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General control line discussion => Open Forum => Topic started by: Motorman on October 13, 2015, 11:37:23 PM
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I've got a Thunder Gazer kit and there's no leading edge stick to glue the sheeting to it just wraps around the ribs. How do you do this without a mold?
Also, the box top says 630 sq. in. wing but when I measure the plans it come out to 660. Does that include the flaps? Are the plans too big, what is the actual wing span, plans measure 61-1/4".
This kit has a take apart wing/tail feature. To me it looks like a ton more plywood and hardware. Anyone know the weight penalty vs non-take apart.
I'm leaning towards selling this kit and scratch building a 550 version to fit an extra electric system I've got. Anyone interested, I'll make you a deal especially if you have a Vector 40 kit to trade.
Thanks,
MM
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I got a lost foam jig from Bob Hunt when I built my Thundergazer. That's the easiest suggestion I can give regarding the wing since you'll then have a mold. One thing I did notice between the kit ribs and the ribs that you make from the lost foam system are different. If I remember correctly, the ribs in the kit had more chord than the lost foam jig.
You don't have to build the plane as a take-apart if you don't have to. You'll be able to save some weight in the end without needing all the hardware to make it a take-apart. My Thundergazer has Dallas Hanna's take apart system because the plane was initially built to go to the worlds back in 2012. If you don't need to make it a take-apart, I would suggest not doing it so that it will be lighter in the end.
The Thundergazer is the best flying airplane I have and one of the best I've ever flown. I've flown Dave's Thundergazer and mine flies almost exactly like his does.
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Matt,
Why would the lost foam jig and the kit have different ribs?
MM,
IIRC the wing area stated does not include the area that is inside the fuse. That would account for the difference you are getting when you measure the wing from the plan.
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Matt,
Why would the lost foam jig and the kit have different ribs?
MM,
IIRC the wing area stated does not include the area that is inside the fuse. That would account for the difference you are getting when you measure the wing from the plan.
Hi Doug,
I really don't know. That was just our observation though. The kit ribs and lost foam jig are up in VT right now so I can't go look at them until thanksgiving
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The lost foam cradle is just another way to get the frame of the wing straight right? I pretty much have that covered. I want to know how you get 1/16th balsa to wrap around the LE without molding it first.
MM
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Well you don't, but making a mold is very easy. You can make it from blue foam & some pieces of plywood, for example. What's wrong with that?
Or, you may modify the ribs to accept a thicker and higher l.e. but you end up using same amount of efford to make something not as good. L
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Or just order a leading edge mold buck from Bob Hunt. He can probably cut one very quickly for you. He can also provide written instructions on molding the LE that make it easy.
Or any one who has a foam cutter can probably cut one for you!
Randy Cuberly
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Well you don't, but making a mold is very easy. You can make it from blue foam & some pieces of plywood, for example. What's wrong with that?
Or, you may modify the ribs to accept a thicker and higher l.e. but you end up using same amount of efford to make something not as good. L
That's what I would to, and I even have a foam cutter. Make a form with a plywood base the span of the airfoil, and the width of the (tapered) thickness, and plywood airfoil sections on each end. Glue a blue foam block in the middle, then carve away everything outside the plywood with a knife, then a rasp or Surform tool, then sandpaper on a long block when you get close. That will give you a mold for the LE. Blue foam is easy to work with, and much cheaper than balsa (which is how we used to do it).
Note that it is exactly like molding a top or bottom block, and it even looks like a really long turtleneck mold. But I would also point out that it doesn't have to be exactly correct. Just about anything with a similar curvature would work, and for years people have molded the conventional top/bottom sheeting by simply pre-curving it on another wing, or just wetting it and curling it so it will lay on the ribs more easily rather than forcing flat wood around it and holding it with pins until the glue dries. It also reduces the tendency toward the "starved horse" effect, although you can still get it from dope shrinking later.
The reason you do it this way is that you end up controlling the shape of the LE a lot better than just eyeball carving it. Ted was the first in the modern era to do it this way and later it was adopted by others who realized some of the airplane-to-airplane performance variations could be explained by how the LE was carved. I also made him put a stringer right at the LE because I didn't want to launch the airplane with just 1/16" balsa in there.
Brett
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If you go to the building section Bobby has it there on molding leading edges.
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- Bob's price for a leading edge mold is very reasonable.
- Leading edge molds are very easy to wire cut -- for that job you can pretty much do it with a car battery and some old .015 flying lines for the cutter
- Molded leading edges are just better
You have no excuses...
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If you ask Bob to cut you a LE mold. It would be a good idea to trace YOUR root and tip rib and send it to him along with the span of each wing panel.
That way you are getting a mold that fits the ribs right out of YOUR kit. The closer the LE mold can be to the real ribs on the wing the easier it is fit the molded balsa to the ribs in their skeleton form.
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You could trim or notch the front of the ribs to accept a standard balsa LE. That being said, a molded LE is superior but the best plan may be to build a less complex model and save this one for later. 8)
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You have no excuses...
Where do you put yourself on the ability spectrum? It just occurred to me that molded leading edges are probably a pain in the behind to repair (I haven't had the occasion). If your title in the Knights of the Round Circle is "Sir Crashalot" then maybe you want to take BB's advise and wait.
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Can't remember the last time I crashed and I'm undefeated in intermediate stunt competition (inside joke). I guess I put the cart before the horse. I should have set up for this construction type before I got the kit.
The ribs are angled so won't the buck come out too thin if you use them for end templates. Maybe it's better that way to give the LE a little grip?
MM
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Can't remember the last time I crashed and I'm undefeated in intermediate stunt competition (inside joke). I guess I put the cart before the horse. I should have set up for this construction type before I got the kit.
The ribs are angled so won't the buck come out too thin if you use them for end templates. Maybe it's better that way to give the LE a little grip?
MM
Actually on a molded leading edge close is good enough for the mold buck. The ribs will do a lot to form the molded sheet to their shape.
When you install them you will use CA with a long thin nozzle to apply the instant CA while you hold the molded sheet in place. It's very easy with a Lost Foam Jig a little more difficult with a simple wire jig but still feasable!
Randy Cuberly
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Can't remember the last time I crashed and I'm undefeated in intermediate stunt competition (inside joke). I guess I put the cart before the horse. I should have set up for this construction type before I got the kit.
There are not straight ribs at root and tip?
You should talk to Bob -- he probably understands the difference between what he supplies and what's in the kit, and probably already has appropriate templates for the kit. He'll tell you if he has what he needs.
I've done a molded LE once, and even though my LE wasn't exactly right, it still went on just fine. Having a LE molding that fits exactly is a Really Good Thing, but all you really need is something that you can coerce into fitting snugly against all the ribs and the spars without either breaking or springing away before the glue dries. That's not to say you should purposely start out with something sub-standard -- just that if you can't achieve perfection you shouldn't throw yourself on your sword.
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Can't remember the last time I crashed and I'm undefeated in intermediate stunt competition (inside joke). I guess I put the cart before the horse. I should have set up for this construction type before I got the kit.
It's a learning curve like any other. You're doing OK so far. This is a pretty complex project even by stunt standards.
Brett
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With ribs from the RSM kit having a longer cord lenght then the lost foam ribs how does that affect the wing installation into the fuse If I build the wing using the lost foam method isn't the wing cut out in fuse from the kit designed around the longer cord?
Charles