HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Mar 07, 2012, 11:06 AM
Chuck 'Em and Chase 'Em
Fly2High's Avatar
United States, NY, Plainview
Joined Aug 2005
8,094 Posts
Quote:
Originally Posted by ShadowFalken View Post
[/COLOR]

. There is no horizontal tail mount. I know that some, such as myself, want to use full-flying. Others would want bolt-on. Different builders may want different tailboom lengths and mount locations/angles... By not putting a mount on, I'm leaving maximum flexability.

From the first post. Are you running a round timer?
CLICK THE BUTTON, CLICK THE BUTTON...

AAAUUUUGH , IT'S NOT STARTING!!!!!!!!

I missed starting the window timer



LOL.

I missed that. Thanks Jim.

Then why did you state you wanted one?
Quote:
Gerald, they look good and are strong. I would love to see the weight in the 40-42 range with the option of adding a tail mount and all carbon nose. Tail mount should be included in my weight spec. (mounted)
Fly2High is online now Find More Posts by Fly2High
Reply With Quote
Sign up now
to remove ads between posts
Old Mar 07, 2012, 11:36 AM
G_T
Registered User
Joined Apr 2009
5,725 Posts
http://www.rcgroups.com/forums/attac...mentid=3146676
http://www.rcgroups.com/forums/attac...mentid=3146671
http://www.rcgroups.com/forums/attac...mentid=3146672

The fuselage is a cleaned up version of this two piece design from our old Edge planes, shown in the pictures above. No nosecone though. Perhaps someday. This is not a fat fuselage but it has enough room. Tailboom is round not oval (roughly the size of the old tailbooms we all used to use), but the layup inside varies around the inside so it is stiffer horizontally than vertically. The fuselages we have made so far are stiffer and stronger than these old Edge ones.

Out of curiosity, why would you want an all carbon nose? That requires sticking the 2.4 wiskers out which is extra drag, easily avoided. That is, unless you are still on 72? Going carbon in the nose area would allow a lighter nose of course (though it is still a good idea to have one layer of Kevlar in there). Then you have to add a bit of nose weight to compensate. I'm not sure of the point of it. These fuses are very solid up front. Yes I could reduce the weight by making the front more flimsy. I don't need carbon to do that! Then you'd just have to add more noseweight anyway, even with 12g tailset. So I went with more fabric instead. I want to be able to land on the ground sub-optimally and not have an issue. I want to be able to come in ballistic and catch the plane without wondering if I'll crush the nose or fold the pod.

Anyway, I'm not going to make a super light fuselage just for the bragging rights of making a light fuselage, that then needs to be reinforced (servo tray, or whatever) before it can actually be used.

I'd expect a good install in one of these fuselages to use roughly 1 to 3 grams noseweight, based on my experience with the Edge fuselages. That is with 2x JR285 servos. If you use LiPO you would likely need more weight of course. I used LiPO for a year and went back to NiMH afterwards.

FWIW, a tail mount should be about 1g or perhaps less (spring-V is less for instance), or it is overbuilt.

Gerald
G_T is offline Find More Posts by G_T
Reply With Quote
Old Mar 07, 2012, 11:36 AM
Aurora Builder
United States, MD, Lusby
Joined Nov 2003
3,437 Posts
Gerald, great looking fuselage! I'll take your "rejects" off your hands if you aren't going to fly them!

Before I go on, I should state that I haven't flown full flying on a DLG, but I will likely try it. However, if you have a fixed stab, you MIGHT have a better chance of saving the model if the elevator fails, at least the plane should still be stable. Probably pointed at the ground, but stable.

The fixed stab mount can be designed to be less drag than a v-mount. Also, if you incorporate the mount into the mold, you can make alignment significantly faster/easier (ala Polaris, Stark etc.). The downside is making this one piece risks trashing a fuselage because the stab mount turned out bad. The solution is to make the stab mount first, then drop into a recessed cavity in the mold that holds alignment while making the fuselage.

The question is always where you spend the time, in the build phase or the assembly phase. Personally, it is usually easier to do things correctly in the build phase than during plane assembly.
samc99us is offline Find More Posts by samc99us
Reply With Quote
Old Mar 07, 2012, 12:23 PM
G_T
Registered User
Joined Apr 2009
5,725 Posts
The v-mount drag vs pylon is not quite as clear cut as it seems at first glance. The pylon generates a turbulent wake that passes directly onto the vertical stabilizer, increasing its drag. It is beyond my abilities to compute the resulting drag with any assurance. Also most commercial v mounts are really more blocky and draggy than need be, and IMO much heavier than needed.

So the full system drag question is in my mind at least a rather open question.

I've become fond of not needing any tools to put on or remove the horizontal stabilizer. There are no little screws to drop. Plus I like the handling characteristics. Additionally I can design a horizontal stabilizer with lower drag than I could ever do with a hinged stabilizer. I don't even have to guess at the appropriate mounting angle since I don't know what wing and what tail someone might choose to put on the fuse!

-----

I have a couple of reasons for making these fuselages. One is I wanted to provide a tougher alternative to what an individual can currently purchase. There is a lot of work that goes into making a good wing. There is a lot of work that goes into making a good fuselage. Few want to do both! So more fuselage options may encourage more people to become builders. I rather like seeing more planes built by individuals and small groups. That is one of the things that makes DLGs great. We can still build them!

Another reason is I'm considering making a kit in conjunction with some others, but not immediately. I consider this fuselage - the experience gained from it - to be a step in that direction.

Another reason of course is to recoup costs that have already gone into this project. It will be the first part I might actually be able to get a little money back for what I've put in! Really I expect that is part of the reason most people doing commercial work got started doing it. They wanted their own planes. They were stuck with the cost of the tooling, materials, and supplies... Might as well sell a few to defray the costs.

One of the things I want to find out in this project is how long it will take me to make a fuselage when I'm fully up to practice and have all the tools set up. Right now, making fuselages one at a time, it takes perhaps 4 hours. This includes things like mold cleanup, wax, PVA, cutting fabric, ramping up pressure, and trimming hatches. Obviously I hope to reduce this time some! Once a layup is finalized, then fabric will be cut in batches so there is one time savings. Wax won't be needed each time as the mold is fairly well seasoned, so there is another. We'll likely come up with other things to save time here and there.

Even using expensive fabric and epoxy, there is not all that much materials cost in each fuselage. But there was a lot of labor and some cost that went into making the molds, the materials need to be bought in quantity because they are not locally available, and some of the required tools are not super cheap. Because of the location of my shop I need to use a quiet compressor for instance. Those are not cheap. But in the end, the biggest cost is the labor. Personally I think some of the fuselages out there may be flimsy because dealing with fewer pieces and fewer types of fabric is cheaper and faster.

This fuses tailboom for instance has some Kevlar in it. This doesn't add much to the bending stiffness - that is done primarily by the HM carbon in there. But it does add quite a bit to the hoop strength and stiffness because of how I used it. That in turn increases the bending strength. One can squeeze these tailbooms fairly firmly and there won't be any cracking noises (I've done this many times with each fuselage). If one has a mid-air and breaks one, there is some chance that it can still be flown back to the ground. In any event it will hold together rather than shatter. Repair should be easier.

Gerald
G_T is offline Find More Posts by G_T
Last edited by G_T; Mar 07, 2012 at 12:49 PM.
Reply With Quote
Old Mar 07, 2012, 12:35 PM
Registered User
United States, CA, Tehachapi
Joined Jun 2011
3,216 Posts
Excellent work Gerald. These look very nice. Would you part with the "rejects" at a discounted price?

Brandon
bwill6 is offline Find More Posts by bwill6
Reply With Quote
Old Mar 07, 2012, 12:36 PM
G_T
Registered User
Joined Apr 2009
5,725 Posts
BTW, I'm not taking a waiting list. So hold the requests... I'll sell them when I have them in hand to sell.

I haven't decided yet whether I'll ever sell seconds, or instead run them through a bandsaw and throw them away. I'll probably fly seconds myself though. After the first two attempts (from the pictures) all the fuses have been fine structurally. But I'm not happy with the cosmetics yet. I probably won't get it perfect, and I'm not going to use a clear-coat. Currently, the finish is glassy. The seams are clean enough that all we generally do is snap off the epoxy. This mold closes quite tight and the edges are sharp. At the thickest the seam is probably about 0.01" thick. Alignment is quite good.

The problem area is the relatively sharp edge of the wing saddle. We get some surface blems in spots along the edges of the carbon tow. This will get solved, most likely by changing the layup order. What we had been using as the outer fabric doesn't conform well in this sort of compound edge. The results have varied between almost perfect, to hmmm...

Once this is solved we'll be ready to move stuff to my little shop for some production.

We'll get you some better pictures when we have something prettier to show!

Gerald
G_T is offline Find More Posts by G_T
Reply With Quote
Old Mar 07, 2012, 12:53 PM
Make Flying Fun
KevinSharbonda's Avatar
United States, MD, Lutherville-Timonium
Joined May 2003
1,469 Posts
Nice GT, how's it feel to be at the feeding trough? Bibs supplied? Nice job keeping the sharks at bay ! ...Thermals, Kev.
KevinSharbonda is offline Find More Posts by KevinSharbonda
RCG Plus Member
Old Mar 07, 2012, 01:44 PM
G_T
Registered User
Joined Apr 2009
5,725 Posts
Dimensions...

Fuselage width is a little over 15/16" at the widest. Height is about 1 5/16". Tailboom region tapers from about 5/8" to about 7/16". Wing hardpoints are 4 1/2" apart. The front threaded hardpoint (6-32) is about 7/8" from the default wing leading edge location. Nose extends 9" in front of the wing. Overall length after we trim is about 40 1/2". Fuselage CG is around the rear wing bolt (with hatch removed), but is subject to change depending on what we do with the layup. Hatch begins 1 3/8" in front of the wing (opening starts farther forwards) and extends 5". Finger width is on the order of 3/4".

Gerald
G_T is offline Find More Posts by G_T
Reply With Quote
Old Mar 07, 2012, 05:27 PM
Registered User
San Gabriel Valley, CA
Joined Mar 2008
1,756 Posts
Quote:
Originally Posted by G_T View Post
These are the first two rejects. They are better now. Actually everything since this point is perfectly flyable. It is just the cosmetics which aren't 100% yet.

Gerald

I will take them. Paypal ready.
Seriously.

Tai
tai626 is offline Find More Posts by tai626
Reply With Quote
Old Mar 07, 2012, 08:13 PM
Who needs a pilot??
danstrider's Avatar
Alexandria, VA
Joined Jul 2002
1,161 Posts
Your first two attempts look quite nice, especially compared to my first attempts. I'm looking forward to seeing your successful parts at the field sometime.

Quote:
Originally Posted by G_T View Post
The problem area is the relatively sharp edge of the wing saddle. We get some surface blems in spots along the edges of the carbon tow. This will get solved, most likely by changing the layup order. What we had been using as the outer fabric doesn't conform well in this sort of compound edge. The results have varied between almost perfect, to hmmm...
I have had good luck with raw epoxy brushed into the crevice and laying in a single 3k tow in the wing saddle corner of my mold. Recently an air bubble or two has migrated/stayed in the corner, but otherwise it has been difficult to tell the tow is outside the surface carbon layer.

Mind sharing how much pressure you've been using in the bladder?

Dan
danstrider is offline Find More Posts by danstrider
Reply With Quote
Old Mar 07, 2012, 10:13 PM
G_T
Registered User
Joined Apr 2009
5,725 Posts
The answer, as always, is 42 (psi) I won't go less than 30psi. Not sure what I'll eventually settle on. I've seen no difference in that range in the resulting parts (compaction, weight, apparent stiffness and strength, or cosmetic defects) so I see no particular reason to go higher. Though honestly, I haven't broken one yet. I have subject each fuselage to higher loads - bending, squeezing - than I'd do with any other fuselage though. You might think of these as sized for what I consider to be appropriate stiffness, and overkill for strength.

The edges of the wing saddle with the tow are just fine. It is actually the transition between the edges of the tow and the fabric which collects some voids. Anyway I have a Plan A and a Plan B ready to go, once the mold is back in service. Hopefully one of these will work.

Of course these prototype fuses could easily be filled with a little splooge and sanded out to fix the cosmetics but I don't plan to be doing that for production.

I figure if one starts putting out so-so parts, then one gets a reputation for putting out so-so parts. Start as you mean to continue. That's why I'm not sure I want to make seconds available.

I don't mind sharing some details, but I possibly won't share everything. I will say the fuses contain high modulus carbon, lesser modulus carbon, various Kevlar, E-glass and S-glass. All that is not likely to change, but the final layup is TBD.

Gerald
G_T is offline Find More Posts by G_T
Reply With Quote
Old Mar 08, 2012, 10:31 AM
Registered User
United States, SC, Mt Pleasant
Joined Nov 2003
1,174 Posts
Your voids aren't even visible in your photos so they must not be that bad!

James
hohensej is offline Find More Posts by hohensej
RCG Plus Member
Latest blog entry: Aerial Information
Reply With Quote
Old Mar 08, 2012, 12:47 PM
G_T
Registered User
Joined Apr 2009
5,725 Posts
If you look closely at the last photo, bottom fuselage, 2:30 from the front bolt hardpoint to intersect the edge of the wing saddle, you'll see one of the defects. Sometimes they are worse than this. A little West fast + 410 lightweight filler + 423 graphite powder and a touch of wet sanding would make the spots go away.

The pictures really aren't very good. They are crops from pictures showing a bunch of stuff other than just the fuses. Clearer pictures would show the issue better.

I guess the only real benefit of pointing out this sort of thing, is to help people appreciate that when they see some manufacturer put out a nearly perfect part, some skill, experience, and thought went into its creation. I think too often we take for granted the toys we have to play with. It isn't as quick or as simple as it sounds to "just" make a plug, pull a mold, and make great parts from it.

I quit watching the $75 DLG thread. Yep, one can make a DLG for $75 IMO. Once one already has purchased and made the required tools, has the materials purchased in quantity, and knows all about how to do the work. All that part, the expensive part, doesn't come for $75.

I used 1.5 to 2 gallons of aerospace grade epoxy (thankfully I got it cheap or that would have been $450 right there) and 50# of washed kiln dried sand as the raw materials when making my mold. Plus a few pounds of powdered aluminum and probably a pound of graphite powder. Probably a few pounds of cabosil. Yep, it is a workout moving that thing around. I don't think I'll ever make one that heavy again! Plus mixing pails, scrap materials for parting plane, plastic covered foam sheet for blocking the mold. Large ball bearings for alignment. It took me more than a month to make the plug. The plug was pulled from a two piece mold I had made previously, but a lot of reshaping and cleanup went into the new plug. It took me two attempts to make a satisfactory mold from the plug and I had to repair the plug between the attempts. If I damage the mold I need to start over. The plug was damaged again in the second attempt. I even made 16 beefy clamps for the thing. $550 for a good quiet compressor (my shop location requires things to stay quiet, unfortunately, otherwise a cheap compressor would work). I haven't built the hot box yet but since I'm using MGS slow for the layup it is required that the part undergo a heat cycle before being pulled from the mold. I can't make a batch and do it afterwards.

6 prototype fuselages so far, before the first part is sold. Perhaps 4 hours each towards the end, but more like 5 at the start. Plus time making fabric patterns. We'll be making several more prototypes before having everything worked out. That's just the learning curve. If I hadn't made a mold and a couple pods before this, and wasn't working with Phil, things would take a lot longer!

Phil has a nice shop, and knows how to use it!

Anyway our toys are really too cheap in many respects.

Sorry I got somewhat OT. I just want to express appreciation for all the manufacturers making nice planes for us, and for all those who are trying to do so. And I'm glad we are not at a stage where we need to purchase everything. We can make great things ourselves if we put the time and effort into it.

Gerald
G_T is offline Find More Posts by G_T
Last edited by G_T; Mar 10, 2012 at 01:03 AM.
Reply With Quote
Old Mar 08, 2012, 10:04 PM
Registered User
Congress, AZ
Joined Sep 2001
4,917 Posts
Gerald,

"I've become fond of not needing any tools to put on or remove the horizontal stabilizer. There are no little screws to drop."

How do you mount a tail that doesn't require a tool to mount and demount?

Do you perhaps plan on a full flying tail in halves that pushes onto rods?

Just curious.

Gary
GaryO is offline Find More Posts by GaryO
Reply With Quote
Old Mar 08, 2012, 10:21 PM
Registered User
Germantown, Maryland
Joined Apr 2004
4,513 Posts
Spring-V full-flying stab mount

http://www.rcgroups.com/forums/showthread.php?t=1072386
Phil Barnes is offline Find More Posts by Phil Barnes
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question 500 & 600 Fuselages flyingfish56 Large Electric Helis 1 Mar 02, 2012 01:24 AM
Sold Sailplane fuselages, LPU, LA SoCal. Area Doubletap Aircraft - Sailplanes (FS/W) 21 Feb 25, 2012 11:40 PM
Sold Two DLG Fuselages, single-piece, oval boom Jonas M. Aircraft - Sailplanes (FS/W) 3 Nov 17, 2011 11:19 AM
Discussion Mini Titan Scale Fuselages Robert Stinson Scale Helicopters 12 Oct 19, 2011 01:54 PM
Help! Fuse box . . . or a box full of fuselages Kookaburra Sailplane Talk 14 Sep 25, 2011 11:16 PM