen of the country which nutures DeHavilland of Canada, birthplace of the Twin Otter.
Posted on: 9/18/2012 1:30 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=11232683
RE: Twin Otter 125inch wingspan
There is a logical explanation for this....really!
Posted on: 9/18/2012 11:12 AM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=11232549
RE: Twin Otter 125inch wingspan
The fiberglass went on with epoxy resin, followed by 6 coats of waterborne polycrylic (4 with talcum powder), then 3 Stits Feather Coat filler primer, and Stits Poly Tone color, single coat so far. Oh, and about 3 months total spent sanding between coats. (That is only a mild exaggeration...ever try sanding 600 corrugation grooves?) If I never see another fiberglass pinhole in my life, I will be a happy man. Seriously, for the next project, I think I might go back to polyspan instead of fiberglass cloth. It finishes so much easier.
Posted on: 8/20/2012 6:12 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=11200252
RE: Twin Otter 125inch wingspan
Well, with a little bit of luck I might get this thing finished before the snow flies. First color coat. A little door detail.
Posted on: 8/20/2012 3:16 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=11200045
RE: Electric starter won't turn it over os .91
Nice woodworking.
Posted on: 6/2/2012 5:54 AM by Author "GoNavy"
in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=11103593
RE: CG - Citabria Pro Balsa USA
I haven't come to a final decision, but I'll probably use monokote.
Posted on: 4/20/2012 7:56 PM by Author "GoNavy"
in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=11050546
RE: CG - Citabria Pro Balsa USA
Roger that pimmnz; On the 14 inch cord 4.5 inches is 32%; 3.5 would be 25%. If I delete the smoke muffler and pump I would save only 3.5 ounces in the nose, and would still require about 8.5 ounces of tail weight. The pumped os 120 is one fine engine, and in the range for a 12 pound aircraft, but it rubs me the wrong way to have to add a half a pound to that. (I was told that I "build light".) I wondered if others choosing big engines faced a similar balance issue. I recall one fellow posted he used the OS 160 which, without a muffler, is as heavy as the os 120 pumped without muffler (32+ ounces). Maybe it's time I tried electric.
Posted on: 4/20/2012 9:03 AM by Author "GoNavy"
in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=11049874
CG - Citabria Pro Balsa USA
I checked the balance on my assembled but not yet covered Balsa USA Citabria Pro, with an OS 120 pumped with smoke muffler and oscillating pump, total weight 37 ounces up front. I put the elevator and rudder servos close to the tail and still needed nearly 10 ounces of tail weight to balance with the CG 4 1/2" back from the leading edge, as shown on the plans and called for in the instructions. I would like to avoid so much additional weight and wonder what experience others have with the amount of tail weight needed. I found one older post where the fellow indicated he flew with the CG only 3 1/2 inches back from the leading edge. I can go with a smaller and lighter engine, for example, the Saito 100 with stock muffler that weighs 22 ounces, and I calculate I would then need about 3 ounces of tail weight, but I have seen older posts of others flying engines larger than the OS 120. The wing is mounted as shown on the plans.
Posted on: 4/19/2012 1:22 PM by Author "GoNavy"
in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=11048856
RE: Finding chord line of wing
[quote]ORIGINAL: smithcreek Try this: lay the wing on a flat surface. Best to use two rulers. Place one ruler in front of the leading edge, measure where it touches the leading edge. Raise the trailing edge up that height of the table. Remeasure the LE again and make any adjustments to the TE. Do this until both rulers measure the same height. Mark the LE at that point. [/quote] Okay...what have we located, the forward chord line?
Posted on: 3/29/2012 11:26 AM by Author "GoNavy"
in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=11020020
RE: Finding chord line of wing
[quote]ORIGINAL: AA5BY I do think the plan notation to be careful in the use of an incidence meter on some airfoils is appropriate. [/quote] I agree, and am working on the assumption that the designer or instruction writer meant what he or she said so emphatically, that an incidence meter should not be used. The kit sat on my shelf for many years, and I suspect was the work of the late Ron Bush, founder of Balsa USA and who is now deceased. I met Ron about 15 years ago and he gave me a tour of his facilities. We talked a lot, and I got the distinct impression he was very knowledgeable, as well as a man who meant what he said and said what he meant. Since I don't know how to find the spot on the leading edge that he referred to, I chose a different method to align the wing so it in the position shown on the plans. I realize that this could be wrong if the plans are incorrect, either because of drafting error or possible distortion (as noted by Wilde, above). Subject to such possible errors, the wing will be positioned per the plans, whatever angle of incidence that is.
Posted on: 3/29/2012 10:43 AM by Author "GoNavy"
in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=11019966
RE: Finding chord line of wing
Just got the response from Balsa USA as follows: "These days it would be a lot easier to use an “incidence meter� then trying to work off the mean cord line. I recommend setting it up using an incidence meter so the wing is at 1/2 and no more then 1 degree positive with the tail at 0.0 degrees. You’ll also need a degree or two of down thrust in the engine. Hope this helps you out!" (No irony there!) The question posted by c-jack was how does one locate the chord line at the leading edge. Mike Connor and Funkworks have offered answers to that question. Wikipedia, quoting a 1975 work (http://en.wikipedia.org/wiki/Chord_%28aircraft%29) says: "In aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil. The chord length is the distance between the trailing edge and the point on the leading edge where the chord intersects the leading edge." Humm...how does one find the "center of curvature" of the leading edge, especially one like the BUSA Citabria Pro with it's complex shape?
Posted on: 3/29/2012 9:01 AM by Author "GoNavy"
in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=11019864
RE: Finding chord line of wing
The instructions say an incidence meter will not measure the angle accurately because of the shape and leading edge radius of the airfoil.
Posted on: 3/28/2012 11:25 AM by Author "GoNavy"
in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=11018709
RE: BUSA Citabria Pro & Incidence Help
[quote]ORIGINAL: bugleboy Okay, I need some help. I am building a Balsa USA Citabria Pro and just finished the metal struts or wing supports, whatever you want to call them. However, the plans show what appears to be a NEGATIVE incidence and the instructions say the wing should have a POSITIVE. I constructed the ''struts'' per the instructions and it appears to have a NEGATIVE incidence. Incidence of the Citabria Pro has been discussed in another thread, but there did not seem to be any concensus. I am open to suggestions/help! How do you all measure incidence without a incidence meter? Maybe that is my problem. [sm=confused.gif] Thanks, Jason [/quote] Yours truly had been staring at the instructions (#5 on page 26 of the manual) and I too was struggling with the method described to determine the wing incidence on the Balsa USA Citabria Pro. I used the method described by Funkworks (post 3 in thread here: http://www.rcuniverse.com/forum/m_6961521/anchors_6961521/mpage_1/key_/anchor/tm.htm#6961521), to determine the chord line, using the profile for the wing as shown on the fuselage plan. I then measured (at right angles) from the datum line specified in the instructions, and got the following results: datum line to forward chord line: 4 29/32" datum line to rear chord line: 5 3/16 " Thus the wing as drawn has a NEGATIVE incidence relative to the datum line (trailing edge is higher than leading edge when aircraft is upright); Using trigonometry I come up with an angle of 1.15 degrees. That is reasonably close to the one degree stated in the instructions. The cited instructions state "(t)he incidence angle in the Citabria Pro is 1 degree positive as shown on the plans (remember the airplane is upside down)." AHAH, MAYBE, JUST MAYBE, he meant positive when viewed UPSIDE down????? If this remains of interest to anyone, I will scan my sketch of the chord line and post it. The question remains for me, do I use the method described in the instructions. I have emailed BUSA.
Posted on: 3/27/2012 7:37 PM by Author "GoNavy"
in the forum "Kit Building"
http://www.rcuniverse.com/forum/fb.asp?m=11017855
RE: Finding chord line of wing
Yours truly had been staring at the instructions (#5 on page 26 of the manual) and I too was struggling with the method described to determine the wing incidence on the Balsa USA Citabria Pro. I used the method described by Funkworks (post 3 above), to determine the chord line, using the profile for the wing as shown on the fuselage plan. I then measured (at right angles) from the datum line specified in the instructions, and got the following results: datum line to forward chord line: 4 29/32" datum line to rear chord line: 5 3/16 " Thus the wing as drawn has a NEGATIVE incidence relative to the datum line (trailing edge is higher than leading edge when aircraft is upright); Using trigonometry I come up with an angle of 1.15 degrees. That is reasonably close to the one degree stated in the instructions. The cited instructions state "(t)he incidence angle in the Citabria Pro is 1 degree positive as shown on the plans (remember the airplane is upside down)." AHAH, MAYBE, JUST MAYBE, he meant positive when viewed UPSIDE down????? If this remains of interest to anyone, I will scan my sketch of the chord line and post it. The question remains for me, do I use the method described in the instructions. I have emailed BUSA.
Posted on: 3/27/2012 7:31 PM by Author "GoNavy"
in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=11017849
RE: Twin Otter 125inch wingspan
I hear you on heating expense. My painting area is insulated but has electric heat. I don't want to spray paint around an electric heater, and the makeup air is too cold now. Those floats you show look huge. It will be great to see your TO during takeoff! I have very limited water takeoff experience, but my guess is you will need lots of power. By the way, there are two TOs available for download to Real Flite simulator, a 60size and one 90size. I have been practicing.
Posted on: 3/9/2012 9:25 AM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10992981
RE: Twin Otter 125inch wingspan
Lins: I added the fairings at the leading edge of the wing and fuselage junction. That structure apparently allows routing of lines into the wing. It took awhile to figure out. I was pleased with the fairings I was able to make at the strut attachment to the wing so the end and bolts will not be visible. I spent some time making a jig to hold the wings for painting, and rotating to let me paint both sides in one session. Have you been posting in the other forum?
Posted on: 3/9/2012 8:15 AM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10992893
RE: Twin Otter 125inch wingspan
Hi Lins: I was priming when the weather got too cold so it's sitting there now, partially primed, waiting for warmer weather. Just ordered an electronic switch for the landing lights. Regards!
Posted on: 3/8/2012 8:04 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10992331
RE: Twin Otter 125inch wingspan
Hi Lins: I was priming when the weather got too cold so it's sitting there now, partially primed, waiting for warmer weather. Just ordered an electronic switch for the landing lights. Regards!
Posted on: 3/8/2012 8:02 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10992328
RE: Twin Otter 125inch wingspan
Hurribox: I sent John an email with a link to your post.
Posted on: 10/15/2011 1:50 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10766803
RE: 1/6 SCALE TWIN OTTER BUILD
This is the set of jigs to support the fuselage crutch when building. If anybody would like them, I will forward them if you pay the shipping.
Posted on: 10/11/2011 9:41 AM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10759798
RE: Twin Otter 125inch wingspan
These are the jigs I used to support the fuselage crutch. If anybody wants them, I will send them if you pay the shipping.
Posted on: 10/11/2011 9:37 AM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10759790
RE: Twin Otter 125inch wingspan
Here, for better or for worse, is a jig I used to cut corrugations. It's not a thing of beauty...okay, it's a Rube Goldberg, but it works. There has got to be a better way. Cutting these takes me a lot of time.
Posted on: 8/23/2011 2:23 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10683905
RE: Twin Otter 125inch wingspan
Lins: The part is called "fixed strut mounting bracket", as shown on the diagram: http://www.robart.com/catalog/secure/uploads/file/RSDim%20Drawings/684.pdf I could not find that part separately listed on their website. I ordered through my LHS, and showed him the diagram and he got the right part. In the for what it's worth department, I used sintered brass (bronze?) washers above and below the mounting block - cheaper than ball bearings and were available at the local hardware store. They are oil impregnated and gear rotates easily. I have two pics of the installation at post #96 in this thread.
Posted on: 8/1/2011 1:07 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10649723
RE: Twin Otter 125inch wingspan
Lins: Are you building yours for both LG and floats? I keep plugging away. You seem to make great progress, but then, it is DH Canada. I think you'll finish before I finish mine. I completed fairings for the wing struts, so most of the aluminum ends and bolts are covered. It took me four days to complete a jig for routing the corrugations. The jig is not a thing of beauty, but it works. By the way, my thanks go out to you who brave the winter weather in Yellowknife, and I thank you for the best picture I could find of the rudder, and from which I scaled the corrugations: http://www.airliners.net/photo/Arctic-Sunwest-Charters/De-Havilland-Canada/1506570/L/&sid=97f2c6e5b5ce5ede3ec0f75dad7c2139
Posted on: 7/30/2011 6:44 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10647097
RE: Twin Otter 125inch wingspan
I'm back at the project. Here are a few photos of the wing strut attachment to the fuselage brackets. I used threaded inserts. They give you a steel nut permanently attached to the aluminum parts so you only need to instal or remove the bolts no need to hold nuts too. I removed the portion of the wing strut upper fairing above the strut attachment. I will try and cover the inserts and bolt ends within a scale-like fairing. Anyone else building?
Posted on: 6/20/2011 5:42 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10584246
RE: Electric starter won't turn it over os .91
I purchased the Harbor Freight 18 volt battery and compared performance of two starters on a Saito 150 (4 stroke). The Sullivan Dynatron would turn the Saito over with the 18 volt, a 12 volt starter battery (450 CCA), but not with a Hobbico 12 volt 7 AH battery. The Hobbico Torquemaster 180 could not turn the Saito over any any battery, even the HF 18 volt. I opened the battery case on the HF and the wiring from the pack to the contacts looked a bit light, maybe 18 AWG. Has anyone replaced that wiring with something heavier and did that make a change in performance? Does anyone have experience with both the HF 18 volt and the Makita 18 volt Lion 3 AH set up (http://www.afineredgemfg.com/), and how do the two compare?
Posted on: 6/13/2011 5:32 PM by Author "GoNavy"
in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=10572253
RE: Electric starter won't turn it over os .91
Gray Beard: Locally we can get what are commonly called disconnects, but I think are sometimes called blade connectors. The male is a simple rectangular shape, the female has a cross section sketched on the attached #1. The curled edges of the female receive and hold the male connector. I don't know the shape of the connectors on the HF battery. A Senco battery I have has connectors like a male disconnect except the one edge abuts the housing, sketch item #2. Thus, a female connector cannot attach to the male connector on the Senco battery, unless one were to remove one of the curled edges of the female connector. I don't think that would be secure. I have seen a female blade connector which does not have curled edges, for example: http://eagleday.stores.yahoo.net/feblte332.html (I will try to attach a copy of the photo from that site). These could work with the connectors on my Senco battery, but I don't know what the connectors are like on the HF battery.
Posted on: 6/10/2011 11:56 AM by Author "GoNavy"
in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=10566858
RE: Electric starter won't turn it over os .91
Could someone describe (perhaps post a photo of) the type of electrical connector they use to connect to the Harbor Freight battery terminals? (In post #2 JohnBuckner refers to "blade connectors".) Does anyone know a source for the connector assembly used on the HF tools that mates with the battery?
Posted on: 6/10/2011 8:37 AM by Author "GoNavy"
in the forum "Questions and Answers"
http://www.rcuniverse.com/forum/fb.asp?m=10566529
RE: Twin Otter 125inch wingspan
F86: I agree about the curves. I also think the outline is too wide at both ends, and that the taper of both the leading and trailing edges are wrong, but I have looked at hundreds of photos and have yet to find a closeup that gives a "top view" of the lower strut. Everything is taken at some angle. The isometric drawing I posted above might be helpful, but has its own limitations.
Posted on: 5/4/2011 7:28 AM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10500834
RE: Twin Otter 125inch wingspan
I will do that. I received a sketch of the gear, which seems to be an isometric. I enlarged it and added (in red) what appear to be the x, y and z axes. (Two years of drafting in high school 1958-1959). Maybe I can generate a reasonably accurate two dimensional sketch of the lower strut fairing ("top view") from this and with your measurements, bring things reasonably into scale. What do you think?
Posted on: 4/29/2011 9:16 PM by Author "GoNavy"
in the forum "Twin & Multi Engine RC Aircraft"
http://www.rcuniverse.com/forum/fb.asp?m=10492533
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