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Molding a Dirty Bridy 60 Fuselage

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Old 03-14-2010, 02:50 AM
  #1
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Default Molding a Dirty Bridy 60 Fuselage



I'll be making a mold out of my Bridi/Great Planes glass Dirty Birdy 60. I learned a lot from this forum so I will try to contribute by posting my progress. This will definitely be a learning experience for me. Special thanks to Atlanta 60 for his thread as this inspired me to give this a try. I hope this will be the first of many so here goes.



I puchased a OKI wide carrage off ebay for $58 including shipping for printing out plans. Box of continuous form feed paper cost $40. I have to say this is a cool way to get a print out of my plans. In this case I used it to print out the fuse outline for tracing onto the fiberboard. I decided to use fiberboard as it already has a very smooth surface and figured it would save me time as I would not have to sand and seal it. I saw a video or thread where a person used it for his mold and just waxed and PVA'ed it Thought about using melamine as it has a very hard plastic surface which might be ideal, but have not heard of anyone using it so fiberboard it is.

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Old 03-14-2010, 02:55 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage



When I first got the DB60 I was totally stoked and figured there wouldn't be a lot of prep work. I figured a little sanding, primer sanding, finish coat, done. After inspecting the fuse there were quite a few blisters and defects in the fuse that will need to be filled before I can start the mold. Also found a small crack right where the canopy starts.



Is this just from age? or maybe from being handled to much? It's an epoxy fuse.

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Old 03-14-2010, 06:52 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

That looks just about right. The older birds looked like a 3 year old laid them up. Your will be much higher quality. Take your time with the prep work, thats where it pays off in the rnd product. Sand, fill and prime to you think its good enough, then do it some more. Try using and epoxy primer instead of the rattle cans. A little longer drying time, but a much harder surface in the end.

Jeff
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Old 03-14-2010, 07:06 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

The finish on the plug (Your existing fuselage) is of paramount importance. It determines the finish in the mold which, in turn determines the finish on the final part. So, the finish on the plug has to be at least as good, (Preferably better) as the required finish on the final part.

A high gloss finish in the mold is for more than cosmetic reasons. A high gloss finish aids the release of the molded part.

Not sealing and finishing the parting board surface is taking a chance. If the resin soaks through into the board you will have a disaster on your hands. Spend a couple of hours and finish the surface. Why risk it?.

See the gloss finish in the mold and along the parting line in the picture? that is what you should be aiming for.

There are no shortcuts in composite work.

Ed S
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Old 03-14-2010, 12:13 PM
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Default RE: Molding a Dirty Bridy 60 Fuselage

Awesome Dude!! Looking forward to this project!!

Have Fun...

Chuck
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Old 03-16-2010, 12:39 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

Thanks Chuck.

Ed you convinced me to prep the parting board as having the epoxy stick to it does not sound like a pleasant outcome.
I agree that if you want a great finish it's all in the preparation so a little bondo, glazing putty and primer will be put to use on this bird. I used 1/8 balsa to close off the opening in the wing saddle and used super glue to tack it into place so I could easily remove it later.
At first I was going to cover just thebalsa with bondo, but inlooking at the wing saddlethis would have left a indent negative area in the mold that I would that would have required thepartsto be pealed back overthe mold to get them apart. So I decided to add bondo to make the plug flush here so the mold would have a straight surface between the two wing saddles.
As I was filling the holes I ran across a crack in the fuse right where the canopy starts. Decided to super glue the crack for now as there’s no access to the inside of the fuse at the moment. Will have to fix this later with epoxy and glass cloth. For now I hope the super glue holds it together.
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Old 03-16-2010, 12:41 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

I decided to stop the filling process and proceeded to set up the tooling so I’d have a place to set the fuse when not working on it.
Can anybody tell what’s wrong with the parting board I cut out, doooooough!
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Old 03-16-2010, 02:20 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

Quote:
ORIGINAL: Roguedog

I decided to stop the filling process and proceeded to set up the tooling so I’d have a place to set the fuse when not working on it.
Can anybody tell what’s wrong with the parting board I cut out, doooooough!
Did you also leave the rudder in?? A lot of work down the drain it looks like. Well, look at the bright side...you now have masterd the art of building parting boards. Teasing ya a little.

One way you can minimize the finishing of the parting board is to monokote it. Parz all on the monokote releases great. BTW, after you cast the first half, only remove the parting board. Rewax and prepare the exposed plug just the same as you did the first half and cast the second half directly over the first. I install maple blocks every 5-6 inches or so on the new section's perimeter flange, which, after drilling and tapping, will hold the halves together when assemblying the fuse halves. I use 1/4-20 caps. Always make sure the threads of the maple are well waxed

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Old 03-16-2010, 07:53 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

I think you forgot to omit the wing.. You could cut a piece and fill it in to form the saddle..
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Old 03-16-2010, 08:01 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

This is constructive advice.

The parting bpoard looks a little thin. You could end up with a wavy joint line.

I would not have filled in the wing saddle. If eventually you join the fuselage halves in the mold (The most accurate method) the only access to the inside will be through the wing saddle.

While on the subject of joining the halves. After the second half of the mold is laid up and you have a solid blob with the plug inside, drill some location holes and screw holes before separating.. The mold halves can then be put together and the cavities will be a perfect match. When joing in the mold the more access holes the better. I create the following holes in the mold. The wing saddle, nose ring and a large enough aperture at the engine position.

The picture shows the fuselage mold with the holes and the clamp screws. There are four (2 at the nose and two at the tail) location pins.

Ed S
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Old 03-16-2010, 08:23 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

You can also take a 3/8" or 1/2" drill bit and just start a hole in your parting board, you want a "V" shaped dimple, this will serve as to match up the two mold halves. I would not worry too much about the parting board, just wax it and use partall (PVA) and it will release.

The rudder being on the parting boards not a problem, I'd just scratch in where the rudder starts, then use that as a reference mark for trimming the fin.

The wing saddle area isn't a problem either, just put a piece in to fill the area, I'd make it an inch or a inch and a half thick, you don't want to have that closed in on the mold anyway.

If your parting board fits the fuse well, I would just get a 3/4" MDF board and cut a rough outline of the fuse out of it, then attach what you have to it. I'd also get some 1x3 pine and make the shadow box out if it and the MDF.
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Old 03-16-2010, 10:29 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

I agree with soarrich's assesment..

I filled in the wing saddle on my "splash" in order to have it smooth and enclosed for my "Master Model"...For the actual molds I was going to have an open hole for access in the wing saddle area as well as the nose ring and end of the rudder...Those areas can be trimmed later...OR...If you wanna be really slick you could do the block concept soarrich eluded to which is what I'll be doing on mine (wish I'd have already gotten to that point...Shucks)

I'm building two slightly different versions of my tools...One which will look just like Ed's with the holes trimmed net and open for access...That way the haves can be joined while wet which is the way CCA builds their fuses...Another set (for me) will have a shelve all the way around for selant tape and vaccum bagging my fuses...Then the parts will be pulled and trimmed to some scribe lines I'll have in the molds then joined in another fixture I intend to make...I know I'm making it complicated and it doesn't need to be but that's the way I am...

Lots of good ideas for indexing already but here is another...I go to home depot and get those little round but tapered rubber thingy's you put on the legs of your chair so you don't mark up the floor...The ones I like are maybe 3/8 or so tapered circles...Whatever you use make sure it's rounded or tapered to some degree...And yes drill your indexing pin locations before seperating the mold halves...

Looking good and have some Fun!!

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Old 03-16-2010, 02:27 PM
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Default RE: Molding a Dirty Bridy 60 Fuselage



Thanks all for the excellent tips.



MTK. I like the idea of monocoating the parting board. CSTSales has a mold tutorial http://www.cstsales.com/tutorials.html that suggests using mylar as a parting surface as most epoxy’s don’t stick to plastic very well. I saw this first hand at Polymer Composites www.polymercompositesinc.com when I went to pick up theepoxy tooling coat he made up for me. He put one coat of wax in a clear plastic drinking cup let it sit for a few minutes then put a layer of his fast epoxy in it and it popped right out when cured. To get the epoxy to go off faster he heated the resin in a microwave for 15 seconds before mixing with the hardener. Cool tip.



Diggs 74, that was it.



In my zeal for cutting the parting board I forgot to cut out the wing section for creating the wing saddle area. Luckily I purchased a 4x8 piece of hardboard ($11.00) from Home Depot and had them cut four 1’ boards out of it. So I had to cut a new one.



This is how I found out that my particular fuse is a ¼” shorter from the wing forward. I guess Bridi was using several different molds when he was producing these fuses.



Ed. Very good ideas and thanks for the pic. I was concerned about having a wavy parting board at first but as I screwed it down it straightened out. I figured I would use more braces under it anyway, but at this point it’s very straight e.g. no surfing on it yet. I closed off the opening to make sure that both saddles were the same.



ED and Rich. Thanks for the tips on access as I definitely want access thru here later. I will definitely build a block into the saddle area of the mold for the opening. As far as the nose I would like to have access there as well. The tail end is another story as it’s only 7/16” wide and closed off. Still would like access thru the tail. One interesting thing I noticed about the original fuse is that whoever molded the halves together didn’t use 1” tape on the tail moment. Whoever epoxyed the halves together here did so, I’m guessing here, by leaving the fiberglass free of resin above the mold half’s then squishing the leftover together with resin when joining them.



I’m definiltely going to index the half’s somehow. Richs’ idea doesn’t require a trip to the depot. I like Atlanta 60’s idea as it would provide excellent indexes for the mold half’s. Not there yet, soIstill have time to decide what to use.



I'm planning of adding a fully symetrical vertical stab to this project as the original required a 3/8 slab of balsa for the fin and rudder. I have always liked the Bridi designs and hope to use this mold to produce a UFO as well. What! Well we'll see.

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Old 03-17-2010, 09:09 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage

Hi

Looks really good.

I told my composite buddy about your project and he is a big pattern guy and a pioneer in composite fabrication. He said he would be interested in one of those fuses. He also said he would like to help you out if you need help.

He is very well known in the movie special effects, JPL, (other 1/2 of Scalecraft back in 1991). One of the finest composite fabricators around.

We fly out of Prado when we can.

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Old 03-17-2010, 09:47 AM
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Default RE: Molding a Dirty Bridy 60 Fuselage


Quote:
ORIGINAL: Roguedog



Thanks all for the excellent tips.



MTK. I like the idea of monocoating the parting board. CSTSales has a mold tutorial http://www.cstsales.com/tutorials.html that suggests using mylar as a parting surface as most epoxy’s don’t stick to plastic very well. I saw this first hand at Polymer Composites www.polymercompositesinc.com when I went to pick up the epoxy tooling coat he made up for me. He put one coat of wax in a clear plastic drinking cup let it sit for a few minutes then put a layer of his fast epoxy in it and it popped right out when cured. To get the epoxy to go off faster he heated the resin in a microwave for 15 seconds before mixing with the hardener. Cool tip.



Diggs 74, that was it.



In my zeal for cutting the parting board I forgot to cut out the wing section for creating the wing saddle area. Luckily I purchased a 4x8 piece of hardboard ($11.00) from Home Depot and had them cut four 1’ boards out of it. So I had to cut a new one.



This is how I found out that my particular fuse is a ¼” shorter from the wing forward. I guess Bridi was using several different molds when he was producing these fuses.



Ed. Very good ideas and thanks for the pic. I was concerned about having a wavy parting board at first but as I screwed it down it straightened out. I figured I would use more braces under it anyway, but at this point it’s very straight e.g. no surfing on it yet. I closed off the opening to make sure that both saddles were the same.



ED and Rich. Thanks for the tips on access as I definitely want access thru here later. I will definitely build a block into the saddle area of the mold for the opening. As far as the nose I would like to have access there as well. The tail end is another story as it’s only 7/16” wide and closed off. Still would like access thru the tail. One interesting thing I noticed about the original fuse is that whoever molded the halves together didn’t use 1” tape on the tail moment. Whoever epoxyed the halves together here did so, I’m guessing here, by leaving the fiberglass free of resin above the mold half’s then squishing the leftover together with resin when joining them.



I’m definiltely going to index the half’s somehow. Richs’ idea doesn’t require a trip to the depot. I like Atlanta 60’s idea as it would provide excellent indexes for the mold half’s. Not there yet, so I still have time to decide what to use.



I'm planning of adding a fully symetrical vertical stab to this project as the original required a 3/8 slab of balsa for the fin and rudder. I have always liked the Bridi designs and hope to use this mold to produce a UFO as well. What! Well we'll see.

Rogue,

FYI-I use simple plumber's putty to fill around the edges between the plug and the parting board, for a sharper corner. But sticky back teflon or vinyl electrical tape would work too.

MattK
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Old 03-19-2010, 08:04 PM
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Default RE: Molding a Dirty Bridy 60 Fuselage

What I use for the alignment pins are plastic feet that you would put on the bottom of wood chairs so they dont scratch the floor. They have a small nail that is molded in them. I drill the parting board and ca the glide or foot to it. Makes a nice size alignment pin that is easy to wax due to the size. Ill post a picture later if you want more info.
Joe
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Old 03-20-2010, 09:06 PM
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Default RE: Molding a Dirty Bridy 60 Fuselage

Very Cool!

We did this fuselage a couple of months ago. I haven't laid one up yet because I've been busy making cowls![:@]

The mold will release from the board fine but it will soak up the wax. I had the same questions you had but forged on with great results.

I'm using the Coverall PVA film from Partall. It works as good as the green PVA from Partall but make sure you get a good cover on both wax and PVA.

If you get the parting plane a little wavey it shouldn't effect the mating piece because it will have the same wave on the other piece but in the opposite direction.

As far as closing up the wing saddle area, I'm going to try to not cover it the next time because you don't mold this part anyway. If you do forget and mold this up you'll have to cut it back out because you have to get your hand up there.

We forgot to buy the little rubber stoppers and made some alignment pins from the clay we used to seal the edges. I've laid up cowls with molds that used the hard plastic chair bases that joe suggested to make the pins. At first I thought if some epoxy would get in there and the two mold halves wouldn't come apart because it's perpendicular to the parting plane but it works fine.

I'm going to PM you some photos but I'll post some finished photos here later.
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Old 03-22-2010, 04:59 PM
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Default RE: Molding a Dirty Bridy 60 Fuselage

Man! Got laid up for 5 days due to the flu. Glad i'm starting to feel better.

Steve,

Thanks for the encouragement. I would be glad to hookup your bud with a fuse, this is my first project of this type and would be glad to except help from him as well.

Matt,
Interesting Idea using plumbers putty. Will try it out and compare it to the molding clay I got for the project.

Joe,
I really like the simplicity of the anti-scratch plasitc feet for the index pegs. I know this is a pretty advanced project for most but would like to make it as simple as possible and to keep costs down so someone following the thread might be inspired to mold one of there own.
I don't imagine the feet would cost that much but theres also gas to to and back from the store so a $3.00 package of feet turns into $9.00 of gas for total of $12for thefeet plus my time.


rangerman,
Thanks for sharing the pics.Using the clay for the indexing sounds like an interesting idea as well. With the clay you could make rectangularvertical and horizontal indexes instead of round indexes. Very interesting idea.


Material costs so far-
Epoxy tooling coat $35
Epoxy for laminating $35 originally purchased 1.5 gals of resin for another project have about 1/2 leftover. Original cost for 1.5 gals $70
Epoxy clay for mold $35
Fiberglass 6oz 3yds $10
Fiberglass 2oz 3yds $10
4x8 sheet of hardboard $12 got 4 12" x 6ft parting boards and 2 12" x4ft parting boards out of it.
1x6 pine boards $8
balsa sheets$10

I happen to have alot of consumables from other projects on hand so kinda hard to give a figure for that stuff as it's left overs form other projects e.g sandpaper, bodyfiller, glazing putty, masking tape etc. But I would imagine anyone willing to try this would have a variety of stuff lying around. Point is, usewhat you got on hand to keep costs down.
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Old 03-22-2010, 05:29 PM
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Default RE: Molding a Dirty Bridy 60 Fuselage

Instead of using the 3/8" slab of balsa for the vertical stab that the plans calls for, I'm going tohave a vertical stab included in my mold with a symetricalairfoil. With a little bit of cad work I was able to print out rib templates with alignment tabsand a small plan to glue everything up with. I also printed out several small pieces to go between the ribs for the leading edge. I doubled up on them and glued them together to give an alignment line for sanding the final shape of the stab. PITA. Should've made these little LE piecesone long piece. Next time. To cover the vert stab I used 1/16" balsa sheet andused alittle bit of bondo for a smooth transistion for top ot bottom to rough it out.
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Old 03-22-2010, 06:08 PM
  #20
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Default RE: Molding a Dirty Bridy 60 Fuselage

Bryan
Very nice work on the stab, Oh, I wish I could do that with a computer program.
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Old 03-26-2010, 10:15 PM
  #21
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Default RE: Molding a Dirty Bridy 60 Fuselage

Skill and talent is what it says to me.

Beautiful stab work. i always look for things like that. It sets a model far above the balsa slab. Its more graceful as well.

I let my buddy know about your thread.

Steve
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Old 05-09-2010, 09:58 AM
  #22
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Default RE: Molding a Dirty Bridy 60 Fuselage

bump.[sm=drowning.gif]
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Old 05-29-2010, 10:04 PM
  #23
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Default RE: Molding a Dirty Bridy 60 Fuselage

Rougedog

I would use tooling resin for the mold . Also when using epoxy for the parts, they have a tendency not to sick. I wax a mold witth 5 coats then spray pva and my parts never sick. I face the partiing board with .010" mylar and nothing sicks to it. I've also used melamine a couple hundred times sprayed with pva and nothing sicks to that either. About all I do to free a part is cut a strip of .014' Mylar about 2" x12" and I radius one end and you can just slip it in and run it around the mold with very little effort the part pops right out. Good Luck! If you need any help or have any questions just PM me, I'll be happy to help.
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Old 05-31-2010, 07:25 PM
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Default RE: Molding a Dirty Bridy 60 Fuselage

I've laid up parts from a mold with 6 oz but you might want to use 9 oz for the outter layers of the mold if you plan on keeping it for a while. 6 oz is good mold material for the first layers though. You might want to save the 2 oz for you actual parts you make but not the mold IMHO.
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Old 08-25-2010, 01:43 AM
  #25
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Default RE: Molding a Dirty Bridy 60 Fuselage

Finally had some time to post, and Man! I sure wish Frequent Flyer would post pics of his molding process and the layup process. He‘s out of control.
I digress, back to the stab.
As beautiful as the vertical stabilizer was I learned a valuable lesson about filler material and balsa and had to trash it. Bummer!
This is what happened –
After finishing the vertical stabilizer I test fitted it to the fuse and then used a laser alignment tool to check that the top was straight. I tacked 2 pieces of hardwood to the sides of the stab to align it to the back of thefuse and I was off an 1/8 to 3/16 of an inch on the top to one side. I must have sanded too much off that side when rounding the top. So I figured no problem, I’ll just use some bondo to build it back up. Worked great, at least that’s what I thought until the next day.
It turns out the bondo shrank the balsa sheeting between the ribs and concaved the space between. Lesson learned, I should have glassed it first than used the bondo to straighten it out.
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