Author Topic: REVOLUTIONS Build Log (Read 7856 times)

TDM · « **Reply #50 on:** May 14, 2010, 07:15:58 PM »

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.

TDM · « **Reply #51 on:** May 19, 2010, 09:15:24 AM »

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.

jose modesto · « **Reply #52 on:** May 19, 2010, 01:54:25 PM »

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

TDM · « **Reply #53 on:** May 19, 2010, 07:13:58 PM »

Alexander is growing.

linheart smith · « **Reply #54 on:** May 20, 2010, 07:10:57 AM »

He (Alexander) is soooooooooo good looking.

TDM · « **Reply #55 on:** May 20, 2010, 08:18:09 AM »

What the plane is good looking?

I knew you was referring to Alexander

Thank you Linheart.

TDM · « **Reply #56 on:** June 01, 2010, 07:54:17 AM »

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.

TDM · « **Reply #57 on:** June 01, 2010, 06:52:43 PM »

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.

Dennis Adamisin · « **Reply #58 on:** June 01, 2010, 09:39:26 PM »

This is quite the building adventure, thank you for sharing it

Alexander is really growing too!

TDM · « **Reply #59 on:** June 04, 2010, 07:05:39 AM »

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.

TDM · « **Reply #60 on:** June 04, 2010, 08:22:52 PM »

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.

TDM · « **Reply #61 on:** June 04, 2010, 08:28:42 PM »

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.

TDM · « **Reply #62 on:** June 04, 2010, 08:31:45 PM »

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.

TDM · « **Reply #63 on:** June 04, 2010, 08:33:45 PM »

The two halves are glued and the glass is joining them together.

TDM · « **Reply #64 on:** June 04, 2010, 08:35:43 PM »

The wing tip is glued included the wing tip rib all in one shot.

Crist Rigotti · « **Reply #65 on:** June 04, 2010, 09:00:53 PM »

Very nice!

Dennis Adamisin · « **Reply #66 on:** June 05, 2010, 05:13:45 AM »

This is really a stunning project. Looking forward to seeing it all come together!

TDM · « **Reply #67 on:** June 05, 2010, 06:05:39 PM »

I pulled out the tip from the mold today.
I am pretty happy with it.

It weights 11gr

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.

Mark Scarborough · « **Reply #68 on:** June 05, 2010, 07:39:08 PM »

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?

all kidding aside, I am really thinking this is really cool. keep up the fine work

TDM · « **Reply #69 on:** June 07, 2010, 08:00:07 PM »

Mark remember i have a new born so i actually do work a good part of the night already

. 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.

TDM · « **Reply #70 on:** June 09, 2010, 07:47:56 PM »

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.

Wynn Robins · « **Reply #71 on:** June 09, 2010, 09:06:35 PM »

Awesome stuff (still) - I cant wait for you to get these planes into production - or parts thereof anyway ........

Larry Cunningham · « **Reply #72 on:** June 13, 2010, 08:51:55 AM »

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

TDM · « **Reply #73 on:** June 23, 2010, 05:43:48 AM »

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?

Mark Scarborough · « **Reply #74 on:** June 23, 2010, 11:35:14 AM »

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

TDM · « **Reply #75 on:** June 24, 2010, 05:37:55 AM »

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.

Mark Scarborough · « **Reply #76 on:** June 24, 2010, 11:52:24 AM »

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.

Howard Rush · « **Reply #77 on:** June 24, 2010, 01:43:39 PM »

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.

TDM · « **Reply #78 on:** June 25, 2010, 05:59:12 AM »

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.

TDM · « **Reply #79 on:** June 25, 2010, 06:03:47 AM »

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.

TDM · « **Reply #80 on:** July 06, 2010, 08:00:06 AM »

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.

TDM · « **Reply #81 on:** July 12, 2010, 02:41:01 PM »

Quote from: Mark Scarborough on June 05, 2010, 07:39:08 PM

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.

TDM · « **Reply #82 on:** July 13, 2010, 08:52:01 AM »

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.

Lauri Malila · « **Reply #83 on:** July 13, 2010, 10:24:39 AM »

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

TDM · « **Reply #84 on:** July 15, 2010, 09:37:02 AM »

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.

TDM · « **Reply #85 on:** July 15, 2010, 08:06:56 PM »

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

TDM · « **Reply #86 on:** July 15, 2010, 08:10:46 PM »

All assembled minus the top half.

TDM · « **Reply #87 on:** July 15, 2010, 08:11:34 PM »

Detail two end plates.

TDM · « **Reply #88 on:** July 27, 2010, 10:39:36 PM »

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.

TDM · « **Reply #89 on:** July 28, 2010, 08:35:18 PM »

The vertical stab and the rudder are done minus the final sand and hinge pockets.
Vstab is 7g #^and the rudder is 9.7g

. 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.

TDM · « **Reply #90 on:** July 28, 2010, 09:09:40 PM »

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.

TDM · « **Reply #91 on:** July 28, 2010, 09:18:44 PM »

I feel I talk like a TV set here.

John Sunderland · « **Reply #92 on:** July 29, 2010, 06:41:18 AM »

Not to worry my man!

We are watching intently..and quietly.

TDM · « **Reply #93 on:** July 29, 2010, 05:16:23 PM »

ALexander now 3 monts and 2 weeks.
15lb and 25 in tall. He is in a rush to grow up.

Wynn Robins · « **Reply #94 on:** July 29, 2010, 07:04:18 PM »

Quote from: Traian Dorin Morosanu on July 29, 2010, 05:16:23 PM

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

TDM · « **Reply #95 on:** August 09, 2010, 12:32:44 PM »

What is the typical thickness of the aluminum or carbon gear?
What is a typical thickness of a canopy?

TDM · « **Reply #96 on:** August 17, 2010, 05:37:40 AM »

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.

RandySmith · « **Reply #97 on:** August 26, 2010, 01:24:46 PM »

Quote from: Traian Dorin Morosanu on August 09, 2010, 12:32:44 PM

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

TDM · « **Reply #98 on:** August 26, 2010, 03:19:49 PM »

Thanks Randy.
The pictures where great good information.

Dennis Adamisin · « **Reply #99 on:** August 26, 2010, 04:07:13 PM »

Keep pluggin away, I am interested in seeing this one AIRBORNE! (bet you do too)