Ringmaster Jr. Build.

Yes that may work.

I don't get concerned about things being overpowered as much as I do about the weight of an engine. Power can be tamed, but nose heavy is nose heavy. I mentioned earlier that I would prefer a .15BB schneurle over a .15X. If it wasn't so darn heavy I would have used it. Now it looks as the .15X will be too heavy. I should have slid the wing forward about 1.5" or lengthened the tail. It was a kit build so I was a bit limited.

I just don't like how unbalanced models perform. It's stressful!   

Cribbs74 wrote:Another hotel job!

I am in Idaho and believe it or not the LHS carries Brodak items so I decided to buy a Ringy Jr. And build something to fly here.

I started last night and here is where I am at. The wing was started around 5:30 mountain time this evening and is probably the quickest wing build I have ever done. Thanks to laser cutting and good wood it's actually straight too.

Power will be a Fox .15 although it's coming out nose heavy so I may go to a Cox TD .09 when I get home.

Shipping should be fun!

Ron

Ron: If the RM Jr is nose heavy and you haven't finished mounting the engine, can't you move it back towards the wing 1/4 - 1/2 - 3/4inch or so to help lessen the tendency to be nose heavy because of the engine?

see picture.


happydad

    

Happydad,

Yes I could move the engine back and yes it would work however, it would mean that O would have to cut down the nose. It's a fine line between functionality and aesthetics.

The way the engine is mounted at the moment is as far as I can go back and still clear the driveplate and spinner.

I know how to correct it all, just venting about it being nose heavy.

Anyway, progress is slow at the moment. I wanted to just paint and monokote this thing, but monokote does not exist here apparently. Dope does, but no silkspan! So I decided to go the dope route. Walmart had some thin polyester dress lining that is supposed to shrink.

Here is the doped plane, tomorrow I will adhere the polyspan type covering and shrink. After that dope and paint!

Ron: Have you figured out how much nose heavy you are? Either by using tail weight or fudging the engine towards the wing. Is it 2 ounces tail weight versus 1/2inch engine movement.or 1 ounce tail weight versus 1/4inch engine movement. You could rubberband the engine on the fuselage to get an idea how far you would have to move the engine toward the wing versus add weights to the tail for correct CG. I'm sure you already know this approach.
    Also the CG may move + or - a little after painting/covering.

   You could always trace the nose profile as you cut it back.

happydad

      

I am a bit heavy handed when finishing but have found that. for me anyway, the C of G can be significantly altered by it.

I am guessing but it looks as if 1g of finish on the tail plane but outbalance the engine by 3g. Overall, the majority of the finishing weight is behind the C of G.

Also the pushy thing, triangle thing and sticky out bit on the elevator doesn't look to be there yet. These could make quite a difference.

If the push rod weighs 2g then that will move the C of G back by 3/2*2 = 3g. The horn, if 1g, would be equivalent to 3g.

So far, tail plane finish 3g, push rod 3g, horn 3g = total 10g reduction to the motor weight. Everything makes some difference

Cribbs74 wrote:Happydad,
...I know how to correct it all, just venting about it being nose heavy...  

Remember that plane was designed for an un-muffled Cub, K&B, Cameron, etc.  

George

Thanks George, I did some research and those engines weigh just as much or more than the .15X.

My guess is that it always built nose heavy.

I just doped a wing for my first time!!!

Congratulations, you can rub elbows with the big guys now.  I hope it shrinks up correctly and makes the nice covering it's supposed to do.
I'm making bits of progress on my build but sanding has flared up my shoulder, so little bits at a time til it loosens up. I wish I had one of those contoured sanding blocks that help shape wingtips. My LE is a 1/2" square dowel. When you come to Columbia I can give you a work table and tools if you bring something to work on.
Rusty

RknRusty wrote:Congratulations, you can rub elbows with the big guys now.  I hope it shrinks up correctly and makes the nice covering it's supposed to do.
I'm making bits of progress on my build but sanding has flared up my shoulder, so little bits at a time til it loosens up. I wish I had one of those contoured sanding blocks that help shape wingtips. My LE is a 1/2" square dowel. When you come to Columbia I can give you a work table and tools if you bring something to work on.
Rusty

I did it different, what you see is dope and dress liner fabric. It dopes on and tightens up with an iron/heat gun. It's like a heavier silkspan.

I may just buy/build something while I am there. Who knows, although if I can fly I would rather do that over building.

Hope your shoulder gets better soon. I used a hobby knife to carefully shape my LE on the Twister which is 1/2" square. A planer would help too.

Here is the wing covered in it's entirety.

That's pretty. How many times will you have to sand and dope?

Did you like the smell? The aroma of dope!

Rusty,

I will have to dope some more to fill in the weave of the fabric. It would be easier if I could spray instead of brushing.

Ian, the smell is strong, but tolerable. Not sure if my maid will like it. I may be walking the streets tonight with a Ringmaster and the clothes on my back!

I'll pass on some advice I've only heard and never done. Be sure and brush it on lightly so it doesn't form droplets like stalactites on the underside of the fabric. I think that's a Ken Cook tidbit.
Rusty

I'm very interested in the poly cloth from walmart. I usually buy polyspan off the net and have to pay high shipping and I alway run short, having to re-order in the middle of a project. How much did it cost? Was it the same as polyspan?

duke.johnson wrote:I'm very interested in the poly cloth from walmart.  I usually buy polyspan off the net and have to pay high shipping and I alway run short, having to re-order in the middle of a project.  How much did it cost? Was it the same as polyspan?

It cost me $1.97 per yard and I bought 1 yard and have a bunch left over. It has to be very thin and 100% polyester. Do a search for "covering wing with dress liner" that is where I found the info. This is my first dope covering so I can't comment if it's the same as polyspan. From what I have read it is very similar. It shrinks with heat and the dope pulls it nice and tight. It works around compound curves well, but I had to pin it to keep it adhered at the tips until the dope dried. The good thing is that dope dries quickly.

The wing feels very light even after covering. If I had a scale with me I could tell you what it weighed before and after. Also appears to be more puncture resistant than monokote.

Rusty,

I had that happen in a couple places on the top side. I did the bottom first and was able to work inside until I covered the top. You can see a couple places where the dope formed a small puddle, but no stalactites.

Still learning, although I am happy for my first try at it.

Ron

Using thinned dope for the first coat or two can prevent drops forming on the inside. The idea is to seal the fabric before trying to fill the weave. The nature of dope is that subsequent coats will soften the previous coats, so incomplete coverage during early coats is a non-issue.

Incomplete coverage of color coats may be a different story.

Phil

Phil,

I was roughly 70/30 thinner to dope. I am running out of dope though!

Thanks Ron, I'll look for it tonight. Thanks for the tip.

I'll be watching this progress. I'm interested in trying it. A blank palate for painting... if I can figure out how to do that in an artistic way. Maybe I could get my sister to do it, she's an artist.
Rusty

Ron, I know your running out of dope, but the high thinner ratio with successive coats can also lift your attachment coats so use caution. Start using just enough thinner to keep the brush from dragging but enough dope to start filling the weave. You already mentioned that you had to pin the wingtips. This is telling me that there wasn't quite enough dope on the tips to melt into the weave and keep it in place. That happens with silk as well. The solution is to mix some Duco cement with dope thinner and use your finger and force it through the weave. If it starts lifting you can CA that area down but don't use thin. Use thick and again use your finger to rub it in.

My suggestion to not have dope drip through fabric or open weave cloth is to brush with the direction of the ribs for the first few coats. If you brush perpendicular, the dope gets forced up and puddles against the rib dripping through the weave. The puddles your describing can also cause shiny spots in the color coats. I usually burnish the clear coats prior to color using a Scotch Brite pad. Sandpaper snags badly on polyester fabric unless you use a light touch with Tri-Mite in the 600-800. The weave also gets easily abraded which fuzzes up and this happens frequently using polyspan and it looks terrible. Don't use paper unless you've done it before. Using a scuff pad works far superior and it also follows compound curves better. Ken

Thanks Ken,

I'll work on it tonight. Hey guess what? I forgot to put tip weight in...  

That's okay just duct tape a bolt to it.