"Eliminator 2" molds under way
 

We're making molds!

As of 11-04-04, we've got the stabiliator mold, vertical fin/dorsal mold, NACA inlet mold, and canopy mold done. ( images attached ) Fuselage mold is next, and should be done within the next week or so. Everything is going well...No problems, and we can't wait to get this baby in the air. ( http://www.nextcraft.com/j47_sportjet01.html )

Excuse the sloppy appearance in these photos. The plugs were just pulled, and they still need to be more neatly trimmed, and all the wax and PVA cleaned off. We'll clean 'em up tomorrow.

RE: "Eliminator 2" molds under way
 

First (top) mold half is done... Second (btm) half coming soon. The stabilator, vertical fin, NACA inlet, and canopy molds are already done, and we've been making test parts with good results. I'm finishing the wing plugs, and they'll be molded soon, too.

Today's updates are at http://www.nextcraft.com/j47_sportjet09.html and the article begins at http://www.nextcraft.com/j47_sportjet01.html

RE: "Eliminator 2" molds under way
 

Mike, i just reviewed your post on the Eliminator build and it is great, I have two questions.

I notice that you use Epoxy for your molds instead of polyester, is there a reason for that?

And will cabosil work with polyester?

Thanks

RE: "Eliminator 2" molds under way
 

Thanks for visiting my site, and for your nice comment. (working on the btm mold half of the fuselage tonight!)

For my purposes, epoxy has better performance. (Opinions will vary about this, but stats are published on most composite supplier's web sites... less shrinkage, etc.... and less smell)

Cabosil (technically, the brand name is Cab-O-Sil) is inert and as far as I know, could be used as a filler with anything, including polyester. See http://www.fibreglast.com/showproduc...llers-111.html

RE: "Eliminator 2" molds under way
 

Bottom mold half is done! (http://www.nextcraft.com/j47_sportjet09.html )

RE: "Eliminator 2" molds under way
 

Ta da!

Fuselage molds are done!

RE: "Eliminator 2" molds under way
 

Mike,

Those molds look great !! I was looking at the mold halves and did not see any alignment pins or provisions to join the halves in the mold. I am assuming that you are going to mold in two pieces and then join outside the mold?? Nice to see another new plane come out of NC.... now if I can just get my Orion molds done....


Dan

Dan Hines
Carolina Custom Aircraft
Rougmont, NC

RE: "Eliminator 2" molds under way
 

Hi Dan,

Thank you.

This mold set is a little different from the usual ones I've done, due to the side pieces being separate. There are no alignment pegs built into the exterior of the mold face, but there are alignment holes for machine screws in all the parts, so the mold becomes self-aligned when assembled. (We'll be vacuum bagging the individual parts, then joining them in the assembled mold.)

An Orion sounds like a cool project... Start a build thread and show us some photos.

RE: "Eliminator 2" molds under way
 

Looks Great Mike,

Can't wait to be the first kid on my block to own and fly a J-47. [8D]

RE: "Eliminator 2" molds under way
 

Hey, thank you, moxjett!

I have a little prelim work to do, and will probably then make the first test fuselage (without all the formers) either today or tomorrow. That's why I'm up at 5am... Haven't slept yet, because I'm just wired about having gotten the fuselage molds done. Pretty exciting, considering some of the ups and downs of the past couple of years.

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Hey Mike... Looking good. I've been looking at your website alot and can't wait for production... I've got a GMS 76 looking for a home.

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Keep up the good work Mike, I really enjoy your site and appreciate your work....it is a great resource for the hobby.

RE: "Eliminator 2" molds under way
 

Wow... Thank you, everyone. I do sincerely appreciate those comments. That's what keeps me going.

Now, if I could just find a few thousand people who feel the same way, we'd be in business!

RE: "Eliminator 2" molds under way
 

The fuselage already has recessed markings for the gear doors, so I made the gear door molds today.

RE: "Eliminator 2" molds under way
 

We're waiting on a glass shipment, before we can make the first "Eliminator 2" for flight testing. So, I've been working on the wing plugs and other odds and ends. I've just finished etching the wing plugs for the control surfaces, which will be skin-hinged. (first photo)

Although we'll be offerering the kit in "raw" glass, or white/light gray primer, I've been giving some thought to possible paint schemes. The red and white one in the upper right hand corner of the 2nd image is the "Edwards-ish" scheme we'll be using for flight tests.

RE: "Eliminator 2" molds under way
 

Hi Mike,

Awesome, can't wait to see how it turns out.

I heard you are waiting on some info from JetCat...what do you need?

RE: "Eliminator 2" molds under way
 

Hi Matt, and thank you!

Since I'm not a turbine flyer at this time, it would be foolish for me to design a "turbine ready" model without doing the research, both for mechanical needs, and to keep it safe. The turbine "specs" themselves are published, as far as figuring the size and thrust requirements. What I'm interested in are some guidlines for designing efficient inlets and an efficient exhaust systems. What I've heard so far is that since turbines combust air and fuel, (expanding it) rather than just blowing it through, the intake requirements are "less area than most people would think", and "not very critical". Ok, but that's not very specific.

Are there some rules of thumb regarding intakes and exhausts for turbines? Thanks! (JetCat has still not responded.)

Images... Added a "Thunderbirds" scheme and a "Blue Angels" scheme, just for fun.

RE: "Eliminator 2" molds under way
 

Mike post your test flight time and date. I may ride down to watch.:)

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Will do, vicman.

Thank you. We're expecting to do the test flights at Triple Tree, in a few weeks. (asap)

RE: "Eliminator 2" molds under way
 

Why go so far?

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My partner wants to do the test flights there, because it's a great place to shoot photos and video, and because there are some people at Triple Tree who have said they want to see the thing fly.

I'm new to this area though, and so if you want to email me and let me know where the closer flying sites are, I'd be interested. Thanks.

RE: "Eliminator 2" molds under way
 

Mike,

I have noticed this on several all composite aircraft with skin hinges on the control surface. The cut angles on the control surface's are not always at ninety degree's to the hinge line, which in turn requires having to relieve the control surface at the leading edge at the point where it meets the hinge line ... hence screwing up your nice tight gaps.

Some insight as too why the control surface cut lines are done like this would be appreciated. Attached is a pic of my Roo II wing to help illustrate. The point came to mind when I saw the pic of your wing in post #14, and the scribe line at the aileron tip & hinge line tangent.

RE: "Eliminator 2" molds under way
 

First, let me say that I'm new to skin hinging, and don't claim to be an expert. I've made a variety of test parts, and read every thread on this I could find, (gliders builders use them a lot) and have also researched BVM, Composite-ARF and other kits, taking closeup photos when I could. So far, this is what I've found.

I understand your Roo problem, which points out the fact that getting tapered control surfaces on a highly tapered wing to work right demands precision. First, as you said, the cut must be 90 degrees to the hinge line. Second, the cut must be 90 degrees in the vertical. (one cut directly above the other.) Since we're trying to have very tight gaps, any error will be a pain.

The cuts on the BVM Composite Bobcats that I recently photographed continued forward into the non-moving part for almost 1/4". The reason for that extra relief isn't obvious to me yet. (image attached) These cuts are on the relieved side of the hinge only, so it's probably just so the skin there can flex a little, since it serves as a "wiper".

For my sport jet, we originally planned to spray primer in the mold. Having done some hinging tests, I now see the advantage to being able to mark the material (on the inside, after vacuum bagging) and to then be able to use these marks visually from the outside, (when the parts are joined) to see exactly what's going on. That's why I took the step of carefully measuring for the etch marks on the PLUGS, before even making the molds. If we cut on the etch marks, the surfaces will be right. And...If I'm not missing something here... If using the etched marks works, then we can go back to our original plan of priming in the mold. (And maybe painting in the mold, later)

One other thing...
These skin hinges must be scored after fabrication, to break the thin exterior epoxy layer and "activate" the hinge. So, depending on whether you score the hinge line first or make the end cuts first, something might get out of whack. Again, I'm hoping to avoid that by using our etched lines as the score line. We'll see...

These "new" processes are always something of a challenge, but I sure like them when they're done right. It's just one more "lighter, stronger. more precise" thing we can add to new models. Worth the effort, I think.

RE: "Eliminator 2" molds under way
 

Mike,

Maybe the accompanying two photos will shed some light on the purpose of the relief's. This is the weird kind of things you get into when the cut lines are not 90 degree's to the hinge line.

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Thanks for sharing the photos.

Don't you just hate it when something is so close to perfect, but ... not quite?

RE: "Eliminator 2" molds under way
 

Mike what type or brand of Epoxy tooling gel do you use? I went to my local (Toronto Canada) composite store and they have not heard of Epoxy based tooling gel, just the polyester based one.

RE: "Eliminator 2" molds under way
 

I have found that having a bunch of people around for the test flights is not a good idea for me anyway. I am very deliborate and slow when it comes to going over everything. People get impatient. They expect you to walk out setup and put it in the air. Never happens on my test flights. They always ask a bunch of questions. Not a problems unless it is during the test flight and it always is. I try and schedule my test flights at a time when there are a minimum of flyers at the field. Then there are the people that can not stand down just for a couple of minutes or they just do not know any better. The third test flight on mine was a good example. There were only three flyers at the field that day. I assumed they would stand down at least until I got it back on or in the ground but the one decided the test fly a new F4U. He was having problems with the motor and kept ground looping it on the runway. He came out and blocked the runway at just about the moment I needed to land. The result was that wild deadstick landing. In the future I will ask the others to please stand down for a couple of minutes.

Ted

RE: "Eliminator 2" molds under way
 

You're right, Ted. It's better to be able to go extra slow, and not be distracted.


Rubble:

I've been using West Systems #1099 "Surfacing Resin" for almost 15 years. (It used to be sold under the name "Akemi", before it became a West Systems product. (It's white, but can be pigmented any color you want. I use black, for molds.)

RE: "Eliminator 2" molds under way
 

Hi Mike,

Well smooth inlets could be very small, maybe 5-7 square inches. If they are a flush cutout (ie not facing forward) , then I would make them 50% bigger.

The key will be getting the right pipe design. Venturi design at the rear of the pipe creates a heavy vacuum at the front of the pipe, and that will pull the air into the inlets. Get the pie right and then just keep cutting the went holes bigger until you don't collapse the fuse!

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Thanks, Matt.

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beautiful work Mike, most I'm learning is from your web site....

RE: "Eliminator 2" molds under way
 

Our required glass hasn't arrived yet, so we've been working on other details such as the parting boards for the wing molds, etc., and are gearing up to make the prototype. In the meantime, I've created a little "Research and Development" page on the plane, for those of you interested in how this airplane came to be, at http://www.nextcraft.com/j47_development.html

Stay tuned!

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That is so cool Mike..... Can't wait till we see The real thing and performance report. Keep it up.

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Thanks Bob.

"On or berfore January 11th" is what we've heard about our glass shipment. So, it shouldn't be long...

RE: "Eliminator 2" molds under way
 

Here we go with the first molded fuselage...

Since we don't have our former patterns finalized for laser-cutting yet, it was always our intention for the first fuselage to be made extra heavy duty, so we could slice it up, check, and create some patterns. Here's the heavy duty fuselage out of the molds, with one of the already-molded canopies in place. The second image is a photo from inside the fuselage, looking forward from the tail.

We got our glass shipment today, so we can keep moving, making the prototype.

RE: "Eliminator 2" molds under way
 

Mike...It looks too good to slice up!!!! Beauitful work, Keep it going

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Here's the fuselage sliced up, and the resulting formers.


Since I'm making the wing molds using the sand/epoxy method, I'll just post those updates in this thread... http://www.rcuniverse.com/forum/m_24...tm.htm#2571257

Today, I've pulled the parting boards from the first halves of the wing molds, and they look good. (See the above thread)

When we start making parts, in a week or so, then I'll posting here again.

RE: "Eliminator 2" molds under way
 

Mike,

Are you planning on glassing in the formers and then matting the two fuse halves together? Or will the formers be installed after the fuse is completely laid up?

Looking good!

JR Gautreaux

RE: "Eliminator 2" molds under way
 

We'll vacuum bag both fuselage halves. Then we'll install the formers in the bottom of the fuselage, (using an "Aeropoxy"-type adhesive) and let them cure long enough that they won't move. Then we'll apply a bead of the same adhesive across the tops of the formers, join the mold halves, and flip the whole assembly upside down. That way, any adhesive that moves will form a nice fillet where the formers join the top fuselage half.

We probably will install all the formers except the firewall, for two reasons: (It can be installed after assembly, through the top hatch)

We have a method of installing the firewall that will accomodate different size engines, and we know that many flyers will automatically install a larger engine than we recommend. The servo and tank support plate that attaches between the firewall and the next former forward is inserted into slots in both pieces. So, if the builder installs the firewall, and then the support plate, The structure will look and function the same, regardless of engine choice. (Even for much larger engines, we're talking about a difference of about 1 inch.)

Second, there are issues to be considered with the muffler. We are specifically making the stock parts to accomodate the OS .61 FX, since it's a very popular sport engine. Those builders who use different engines and mufflers may have to modify the interior of the tail a bit. Our system routes air into the engine compartment directly, through NACA inlets, then through ducts on the inside walls of the fuselage, creating a plenum effect in the "cowling". The air can only exit the cowling two ways... It can exit through the rear of the tail, through pre-defined outlets on each side of the spinner, and we're providing a molded and heat-treated fiberglass duct which surrounds the stock muffler where it goes through the firewall, and directs it out through the bottom of the plane. That way, no "goop" gets blown all over the inside of the airplane, and both the engine and muffler get cooling air forced over them. There's an opening in the former just in front of the firewall, through which additional air can enter the muffler compartment, when the gear is down and the gear doors are open.

I've attached a couple of our CAD images which illustrate what I'm saying.

RE: "Eliminator 2" molds under way
 

Mike,

Thanks for the explanation, looks like you got everything covered. Say, what CAD program are you using? I like the drawings.

JR Gautreaux