# Wing and fuselage mold costs

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#### WonderousMountain

##### Well-Known Member
I was wondering what the cost of accurate molds are. It's not realistic to expect me to be able to produce them anytime soon. Does it cost for the area needed, time required to make the mold? Material cost?

Gracias,

Wonderous Mountain

#### Jay Kempf

##### Curmudgeon in Training (CIT)
I was wondering what the cost of accurate molds are. It's not realistic to expect me to be able to produce them anytime soon. Does it cost for the area needed, time required to make the mold? Material cost?

Gracias,

Wonderous Mountain
What is the depth of half of the fuselage and length. Wingspan?

#### WonderousMountain

##### Well-Known Member
12-15 inches in depth, and less than fifteen feet in length. (~.35m depth, <5M length) Wingspan possibly 30ft ~9M.

I'm obviously still a ways off from order date, but it's better to ask early than find out too late.

#### orion

##### Well-Known Member
Really depends on how you want to make the molds, what process you'll use to make the parts and how long you want the molds to last. Also, often times you can trade off work and an extended timeline for dollars so any costs you might get herein might have lots of flexibility. For instance, we get CNC machined tools for all our work however, those tools are designed for room temperature cured parts. Since however we only need one set of parts from each tool, we do use prepreg and cure all up to 270 deg. F. But the result is that the tools are nearly useless after one or two pulls. Those tools, made by Janicki industries, cost us between $180 and about$250 per square foot. Yes, it's pricey but if we look at doing the tools any other way, with us doing the work, by the time we're done the cost savings is relatively small but the timeline of the project is significantly extended. As such. for our customers this approach makes sense. But for someone doing his own, probably not since that person probably has much more time than available funds.

#### berridos

##### Well-Known Member
Here in Spain a boatbuilder with a 5 axis cnc machine offered to cut my fuselage plug for 2000euros.
At the end I spend those 2000euros in building my own 4 axis cnc router.
Building the router has been fun and at times a nightmare. The quality of the router is very doubtful but at the end I think he will do the job. You will need to rebuild it 4 or 5 times until you find an acceptable configuration.
I am at 99,9% of completion waiting for an electronics device from china.
By the way I was very unlucky with the chip provider. He made me loose half a year with a dozen of problems.

You need to decide if you want to build a cnc cutter or an airplane.

The wing molds I have budgeted at less than 1000euros, but with no taper I will build only one semispan mold.
I am grumbling how I could lay into the main mold a mold that would allow a slat version of the wings.
My long term target is to build three different sets of wings out of the same mold.
One stoll wing with 143sqft, one cruise wing with 107sqft and one super stoll wing with 143sqft and slats.

I am planning the horizontal and vertical tail molds in a way I can get different one piece tail surfaces with diferent ARs and different tail volumes. One tail with 0,65 tail volume and one tail with 0,5 tail volume and both with 60% of the Aspect Ratio of there corresponding wing ARs.
The same for the removable vertical surface. One small vertical surface with AR of 1 and one large vertical tail with a AR of 2.

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#### Mac790

##### Well-Known Member
... offered to cut my fuselage plug for 2000euros.
At the end I spend those 2000euros in building my own 4 axis cnc router.
Nice approach I like it, I'm surprised that you can build router for 2000 E, the current car I'm building (just for tests, and "gain" some skills, which I almost lose) will cost me 9-10.000$(still need to decide between machined uprights and custom axles vs welded uprights and standard axles), it seems that I could build 2-3 routers for that . When you finish building it, don't forget to make some nice pictures, and create a thread for it, if I succeed with my current car, I'm going also to build my own router, for my own projects, can't build d.. replicas for whole life. CNC is a way to go, I have a lot of parts CNC laser cut now, and I really love it. Have fun, I'm back to work . Seb #### berridos ##### Well-Known Member Its a cnc hotwiring machine I could have build it cheaper. Maybe if well planned and executed I could have spend 1200-1300 euros. I used standard preloaded Hiwin linear guides and carriages. The stepper motors and the electronics out of china do the job fine. And the structure out of cheap iron. The whole thing due to its size is belt driven without spindles as the cutting area is 1,4m x 0,7m However everything is linear. So I will need to cnc hotwire the fuselage out of slices. The day I cut the first succesful piece I will take some pics and post them. #### Mac790 ##### Well-Known Member Its a cnc hotwiring machine Seems that you moderated your post when I was typing, I thought you were talking about router my own 4 axis cnc router especially that all guys above spoke about cutting (milling) plugs/molds. I was really surprised with that 2000E, my initial estimates says 8-16.000$ for a router.

But now reading your moderated post it's clear that you are talking about hotwire cutter, rather than router. It won't work for my applications, anyway have fun and post some pics when it's done.

Seb

#### berridos

##### Well-Known Member
If you want to mill directly standard mold material without passing thru a plug the lion share of your costs will be the mold material not the cnc router.

#### WonderousMountain

##### Well-Known Member
A CNC router would be a good solution, but the accuracy would have to be good enough to sustain reasonable laminar flow, and not just a fair proximity of the shape. Actually, I'm neither surprised nor appalled at those prices Orion. It's likely beyond my budget, but that's okay for now. It's far preferable that the molds remain usable for quite a number of pulls- or that they be affordable. Post-curing isn't a necessity, though it is a nice touch. I'll probably use the fuselage again for a self launching glider, as that is where my heart steers me.

Wonderous Mountain

#### orion

##### Well-Known Member
We're actually looking at getting a CNC router in-house ourselves in order to mitigate some of these tooling costs (we think we can do simple tools for less than half that cost). With a properly designed router (stiffness of the head is the main issue), accuracy should be able to be maintained to better than .040" over the general expanse of the tool. Even the tools we get from Janicki (which are more than good enough for the considerations you mention) are guaranteed to be within .035".

But again, this is over the whole tool surface - this does not mean that you have localized .035" variations.

##### Well-Known Member
If you want to mill directly standard mold material without passing thru a plug the lion share of your costs will be the mold material not the cnc router.
Really? What material is so expensive that it is several tens of thousands of euro's for a small fuselage? The numbers I've seen and the quotes I've got didn't support that conclusion. The link I mentioned in my last post is a great resource for a specification of cost and that's mainly the time the CNC-rig actually works.

#### orion

##### Well-Known Member
Really depends on how you build the mold but in general we've found that 'berridos' is right when talking in the direction of production quality molds. If you're talking about cutting things out of foam and then glassing over, then the programming and CNC time might be the bigger of the two costs. But anything more extensive and the materials really add up. One such quick tool (semi-production capable) that Janicki made was a wooden structural form that was glassed over and then gun-sprayed with chopped graphite. This was cooked and then machined to net shape. Much pricier than our filled resin system tools. Beautiful but costly.

#### berridos

##### Well-Known Member
I came across several high density foams for mold construction. For a plane you need cubic meters and I always got into several thousands.
The other way are aluminium molds. And massive aluminium isnt cheap either.
I am planning to svage an iron structure than use gel coat and acylic plaster. Some sort of acrylic paste that wets out really thick glass cloth.
Very cheap (much cheaper than epoxy), heat resistant (up to 150ºC) and no thermal deformation/expansion.

#### Mac790

##### Well-Known Member
If you want to mill directly standard mold material without passing thru a plug the lion share of your costs will be the mold material not the cnc router.
Well if you read any of my previous post in relation to composites, you will see that I was never ever recommending this approach. I wrote plug/mold because I got the feeling that some people here just mixing this terms. It happens also here (in my country), some people (unfamiliar with method) calls "molds" on everything, if someone here call mold on plug I know immediately that he/she doesn't know much about it.

I don't see also much sens in this sentence for example I was wondering what the cost of accurate molds are. cost of molds is pretty simple to calculate, you need to know size/area of the surface in m^2(any CAD software can give those informations with usually one click), next number of layers, cost per layer (glass + resin per m^2, prepreg per m^2, etc), it's simple to calculate. The question is also what does "accurate molds" mean +/-1mm, +/- 0.1mm etc., should be rather what the cost of accurate plugs are?

Cost of a plug is harder to calculate, but there was a couple of method on budget described, by Orion, me, and other guys, usually foam, glass, putty.

Seb

##### Well-Known Member
I came across several high density foams for mold construction. For a plane you need cubic meters and I always got into several thousands.
I guesstimated something like that too, 2-3K. But since the CNC routing alone would go beyond 10K for a small aircraft, I was a bit surprised by your statement. For Orion I can understand, high-temp prepregs that have to be very accurate are a bit more demanding as a shiny homebuilt mold.

Well, I guess I favored a foam plug for good reason..

#### WonderousMountain

##### Well-Known Member
I'm looking at a wing area of ~10M (top & bottom), and a fuselage area of 6M (both sides). Wing depth max ~.075 M So the foam for the wings might be reasonably affordable. As to mac's post, I'm not certain I understand the difference between a plug and a mold. I was using the term mold for any male or female surface used as the primary tool in part manufacture. I'm certainly not asking the cost of laying the skins, vacuum system post-curing or anything like that.

This is the most successful thread I've started yet....

Wonderous Mountain

#### Mac790

##### Well-Known Member
As to mac's post, I'm not certain I understand the difference between a plug and a mold.
That pic should clear it to you.

Seb

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#### orion

##### Well-Known Member
A plug is generally the male, or positive tool while the mold is the female that creates the actual parts. If you're CNC cutting, you might as well go directly to the female mold and save a bunch of steps and material.

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