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Old Mar 28, 2012, 01:12 PM
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Yep, I'll have one please!...
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Old Mar 28, 2012, 01:22 PM
G_T
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@#$!@#$ that was fast!

Ok, it is yours. PM should be in your box. Send me an address...

Gerald
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Old Mar 28, 2012, 01:38 PM
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Thank You! ! ! !
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Old Mar 28, 2012, 01:55 PM
But I am learning
I_Can't_Fly's Avatar
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Lol, that just goes to show what the demand is like out there Gerald.

Brian P.
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Old Mar 28, 2012, 03:32 PM
Aurora Builder
United States, MD, Lusby
Joined Nov 2003
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Quote:
Originally Posted by G_T View Post
@#$!@#$ that was fast!

Ok, it is yours. PM should be in your box. Send me an address...

Gerald
Gerald,

I sent you an email a while back on fuselage work, not sure if you missed it?

Thanks,
Sam
P.S-Eric is putting a prototype plane together with this fuselage, he knows what's up, or will send it to me if it breaks
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Old Mar 28, 2012, 06:04 PM
G_T
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Well, when you guys see it I think you'll conclude that breaking it is not all that likely. More likely that the rest of the plane is broken and the fuselage is re-usable! Feel free to give it a squeeze test and bend tests. It is not delicate unlike many fuselages out there.

I'll have to dig through my emails to see if I can find the message. I'm not recalling one about fuselages but I've been so busy with so many things I may have screwed that up somewhere.

Gerald
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Old Mar 28, 2012, 06:22 PM
Just fly it!
wyowindworks's Avatar
Cody, WY
Joined Nov 2007
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Gerald, how much weight do you have to add to the nose to get the fuse to balance at 75 mm or 80mm?

I've been trying to come up with a new way to classify the weight of my fuses. Using simple weight is rather nebulous and even using the fuse balance point isn't super informative. I think I'm going to start using a balanced at 80mm or 75 mm classification. This would tell the buyer how much the fuse is really going to weigh with the needed nose lead to balance just the fuse.
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Old Mar 28, 2012, 07:04 PM
G_T
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That will depend greatly on the installed components.

This fuselage is a 1-piece evolution of the fuselage Phil and I used for our Edge planes. I think balance is similar. With intended components (what we intended, not necessarily what someone else would intend) it is likely on the order of 2g. But I'd like feedback from some of the early builders so I know better.

I could certainly drop some fabric from the front and middle of the fuselage to chase some weight. Heck, many of the commercial fuselages do that. Some of those require a servo tray to make the fuselage strong enough to survive. Once that is glued in, then we are approaching the real weight of such a fuselage (Ditto hardpoints which are in mine and yours, and tail mount which is not in mine). I'd rather just use fabric and as a manufacturer have no concerns about how the recipient chooses to mount gear.

I could also ditch some fabric in the tailboom as it is quite stiff and strong at present. But I like it that way.

I want more feedback from more samples though before I decide whether or not I'm overbuilt. I'm thinking the first time someone trashes a plane with one of my fuselages and it comes out better than they expect, or the first time it doesn't take damage when they expect it would have broken other planes, is the time when perhaps people consider that a couple extra grams might just be worth it if used for real benefit. Really I think the percentage of people who can actually benefit from a super light fuselage is pretty small, but the cost of such fuselages is high in $$ in the long run as they are not as survivable and often take the rest of the plane out when they fail.

I'm also not concerned with the bragging rights of making a super light fuselage.

I just re-read your post. You mean to add noseweight to the empty fuse to shift its CG to that location range? Honestly I have no idea offhand, and the last sample I could check that with is going out the door. I'll have to wait until I make more.

The starting of a proper characterization would be mass, CG, and moments of inertia about the intended final CG. Too much work...

Then there is the issue that larger fuselages may be made lighter but have higher drag. Both mass and drag negatively affect sink rate (actually both factor down to drag since it requires lift to hold up weight and along with that lift comes a drag penalty). Drag negatively affects launch height but mass does not, depending on the distribution. I think right there is the simplest expression of the reason I went with a somewhat skinny design with thicker walls.

Gerald
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Old Mar 28, 2012, 07:08 PM
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United States, AZ, Arizona City
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Adam,

I'd think it's only really necessary to tell the buyer where the fuse balances. They can figure out the rest.

Gary
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Old Mar 28, 2012, 08:58 PM
Make Flying Fun
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United States, MD, Lutherville-Timonium
Joined May 2003
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Good on you GT, I think it is only part of the building process. Balance point on the fuse, cg etc. is all part of the building process along with the moment arm, foils, equipment and the desired result. Of course if you launch high and fly far you might receive some aditional benefits.
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Old Mar 28, 2012, 09:53 PM
Just fly it!
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Cody, WY
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Quote:
Originally Posted by G_T View Post
I just re-read your post. You mean to add noseweight to the empty fuse to shift its CG to that location range? Honestly I have no idea offhand, and the last sample I could check that with is going out the door. I'll have to wait until I make more.
I'm talking about dry balanced weight. Weight is added to the raw fuse until the fuse balances at 80 mm or 75 mm. The fuse is then weighed with the nose weight. This gives a very simple understanding of the weight distribution.

Knowing that a fuse is 35 grams doesn't really tell you anything. If you have to add 10 grams to the nose then the fuse weight doesn't mean much.

I'm just trying to come up with an easy way for my customers to understand the weight distribution of the fuses in my line. Knowing just the balance point means that my customers need to understand and do leverage math from the fuse balance point. They would also need to know the exact moments to draw conclusions about which fuse could build out actually lighter.

The total weight of the fuse balanced at a known and similar point gives someone a more intuitive understanding of what the differences are in respect to final build weight potential.

I was just simply curious how Gerald's fuses compared with mine in terms of mass distribution.
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Old Mar 28, 2012, 10:59 PM
Thermal, where art thou?
BavarianCharles's Avatar
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CG Calcs

Here's what I use to estimate the CG of a wing/fuse

CG Estimates for V2 Wing ...

Works for any wing/fuse combo if you have the weight and CG. I balance my wings on a pencil(eraser) to find the CG.

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Old Mar 29, 2012, 12:37 AM
G_T
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Ok, since you wanted to know, I unpacked the fuselage to check it since I hadn't shipped it yet. 7.3g or thereabouts is needed in the nose. Raw weight is 44.2g for #6. This is with the caveats that the tailboom isn't trimmed yet, the hatch is very slightly oversized (perhaps 1mm or something of that order), and the fuselage cutout is rough trimmed so by definition it is a little undersized compared to what the builder will likely choose. Different layup will affect the result as well, and so far I think I haven't done exactly the same layup twice.

Without other measures such as stiffness and strength, in flex and crush, for front, middle, boom, and hatch, this really doesn't help much. Someone could make a fuselage with one layer of fabric. It wouldn't be usable. Distribution of mass matters as well, not just total mass and CG. Shape is also important. Too many variables for simple comparisons to be valid IMHO.

Gerald
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Old Mar 29, 2012, 03:29 PM
G_T
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The fuselage went out express mail earlier today. Given that we are practically neighbors you should have it in the next couple of days.

A subtle point about the hatch. The shape is pretty nearly symmetric, but the side profile is not. One end has more upper surface curve - that goes towards the front. It would probably be obvious anyway, but just wanted to make sure.

Gerald
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Old Mar 29, 2012, 10:21 PM
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United States, NC, Raleigh
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Quote:
Originally Posted by G_T View Post
The fuselage went out express mail earlier today. Given that we are practically neighbors you should have it in the next couple of days.

A subtle point about the hatch. The shape is pretty nearly symmetric, but the side profile is not. One end has more upper surface curve - that goes towards the front. It would probably be obvious anyway, but just wanted to make sure.

Gerald
Not a problem, I'll keep an eye on things when it arrives.
I have a good idea this will be a keeper, you don't exactly keep low standards when it comes to DLG's or it's parts!

Thanks again Gerald.

Eric
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