stunthanger.com
Electric Stunt => Gettin all AMP'ed up! => Topic started by: TDM on March 03, 2010, 04:50:19 PM
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Hi my name is Traian Dorin Morosanu and it is my pleasure to introduce you to some of the technologies I am in corporating in the new project REvolution. After two years of development I decided to move away from the classic stile of building a stunt plane and I foud it necessary to lave the old behind and introduce the new. All the design for this plane is done in CAD (Computer Aided Design) and all the molds are done on CNC (Computer Numeric Control Machines) The most deviation on these machines is about .0001 in (that is one thousand of an inch) and this allows me to make components separate ignoring the logic sequence and then assemble them later with minimum fitting work.
Dorin.
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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.
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interesting techniques......I like your idea for the flaps...
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Wynn I am just warming up. Get your popcorn. #^ #^ #^
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First Move
The first thing I did was to decide what kind of plane I wanted to build and in witch direction did I wanted to go. This is an individual preference. Or simply copy a plane that you like.
Second is to decide what my overall goal is.
In this case REVOLUTIONS
1 will be made so that I can make a plane in a week minus the paint
2 the completed plane will be 95% ready for the final coat of silver that means one coat of silver make the final touches and the second coat of silver then go put the color on.
3 Interchangeable parts this is the big one because the fit between the parts and the consistency must be bullet proof the idea is that if someone who flies my bird 2000 miles away and needs a spare part I should be able to make It blindly have them put in on the plane without any work other than a new coat of paint and go fly.
4 all the mating fits will have a maximum gap the size of a piece of tissue paper
5 take apart plug in system
6 electric from the ground up but I ended up with an option of a wet setup too
First Order of business is the design. CAD Computer Aided Design. If you know where you are heading it is a matter of 3 weeks worth of work but if you do not it can take years. I attached a picture of a CAD rendering for my plane.
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what have you got planed for battery installation and removal etc - would be interested in seeing details
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That will be towards the end.
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OK control surfaces:
Flaps, Elevator, Rudder, Vertical Fin. S?P S?P #^ #^
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.
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I was playing with the flaps horn.
It is twistable Adjustable about 5 degrees 10 degrees total with infinite adjustability. This will eliminate the need of an outboard Trim tab and all the work that it involves.
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Awesome stuff Dorin! H^^ That stuff looks more like fine jewelry than a control system....very nice!
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Wow. That is impressive. Are you selling that control horn assembly? I want one (if I can afford it).
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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.
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The work is on the way.
I have started the construction.
Since the work will be done by the machine I have transferred the physical work to the PC work. The first thing I do is to break down the design in to smaller pieces that I want to work on. For this example it will be the Wing tip. So what I did was that I copied the tip shape and geometry on a new file. Then I reorient it inside the virtual CAD space. The master plan is to make the two halves like you would make a wheel pant then join them in the mold and add an insert on the base that way I can glue on to the wing tip. Because of that I need to align as I close the two halves. This will be accomplished using shoulder bolts. Then I created a cutter path loaded the part in the machine and I let the machine do it’s magic. Then 40 min later here we go we have a plug in our hands.
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My next plane won't have a pipe, so there will be room for your flap control horn.
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You an see from the pictures what I did in real life. The stock material is cut to size then it is stacked up with plenty of extra then I cut it with the machine. After machining it is sanded off till the cutter marks disappear. I use a contrasting color marker to see what sanded off or not. These parts are not polished yet but soon they will be.
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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.
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Hello Dorin,
Corian as a material for the master! I assume it machines nicely ... any hints for those of us contemplating this?
Was the sorian cheaper than trying to buy a big block of Delrin or just easier to obtain?
Thanks,
Dean
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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.
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Sir ... you are a genius!
later,
Dean
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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
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Dorin
Awesome work - I for one cant wait to see this thing progress further
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Are you going to make parts over the male molds, or will you cast female molds from them?
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I will make molds from these plugs.
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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.
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I am trying to lay out some PVA on the mold plugs but it comes out with fish eyes, I can use some tips here.
Did you use a silicone based polishing compound? - Make sure all the residue from polishing is removed - It will be the silicone that is causing you the problem - tho I could be wrong.
Regards
Peter
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Peter I was wrong it is the Orange peel problem that I have.
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I think I found a solution. The problem here is heat and dust. So what I will try is my big cooler I have at home with a few ice cubes in side. I will spray the mold upside down and will put the plug right in the cooler. Moreover i will thin out the PVA with 40% water to help with it laying out a bit flatter. I can't wait to go home today. :)
Yes it did work. 1part PVA 1/2part water. One mist super thin coat like you air brush it on the mold. Make sure it is dry before one more thinset wet coat of PVA you can put on folowed by placing it in to the box with a bit of ice inside. If your shop is about 70 Degrees then skip the ice box my garage is about 85 degrees. Tomorrow I am starting the mold making process.
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Good news!
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Good to know you've got to the bottom of the problem Dorin :) - I'm following this project with great interest, there's some really good engineering going on here. Wishing you all the success.
Regards
Peter
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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.
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One stop shopping place for the stuff pictured in the previous post.
http://www.theengineerguy.com
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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
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Gentleman thank you for all the kind words.
Here we go after I let the mold cure overnight now I have the Mold. During the molding of the part process I will use the shoulder bolts to close the molds. Shoulder bolts have a precision grinded shaft built in to them so I use for both a bolt and as a dowel pin locator.
Now that I am sure that my process works I am ready to pour the other molds tonight.
Could this be the western answer to the Yatsenko's stunters?
This model is available on the market and the line is already forming.
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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.
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My observation of PVA vs. other mold releases is that the PVA is more reliable about releasing, but is thick and leaves a poor surface finish. You are starting with nice molds, so I think you'll prefer the spray stuff.
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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.
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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. #^ #^ #^ #^ #^ #^ #^
On the building side I still want to have a gel coat on the molds and had inconsistent luck with laying a nice coat of PVA. As a result I did get a semi permanent mold release for class A surfaces from REXCO and i will start to apply it on today. It is called Formula Five® semi-permanent mold release system.
I got a sample from them and it should last me for the whole project all I payed was 30$ for shipping.
http://www.rexco-usa.com/five.htm
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Dorin,
Congratulation. Beautiful family.
linheart
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Wonderful, Dorin!
You and Mama do nice work ... a Scale model people.
all the best,
Dean P.
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Funny but the consensus at my workplace is that ugly dads make cute Babies.
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I had to put a stop to insanity. You know try the same thing over and over again etc etc….
I wasted a few weeks trying to put PVA on my mold and use a less expensive gel coat and then I got some info and changed everything.
This is the most user friendly system that works for me. It is not cheap but it is so easy to use.
First the release system:
It comes from REXCO and It is called Formula 5. This is a semi permanent mold release that bonds to the surface of the mold and it allows you to have multiple plus without having to reapply the release. It comes with more subcomponents there is a Formula 5 Cleaner, a Formula 5 Sealer and a Formula 5 Top coat. Read the instructions and apply it using paper towels. Dust is not an issue no spraying no bubbles the temperature is irrelevant and it has no thickness and it works all the time.
The only draw back is that the surface tension is so low the top coat has to be applied in thin layers on e after another but 2-3 thin coats will get the job done.
Second the gel coat:
The Gel coat I am using is an Epoxy based Gel coat and it is tough and thick that works well with the release system. This coat is applied in subsequent coats that are brushed on. I use a cheap 75c brush.
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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.
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Ok I have wing tip molds made but the question is what is a good layout for such a part.
Some options include a balsa fiberglass layout. Other just fiberglass. I have weighted a carbon only and it came out to be about 14g plus resin witch I think is a bit heavy. But I keep coming back to the balsa and fiberglass sandwich with has a small problem and that is the pre molding of the balsa.
Any suggestions here?
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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!
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Thank you. Thank you very much! #^ #^ #^
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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
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Jose we are on the same page here. I talked to Windy and he said that carbon is not the right material for the wing tip. Also he said that he best layout is .5 glass balsa .5 glass sandwich.
Thank you for the advice.
May I comment on your wing? It will be heavy.
You do not need ribs you do not need the carbon and if you worry about the wing collapsing because there are no ribs then use a couple of ribs at 33% an 66% of the span. Winy said that you only need .5 balsa .5glass. And that will do.
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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
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I have a lot on my plate when I get home today.
I have pre molded a piece of balsa for the wing tip and I can't wait to go home and see how it turned out. And the biggest question is did it dry out overnight? This is one of the milestones in my project. If it did I will mold a half wing tip today.
Also I have a bunch of molds prepped and ready to go. I have the release system on and the tooling gel coat and all that remains is to cast the molds.
The first infusion molding two blade prop is ready to go to so it will also be casted today.
Pictures will follow soon.
I am like a kid with a new toy.
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#^ #^ #^
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.
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How to mold balsa over compound corners
The problem here Is that balsa usually likes to mold in a single direction much like you take a sheet of paper and warp it in any direction. As soon as you want to warp it in the second direction it does not want to do it. This works great for leading edges or the top of the fuse shells but when it comes to a hard turning wing tip or front of the fuse around the nose or an engine cover it gets very interesting.
Here is my solution.
Instead of having a whole sheet and try to warp it to the mold shape why not have thin slices that warp around the mold.
Here is what I am doing.
First you need the mold and I assume you have a mold.
Then you cut a piece of paper a bit larger than the surface of the mold. This paper simulates the balsa sheet. I silted the paper in the direction of the grain of the wood about every .5in and only at the spots that turn hard. You only what to address those areas. Then I wetted the paper with water. Then I placed the paper in the mold and carefully laid one slit at the time inside the mold and I allowed it to dry out. After it was dry I proceeded to use a pencil and I marked the overlapping areas and the edge of the part. Next step was to make a template. Simply you transfer the formed paper shape to the piece of plywood. Once the template was made you can now cut the balsa. Wet the balsa and form it in the mold or over the plug using your favorite method.
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How to make a pre mold of a tough to mold part. One that turns 3D like a wing tip or a nose section on a fuselage.
And by the way I saw that Jose you have the same issue here.
1 Cut a piece of paper oversize.
2 Trace lines on it every .5in but only on the sections that turn hard in my case the wing tip front about 33% from the front.
3 Wet the paper and place it in the mold. Do not try to pull on it just let it lay down by intself slice by slice and allow it to overlap.
4 Let it dry.
5 Use a pencil and trace the overlapping areas of the paper and the edge.
6 Lay this paper on a piece of 1/16 ply with 3M77 contact cement.
7 Cut the template.
8 Use this template to cut the balsa.
9 Mold the balsa.
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Dorin here is a photo of a Shark wing tip. i think we all have that same challenge. As i mold with balsa i also discovered that A grain that is matched will follow a consistent curb with less seams at the tip.
Dorin I follow the way that Rabe and Werwage mold the wood when it comes to multiple curbs they just simply slit,fold and let the wood overlap when dry just cut the area of the overlap and close the open area just as you are doing in creating the pattern. My only challenge with the pattern is the incosintency of wood grain and getting the wood to follow the precut pattern at all times.
Jose modesto
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;D ;D ;D ;D #^ #^ #^ #^
Alexander is growing.
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He (Alexander) is soooooooooo good looking.
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What the plane is good looking? ;D ;D ;D I knew you was referring to Alexander #^
Thank you Linheart.
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I am changing directions slightly yet again. I have decided to go straight to mold for the small components on this plane. What I mean by this is i will cut the negative and make the mold directly from Corian to save some materials and time. So I will cut the Corian to size I will sand and polish it put PMR on it and will go make parts from it.
Over the Memorial day weekend I vaccum ed bagged the first wing tip. This is in my opinion the hardest to produce part in the whole plane and it went smoothly and easy. Also I refined the original template to the point that I do not need any additional trimming after the pre mold balsa process.
Vaccum baggig pre molding balsa is working great.
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I just took out the wing tip from the bag and i have no complains here. I am super happy.
I needed to change gears to finish the wing tip.
It has a flat rib on it's base so I made, well I put in the bag 6 sheets of 1/6 Balsa laminated with 1.6 oz/yd glass on both sides. So tomorrow I will see if the laminate is good. I see no reasons to think it will not turn out. The choice for the thicker fiberglass was made because i plan to thin out these ribs to the max so I needed some extra strength.
This is how I laminate this prepreg. I cut the glass, the bags and prepare two rollers a 3in paint roller and a 3 in Hard roller the paper towels. Then i put a sheet of plastic con the table.
After I mix the epoxy about 50g at the time I put the epoxy in a paper plate. Then with the paint roller I spread a thin coat of epoxy on the balsa then I place the glass on top carefull pulling on it to stay straight and I lay in down on the balsa. Then still with the paint roller I press and wet the glass. When it is all wet I take a paper towel long enough to cover the whole sheet and I use the hard roller to take out all of the excess resin from this side of the wood. I then flip it over on the other side and repeat the operation. When all is done I place the laminated balsa sheet in a piece of plastic or you can use Saran Wrap or Mylar then I throw it in the bag and that is it. Tomorrow I will take it out of the bag.
These prepregs will also be used thorough the plane as ribs half ribs etc.
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This is quite the building adventure, thank you for sharing it
Alexander is really growing too!
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I have spent some time yesterday and I cut the ribs for the wing tip and I fine tuned the pockets in the mold that will accept the shoulder bolts. Also I have a fixture that will help glue the rib in place. If I find 30 min tonight I will glue the tip halves and the rib in place. So far double stick tape is working great for machining the ribs. In the future they will be laser cut.
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I cut a pocket to accept the nut inside. Since I did not want to have it lost I made the pocket a little tight so that the nut is press fit inside.
The shoulder bolt is inserted from the opposite side and it aligns the two halves as well as it clamps the halves flat on flat on the parting line.
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About this fixture
I needed a way to glue the rib in place flat in the correct position square to the parting line. This fixture has a few clearance holes for 4-40 screws and also there is clearance all around because the balsa on the two halves is extra long so I can flat finish sand it in place
Here in the pic it is bolted and with glue on it awaiting the bond. The screws are just finger tight.
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Here are the molds the fixture for the root rib some glass for the joint and the shoulder bolts ready to go.
The two halves are finished prior to this operation.
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The two halves are glued and the glass is joining them together.
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The wing tip is glued included the wing tip rib all in one shot.
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Very nice!
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This is really a stunning project. Looking forward to seeing it all come together!
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I pulled out the tip from the mold today.
I am pretty happy with it. #^ #^ #^ It weights 11gr ;D and considering it is my first one and I could use a lighter Glass and better glue joints for the two halves I think I am going in the right direction. The finish is great. Enjoy the pictures.
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I would say that is a success! looks really well done!
the only problem is,, could you maybe work faster? I am going crazy waiting for the next installment here, I mean, is sleep really that neccessary? LL~
all kidding aside, I am really thinking this is really cool. keep up the fine work
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Mark remember i have a new born so i actually do work a good part of the night already n~ n~ n~. But this plane is done in between whenever i have the time. I am already looking to improve on what i have already done. but 11gr for that part is perfect for a outboard tip considering that the flaps is not full length it is pretty good you are right.
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I thought this might be interesting.
I put a few pictures I took today playing with my toys. The first one is the CAD/CAM and the pc you can see the Horizontal stab on the screen. The second is the picture of my CNC machine, and the next there it is working hard to make the stab mold. It took about 45min to finish a side. Finally the two stab sides finished.
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Awesome stuff (still) - I cant wait for you to get these planes into production - or parts thereof anyway ........
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Wow.. Superb thread!
It's rather awesome seeing how it is *really* done. Thank you for posting this informative thread.
Although I never expect to get to this level of molding technology, it gives me a couple ideas. I'm
stealing from you already! ;->
Great work, it's a pleasure to look at the quality of everything.
Best regards,
L.
"Basic research is what I am doing when I don't know what I'm doing." -Wernher von Braun
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I need some help.
I am looking for a semi permanent release system for the molding. I have problems with the current one and I am looking for a new one. Among I found Frecote and a product from McLube. Any ideas?
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When I was molding parts for ful scale aviation, we used Freecoat, I think it was number 77?
It worked very well. However one thing I discovered, with every mold I made, the first several parts were typically a BEAR to get out, upon further investigation from those in the know and years of experience, apparantly, the first several parts help to finish cure the mold and until that time, the parts are fairly hard to get out. In your case, the only thing not cured would be your finish system. Perhaps some prolonged exposure to higher temps would help, and I LOVED the freecoat mold release, was reliable, easy to apply, and worked well for me
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Thanks Mark
I am also looking at the Frecote 770-nc. I hear good things about it.
Also what else I found out is that before you start to make a molds is to mock test the system you intend to use from beginning to end.
I think I may also have a problem from a mold that is not fully cured yet and it still cross links.
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Glad to have a bit of real world wisdom to share!
One thing I ended up doing was to make several sacrificial parts in the mold, scrap cloth, resin, and just throw a part together in the mold to let it cure out. Then pop it out, it doesnt matter if the sacrificial part gets damaged in removal it will have served its purpose.
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I found that you can't use Frekote on a mold with a dope finish. The part will stick to the mold. Frekote works fine for metal or wood with an epoxy finish.
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Thank you gentleman for your impute.
I also have a sample here from McLube. It is called MAC 971 and MAC 1038.
I know a pro that does this for a living and he sais that he paints over Frecote. I am sure that it is not Butyrate Dope but a test will tell me what I need to know.
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I am making mini kits for each component needed to make the plane.
I put everything I need to make the stab tip for example in a box. I put inside molds vacuum bags all the templates necessary to cut the balsa or the fiberglass pre cut inserts fixtures so that when I have to make this part again I pull out the box for the part and I go at it and make it.
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I was advising with several people over the last few weeks and I found a common denominator. That is test before you commit to a system. That is test from the beginning to the end. Not all gel coats and release systems are compatible with one another. But once you find something that works then you are in business.
So I will take this week and maybe a good part of the next week too to test the full system from making the mold to making the part. I will make molds from Corian painted plugs. Also I will make the part from aluminum molds from Corian molds and from Gelcoat+cast molds. Then I want to test making a part in two methods one with applying paint or primer in the mold then make the part or jut go with the part directly, some of us like the look of the wood grain with some stripes showing.
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I am going crazy waiting for the next installment here, I mean, is sleep really that neccessary?
All kidding aside I believe I will start to work in the night to finish this project and will actually take your advice.
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Testing is complete for the aluminum mold.
I have tested 3 formulations of semipermanent release agents. So far they all work great on aluminum one of them is outstanding specially on the parts that have the primer painted in to the mold. You really can go to color paint right after. It would be interesting to see if I can paint the mild and when it is out of mold simply touch up the joining areas where the two halves come together apply the ink lines and it is ready for clear.
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Hi.
I have found some problems with parts that have primer painted in mold. It is of course an easier and perhaps also lighter way, but problems come with heat in finished parts. I allways try to make sure that glue joints are made as strong as possible, and with epoxy glue it means curing the glue in raised temperature. When you lay the laminate over painted surface, there is allways air bubbles trapped in the cloth. Especially when the cloth should have as little epoxy in it as possible. When heated, the pressure raises in these bubbles and you can see it in the painted surface. It can also happend when the model sits in a hot car.
I don't care of a few extra grams of weight, a more solid surface can be made by painting the surface afterwards with a good 2-component sandable auto primer. I use Spies & Hecker Percotex, propably all brands have similar stuff available. I dilute it 1:1 and spread it with a brush, usually 4-6 coats. It's very easy to sand but of course means more work. L
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Today I will test the painted Corian and the gel coated surface. So far I had good luck.
Lauri thank you for the advice. In my endeavourers of molding I found out that I should not try to save too much weight on the outer skin. I found out that you either fill the gaps with filler or epoxy so when I lay the outer skin of fiberglass I squeegee it until the grain of the glass starts to show up then I stop. My first layout was pretty dry and I found out that it had a weak adhesion to the balsa skin. You could pill the glass right off. I do not post cure the shell because I use a resin that does not require it yet it is sill tough and in a couple of weeks it gets hard.
I will make another test based on your advice. Maybe I should make a part and put it in the car to bake and see what happens.
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The two halves are joined with shoulder screws. The end plates are used as a hands free gluing fixture. With the 4 dowels on the end they align symmetric on the symmetry plane of the stab. In the same time they hold the root or tip rib in place perpendicular on the symmetry plane. Also you can see the two dowels that locate the root rib in place and in the future those holes will be used during the take apart of the stab. The vertical aluminum is for the rectangular tube to be glued in place. The idea here is to make the two halves of the stab first and the rectangular tube in a day and during the second day I want to glue the two halves the root and tip rib the wall inside and the rectangular tube witch will receive the I beam spar all in one shot with absolute precision
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All assembled minus the top half.
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Detail two end plates.
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I have been gone for a while but I have learned to be an owl. My shop hours are 10-11pm to 1am actually it is 12:30am now and I am posting this message.
Ok I am focusing on the back of the plane in particular the rudder and the vertical stab. I have discovered that it is possible to mold the rudder in the mold if you use bleeder Phelps cloth it dries out just fine and it works.
After I form the balsa I proceed to lay the part Paint (white primer) Fiberglass Balsa Fiberglass once I am done with the fiberglass I place a paper towel on top of it and suck the excess resin by applying pressure on the towel. Then I place the balsa on top and the fiberglass after witch I again use the paper towel to remove the excess resin out of the mold. Finally I vacuum bag the shell.
Next day I install the balsa blocks for the hinges or other hardware as needed then I close the two halves.
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The vertical stab and the rudder are done minus the final sand and hinge pockets.
Vstab is 7g #^and the rudder is 9.7g ;D. I know :! :! I can do a bit better on the rudder but for first try it is good the finish is excelent if i was to paint these parts it would be a no brainer.
I need 1/32 balsa for the stab an I will start to make those components too.
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Basically there is an I beam section with rectangular receiver made of carbon sleeve plated with 1/32 balsa.
Total weight is 7 grams plus 2 small screws. I could get away with taping the stab to the fuse but it is not pretty.
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I feel I talk like a TV set here. ??? ??? ??? ??? ???
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Not to worry my man! ;D We are watching intently..and quietly. :-X
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ALexander now 3 monts and 2 weeks.
15lb and 25 in tall. He is in a rush to grow up.
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ALexander now 3 monts and 2 weeks.
15lb and 25 in tall. He is in a rush to grow up.
are you comparing his growth to your progress on the revolutions??? HA HA......
Spend as much time with him as you can - the time sure flies by.................
Your build is far more interesting than TV - I think a lot of us are amazed at what you are doing - so cant really comment
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What is the typical thickness of the aluminum or carbon gear?
What is a typical thickness of a canopy?
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I am still here.
I have a shortage of wood so I can not make any parts that I have the molds finished so I have switched focus. I have cut the flaps mold and the top fuse structure mold and they await sanding blending and polishing. Also I have sprayed auto clear cote on the fuse and the wing molds and they also await sanding polishing and buffing. After I pour the wing and fuse molds then is on to making parts and some miscellaneous fixtures. More work it is relentless but I hope it was worth the journey.
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What is the typical thickness of the aluminum or carbon gear?
What is a typical thickness of a canopy?
What is the typical thickness of the aluminum or carbon gear? 3\32 inch
What is a typical thickness of a canopy? .030 in PTEG
did the pictures I sent of the B.C. and AL wing mount help ?
Randy
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Thanks Randy.
The pictures where great good information.
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Keep pluggin away, I am interested in seeing this one AIRBORNE! (bet you do too)
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It is 11:30 and I am back from the shop today I worked more than the usual I stayed from 9:45 to 11:30 a whole 2 hours. I only work after we put Alex to bed Z@@ZZZ Z@@ZZZ.
So far I am putting the final finish on the wing and fuse molds. Also I am sanding the flaps and top fuse structure molds whitch are made of aluminum. It is a lot of work and not much time. I am sure it could fly in a month or two. I think I have zeroed in on the Sultan setup for power with the addition of a cooling fan on the motor.
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Does anyone know what happen to this thread. Is Dorin Morosanu OK?
linheart
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Dorin is Ok project on temporary hold . Should be up and going again soon.
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As long as he and the family are alright!
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I am OK the family is OK. Speaking of which Alex is 9 months old now 30 in tall and 22lb healthy and happy. I am very busy stating something new. Soon I will get back to it.
Thanks
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That's all I wanted to hear.
Dean
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I have been busy with another project and now I am ready to start pecking at his project.
Adventures in balsa forming
Well I started to form the balsa in the vaccum bag but I believe you nee a bit of heat to dry it in vaccum so I ended up with the piece formed but not dried. OK back to plan B. I put a napkin on top of it and on the top of the napkin I put some sh...... ,well it is not sh.... it is sand, to hold it down in place I hop it is dry tomorrow.
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Hi Dorin,
I am confused. Freeze drying works in exactly this way.
Can you pull a hard enough vacuum on the wood to evaporate the water or will the wood crush?
Now I have to go look up the vapor pressure of water at room temp.
Dean
Found it.
0.025 atmospheres should do at room temp. Does wood crush there?
0.05 atmospheres will do at 100 F with some margin.
I have no idea at what pressure balsa crushes into junk.
Regards,
Dean