REvolution Control Surfaces
Flaps Elevator Ruder

I was looking for a better way to make these types of control surfaces and I had good success in using a technique by which I cut two peaces of 1/16 balsa to size and then I was spreading them out against a mold using triangles of balsa against a mold then a cap was added to the leading edge to complete the surface. It worked great and it was a lot lighter than the traditional sanding using rods of a C grain balsa sheet. We all know how hard is to come by a light C grain piece of balsa. But even though you still have to add finish paint etc.
 

Upon studying construction techniques used by the RC Glider constructors I started to implement them in to my building techniques
What I ended up with was a hybrid build construction and it is very similar to the way we build sheeted foam wings today.
These components are both stiff and light and as a bonus they can be built pre finished.
I will go through step by step on preparation and execution.


Preparation
   Leading edge spar
Wood selection is not critical the softer the easier to cut. And the grain has to be as straight as possible.
Since I never need to use more than 30 degrees of travel up and down on any of my control surfaces I decided to build a fixture that will cut the leading edge balsa cap at 120 degrees. This can be easily done from ½ plywood scrap that is around the shop and if you have a disc sander with a 90 degrees wall there is no problem to make such s fixture. This can be applied for any desired angle. Below the next images are a guide as how such a fixture can be made. After the fixture is glued glue two Xacto Knife blades on the two slopes

After the fixture is completed lay your balsa wood on the table flip the fixture over and glide against the straight edge of the balsa for a perfect triangular cut.  

Wynn I am just warming up. Get your popcorn.  

what have you got planed for battery installation and removal etc - would be interested in seeing details

OK control surfaces:
Flaps, Elevator, Rudder, Vertical Fin.      

The construction is straight forward. Foam core balsa sheeted with a 1/64 ply insert on the tip and a Aluminum housing for the control horn. What I did is first I glued the triangular leading edge on the foam core with 3M 77 contact cement. Do not put too much glue because it will melt the foam a light spray is all you need. Note when I made the triangular stock I made it extra long so the sheeting will but against this edge. Then I squared the root with sand paper. Then I glued the Aluminum insert on the base. The sheeting was next. The sheeting goes end to end and it glues on the top of the foam and the top of the insert so that the insert is sandwiched between the two balsa sheeting blocks. Then I squared the other end to size and placed a sheet of 1/64 ply on that end. The stab in the picture weights 10g and the flaps is 17g at this station ready for the glass.
Light foam 1lb (I may move to a closed cell 1.5 lb foam in the future because it is more user friendly during the bagging operation),  1/32 balsa, 1/64 ply, Aluminum inserts ( I have two styles with slop and without slop)
The balsa cap on the end of the flaps will be cut off after the bagging with fiberglass.

Awesome stuff Dorin! That stuff looks more like fine jewelry than a control system....very nice!

Howard

This setup is designed for an electric plane or one that does not use a tuned pipe. The reason behind the long legs for adjustment is to have a easy reach through a small hatch under the plane that allows me or the end user to easily reach the legs for adjustment. Of course a tuned pipe setup would look completely unlike this one. The adjustment leg would go perhaps 30 degrees up to allow the pipe and the pipe tunnel and a hatch for adjustment. Or plan B would be to use this set up and bias the control close to one side say the outboard and bias the pipe a bit on the inside wall with a much shorter under leg for the adjustment.

My next plane won't have a pipe, so there will be room for your flap control horn. 

I have spent the better part of last week to sand and polish the Corian molds. I will put some pictures in to show the progress. Also I made a decision to remake some of the original molds for the stab and stab tip to incorporate a better alignment.

Also new to this project I am punting the foam stab idea. It is still a great idea but I think it is a bit on the labor intensive it has more room for error and the finish may not end up flat because of the open cell light foam. Moreover it ads more work on the leading edge to blend in the vacuum bag creases. Consequently I decided to mold the stab surfaces too witch will become a lot more reliable and I am only swapping a foam core for a layer of .5o glass on the inside and the inserts become more compact witch will lower the weigh yet again.

Corian has properties and advantages that Delrin or Aluminum does not have.
1 Corian is cheaper. I went on the Craig’s list and bought scrap countertops from people that throws them away and at 150$ and it was worth it.
2 Delrin can not be sanded polished or painted. If you need to make a mold this is critical for the release of the part.
3 Delrin is not a very stable material. As soon as you are cutting it you may have to re cut it to take the warp out from the stress relief. On the other hand Corian is very stable and much more rigid and brittle. 
4 Aluminum molds are nice but it takes 4 times more to cut and then there is the sanding buffing that you have to deal with. I would still be sanding a small mold now a week after I cut it.
5The only bad thing about Corian is that you have to stack it up in .5in increments and glue it together. After you cut it you may have to fill in a few spots here and there but this is still a lot easier than buffing a billet of aluminum for weeks.

I have spent the last week or so polishing the molds on hand. This was done in maybe 2-3 hours of sanding and polishing a night. The fuse was done a while ago using another technique i was using Brodack white primer. It worked fine but I do not think it is necessary.

Note all the mating surfaces are built in to the fuse mold and the attachment is flat on flat

Are you going to make parts over the male molds, or will you cast female molds from them?

I am trying to lay out some PVA on the mold plugs but it comes out with fish eyes orange peel , I can use some tips here.

Peter I was wrong it is the Orange peel problem that I have.

Good news!

Here we go again.
I have punted the idea of PVA because it is way too unstable and it is hot here. Moreover my intention was to have a hard gel coat surface to work off of because in the past i had a bit of a problem with the material imprinted on the surface. But since i do not use such high pressures I decided that it is unnecessary. So I am keeping it simple for now.
This is what I call the MOLD MAKING FOR DUMMIES.
How much time do we spend to make a fiberglass mold? We start with PVA then Spray gel coat then we lay one layer at the time and then we have to stop and repeat the next day again and so on. At best in two or three days later we have a mold and sometimes we find that the excess resin has heated and pulled away the mold forcing us to remake it from the beginning.
Here is my two cent in to this.
1 Spray the release agent. Follow the instruction on the can. I use casting release agent made by Smooth-ON.
2 then I places foam on the edge on the mold. After the foam then I put the dowel pins which will help later with the alignment.
3 I mix the casting compound, with a power drill and the mixing attachment I bought from Home Depot, for about 2 minutes.
4 The hard part is to pour it in the mold. Be careful here. Do not to pour it very fast the slower you do it the more bubbles you eliminate.
That is it.

Mr. Morosanu,
That's an absolutely FIRST CLASS job you have there. I'm speechless...
How nice is to see someone using State-Of-The-Art technology to build a CL Stunter! And THAT flap horn looks like a NASA thing!

Could this be the western answer to the Yatsenko's stunters?

I really wish you all the BEST with this outstanding project. (and I'm sure you will succeed).
I look forward to see more of it as you progress...

Best regards,
Claudio
ARGENTINA

There is one thing I did not think about. That thing id the PVA I have is very old and it stayed in the basement probably even got frozen so because I still would like to have the gel coat on the mold today I will buy a new PVA but not the water based one I had in the past. Meanwhile I will start to make the molded parts for the tip etc. using the molds I have now. It will be interesting to see if there is any difference between the two procedures.

The problem with the spray stuff is that it does not allow me to use gel coat for a firmer work surface. But since I have a few molds already made without the gel coat I will try and see if it works like this. I f yes then It will make things a lot easier.

Dorin,

Congratulation.  Beautiful family. 

linheart

Funny but the consensus at my workplace is that ugly dads make cute Babies.

Here is an example.
I am making my 2Blade 15x4.5 prop mold. This mold has been prepared with the formula5 semipermanent release system.
then i brushed on a thin coat of Gel coat. Then I made some foam walls that will be used as a dam for the casting material.

Well I had a slow down in the building of the plane so far I think the pictures show exactly the cause of it.

14 Apr 2010 at 4:57 pm Alexander Kaitan Morosanu was born. Mama and Bebe are doing fine and there is a proud papa somewhere in there too.  

Dorin:
Somehow I completely MISSED the announcement of your newest scale model.  God Bless Alexander and his family!

Dorin congratulation on the new addition.
As to tips, the molded balsa is the lightest that i have made.
The Yatsenko's are molding balsa skins with wing tip incorporated into wing panel.
a couple of photos of my current experimental wing.
A comparable system is with foam sheets 1/8" i will add a photo of material the Yatsenko's called this synthetic Balsa.
Jose Modesto

Dorin this wing is only and experiment in combining Bob Hunt's the lost foam system and my shell construction. The ribs are from a Hunt lost foam jig if i was making my own i would use 5 ribs per panel as the SHARK uses.
 You would be surprised at what a Shark wing weight 9.5oz per panel that's 19oz for a finish wing and the model weighs 60oz ready to fly.
The carbon was used as all other parts (stab, fuse,flaps were made with carbon cloth and i wanted to build one with this material.
Dorin for me the gold standard is the Yatsenko SHARK and the new Sharks wings are made with molded balsa shells that include the tip as shown in my photo with 1oz/SY glass cloth inside and out, with 5 1/16" balsa ribs.
 Heavy is in the eye of the beholder. i want my model weight at 62 to 65 not any lighter,at 720 SI my wing loading is comparable to most Nats planes.
Included Photo of another use of the molded shell construction to build a built up wing.
Dorin working with the balsa and glass cloth the tips require multiple layers of glass cloth for stiffness i have already done this,as you are making separate wing tips this does not apply to your method.
Dorin your work is fantastic please keep posting your work its very informative.Dorin i added a third photo showing the balsa with glass cloth at the time i was making carbon fiber mat and glass cloth tips,now i mold in balsa and glass cloth
Jose Modesto

 
Success

The vaccum molding worked just fine. I have a dry part that has a super shape and it is ready to be molded in to a wing tip.