Scratch building a new plane - without plans, just an idea

**RknRusty** Wed Aug 29, 2012 9:19 pm

I want to build another plane, because if the Streak gets grounded for any reason, I want another quality flier. As I said when I flew it full out for the first time, it makes all of my others seem like lightweight toys. I need to build a plane that will fly well with the Norvel .061.

At first, I thought I can just scratch build another Streak. Then I was browsing threads the other night and saw a Cox Hyper Viper and loved the shape and lines on it. I thought maybe I could build a profile model that has the same look. I have the Baby Flite streak plans and the airfoil punch out from the fuse that I could use to shape the ribs with. But I can't exactly duplicate the streak, just using different shapes for the fuse and rudder and wingtips because the wing on the Viper is set way back. I wouldn't have guessed such a long nosed plane was a good stunter, but I obviously know very little about what I'm doing, and I don't want to build a kludge.

I do feel like I could build a streak knockoff with a few cosmetic changes that look sort of Viper-like and with some simplifications that might fly right, but I'd really like something different. So, I need advice. What are the chances that I could build a quality plane in the fashion I'm describing? Where to start. I suppose sketching out the plans and building a wing would be the first thing. Am I biting off more than I can chew here?

Here's the Viper:
Scratch building a new plane - without plans, just an idea Cox_hyper_viper_1

Scratch building a new plane - without plans, just an idea Cox_hyper_viper_1

Scratch building a new plane - without plans, just an idea 47-28

Scratch building a new plane - without plans, just an idea Cox_hyper_viper_2

**RknRusty** Wed Aug 29, 2012 9:28 pm

Actually the distance from TE to Stab looks about the same. The Viper nose is just longer. The rearward placement of the cockpit may add some illusion to that.

lousyflyer Wed Aug 29, 2012 9:53 pm

My Viper was fast for a stunter.

**Cribbs74** Wed Aug 29, 2012 10:08 pm

Scratchbuilding, especially a profile is quite easy.

All you would need to do is draw it up and work off your drawings. Since it's your own design you can change it to suit your needs. I think at this point in the game you are more than accomplished enough to do it.

This site will help ensure you are building a plane that will fly the way you want it. It's for RC mainly, but it will help from an engineering standpoint.

http://adamone.rchomepage.com/

Ron

**RknRusty** Wed Aug 29, 2012 10:26 pm

Thanks Ron, that looks like a great site. I definitely need the calculators.

**Cribbs74** Wed Aug 29, 2012 10:41 pm

No prob, cant wait to see the finished product and subsequent video!

If your successful then I may design something myself. Judging by Kim's many 60's magazine snippets just about everybody came up with their own design. Their innovation made the hobby what it is today!

Ron

Mark Boesen Wed Aug 29, 2012 10:55 pm

designing a 1/2a ukie is pretty easy...and a lot of fun! Go for it, you'll do well just don't try to re-invent the wheel.

Here's one of my very first designs, built in sixth grade, photo taken after i made it a biplane...flew better with one wing.

Scratch building a new plane - without plans, just an idea Origin11

**RknRusty** Wed Aug 29, 2012 11:12 pm

When you make ribs, I suppose you just stack a bunch of rectangular sheets together and sand them to shape? I have a 2" belt table sander. I guess it's best to bore a couple of holes through the stack and hold them in place with dowels when I sand them.

When I made the LE for the Li'l Satan, I had a square dowel and worked it down with a razor plane and then sandpaper. But it was so small I could just eyeball it and it came out right. This longer one will be harder to shape. Maybe I can make a LE foil shaped sanding block.

Hi Mark, that's a pretty neat little plane.

Okay, I've got the wheels turning now. I probably have most of the wood too.

happydad Thu Aug 30, 2012 2:04 am

cribbs74 wrote:Scratchbuilding, especially a profile is quite easy.

All you would need to do is draw it up and work off your drawings. Since it's your own design you can change it to suit your needs. I think at this point in the game you are more than accomplished enough to do it.

This site will help ensure you are building a plane that will fly the way you want it. It's for RC mainly, but it will help from an engineering standpoint.

http://adamone.rchomepage.com/

Ron

ahh shucks all i ever did was build it and test glide it. if the CG was close to 1/3 of wing chord back from LE it would usually glide. if it doesn't glide o.k. it most likely wont fly. but then again i fly mostly gliders. same principles apply.
good charts Ron. now your secrets out. happydad Small Cox Logo

**RknRusty** Thu Aug 30, 2012 6:28 am

happydad wrote:ahh shucks all i ever did was build it and test glide it. if the CG was close to 1/3 of wing chord back from LE it would usually glide. if it doesn't glide o.k. it most likely wont fly. but then again i fly mostly gliders. same principles apply.
good charts Ron. now your secrets out. happydad

That's true, I could test it like that over the grass. One time after I planted my Jumpin' Bean I got so mad I picked it up and hurled it as hard as I could throw and it floated through the air and did a rolling landing on the sidewalk by the stooge. Surprised

**Cribbs74** Thu Aug 30, 2012 9:20 am

RknRusty wrote:
happydad wrote:ahh shucks all i ever did was build it and test glide it. if the CG was close to 1/3 of wing chord back from LE it would usually glide. if it doesn't glide o.k. it most likely wont fly. but then again i fly mostly gliders. same principles apply.
good charts Ron. now your secrets out. happydad

That's true, I could test it like that over the grass. One time after I planted my Jumpin' Bean I got so mad I picked it up and hurled it as hard as I could throw and it floated through the air and did a rolling landing on the sidewalk by the stooge.

I guess the Bean showed you! Kinda like "Hey man, I can fly just fine"

I have a Brodak Bean to build next, probably followed by a Baby Clown. All this leading into a scratch built Veco Scout. Kim mailed me some wicked nice plans for one.

**Cribbs74** Thu Aug 30, 2012 9:24 am

RknRusty wrote:When you make ribs, I suppose you just stack a bunch of rectangular sheets together and sand them to shape? I have a 2" belt table sander. I guess it's best to bore a couple of holes through the stack and hold them in place with dowels when I sand them.

When I made the LE for the Li'l Satan, I had a square dowel and worked it down with a razor plane and then sandpaper. But it was so small I could just eyeball it and it came out right. This longer one will be harder to shape. Maybe I can make a LE foil shaped sanding block.

Hi Mark, that's a pretty neat little plane.

Okay, I've got the wheels turning now. I probably have most of the wood too.

What I do is just make an extra set of plans, cut it up and then cut ribs using the plans as templates. Then I sand them as you suggested. If you have a belt sander it would save some time.

**RknRusty** Thu Aug 30, 2012 9:48 am

Yeah, I don't think I'll have any trouble. There are a gazillion threads on RCG, each one with with twenty seven eight-by-ten color glossy photographs with circles and arrows and a paragraph on the back of each one explaining how each one was to be used... pictures of the approach, the getaway, the northwest corner the southwest corner and that's not to mention the aerial photography... if you know what I mean.

**RknRusty** Thu Aug 30, 2012 3:07 pm

Inventorying my wood and supplies, I looked at the old sheets of balsa that the Baby Flite Streak ribs came from and they looked like 1/16" of pretty soft long grain wood. So I went to my spare sheets and picked one out with a label on it that said 1/16" and it's much harder short grain balsa and looks thicker. The caliper says the old rib sheets are .060"(1/16"). The Wood labeled 1/16" in my supply measures .07+". I thought maybe it was mis-labeled 3/32, but that would be .09". Strange. I guess the balsa mill just isn't all that accurate. Who warned me not to over think this??? Not a question about the wood, just an observation. I'm using what I've got.

I also found a pack of Sugru my son gave me for Christmas. I can make a foil shaped sanding block with it. If I cover the Streak's LE with plastic wrap and pack the sugru over it and let it set, voila, I have a perfectly shaped sanding block. Anyone ever used Sugru? It'll be my first time.

lousyflyer Thu Aug 30, 2012 3:23 pm

I must confess that I had never heard of sugru until now. How big is a pack of sugru?

**RknRusty** Thu Aug 30, 2012 5:35 pm

I'll have to check. It looks like 6 or 8 ounces. Did you look it up?

lousyflyer Thu Aug 30, 2012 6:04 pm

RknRusty wrote:I'll have to check. It looks like 6 or 8 ounces. Did you look it up?

Yes. Like modern day Play-doh

Ken Cook Thu Aug 30, 2012 6:59 pm

Many times you have wings that are tapered. If the plans don't have individual ribs designating each one this can be problematic. If you have the root rib, (center) and the tip rib you can proceed. You make a plywood template of each with centerlines. Lay the tip rib on top of the root matching centerlines. At this point, I like to tack glue them together on their centerlines and drill two holes in from each end. You can then count the ribs needed from the plan and cut yourself blanks of balsa in the number required. You sandwich the blanks between the templates and through drill the stack. I bolt them in a big sandwich. Make sure all is square and then you sand down to your templates. This will get you real close. I leave them a touch heavy and final sand them after I removed them from the templates due to the fact that it sands the ribs on a angle. I square them individually. Ken

**RknRusty** Thu Aug 30, 2012 7:44 pm

I have filed that useful tip away where I can use it when I build a tapered wing. Luckily they're all the same size on this wing except the two root ribs that have to make room for the 1/16" sheeting. I'll make them all the same size and sand the two narrower root ribs to fit.

**RknRusty** Fri Aug 31, 2012 6:43 pm

So to summarize, I'm going to build a plane with the Hyper Viper lines and angles, but out of fear of building a kludge, I plan to put the wing, stab, tail and nose in the same positions as they are on the BFS, which I know is a flyable configuration. But this one is going to be flying with an engine that puts out maybe twice the power of a Tee Dee(if what I read on RCG is accurate). I know power to weight ratio is far from linear.

My question is about scaling. I'm wondering if I make every measurement a certain percentage larger than the BFS, say 5% or so, what kinds of difference it will make in it's flight characteristics. My goal here is to not have to find a bigger field and to still have a fun plane. Honestly, I couldn't handle the BFS and still smile while I was flying if it was much faster.
Rambling Rusty

happydad Fri Aug 31, 2012 7:04 pm

RknRusty wrote:So to summarize, I'm going to build a plane with the Hyper Viper lines and angles, but out of fear of building a kludge, I plan to put the wing, stab, tail and nose in the same positions as they are on the BFS, which I know is a flyable configuration. But this one is going to be flying with an engine that puts out maybe twice the power of a Tee Dee(if what I read on RCG is accurate). I know power to weight ratio is far from linear.

My question is about scaling. I'm wondering if I make every measurement a certain percentage larger than the BFS, say 5% or so, what kinds of difference it will make in it's flight characteristics. My goal here is to not have to find a bigger field and to still have a fun plane. Honestly, I couldn't handle the BFS and still smile while I was flying if it was much faster.
Rambling Rusty

Rusty: if you are going to start with 2X horsepower, for lack of a better word, what are you going to give up if you want the same line length for the same field and the same plane speed?? the only thing i can think of is a geared prop setup and i'm not to keen on that idea or know who is. otherwise physics still applies. 2x horsepower x ?? = faster speed ?? needs to be less than 2. my two cents

happydad

**RknRusty** Fri Aug 31, 2012 8:54 pm

Twice the HP(I read the .061 was 140watts) is only a small increase in speed for the same weight, so the plane only has to be slightly larger to spend the extra power. A couple of inches longer and wider, I think.

I compared the measurement differences between the two planes and it's enough difference that I'm just going to have to draw what I want it to look like and wing it from there. I'll copy the BFS wing which has a wider chord than the Viper and maybe add one rib width. The Viper fuse is already longer. I'll draw it up and think about it. One way or another it will fly.

happydad Fri Aug 31, 2012 9:59 pm

RknRusty wrote:Twice the HP(I read the .061 was 140watts) is only a small increase in speed for the same weight, so the plane only has to be slightly larger to spend the extra power. A couple of inches longer and wider, I think.

I compared the measurement differences between the two planes and it's enough difference that I'm just going to have to draw what I want it to look like and wing it from there. I'll copy the BFS wing which has a wider chord than the Viper and maybe add one rib width. The Viper fuse is already longer. I'll draw it up and think about it. One way or another it will fly.

if you know what size wingspan you want, just copy your plan at +8% and that will make the wing larger by about 2inches on my hp 3030 lazer printer, each printer is different of course. when you reach the wingspan you want, copy and paste the entire plan. that is what i do for small increases. that is a good starting point for your new design.
when i converted a 2meter wingspan glider to 1meter wingspan i maintained winspan to elevatorspan, wing chord to elevator chord and etc. the only thing i ever messed with was the fuselage width. i basically sketched it all out from there using the fullsize 2meter plan as an outline. the concepts seemed to work perfectly and the 1meter glider flies great and very gentle. again my two cents.

happydad.

**RknRusty** Fri Aug 31, 2012 10:48 pm

Thanks Dad. It's time for me to start building and just do it. When I have something to show, I'll post it.

happydad Sat Sep 01, 2012 2:32 am

RknRusty wrote:Thanks Dad. It's time for me to start building and just do it. When I have something to show, I'll post it.

i wasn't up on the flite streak so i looked it up on google. were you aware that the original baby flite streak design had a 26inch wing? Huh...

(duh) i thought it was more like the baby ringmaster in the 21inch range. the flite streak jr has a 31inch wing, brodak i think, for a .15 to .29 size engine. not much more wing for a lot more engine. Two Cents

happydad

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