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fins size
Hey guys
You can see on the template for the fin that there is a version 1 and 2. Version one is the original fin that is in the video. After about 8 flights I started to see that the height was more than enough. I found that the only down side to this size of fin is that, because it is so tall, the resultant aerodynamic loads are such that when you fly the bird inverted, you need just a hair extra down elevator to hold it level in relation to the winglet version of the plane. I went home and took the fins to my router and knocked about 20% off the height and went back flying to test my idea and it was dead on. Fin version 2 offers the same effect but requires only about 1/2 the down elevon in inverted flight as the version 1 fin. It does not look as cool but . . . if you are looking for just a little extra performance, version two is the way to go while still achieving the goal of counteracting adverse yaw. I got an email from someone asking about whether the carbon was really needed in the fins***Please remember that there is a thin strip of CF running up the fin, this gives the fin considerable rigidity at high speeds. I used 2 pcs of 6mm bluecore foam laminated together with spray 77 to give me the stability. You can use Midwest Cellfoam, Depron, Bluecore, Pink fan fold, thin pink or blue but you really need the laminations to make it work and be durable enough to endure speeds above 60 mph . . . |
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adverse What???
lots of Qs on adverse yaw
. . . . . . . . . . here ya go . . . nature of aerodynamics not specific to any one plane but all planes http://en.wikipedia.org/wiki/Adverse_yaw hope this assists so all understand why we need winglets, fins or spoilers. |
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Hello all,
I had a chance to talk with Jeff McClain a few days ago and it looks like there are a bunch of you that have picked up a Starfire. Some are asking about Slope setups over powered set ups and I will try to relay that information in a later post. Whichever way you set this airplane up, you will be pleased. It is so versatile and maneuverable that I have not flown much else for the last couple of months. It just “fits” the bill where ever I decide to fly it, The Beta 2 has not left my trunk for the last couple of weeks as it seems that flying time has to be squeezed in where ever and whenever it can with my work schedule and the kid’s stuff. Of all of the iterations, I have fallen in love with the mid motor version Beta 2 and like it best with just the winglets. I have installed the fins to be removable as are the winglets …so . . .I can swap back and forth with 4 nylon bolts. For those that do not have computer radios with the ability to input differential aileron, the fins are the perfect option to make the yaw control more positive. Even if you have the computer radio, the fins are just too cool looking in the air. We have input templates for two different shapes. The initial, version 1, works great and looks ultra cool but is just a little on the tall side. The second fin is just right on the height required to achieve the goal of the fins. If you want fins but don’t want them that big, you now know how short you can cut them down. The best flying version of the airplane was the heavier, high speed, monster version, beta 1. The roll and cornering was incredible and the ability to put it where you want it was neutrally stable, more in line with a pylon racer that has the ability to turn on a dime. It flew like it was on rails but it was really fast! |
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Now that I have had a chance to digest the alpha program and both betas, there are a few areas that I would like to address in the builds to make the best go of the models you are now building.
The airplane flies well light as well as heavy but grooves best with the higher wing loading. I highly recommend using std servos in this bird and adding a nice sized battery pack. Weight truly is your friend. The lighter build is very aerobatic and can be flown in a very tight area. I fly mine off the baseball diamond at my son’s school, it has trees completely around it. I climb up then do my stuff circling down through the trees and landing on home plate! It does well in any wind condition and will thermal in medium to high lift conditions while the heavier build is more suited for the slopes and powered up for speed. Set up for the lighter builds is pretty open and just about anything works. You really want to swing a larger prop with a higher rpm for climbs and aerobatics. I like anything that will swing an 8X4-8X6 prop with the mid motor set up. I would highly recommend the AXI 2112-20 as the first choice as it has a super low draw and lots of thrust with good speed with an 8” prop. AXI 2112-20 http://www.hobby-lobby.com/axi_gold_..._3013_prd1.htm Scorpion 22-12-1900 http://www.innov8tivedesigns.com/pro...roducts_id=383 Turnigy 28-22 http://www.hobbycity.com/hobbycity/s..._1350Kv_/_260W SCM 3223 1550KV http://www.hobbycity.com/hobbycity/s...less_Outrunner I have had it up to 4 lbs and it flew well, penetration in the wind was sublime! The highest speed I was able to achieve was 107.5 clocked with a radar gun but the design is fully capable of much much more. I was using the Dons Wicked 2700 turning an APC 5X5 prop on a 4s 2200Mah pack with a 60 amp esc. For the faster build I recommend the Dons Wicked motors as the first choice. These are by far, the best bang for the buck in my book. If you want all out speed though, nothing replaces the ARCs. Run these on the appropriate props from 4”-5” apc for the Dons and 6X4 for the ARCs. Dons Wicked 2700 http://donsrc.com/cart/index.php?act...d&productId=12 Dons Wicked 3000 http://donsrc.com/cart/index.php?act...d&productId=65 ARC 28-47 1.5 turn http://www.lightflightrc.com/HTML/pr...-28-47-1.5.htm ARC 28-47 2 turn http://www.lightflightrc.com/HTML/pr...RC-28-47-2.htm The limitation on mine was my poor choice to use the lighter walled Carbon Fiber spar material and leave it unsupported in the middle of the wing with nothing other than the fiberglass cloth to provide support. I should have known better, been building fast airplanes for years and there was no reason I can give for my choice of the thin walled spars other than trying to cut down weight in something that I really did not need to. The main lesson to be learned is in the use of the appropriate sparing material for the proper application and do not hesitate to add a little more if you really plan on wringing it out. Both of the Betas have had some retooling on the spars as a result of the thin walled CF tubes. These are great for light park foamies but poor for anything that is able to maneuver or accelerate to the speeds that these models are capable of. When we put together the Alpha, we used a heavy walled 6mm Carbon Fiber tube that ran across the wing just in front of the CG. This offered a very solid base and resisted many of the hard hits the plane endured throughout the alpha program. In the end, the single heavy spar was quite appropriate for the speeds and loads we were pulling . . 2- 3 lb airplane and below 90 mph. This config would also work well with the slope folks as it offers more than enough rigidity while also offering some flexibility to absorb the impact in a crash. For the powered build I used the single CF tube method again but dropped down to the thin walled 5mm spar and ended up leaving a portion of it in the middle of the wing with very little foam around it to add support. In the first days of flying the Beta 1 (speed version), I had a hard landing and caught a post in the ground out at the wing tip that I believe crimped the spar. As the speed and flight maneuvering envelope got pushed higher and higher and the stresses of very high speed flight started to work, the spar gave way and cracked on a high speed pass under load and folded the wing. After triage, the spar crack was the obvious cause of the structural failure. I had the opportunity to check out the rest of the airframe and found no other damage other than that from point where the spar failure extended from. I want to make it clear that the “normal” flight speeds for a light weight sport flying wing, the thin walled tubes are fine. If you intend on pushing this plane into the high speed realm, you need to take the appropriate approach to reinforcing it to handle that type of flying. To prevent this from happening, I recommend either using the same configuration I have used on the other wings with a three tube support system in the shape of an A – one spar down the leading edge of each half just behind the EPP (2” back for the folks with the all EPP version) as well as one spar going across the center section of the wing on the bottom in the CG range and clear of your radio gear. For a lighter weight version, you could also use a heavy walled CF tube on the underside of the wing going as far aft as you can and extending out as far as possible (about 8”-9” aft of the nose) and taking a piece of Dave brown .0014 X ½ X 36 CF tape and laminating it to a piece of 1/32 X ¼ X 36 CF strip then imbedding it height wise just behind the battery bay or just above and in front of the tube. Use a razor blade to cut the initial slot then make another cut parallel to accommodate the laminate that is only1/4” deep. Use Gorilla glue in the slot and apply gorilla glue evenly and completely to the spar then sprinkle some water before you install the spar. Apply wax paper apply a long even weight like a 2X4 that is a little longer than the spar then weigh it down so that the foaming action will be directed into the wing rather than outside of the slot. Make extra sure that the CF laminated spar is completely in the wing before you set it as the material is a bear to sand once it is glued in to make it flush. I also highly recommend the use of the Henry's 183 with the spray 77 or spray 90 depending on the version you are building. This provides a tremendous amount of impact resistance to the model. The water based poly with the glass cloth worked well too but is far more brittle than the Henry's 183 and not much more work. I also tried the Silk Span on the bottom of the wing using water based poly to adhere it. I feel that the silk span has proven to be pretty impressive in both its ability to resist cracking on impact as well as to fill in with minimal coats. It is a little heavier than the glass cloth but it looks much nicer in the end as it fills with two coats where the glass cloth takes two plus two coats of filler to make it smooth over the EPP. The white foam is easy, it is that EPP that has the large cells and is difficult to make the finish smooth with the thin glass cloth. I hope this sheds some more detailed light on the builds and the changes since the original building has been completed. Phil |
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Last edited by pval3; Apr 26, 2010 at 10:16 AM.
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fin install on beta 2
Hey guys
I completely forgot about these photos of the install of the fins on the beta 2. I set the plane up for the fins early on rather than after the fact as I ended up doing on the beta 1........It also shows the instal with the std pusher version rather than the mid motor version..... Here is the start with the parallel lines on the foam just outside the prop arc. I use the sanding drum with a Dremel moto tool router head. Make sure the lines for the fins are parallel to each other . . . exactly parallel to each other. I used the center line of the cores as the base for the alignment of one side then just duplicated it on the other side. Take your time with the dremel and make sure that your depth is enough to support the fins at high speed. |
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test fit test fit test fit. . . . make sure that it all fits nice and tight before you proceed.
If you want the fins to cant in or out, take a piece of 1/32" balsa under the the left or right outer side of the router base and gently and slowly pull it though, this will make the base with an angle to support squarely the fin. |
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tape it up
to make sure you will have something to set after you cover the airplane you need to make sure that you seal the gaps to prevent the spray glue from polluting the slots.
Take painters tape and cut it into three pieces, take one on each side and one in the middle. Work it into the corners then trim flush with the top of the airfoil. This tape holds perfectly well for about 4 days... after that, it becomes incredibly difficult to get off without heat from a heat gun ..otherwise it will take some of the foam up . . . . Once you have it covered, go ahead with your normal kellys or WBPU . . .strapping tape . . .etc.. |
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back to the conversion table again
while I await the arrival of the MCW 84 I am bringing the Alpha model back from the depths of the hobby crypt for the conversion to a twin!
Like I have nothing better to do - -riiiight Going to have to do quite a bit of surgery to get the battery compartment large enough to accommodate the higher C rating cells as well as two esc. Cut outs in the wing are accomplished, motor mounts are picked and cut outs are done and I have been working a new hatch as the old one was purely "alpha" caliber! In time In time! |
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all three versions of the starfire were the composite type.
All EPP cuts a few steps out of the process as you do not have to join the le to the main part of the wing. Use a thick walled spar on the top and bottom and run as far out to the tips as you can to give the epp the same rigidity. I would leave the last 1/2" - 1" of wing free of spar to give it some squishee on the tips in case of cartwheels. Use a VERY sharp (spell - - new blade) and clean straight edge (box cutter) blade with a metal ruler to cut the bevel in the elevons as epp has a tendency to tear if you get the blade catching while cutting . . makes a not so nice cut! Other than that, same ol same ol in the build How are you planning to set it up?? Phil |
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I have this ugly twin project I am planning to maiden tomorrow...if it is still a dog i'll probabaly go with with the mid engine version with the high vertical fins.. like that look a lot... how did you like the durability of the blended kits? pretty crash worthy? can' t make up my mind on blended or all epp but leaning toward the latter.. thanks
also what was the AUW of your heavy setup again? and where did you get your dremel router adapter? I wonder if it would fit a different brand or dremel? thank you |
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Last edited by grfcon; Dec 17, 2009 at 12:01 PM.
Reason: adding questions
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what twin are you working on . . .
I have a weakness for twins . . . without going back, I think the fast one AUW was somewhere in the 3 lb range. It wasnt as much heavy as reinforced for heavy abuse at high speed. I generally build light but strong. Dremel router head ..I would try Amazon, Lowes or Home Depot . . I think I got mine at Amazon and it was on sale for something like 12 bucks, regular price is somewhere in the 20's. I have tried so many different tools and bits but none of them even come close to the Dremel. It is worth every penny . . . . check out the Amazon sales though, I have picked up more bits on their weekly sale sheet than I care to admit to. harbour Freight just started selling a heated exacto tool that works great on the foam, best part is it sells for 8 bucks with a boat load of tips to go with it... I would recommend that for your spars and the general cut outs . . esp if you are going with the all EPP version.. I found the composite to be just as durable as the all EPP planes I have flown in the past. I was suprised as I did not think I would be as happy with it was I was . . more so in some respects as I think the composite offers a more solid build. I had a full blown radio lockup at full throttle and about 70 mph . . .plane tucked right into the ground with the Alpha. It was finished with the WBP and glass cloth so it was not the most durable set up to endure a beating like that. Plane had a nice crack from the side of the prop cut out to the spar. After soaking 12 hr epoxy into the joint and letting it sit, the airframe is ready for it's resurrection. It will become the twin some time in the future. I realize a lot of folks are just stuck on the EPP and I love it too, but the blended kits are a little stiffer from the start. The virgin foam is easy to work with for setting up your radio gear and cuts easier. The epp is simpler in that you do not need to join the LE to the TE, just the 4 panels so there is less to align. it is mushier so it takes a severe beating well . . ..You are kind of limited in the finish in that you are going to be covering it with the Kellys cloth and monocoat as the bead for the EPP is far to open to just slap a coat of WBP over it and seal it without a lot of work. If I was a beginning to intermediate pilot and doing 1 and only 1 plane: If I was going to power it, I would do the EPP (plus you can use the 3M spray 90 which dries quicker) If i was building a sport to advanced pilot I would go with the composite again. I have three of them under my belt and I would gladly build another this way. Either way . . .If you are powering it make sure you use two spars and no thin walled stuff if you are planning on going fast.... Phil |
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Hey Phil
thanks for all the info and tips on the dremel router attachment and stuff. and for all you hard work on this plane. Have you ever used the "new stuff" laminate film? it is pretty tough and way thicker than monokote. here is a link to the twin I fly yesterday.. it flew great!! I had a friend take a video which I will post eventually. https://www.rcgroups.com/forums/show....php?t=1153309 there are a few guys who use the laminate..I had it on my wing..it works great on all EPP and the DS guys are sometimes using it instead of gooping and taping epp over and over. canuck engineering is one place that sells it pretty reasonably by the foot in different thicknesses. not sure which way I am gonna go on the kit yet. thanks for the info and your help Gary |
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