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Joined: 12/27/2006 From: Westford,
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My 9 year old wants to build her own plane, so we started on a SPAD trainer today. I am building it sort of per the BUHOR 25 plan, but enlarging it a bit. I am also adding a coro fuselage to hide/protect the radio gear and fuel tank, and to raise the wing up a little higher for better stability. Make sense?
So far we have the coro fuse, aluminum channel, engine mount, and wing pretty much fabricated. Right now, the wing span is 72", but the spar is shorter, so I'll probably trim the wing by 6-8". I'll see how stiff it is after it's all done and mounted. The wing is 2mm and the fuse & ailerons are 4mm. The tail will be built per the BUHOR 25 plan using 4mm.
I'm thinking that we will power it by a .32 BB engine, maybe a Magnum. Maybe even a .40LA. I am shooting for a nice, slow, stable flyer, suitable for training a 9 year old.
I am going to swipe the servos from the SPA3DT I started. I'm going to shelve that thing for a while.
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I think you're going to need something bigger than a .40 LA. I know you started out with the plans for a .25, but you've made the wing bigger, added a fuse, and I'm hoping you enlarge the tail feathers as well. It will take at the minimum a .46. If you make the wing bigger, the fuse needs to be longer and tail feathers need to be bigger. All that adds up to extra weight. I have an excel spreadsheet called design.xls that I use when I'm enlarging plans. You can look it up on the net or e-mail me and I can e-mail it to you. broke_n_bummin@alltel.net
< Message edited by broke_n_bummin -- 12/9/2007 11:58:01 PM >
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that looks good. you will probably need the 46 size engine. I am flying the debonair. it has a smaller wing. but it sure is indesctructable. have fun, Im forgeting about balsa right now.
first.... If your going to enlarge the wing, you need to enlarge the tail, and fuse length proportionally. Second, on the fuse - pick one. You don't need both the angle and the corofuse, its overkill. Third, the difference in stability of a high wing coro fuse, vs the aluminum channel is negligible. While there is some pendulum effect, the difference isn't enough to be noticable. I'm not trying to be negative, but, your changes, while looking good on paper will most likely result in a plane that won't fly nearly as well as one built by the plans.
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Joined: 12/27/2006 From: Westford,
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Thanks for the input. The larger engine does make sense, and there really isn't much of a price difference. I did scale up the tail a bit as well.
Here is everything dry-fit to show it's proportions. I'll weigh it after all of the gear is installed, minus the engine, and then we'll decide which engine to put in it. The way I'm mounting the fuse onto the rail, I can slide the whole assembly to correct for CG at the end.
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If all of your friends were named Cliff, would you jump off them? - Hugh Neutron
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Chris,
Thanks for your input. If you don't think the coro fuse is worth the bother, then maybe we'll ditch it. So far, following plans have worked out much better for me than making it up as I go
I appreciate the advice.
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It might be the angle of the pic, but that fuse looks kind of short. A typical trainer with a 60" wing span should have roughly a 40" fuse. According to my excel program, a 72" wing would call for a 50.4" fuse, a 19.5" horizontal stabilizer and a 9" vertical stabilizer. It says a .45 will fly it. a .46 LA with a 11X5 prop would drag it around just fine for a trainer.
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I may have to give up R/C Airplanes and Golf ... They make my Torrets act up...
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Yes, the fuse is too short for that wingspan. I need to pick up another piece of channel and cut a longer one, and I am going to shorten the wing to 60 inches.
Thanks.
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If all of your friends were named Cliff, would you jump off them? - Hugh Neutron
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Nice wing! that size is close to a SPADET wing. take a look at those plans and modify your fuse to match. I think you are spot on in the wing. I have built a simular one for my nieces. I used the fuse building method That a SWIZZLE stick has and spad wing almost like yours. Here is a pic and it flys very slow and gracefully as you would want it to for a youngster. This plane has 2 pine door strips for fuse and a 1/4" balsa wing box with all the goodies in it. conventional balsa monokote tail for lite weight. the wing box wasn't glued to the rails until balancing time just like most spads.
< Message edited by OzMo -- 12/19/2007 4:02:52 AM >
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Joined: 12/27/2006 From: Westford,
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Thanks. Progress has been a bit slow lately. It's hard to motivate a 9 year old to finish a project that she won't be able to use for 5 months.
We have mostly been gathering pieces, and we pretty much have everything now. I decided to try a Super Tigre 40. I have had good luck with my ST 45, and the ST 40 is only $49.99 and I had a $10 coupon code for Tower. I picked up a radio yesterday, JR Sport S400, same as in two of my other planes. I went with JR Sport because their servos are slightly narrower than Hitec and Futaba, and will fit into the 3/4" channel. I also have 3 other JR boxes to buddy with.
I have extended the fuse to 42". I am leaving the wing as-is for now. I'll bring a pair of scissors to the maiden flight, and I can trim a few inches off each wingtip if need be.
I'll post some pictures when it gets closer to finished. Thanks
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If all of your friends were named Cliff, would you jump off them? - Hugh Neutron
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Joined: 12/27/2006 From: Westford,
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We have made a little more progress on the trainer. We are going to leave the coro fuselage on for now. It only weighs a couple of ounces and we like the way it looks. It balances right on the spar as-is. We just need to install the radio gear. The only thing I don't like right now is the center of the wing. I think I am going to replace the yellow strip with a wider one that covers the whole rubber band area and wraps under the front of the wing.
I don't have a scale that can wiegh it, but it's definitely lighter than my Alpha 40.
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Building a SPAD Trainer - 
