|Feb 23, 2013, 08:34 PM|
I have spitfire-itis. only curable by building a spitfire!
Like I said I have the obsessive disease of Spitfire-itis. Something that has only one known cure. Building a spitfire. Since I don't have room for a real one, I'm going to build a foam parkflyer one.
I have ben reading just about everytning I can consume about spitfires and poured over the internet looking at the available kits from different manufacturers. there are a few main ones available that are pretty nice, but they all have things about them that don't really fit my requirements.
the parkzone Mk.IX is the best, by far, of all available spit ARFs at this time. an amazing looking ARF indeed. However it's wingspan is only 43". normally this would be fine, but I am looking for a spit model that is
big enough for me to install a sound system in it, and it not have a heavy wingloading because of it. I like light. Everything a build is very light.
I picked up an old Sure flight Industries foam spitfire kit for a song at the local swap and shop last december. At the time I didn't really think about the sound system, or even building it soon. But as my disease (spititis for short) has developed further I realized that I had been luckier than I thought when I found this plane. I had been reading and looking at the Dynam spit and the FMS/airfield spit and seeing that even after spending the money they wuld need significant modification to be proper. leaving them improper would not cure the disease at all. the Sureflight kit needs modification, but the foam is of amazing quality. extremely dense cell foam. easy to sand and work with. extremely strong, stiff foam you cannot buy in raw form that I am aware of.
so after looking at the Dynam spit and the FMS/Airfield spit, and all the modifications, the sureflights size was right in the middle of them and would end up being more gratifying to build without a doubt.
Now I am not bagging on anybody who bought one of these other spit models mentioned. they are pretty damn nice models. It's just an affliction I have with wanting to see fairly accurate scale details and the feeling of building my own plane that I just need to fulfill the best way I know how.
So enough explanation.
I decided to build a spitfire Mk.1a. Something flown in the Battle of Britain. I found a pilot I liked, Eric Lock. I successful pilot who basically opitomizes the situation and national pride of the English during the Battle of Britain. ther is a static model build of this plane that I am going to use for reference here: http://forum.largescaleplanes.com/in...howtopic=40501
An AMAZING model builder indeed.
I found some great drawings that were in .tiff files that blew up to 1:1 scale with my model's 50" wingspan. very useful indeed. but the plans showed the dimensional problems with the sureflight kit. First of which was the location of the wing on the fuse. It is too far back on the the kit. second the cockpit cut out is HUGE. and the canopy is the wrong size too (of course). Also the elevator and rudder are over sized way too much! Not my cup of tea at all.
all in all though, these things are easily rectified and are not anymore of a problem than the issues I see with the other kits available(except the parkzone spit which is very, very nice) and the sureflight kit only cost $ 25, not $120 or more.
|Feb 23, 2013, 10:14 PM|
Wow, this foam is dense and heavy. the foam parts of the plane wiegh 18 ounces by themselves! yikes! that's alright, as I am going to cut them down and lean them up.
So the first modification are going to be to the shape of the kit.
starting with the wings. they have a very fat symetrical airfoil. It just doesn't look like a spitfire wing from a front, or airfoil view. the real spitfire airfoil is very thin and not symetrical at all. the shape is right, and the dihedral is right , but that fat symetrical airfoil has got to go!
I asked J Morgan if he had ever "shaved" the airfoil of a wing down, and he said that he wouldn't really recommend doing it, as the Sure Flight planes do fly well, just like they are. Well, I respect and appreciate his opinion and advice, but I just can't take it! that wing is not creating the illusion of scale reality for me.
So, I have taken on the task of shaving a 1/4" off the bottom of the wing with a hot wire foam cutting rig. I had to make the rig first! I haven't made one before, but Iam an electrician and I have lot's of parts to use. so I made a power supply from a large 24 vac transformer, a universal dimmer and the usual cord,switch and fuse holder.. then I made a bow using a scrap of 1/2" emt, some brass strip, brass screws,wire , dow rods,and a .017 guitar string.
then I made some "wing holders" out of pink wall foam using a few simple tools to get the shape right. I used some scrap trim board for runners that will dictate the point that the hot wire will ride across. anything above this point gets shaved off.
I put the wing holders in between the rails and put the wing on top to make measurements. I shimmed the holders on the bottom, until I like what I saw. I took some scrap aluminum flat bar and taped 1/4" shims on it and ran it across the top of the wing making sure I was not cutting off too much foam.
I made I slow cut, and It came out great. man this foam is dense! I did the other wing, flipping the wing holders around and adjusting. then I cut the middle down too. I am happy with the results. so far it has removed 1.5 ounces! the whole thing needs a good sanding, and then it's on to the fuse tomorrow as it is too fat also.
|Feb 23, 2013, 11:56 PM|
I came this close to buying a Sureflite spit about a year ago off the classifieds, I settled for a GWS Spit. Now I want another one!!
|Feb 24, 2013, 01:26 AM|
yes thank you for your interest. I wasn't sure if this was the right forum for this build thread. but it seemed like a good place to try.
I should have stated that my plan is most definitely to make a "proper spit" indeed.
proper landing gear size, shape, and stance, with some nice servoless retracts, some scale flaps, hidden linkage(if my patience holds out) a nice cockpit/pilot and canopy, scale panel lines(perhaps a few rivets and bolts) accurate markings, a sound system from MR RC sound, and a proper 3 blade prop for a Mk.1a spit.
I figure this will help me "move on" to obsessing about different plane after I get this out of my system.
|Feb 24, 2013, 09:49 AM|
Welcome to the wonderful world of Sureflite. This is my old build thread: http://www.rcgroups.com/forums/showthread.php?t=1204048 It may save you some duplication of effort and hopefully you can avoid some of my mstakes. I left my "fat" wing intact. The thickness isn't that noticeable, especially if you correct the fuselage dimension. The original kit was designed without a spar, so the thick foam was needed for strength.
Mine built "heavy" but was a beautiful flier once I got it all sorted. I have a replacement I got from a friend here on rcgroups but haven't started it yet, too many irons in the fire. When I build the new one I will stick to the same power system (Power 46 on 5S, 13/8/3 prop) b/c is is perfect for this airframe. I will use electric rather than mechanical retracts, purely for ease of installation.
Watching the build with interest. Kind of a vicarious thrill.
|Feb 24, 2013, 11:24 AM|
JHspring, Did you notice the 'Veiw all pics in images" option now installed in you thread? Nice upgrade moderators!
That Spitty really turned out nice.
|Feb 24, 2013, 08:20 PM|
well Jhspring it's good to see someone has one of these things! in the end, it looks like you have a good lookin' spitfire !
well not much progress today. sanded the wing completely and I'm liking how it looks. need to spackle it up and sand it down again tomorrow. wife, kids, and life took up most of the day today. I tried to make a before and after picture of the wing, but it's hard to see the difference.
I did notice that the tail feathers are way oversized! wow. the elevator is 16.5" span when it should be 14.5". it's a bit long in chord too. but only about a 1/4". the rudder is much larger too. I knoe everybody does this on purpose but it is not always necesarry. I have made a smaller spit before with exact scale sized tail feather and it flies great. So I will be making plans to cut them down to scale.
I haven't really come up with a plan to cut the body down, need to do some more thinking on that problem.
As far as similar models go, the Eflite hurricane 25e is similar in size, I am curious to investigate the components of that model and look at it's construction. might be useful....
|Feb 25, 2013, 08:45 AM|
dc, a lot depends on how much time you want to put in and I speak as one who is masterful at creating unnecessary extra work for himself. The horizontal and vertical stabs are only about 10% oversize which is not noticeable once the fuse proportions are corrected. Jim Fox, of Fox Composites found that his Spitfire was very sensitive to reducing the tailplane to scale dimension. It became nearly uncontrollable when the flaps were deployed and he had to go back to the original 10% oversize.
B/c the wing saddle is a fairly complex shape, I didn't try to move it, but rather used it as my datum point and altered the fuse in front and behind. Since you have a got wire cutter (I was using a bandsaw), you can probably slice a longitudinal strip out of the center of the fuse to get the correct depth and save yourself a lot of work shaping the oval sections. I guess the only other caution I would add to try and use foam of similar density when you are altering things or making wing fillets. Using foam that was less dense and too soft was the worst mistake I made.
I am quite keen to see how you go with the fuse. Making notes for my #2.
|Feb 25, 2013, 06:29 PM|
well I am taking the easy way out on which spit Mk. I am doing.
the spitfire Mk.I has the shortest fuse of all the spits. the nose kept getting longer on later Mks due to the larger more powerful engines. the ratio of fuse to wing is 81% for Mk.Is if I remember right. I really don't need to lengthen the fuse for a Mk.I
So I lucked out there. I noticed they purposely moved the wing back and oversized the tail feathers to make it easier to fly. moving the wing is essentially making ther nose longer, making it easier to " imitate " whatever Mk. of spit you want, and easier to get the CG..
the fuse is too tall for sure, and you make a great point. I could stick them together and slice a section out of the middle. I'll have to look at how that will affect the fuse.
I really don't like the oversized elevator and rudder. 16.5" divided by the actual 14.5 it should be means it's 113.79 % oversized. it just seems totally unnecessary. Maybe I will examine the parkzone Mk.IX elevator and see if it's oversized and by how much, because everybody says it flies great with flaps. like I said I made a 40" spit with all scale surfaces and it flies great. however it's only 18 ounces, so the wingloading is pretty low compared to everybody elses I've seen.
The rudder is 8.75" divided by the scale 7.375, so it's 118.6 % oversized. yikes!
If you look at real spitfires enough you will definitely notice that this is way oversized.
personally, I look at wing loading more than anything. a heavy plane handles like crap at low speed.
I thought about the issues of disimilar foams. that is a darn good point that you make.
So I am going to take your advice on the foam and the cutting the fuse center and see how to go about that approach.
the oversized tail will get reduced, but I will take a look at other models that fly well to see how much i want to reduce it by.
Make no mistake I started the build thread because I really have no idea what I am doing, and I definitely need help so thank you for the good info
|Feb 26, 2013, 09:05 PM|
So the second 12" snowstorm has occurred last night. the second in 5 days. kinda slow me down on my progress. I have to clear 150' of driveway, plus a turn around. my snowblower could not handle the 12" of almost slush snow. It's so heavy it's like shoveling ice cream. My kids love it.
anyway, I have not been idle, just busy.
I have been working on the fuse drawings and analyzing the sureflight fuselage. This thing is fat in every direction, Except the very front is right on the money. Which makes modification complicated. It would be easier if it was fat all the way dow the line. So the main reason this model builds heavy is because it's tail heavy big time with all the extra bulk in the tail section of the fuse. it's .500" too tall, and at one point it's a whole inch too thick behind the cockpit half way to the tail. So I'm making a plan to cut the width down and then deal with the height of it, then move the wing up a good 3/4". this may make the CG closer to the nose, but it put the wing and landing gear back where it's supposed to be
As far as the tail feathers being way oversized, I will be cutting them down to be about 7% oversized. this will make the dimmensions still fit the model, and look very scale too.
I analyzed the parkzone Mk.IX spit and it's tail surfaces are approx. 10% oversized. the rudder is definitely noticeable, but doesn't look bad.
All of this pre modification of cutting the tail wieght will more than likely cut the foam components down from 18 ounces to about 13 ounces, and make the model not only lighter, but easier to balance.....I hope.
Other thoughts, I have looked at the vacuum molded parts and most are way too small. the carb scoop looks like it's for a 1/12 scale model. lol. Th e only thing that is close is the exhaust stacks. which that's good.
gonna have to make a fuse foam cutting jig tomorrow....since it's supposed to snow 4 to 7 more inches tonight..
|Feb 28, 2013, 04:50 PM|
did some work on the fuselage.
after lot's of measuring and more measuring I deciced to cut out a center section of the fuse length wise. in order to take the "fat" part out of the fuse aft of the cockpit and not as much everywhere else I bowed the foam when I secured it. worked pretty good!
then I got a little crazy and used some foil tape on the bottom of the fuse to mark where to take the next cut, and used it to guide the wire. it worked, but not as good. not as clean of a cut. buy it did work. I could using something a little stiffer could be the answer for quick alignment and prep for hot wire cuts.
I did some sanding on the fuse and it looks like it'ss gonna work out pretty good.
then I made a couple of wing cut out templates and screwed them in place where the wing is supposed to be. I didn't move it as far forward as my drawings show, just .5" and up into the fuse about 5/16" the templates are made of scrap masonite beadboard. I cut them with a little craftsman 10" bandsaw that works great. worth every penny.
it made a nice foam cut. sanding the templates smooth is key to a nice cut. I'm learnin"
so that cut 2 ounces of weight off the fuse, 90% of which was behind the CG point.
gonna get rid of some extra foam on the inside tonight, and work on the rudder and elevator.
I'm starting to wonder if I should move this thread to the scratch built foamy forum
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