Hybrid-Profile Flite Streak/Cox Hyper Viper scratch build

I'll be cutting wood soon. That wing is going to be a beeotch. I might have to shop for a couple of good small Japanese type hand saws. And I have a 1.5" belt sander. Those tools and my exacto knife have some manual labor in store for us. I have no idea how long it will take, but barring a blown shoulder or sutures, it'll be ready this flying season.

I have great faith in your abilities. Buy your Xacto blades by the 100 and change them often.

lousyflyer wrote:I have great faith in your abilities. Buy your Xacto blades by the 100 and change them often.

Ditto!

The dawing looks really sharp! I am looking forward to watching this.

Good Luck,

Bob

What's the best way to get the plans from the drawing to the wood? I figured I would use tracing paper to copy the plan. Then what? Tape the tracing to the wood and use a sharp pencil to dot dot dot... outline it onto the wood?
I'm still working on the wing drawing. But I want to go ahead and mark the fuselage.

I have read that when building for scratch, you have to watch the absolute wing trailing edge to elevator leading edge distance carefully. If that distance is to close, it would be very twitchy on controlling. Never built from scratch myself, so I can't confirm or deny.

Maybe just build a test mule, so you can add or subtract wherever you might need to, to get the final configuration.

PV Pilot wrote:...
Maybe just build a test mule, so you can add or subtract wherever you might need to, to get the final configuration.

I did. I call it the Baby Flite Streak.
All of the distances and dimensions on this build are the same as the BFS. Only the cosmetic shapes are changing. The stab, rudder and wingtips will be shaped like the Hyper Viper, and If they cause any flyability problems, I'll deal with those after the fact. The fuse has the wing cutout and the stab notch cut the same as the BFS and the rearward cockpit gives the fuselage the illusion of being very differently shaped where it's really not.

I know I have seen posts on either RCG or RCU that say you can use some chemical ( something like lacquer thinner or mineral spirits but I do not remember) to get the ink to soak throught the plans and onto the wood. If I find it I will post it here.

Bob

INK! Bingo, thanks, Bob. I can take it from here. If I can't come up with it, my son is a chemist.

EDIT: I just searched woodworking forums. There are a gazillion ways to do it. Carbon paper, graphite, chemicals to transfer toner from ink or a copy machine image, yada yada yada...

EDIT#2: Hobby Lobby(the Martha Stewartish one) has graphite transfer paper. $3.99 for an 18"x24" sheet.

And for my next question, the wood for the fuselage.
The Streak is built with a 1/4" fuse. I have a slat that I planned to cut it from. The grain looks a lot like what the Streak kit supplied. I could use some tips about how to select the wood.

I was also wondering if it might be a good idea to use 3/8" balsa for the fuse. Considering the TD pulls the Streak around at about 60 MPH and the new plane will have a much more powerful .061 Big Mig. I'll be making a balsa run to the LHS, but I have to wait on the paycheck first, so I have some time to consider my options until I jump all the way in.

Here's the 1/4" slat I have



Here's the wood from the BFS kit for comparison

Rusty,

I usually try and find the denser wood from the inner part of the tree when selecting fuselage lumber. It is usually darker in color than the new growth and has a harder feel when I use my patented "fingernail" test. In addition if you can find a piece with those attributes and the grain also runs on a slight diagonal then you have a winner.

That's what I do anyway. Of course 60MPH into the ground is going to stress any structure no matter how perfect your wood selection is.

Edit: BTW the picture of your slat looks to be almost perfect. I can't tell how the hardness is though.

Ron

As far as I can tell, it's about the same hardness and flexibility as the Streak sample. With the Norvel on it, it would be moving faster than 60 if the planes weighed the same. That's why I'm thinking of getting a 3/8" piece, for weight and strength. But that could make it require too much more nose weight. I could counter that some by bolstering the nose with thicker doublers. I don't want to ruin the flyability by changing something too much like that. The more I think about it I realize this seems like a critical decision.
I'll try to find similar looking wood. If the LHS doesn't have it, I'll order it from Sig or somewhere.

I would certainly watch the weight. If for instance, the wood you choose is quite flexible. This sometimes happens to me. I sand the wood tapering the edges until they're paper thin. To regain the strength, I either glue a small piece of spruce or bass onto the edge that has become weak. In the event it's the fuse, 3 -4 coats of (thinned) dope and proceed with OO silkspan from doubler to tail. You would certainly be amazed at the strength you gain from this with very little weight penalty. Thinned white glue could also be used to install the silkspan which works amazing. This can really tighten up the fuse. I would keep your doubler material as thin as possible. I use 1/64th ply for my doublers as most use 1/32". The 1/32' can add weight which you don't need. I see absolutely no need for you to use 3/8" material unless that would be the look your trying to achieve. If you did choose the 3/8" I would certainly be weighing the pieces to find the lightest. Having a scale on hand is a real handy tool. It allows you to place the heavier wood to the outboard wing eliminating tip weight for one. It also allows you to see the weights of the wood on hand. I've saved almost 2 oz's on full size stunters just in wood selection. Ken

Thanks Ken. I'll take your advice and stick with the 1/4" fuse. My sheet of wood hardly has any flexibility at all in either direction. As for the strip of basswood you're talking about, do you apply a strip to just one side or both sides of the fuse? I also have a 1/16"x3/8" strip of carbon fiber. Do you have any use for that as a reinforcement component?

When I stupidly maidened my tail heavy Streak with too much fuel on board and belly bashed it, I cracked the fuse below the stab, so I may very well consider that addition. The Streak now has a fiberglass and epoxy patch to strengthen it. Luckily it flies nicely after I got it balanced. I didn't fully appreciate how much a 3/16" shift in CG affects flyability. I do now.

Rusty, since I taper my fuse generally from top to bottom the underside becomes quite thin. As you know when balsa is tapered into a point it has very little side to side resistance and can break off. This would be an area that I would glue a piece of bass on. Many times however if I don't feel the strength is in the wood itself for the fuse, I've even split the fuse down the middle and glued a 1/4" x 1/4" piece of bass or even white pine down the center. Ken

I'm going to learn a lot from this build. I've looked at 20 or so square 3/8" dowels for the LE. I have yet to find a straight one. I suppose I'll get good at straightening wood by the time I get this thing built. My 1/4" fuse board is nice and flat though. I've brought all of my wood into the house for a constant humidity, as the shop is very drafty.

Looks a lot like the Zingers I am building.

http://aeromaniacs.com/Zinger.htm

Before you cut the fuse, build the wing and tail structures then rubber band and pin this to a stick with the motor and fuel tank to see if the nose is approximately the right length to not need more weights added.

I was stressing pretty heavily about balance with the sketchy plans on the website, and a slight scale error from the printer. I have the wings covered, fuselage glued up with sanding sealer on it and with a motor pinned to the end it balances reasonably well on both planes I am building (when crashes are expected I build duplicates)

Phil

That's going to be my Dead Cold of Winter project. It's really just a Baby Flite Streak with different lines, but the critical dimensions are all identical.