Q-40 Racing Discuss AMA 422 and any other variants of Quarter 40 racing

Lets Try To Mold A Moldie!

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Old 04-22-2010, 05:26 PM
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D.E.
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Default Lets Try To Mold A Moldie!

Well since I made a mess of my last AR6 Its time to build more. The deadline is going to be the basin race in June, The goal is to get THREE done by then!

My goal here is to have some fun and maybe I can learn something from you guys while I am at it, I am going to document the build of one of the three from cloth to flying with someone who flys better than I do. Please feel free to share any different techniques that you all use so I can steal them.

This picture is why I need to do this.
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Old 04-22-2010, 05:34 PM
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D.E.
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Default RE: Lets Try To Mold A Moldie!

Here are some pics of my molds as you can see no fancy aluminum here, not because I didnt want it though it just wasnt in the budget!

I think this shows that ANYONE can do this and it doesnt need to cost a fortune, you dont even need a computer! This airplane is very fast and flies great so they tell me.
Now lets get to molding.

Dave E.
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Old 04-22-2010, 05:49 PM
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Default RE: Lets Try To Mold A Moldie!

Well tonite I need to put one more coat of wax on the molds I use Meguires Carnuba wax I know there are better but I use PVA over the wax as I am afraid of sticking ( dont want to make any new molds just yet. ) My molds arent quite good enough to paint in the mold so I just put a lite coat of primer over the PVA to help with pinholes, I will show all of this later.

The second pic is of the three fuselages in bags I like to keep the different weights and types of glass in there own separate bags. When you run out of bags you should have a fuse.

Thisis going to only be AR6 #s 8,9,and10 so I am far from an expert. Tomorrow I will get a fuse in the mold and a horizontal in the vacuum bag.

Dave E.
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Old 04-22-2010, 09:20 PM
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Lewis S.
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Default RE: Lets Try To Mold A Moldie!

Hi Dave,
This will be e great thread to follow. I have done a few pattern ship fuselages in molds I made, but nothing like this. Look forward to following it.

Lewis
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Old 04-22-2010, 09:50 PM
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Randy Etken
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Default RE: Lets Try To Mold A Moldie!

Hi Dave
What black tooling epoxy did you use for your molds?
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Old 04-23-2010, 07:58 AM
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Default RE: Lets Try To Mold A Moldie!

Should be interesting Dave.. Really looking forward to it.. Maybe it will help spur me along on my AR-6 molds...
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Old 04-23-2010, 08:34 AM
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Default RE: Lets Try To Mold A Moldie!

Hello All,

Glad to see someone is watching I will try to do a good job with lots of pics.

Randy E.
I used Fibre Glast 1099 from Aircraft Spruce, I get probably 80% of the stuff to build one of these from them, great service. The 1099 comes out of the can white but I got a black pigment from them also.

That being said as the 1099 is a little expensive you can also make your own tooling coat using your epoxy thickened with Cab-o-Sil and a little graphite powder added but I dont think it is quite as tough as the real tooling coat.

Dave E.
who is going into the garage to mix some epoxy now.
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Old 04-23-2010, 10:53 AM
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daven
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Default RE: Lets Try To Mold A Moldie!

Definately watching, now get those molds waxed!
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Old 04-23-2010, 12:51 PM
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Default RE: Lets Try To Mold A Moldie!

I am thinking of trying to make a wing tip mold for balsa and foam qwickie wings. Can i make a one piece mold or do i have to split it top and bottom??? Sorry for the hyjack Dave , but i thought i would post it here since all the good builders are watching this thread??
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Old 04-23-2010, 01:14 PM
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Default RE: Lets Try To Mold A Moldie!

PylonDave,

I would think you could make a one piece mold providing it is not excesively deep (much over 2 1/2 inches) and you have tip that is thinner at the outer tip and thicker at the root which I am sure it would be. At worst you could make it one piece and then cut it in half with a razor saw, instant two piece mold.

Dave E.

P.S. no problem about the hi jack that is what this is for to throw some ideas around.
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Old 04-23-2010, 01:32 PM
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Default RE: Lets Try To Mold A Moldie!

Well I laid up the fuse halves, Have a look


#1 This is my faithful assistant Sadie she likes getting oversprayed, My wife doesnt think it is to funny though.

#2 This is the mold release I use PVA from Aircraft Spruce.

#3 Molds ready to PVA I spray two lite mist coats on them and then one good wet coat then let dry for 1/2 an hour.

D.E.
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Old 04-23-2010, 01:40 PM
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Default RE: Lets Try To Mold A Moldie!

Next,

#1 I sprayed some primer over the dried PVA I just use some cheap rattle can primer here just to keep away from some pinholes.

#2 This is the epoxy I use it is MGS brand from Aircraft Spruce it is kind of pricey but it goes a long way. I like it because it is thinner than most others and wets out eaisly.

D.E.
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Old 04-23-2010, 01:55 PM
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Default RE: Lets Try To Mold A Moldie!

Next,

#1 Mix a little epoxy on the scale, yes I got the scale at aircraft spruce too.

#2 Add in a little Cab-O-Sil which I got at ,,, All together now AIRCRAFT SPRUCE. dont add to much as it will make the epoxy to thick and brittle just add a little at a time until it is about the consistancy of ketchup ( I think there is an s in there somwhere but you get the idea )

#3 Put the mix in a little baggie, cut the corner off and squirt it in all of the hard to get to areas.

#4 I put it around the tail and stabilizer area.

#5 Since this airplane has rather large fillets as the orignal does I also put some in there.

D.E.
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Old 04-23-2010, 02:09 PM
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Default RE: Lets Try To Mold A Moldie!

Next,

#1 After I brush a thin layer of epoxy into yhe mold I lay a piece of 3 oz. Crowsfoot weave glass into the mold now I know it is to big but I havent gotten around to making a proper template for it yet and I only need about 5 dollars worth for a fuse.One trip to McDonalds.

#2 Get the glass all laid in and smooth. And yes I got the glass at A.S. also

#3 After the 3 oz. I put a piece of 6 oz. in the wing saddel fillet area.


D.E.
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Old 04-23-2010, 02:19 PM
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Default RE: Lets Try To Mold A Moldie!

Next,


#1 I put some 5.4 oz. carbon in the tail area. This airplane has an extremely skiny fuse at the rear as does the fullsize one the carbon makes this area very rigid.

#2 Then some carbon in the nosefrom the wing saddel to just past the firewall.

#3After that I put another layer of 3 oz. over the whole thing.

Now to do the same thing to the other half.

D.E.
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Old 04-23-2010, 02:26 PM
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Default RE: Lets Try To Mold A Moldie!

Next,

#1 On this half the carbon in the nose goes from the wing saddel to just past the front of the motor mount tie in area.

#2 Both halves finished.

Next will be to trim fuse halves and join, that wii be tomorrow along with starting on some wing skins. Tonite I will get a horizontal into the vacuum bag.


Now to give the dog a bath to get the overspray off.
Dave E.
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Old 04-23-2010, 03:14 PM
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Default RE: Lets Try To Mold A Moldie!

Hint for you,carbon in the nose from the wing saddle, It should go to the back of front wing bolts block so it locks it all together.
That is what I do.


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Old 04-23-2010, 04:08 PM
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Default RE: Lets Try To Mold A Moldie!

I would guess you put another layer of at least 3oz over the CF? I wouldn't think one layer of 3oz would be heavy enough even with the CF and 6oz in the saddle.. On my quickies I do a layer of 3oz, the CF in the nose and LG area and then a layer of 6oz.. This seems borderline too light but so far they are holding together..
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Old 04-23-2010, 04:29 PM
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Default RE: Lets Try To Mold A Moldie!

I think I caught that in post 15 - he doesn't show a pic, but mentions another layer of 3 oz on top of the CF and 6oz saddle reinforcement.

This is a good thread, guys, I've always wanted to see how this is done.

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Old 04-23-2010, 04:41 PM
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Default RE: Lets Try To Mold A Moldie!

Yeah, Dave's using a layer of 3oz, then the 6oz and carbon in higher stress areas, and then another layer of 3oz over the whole thing. It doesn't seem like much, and is a lighter layup than Jim Allen's used on our Proud Birds, but it's been more than enough. The "round" shape and compound curves of the airplane add a lot to the strength so you don't need as much actual structure.
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Old 04-23-2010, 04:42 PM
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Default RE: Lets Try To Mold A Moldie!

Can you share what Jim does in the proud birds, just for educational purposes? I've never done this, but am interested in watching the process and learning.
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Old 04-23-2010, 04:56 PM
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Default RE: Lets Try To Mold A Moldie!

Jim does the same thing Dave does except his last layer is 6oz crowfoot instead of 3oz. Jim also trims the two sides while they're still "green", leaving an overlap on one side to make a wet lap joint, rather than letting them cure and doing on the seem.
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Old 04-23-2010, 05:17 PM
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Default RE: Lets Try To Mold A Moldie!

Hello All,

Gary is correct with all of the compound curves on this model it doesnt take to much to make it strong. That is how cars are using such thin metal now they have lots of big slight compound curves.

Kevin,
That is a good idea I will use it on the next one, although with the three that have crashed so far we havent had a failure in that area yet. It usually pulls the bolt area out of the wing.

Lee,
Yes there is another layer of three ounce over everything. The first one I did was 8 oz. over but the last three we had to add weight and that is a good problem to have.

Well its off to the heart doctor and then get a tail in the bag.

Dave E.
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Old 04-23-2010, 05:36 PM
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Default RE: Lets Try To Mold A Moldie!

Hi DE, this tread is excellent, thanks. I'm learning too much. And I have a question: I did try some molding once but when spraying the PVA it make little pinholes. Seems to have grease in the mold after putting the wax. Did it happen to you anytime? what could be wrong?

keep writting.

regards,
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Old 04-23-2010, 05:37 PM
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Default RE: Lets Try To Mold A Moldie!

This is ready to do a wet lap seam
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