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Old Nov 03, 2012, 10:44 PM
Thermal, where art thou?
BavarianCharles's Avatar
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Quote:
Originally Posted by G_T View Post
PVA cleaned off and screws installed, but the hatch opening isn't cut yet and the hatch is not trimmed. So it should end up gaining perhaps 1g from where it is now. Were it one of my planes, I'd be cutting about 2.4" off the tailboom. You don't have to of course - I just prefer the booms not as long as some. That would remove perhaps a couple of grams. Current weight is 47.4g. So I expect the final weight to be somewhere in the neighborhood of 48.5g before any trimming of the tailboom.

Gerald

PS - Send me a PM with your address. Usual rules - don't send payment until you have inspected it and decided to keep it. Otherwise just send it back. I may get it shipped on Monday.
PM sent! Don't sweat the shipment ...

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Old Feb 11, 2013, 12:06 AM
G_T
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Hello everyone waiting on a fuselage,

I've been busy cutting up some fabric for a batch of 10. This should get me caught up for everyone who has asked for one. I probably need another couple days to complete cutting the fabric, there being hundreds of pieces, then I'll start laying them up. They should start coming out soon. Probably everyone will have them by 6wks from now. That's my intent anyway.

Front screw will be titanium now, rear is still aluminum, and outer carbon fabric is now Samurai. Otherwise the fuselage is the same as the previous ones. I did not want to change things up very much. These should be perhaps two grams lighter on average; we'll see. So some of them might come out sub 40g with screws and still using the steel hardpoints.

An order has been placed for more fabric. I don't have much left of some of what goes into these fuselages. I'm out of the carbon I was using for the outer layer so I'll be using Samurai for a bit.

It seems I did get stiffed for one fuselage. If it happens again I'll have to re-evaluate my ship before payment policy.

I expect to be working to get a CNC router running by summer. Once that is going, and I learn how to use it, things should get interesting!

Gerald
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Old Feb 11, 2013, 12:21 AM
Canada
Joined Jun 2009
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Gerald, if you have any seconds put me down for one too please. I will Paypal you prior to shipment after production.
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Old Feb 11, 2013, 01:06 AM
G_T
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Paul, you are the first on the list. You asked for one a long time ago, but then I couldn't contact you... I'm planning to lay yours up this week sometime. Please PM me your address as I don't have it. Don't pay first; I don't know what shipping will be to Canada. What I have been charging for shipping is an average of what it ends up being for the continental US but it won't be the same for other countries. Probably not much more for Canada though.

If you NEED it to be a second (price, for instance), then PM me that info. But I don't intend to be making seconds if I can help it!

Gerald
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Old Feb 11, 2013, 11:09 AM
Aurora Builder
United States, MD, Lusby
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Sub 40g fuselage will rock Gerald! I'm excited to see the first Samurai batch
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Old Mar 14, 2013, 01:44 AM
G_T
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What a friggin pain in the @%%. Samurai is the most annoying fabric I've ever tried to use in a fuselage.

The outer fabric in the middle and tailboom portion of my fuse is a laminate (3M77) of HM uni to woven carbon - Samurai in this instance. This ends up being rather stiff, easily twice as stiff as the previous layup using 1K carbon outer fabric. That is stiff while I'm putting it in the mold, not necessarily stiff in the finished fuselage. So, the fabric keeps popping itself back out of the mold!

I couldn't use my normal technique of putting dry fabric on wet mold. The fabric wouldn't stick. So, I saturated it on the bench. It still popped out. The epoxy had to actually thicken a little before the fabric would stay in place long enough for me to get the other layers in place which then locked in the shape.

If this fuselage doesn't come out nearly frigging perfect, I'm not doing this layup again. The aggrevation level is way too high.

The fabric even resisted being held down by thread; it kept popping fingers back out. I may not have gotten them all down successfully so the mold line may not be as good as usual.

Grrrrrrr.

Gerald
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Old Mar 14, 2013, 06:58 AM
Father of Fr3aK, DLG Pilot
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Gerald, buy some 1/4" music wire and cut it to length for your boom. Lay in the materials and put a music wire piece in place to weight it down while you lay up the rest.
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Old Mar 14, 2013, 08:24 AM
Aurora Builder
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Gerald I think you may find that to be an issue with any of the spread tows. Samurai is the more supple of the group. Hopefully Tom's trick will do the job.
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Old Mar 14, 2013, 09:32 AM
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Yep, also a 1/4" coppper tube from the plumbing shop used to hold the balloon bladder helps wrangle the cloths as well when placed over the layup early sometimes. I have a small diameter boom in some molds and that works more often than not. Used a piece of the left over tubing as a weight in the boom area until the cloth settles down.
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Old Mar 14, 2013, 02:37 PM
G_T
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I had less trouble with the Oxeon fabric when I tried it the first time, sometime in the first few fuse pulls. But it wasn't laminated to anything else to help keep it together (at least one of the times). As I recall the area I had issues with then was the roughly 90 degree transitions along the edge of the wing saddle. There is some carbon tow there to improve the situation, but stiff fabric still resists that shape.

All I ever had of any Oxeon fabric was some scraps so I've only done two pulls with it so far. But now I have my fabric order and I have Oxeon. We'll see how it goes.

The problem with the rod method is I have extra layers to add and if I remove the rod, the existing fabric pops out! Otherwise, I have to wait until the epoxy thickens some so it can stick the fabric down.

It wasn't related to wetout as I tried dry fabric first, as usual, and it didn't stay. Then I pretty much soaked the fabric on the bench and rolled it in before trying the second time, and it wasn't really any better.

I think the biggest difference is the previous fabric was a somewhat open weave until I mashed it into place. The spread tow fabrics are not open weave and the tows don't like to shift. I may end up having to go back to the previous fabric assuming I can find any. But first I'll be playing with spread tow some more.

Late this evening I'll crack open the mold and I'll let you all know how this one comes out. My hopes are not high but my fingers are crossed. If it is a keeper and passes inspection someone is going to get it, so to speak. Since it took me longer and extra epoxy to lay it up, I cracked the mold a bit wider than usual and ran the pressure up a little higher. That has its own risk with potentially pushing fibers out on the mold flange. Plenty of epoxy came out so it probably isn't carrying much if any extra mass.

One trick I could use is faster epoxy painted into the mold. It gets thicker more quickly. But then when the layers and slow epoxy go in, it gets mixed some which delays the cure. One still has to work a bit faster than my usual speed or the weight ends up higher.

Gerald
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Old Mar 14, 2013, 04:03 PM
Father of Fr3aK, DLG Pilot
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I've noticed that if you start with a faster cure epoxy and add slower stuff over top, the faster stuff kicks off and exotherms more quickly, causing the slower cure to get faster too. It's worth a try though.
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Old Mar 14, 2013, 04:10 PM
I ♥ Carbon Fiber
Jonas M.'s Avatar
Germany
Joined Apr 2006
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I made a fuse with samurai at 45 sandwiched between two layers of 100gsm HM uni. It stayed in the mold as it's supposed to. I always wet out the fabric sandwich first and put it in the dry mold.

Best of luck with your fuses!

Jonas
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Old Mar 14, 2013, 05:00 PM
G_T
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I don't recall the exact figure but the back of my fuselage is perhaps 3/8" diameter. So a fabric which exhibits any stiffness can spring out. What is the diameter of the fuselage at the back on yours? I wonder if yours being on a bias and mine being 0-90 makes a large difference? I'm thinking it might. I don't have interest in going biased on that layer, for various reasons. But interesting data!

Gerald
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Old Mar 14, 2013, 06:07 PM
I ♥ Carbon Fiber
Jonas M.'s Avatar
Germany
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My fuselages are about the same diameter as your at the rear.

When you put a sandwich of several layers in he mold is the 3M77 loosening up and only the Samurai fabric lifts itself up or does it pull the other fabric up too?

I saturate the fabrics with resin which them dissolves the 3M77 and softens up the whole sandwich. Do you work with templates for the fabric or do you cut it to shape after it's in the mold?

I think the fiber direction matters a lot. But I don't even have problems when using much heavier fabrics. My current layup consists of one layer 100gsm uni on the outside and a layer 160gsm carbon fabric at 0/90. This makes 80gsm of carbon at 90deg to the boom.
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Old Mar 15, 2013, 12:36 AM
G_T
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With screws installed in hardpoints, hatch used for molding still in place and fuselage cutout not done, PVA not cleaned off, it is 40.2g. So this one should be < 40g cleaned up.

The surface is just fine - bubble free. Fabric shifted some though with my having to horse around so much with the Samurai layer. Usually the upper and lower carbon layers line up nicely, but not this time. The bottom layer extends notably more forward than the upper layer. It also shifted laterally a little so there is a strip of Kevler visible on the side where usually it is under the carbon. Some Kevlar threads poked out the side of the tailboom and made it onto the flange in two areas along the tailboom. The very back is not what I'd call usable but I make these overlength anyway. I'll probably clean it up the rest of the way tomorrow and make a final assessment. Most of the cosmetics can be readily hidden with a sharpie.

Anyway at first glance it looks quite usable though not perfect. The loss of a few grams is rather noticable when holding it. I can't help but think it isn't going to be quite as tough as the old one being lighter, but people kept asking for < 40g fuselages. I'm guessing it will be < 39g when trimmed to length, so assuming a typical 1g tail mount, it should finish at under 40g with screws. Sufficient?

Note that some of the weight reduction is from swapping the front bolt out from steel to some custom titanium bolts I had made. The rear bolt is still aluminum. I just don't trust aluminum long term for the loads of the front, not as a single bolt. The use of various metals for bolts mixed with steel for hardpoints and the presense of carbon may require the use of something on the threads to prevent galvanic corrosion long-term, particularly if subject to rain. The aluminum bolt being anodized should help.

I haven't decided if I'll keep this one or sell it. I need fuselages and I need to stop messing with everything else and build some planes sometime soon. It's funny though, I do a good job but I dislike building planes a lot more than making the parts.

Gerald
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