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Building Tips and technical articles. => 1/2 A building. => Topic started by: Chris Keller on October 21, 2008, 07:43:29 PM
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I know that I appreciate seeing halfa's that are different from the readily available kits, so here is one that I scratch built from an idea in my head. Wingspan is 28", Length about 12", wing area about 155 sq. inches. I plan on powering it with either a brodak mk II or an .061, probably the .049 on about 40' lines. I think I'll call it the ScrewDriver. Let me know what you guys think, and if there is any thing that sticks out that may need attention. I built a slight bit of offset into the nose, as you might be able to see. I think I may need to put a strip on the trailing edge, but I'm not sure. it will be covered in tissue. I'll try to get a weight before I
crash fly it:
(http://i48.photobucket.com/albums/f218/wish4fish/DSCF3001.jpg)
(http://i48.photobucket.com/albums/f218/wish4fish/DSCF3006.jpg)
(http://i48.photobucket.com/albums/f218/wish4fish/DSCF3005.jpg)
(http://i48.photobucket.com/albums/f218/wish4fish/DSCF3004.jpg)
(http://i48.photobucket.com/albums/f218/wish4fish/DSCF3002.jpg)
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what part of the country do fly in ? also there are some very nice glass props that work real well. try kittingitogether.
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Oughtta be fun, nice fat airfoil, looks light...a little reminiscent of a baby Equalizer.
Aptly named, liable to screw you into the ground with an .061--my slightly larger combat planes (30" span, 180 squares) do about 70-75 mph with a Norvel BigMig .061, that's about 2.5 sec. laps on 42' lines. 40' lines minimum are a good idea, you probably should try it with the .049 first. I think the Brodak and Norvel share the same bolt pattern.
Well thought-out design, booms are centered over ribs, planking extended to give enough surface to stick covering to. You might want to blunt that LE a little, really the rounder the better. Styrofoam wedges in the TE between the ribs would help support it without adding any weight to speak of.
Depending on where the CG comes out, you might consider moving that front leadout back a little. 1/2" between them is enough, and it sure needs to be behind the CG.
Can't think of anything else, it looks really good--and mean! Be sure and post a flight report.
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Let me know what you guys think, and if there is any thing that sticks out that may need attention. [/color]
Neat!
If that is a notch in the LE for tank clearnce, I would strengthen it with a 1" wide strip if thin FG cloth.
But then, I'm a belt and suspenders guy.
Good Luck!
Screwdriver looks like a very appropriate name, especially w/ a Norvel. Hang on!!!!!! #^
Roger v.
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Thanks for the replies! I fly in Northeastern ohio and northwester pa. My dad and I are getting back into flying after about a decade or so of absence. We fly only 1/2a's at the moment. They're fun, smal and cheap enough to build plane after plane. We have a lot of cox engines, but I recently bought a brodak mk II and definately see that a venturi motor with a standard glow plug is the way to go. No more running backwards! I wish there were more 1/2a kits that were designed for beam mounts.
That little cutout in the leading edge is for a tank, but its so shallow I'm not really worried about the strength issue. The plane is pretty lite, but nto as much as it could be. I used heavy weight balsa in the nose and the booms and basswood for the spars. I want this thing to last! We'll see. I get home from a business trip this afternoon and am going to try to get it covered tonight so I can fly it this weekend. I'm going to look into moving the leadout too, thanks for the tip. I guess I should mount the motor and tank before I cover it to find the CG
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Chris,
That is a very neat looking model. Looks like it will fly really well.
As to beam mount planes we make several that use either type of engine and we have just developed a method to incorporate a conversion set up in 80% of all of our 1/2A kits. We will be putting it into our kits starting next month. Most other kits on the market can be converted with motor mounts that are available.
LARRY
Black Hawk Models
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Also virtually all of mine--I can set up the kit however you want it, beam or radial, most any engine.
I'm nearly in shape to begin cutting again.
Minnesotamodeler
http://snipurl.com/9igp
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Hello Chris,
Thirty years ago I raced motorcycles at
Nelson Ledges just north of Akron. Ahhh.. good times!
I know that you're concentrating on 1/2A's for now,
but I wanted to extend an invitation to come to a
contest or two at Niagara Falls Ontario, next summer.
The circle is close enough to the Falls that you can
see the mist plume on a clear day.
The combat guys are starting to compete again
over in Buffalo. They play hardball but everyone is
friendly and welcoming.
You can get an idea of what's going on by checking
out the contest reports and news at
www.balsabeavers.ca
If you're new to competion, bring a plane and
fly the "Jim Walker". We would love to see you
there. y1
Cheers! - Keith Morgan (Goozgog)
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It looks good to me. It will be a scorcher even with a Brodak Mk II, and blinding with a .061. Consider covering with Coverlite. It is totally fuelproof as is and needs no doping. It is lighter than doped Japanese Tissue and WAY tougher! Sig Stix-it or Balsarite on the wood, then iron it on. I have it on my Sky Sport and it has NO holes after 3 years.
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Hi Chris- in regards to the leading edge notch for the tank. At a minimum you want to sand a taper or radius at the corners of the cut-out. Sharp 90 degree angles will concentrate stress at that point and may cause problems after flying it a bit- especially if you doink it into the ground.
If you dont have any lite fiberglass cloth- an extra layer of tissue or silk with the edges tapered to distribute the stress doped over the area will help without a noticeable weight gain.
On full scale aircraft you will almost never see a sharp angle / thickness change in a structural component. Experience has proven that they are a bad idea - more than a few planes have gone due to stress cracks starting at places like that.
FYI - I love the plane-and if it flies too fast and ya get dizzy I'm sure you could stand in one spot and do lazy 8's until you regain your balance. It sure looks like it will do some nice inside / outside loops!
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looks good chris!!!!! How many fingers will get sliced open starting it?? :-X :-X :-X
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you know I didn't cut myself at all last time I flew, but we'll see, haha. I'm currently doping it in my bathroom because of the exhaust fan. I wish it was a little stronger. I've got a nice little butyrate buzz going on, but I just hope it dries before amy gets home.
That notch will be fine, really all that I did was to make a more pronounced radius in the leading edge. Its a pretty smooth transition (I sanded a little more since the pictures), and really not deep enough to effect the structural integrity of the leading edge. There is a lot of support under that sheeting as well.
The cool part on this model is that the 45's coming off the tail are the stops for the elevator. I probably could stand in one spot! n~
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Chris, that is my kind of plane!! Love the airfoil shape, what kind of tank are you planning on using? Tank choices and position are critical on 1/2a combat types for good runs. Please report overall weight and cg after engine is mounted. Hurry, flying season is about to end, never mind , flying season never ends!! LL~
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Hello Chris
Looks great - hope to see you back out with our group again
Dalton H.
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... I wish there were more 1/2a kits that were designed for beam mounts...
Since you bought a Brodak engine I am guessing that you have seen his offerings.
For scratch building, there are LOTS of Dick Sarpolus' sheet-wing designs published in Flying Models over the years. Most used a TD .049 for power. Some of the smaller ones offered an option of installing a tank mounted engine. My favorite is the Zlin Akrobat.
SIG makes the Skyray, which is an excellent sheet-winger but must be modified to use a beam mount.
These, plus the ones mentioned above should provide a good selection to choose from.
George
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Here is the finished plane! heavy tissue, two coats of supercoat clear over the tissue, two coats of color, no top clear. The weight was 6.8 ounces with the engine and tank mounted. I flew it on sunday in near gail force winds. On 25% Nitro, with a 5.5 x 3 tornado prop, I was flying 3 laps in about 8 seconds, so not too bad. Handles really nice, doesn't hunt or anything. Balance point is a fraction of an inch in front of the leadout. Flies nice and steady level, but the outboard wing is a bit high. I'll have to put another nickel in the tip sometime. I'm trying to figure out a way to put its name, ScrewDriver on the plane. The wind was really bad, so I didn't get to experiment as much as I would have liked. 2 flights was all I could manage. Hope you like it, I think it has a sort of "old school" look to it:
(http://i48.photobucket.com/albums/f218/wish4fish/DSCF3008.jpg)
(http://i48.photobucket.com/albums/f218/wish4fish/DSCF3009.jpg)
(http://i48.photobucket.com/albums/f218/wish4fish/DSCF3010.jpg)
Here is my dad and I with a few of our fleet: I have a baby flight streak and the screwdriver, and my dad has a flight streak and a baby lightning streak. We have a few more than this, and the collection is getting bigger. thats what i like about half a:
(http://i48.photobucket.com/albums/f218/wish4fish/DSCI0003.jpg)
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Your "fleet" looks good, also the dog!
What is that picture on the far left, with the photos arranged in a circle? I've seen a very similar one before.
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I'll have to put another nickel in the tip sometime. I'm trying to figure out a way to put its name, ScrewDriver on the plane.
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Hi Chris,
Here's one way to do the name. See: http://www.youtube.com/watch?v=8NhLZ-4V1pM
On the tip weight - - If you already have a nickel in the outboard wing, that may be enough; you may have a tiny warp in the wing. The only way to tell is to try level inverted flight and see if the outboard tip is still high. If it is, then you do need more tipweight.
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What is that picture on the far left, with the photos arranged in a circle? I've seen a very similar one before.
Not to answer for Chris - but it looks like a succesive school year photo frame. We have one for our daughter and it starts in 1st grade ... all the way to high school graduation.
FlySafe! Larry (Larrys4227)
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Guess it's a fairly common way of arranging multiple photos.