The Making of a Mold

I tried my hand at making a mold of the “glove box” top so that I can have someone make a carbon fiber copy of it. Well it didn’t come out terrible, but it didn’t come out great either. Probably not good enough to use for the infusion process. A few things I learned and need to do different. First I used polyester epoxy gel coat which is better then the regular epoxy gel coat, however this stuff really needs to be sprayed on rather then brushed on. Since I don’t want to spend a bunch of money on a spray, I think I’ll try regular epoxy gel coat which I believe is a bit more forgiving when brushed on. I tried to use Bondo as a backing for the mold, but it’s still too flexible. I suppose I could use a lot more and a build up a thicker mold, but I really don’t like the process of using the Bondo anyways so I’ll just abort this idea and use the layered fiberglass and resin method instead. The last thing is that I covered the part with 3M wrap to hide the holes, but the gel coat gets so hot that it softened the wrap and the holes still showed through so I’ll instead fill the holes with epoxy or something.


The mold ready for the mold release then gel coat.


Sprayed the mold release onto the mold. I need a better sprayer though. It supposed to just be misted on, this spray got it a bit too wet.


Well I forgot to take a photo after I put on the gel coat… probably because I was frustrated that it didn’t go on so well. When that got tacky I put on the Bondo. Looks like a tasty cake, but doesn’t smell so good.


I let that all dry over night and inn the morning after carefully prying it free from the board and other mold parts this is what I ended up with. You can see that the 3M wrap didn’t work so well because the holes are still quite visible. The mold also cracked a little when I was prying it off because the bondo was too flexible. Overall though it didn’t come out too bad. I was hoping to get it right on the first try, but I think the second will be the one. I need to order some epoxy gel coat and I’ll try again.

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Carbon Fiber Parts

It’s been bugging me that some of the parts in the Sling interior are a sticker that looks like Carbon Fiber. The sticker eventually rubs off, especially on the throttle console. I believe 3M also makes a better Carbon Fiber covering, but still it’s a covering. I’ve been doing some research and am going to attempt to first make a mold of the throttle and glove box covers. From these moulds I should be able to either make a carbon fiber replica or have someone do it for me. The instrument panel is somewhat straight forward since it’s just a flat piece and then needs to be CNC’d

From what I’ve found about making the mould is that you use a release agent (PVA and Parting Wax) on the part (called the plug) and coat it with a gel coat resin (and MKEP hardener) that you brush (or spray) onto the part. This forms a negative or positive mould depending on how you mould the part. You then cover the gel coat with layers of chopped strand mat to build up some rigidity of the mould. Fiber Glast has a good tutorial of the process and there are a few videos on YouTube. You can also use an epoxy putty or Bondo to form the rigid part of the mould if you like. It really depends on how big the part is, the shape and how durable a mould you need. It’s got me intrigued enough to want to see if I can at least make a mould of the two parts.

I ordered the following from Amazon

  • Creativity Street Modeling Dough, Blue, 3.3-lb. Tub (AC4070)
  • Fibre Glast FibRelease
  • Fibre Glast Orange Tooling Gel Coat – Quart w/ hardener

The creative dough is a filler so that the gel coat doesn’t seep through holes and cracks in the plug. I’ve seen people using the Pelikan Nakiplast modeling clay, but it’s around $30, so I figured I’d give this other one a try. The FibRelease is a new way of coating the plug instead of using both the PVA and parting wax.

On another note I found this cool 3D CNC machine for around $1600 called XCarve from Inventables. Theres a 500, 750, and 1000mm wide version and also more parts where you can expand it even larger. It uses free software called Easel to create and sending it to the CNC machine. I suppose if I were going to make more parts for the plane then this might come in handy but right now the only thing I’d use for is cutting the panel which I can probably do cheaper then $1600, but still very cool and Christmas isn’t too far away so maybe, just maybe I might get one.

I should be the materials in a week so I’ll post my success or failure on the blog. If the moulds come out good and I can find someone to do the Carbon Fiber then I’d be happy to offer the use to the builders who might want to do the same. I can’t say it’s going to b really cheap, but probably fairly reasonable.

 

Wire Run Spreadsheet

I’ve been trying to organize the wiring for the project. I had previously created an Excel Spreadsheet (Well I actually use Apple Numbers) which I uploaded in the Links section of this site, but I didn’t have a way to detail individual cable runs inside a multicore cable (like an M27500 cable). Also I really didn’t have any way to identify connectors and the pins that the wires come up on. I’ve added these things to the spreadsheet, but it’s a pretty manual process to build the sheet with the connector pinouts. I have to copy and paste for the main spreadsheet to the connector pins one. Maybe if I used Excel there would be an automatic way to do it. I had found a really nice piece of software called RapidHarness which lets you pit together wire harnesses and is fairly detailed in how you can show the cables and connectors. They offer a free version which only allows for 30 connections. If you want to go beyond that (I think to 500) it costs $200/month. So well that’s just a bit too pricy for me so I guess my spreadsheet will have to do. I’ll upload a copy when I have it all updated, but here’s a few screen shots of what I’ve been trying to do.

This is the main wire run list. I added the Connector A and Connector B column as well as the wire color image… well it’s not really an image it’s a background gradient for the multi-color wires and just a background color for the solid color cables. I was trying to find a way to set this field automatically based on the “color” cell, but can’t quite seem to figure that out. Maybe if I use an actual image I could use a calculation field to set it… HMMM

I Added another table with the list of connectors and some info about them. I was thinking that maybe I should call the ones that have a named mating connector the same as that connector. So instead of calling the connector C1 call it something like C111-1 in case you have more then one. I will probably want to label the physical connector in the airplane with this label so that it’s more easily identified in the future. Like if changes are needed to be made to the connector I can look in the spreadsheet and see how it’s wired.

This is the new sheet that basically takes the Connector A/Term A columns and Connector B/Term B column and combines them into one table. This needs to be done because sometimes a connector may be referenced under Connector A or ConnectorB and we want to know all the occurrences of it so we have all the wires/pins that are in the connector. Build this table is manual so if anything changes in the main wire list then I have to rebuild it…. which sucks. I do like the wire color icon column… it makes it look pretty cool and is actually really useful in finding stuff.

Deburring Tool

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I found this deburring tool (Burraway by Cogsdill) and ended up buying a 1/8″ (3.2mm) and a 5/32″ (4mm) from eBay for about $35 each. I wish I found this earlier. Basically it deburs the front and back of a hole with one simple operation with only access to one side of the hole. As you insert the tool into the hole the cutter deburs the front of the hole then as you push the cutter collapses and slips through the hole. As you pull back the cutter now deburs the other side of the hole and then it collapses and the tool comes out of the hole. This is great for deburring the channel type parts where you can’t get the normal deburring tool in the back or if you have to ream a hole or two in an area that you can’t get to the back and you’ve already riveted things together. The tools works really well, though if its a big burr you need to go a bit slow to make sure it removes all the burr. Eventually the cutter will wear out and will need to be replaced, but it should be good for a few thousand holes.

Labeling Wires

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One of the other builders asked if I could post what I was using for labeling the wiring on the plane. I’m using a Rhino 6000 labler with heat shink tubing labels. I believe the labeler was around $300. I think there is also a less expensive model that can also use the heat shink cartridges. Also I think there is a model above that can connect to the computer via USB and act as a printer so you can print wire labels from a spreadsheet, etc. So far the labeler and heat shrink labels have worked ok great. I really don’t have anything bad to say about either one. 

Battery alternative

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EarthX PC1200

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I saw this in the Kitplanes September 2016 issue. These are lithium batteries and weigh quite a bit less then other dry-cell batteries like the Odyssey that are typically used in aircraft. For example the Odessy PC1200 weighs around 39lbs while the EarthX ETX1200 only weighs about 8lbs, both have around 600CCA. They’re a bit pricey though, around $700 for the ETX1200 (above). Aircraft Spruce sells them and also found them at Battery Mart. I will need to do some more research on them and what size battery I would need for the Sling. It might be a good option if weight is an issue, though since the tech is still a bit new I’m sure there are problems.

Here’s a comparison (at the bottom of the page) between Odyssey and EarthX (it was done by EarthX) so it’s a bit biased.

 

 

Wire Run List

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Having been an audio engineer I was familiar with the idea of creating wire run list for all the cable runs in a studio (and there are many). So I thought I’d do something similar for the Sling build. I’m posting this just in case someone might find this useful. I’m also hoping it will help me estimate the quanity of all the different wiring that I need. I’m just posting a screen shot of what I did. If you’re interested let me know and I can send you a copy of the file. Having this in a spread sheet is pretty cool actually because if you sort the columns you can identify all the wires going to a device. There is an issue where if you’re not consistent with saying something is always the source then you need to sort by “Location A” and also by “Location B” to find all the connections to/from a device. I also was able to add some calculations to add all the different types of cabling to give me a total of all that type of wire I need, also there are calculations that count usage (if an “X” is placed under the “Installed”column for a run). By using the calculations I can roughly see what wiring I still need (in red) or if I have extra. As more wiring is purchased I can just increment the purchased column in the Inventory table.

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