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Jun 06, 2012, 10:01 AM
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Build Log

Going Light on a small budget


I thought it was time to do a build log on something I have been thinking about for a long time. This is not a build log for a specific plane. It is a How-To for anyone wanting to build a basic high performance plane on a really small budget. Since this is a how to there will be plenty of pictures, plenty of room to try new ideas and above all no rules or specific parts that must be used.

Due to budgetary issues I had chose to go back to a 2pc fuse. The more I thought about that whole concept the more I realizd the planes from a couple years ago were actually well designed and thought out. Inb particular the Taboo and the SGII came to mind. If you want to build a sub 8oz plane for less than $250 keep reading.

In order to pursue this project Nate and I broke down the plane into it's parts and the functions of those parts. In terms of the wings there are many nice wings available so unless you want to invest a bunch of $$$ buy one. Getting into bagging or molding wings is expensive due to the learning curve. I am sure between Tom and I we could scare anyone out of trying that whole game. Well, Sam was crazy enough to follow us down that dark path....

The fuse on the other hand leaves plenty of room for improvement. The basic parts of the fuse are the pod, wing saddle and boom. Even the very nice 1pc fuses can be broken down into these basic components.

Tghe only real purpose of the pod is to clean up the airflow around our electronics and to protect them. This has been proven by the many planes that use very light shells for the pod with a structure underneath to support the nose area. So, why do so many planes mount the wing to the pod? Simply put to make constructiuon easier.

In the past many buuilders including myself would mount the boom to the back of the pod which made sense, right? The problem is, that put this joint behind the intended CG of the plane. The SGII solved this problem by mounting the wing to the boom. The Taboo complimised and part of the wing mounted to the pod and part to the boom.

So the whole issue revolves around the wing mount and how to put most of our weight budget infront of it. Here is where the little jig in the piucture comes in. In this case I used two 6-32 T-nuts. In the future I will be using aluminum binding posts. If the crown is ground flat and they are then put in the jig they will sit very cleanly on the boom.

As you can see in the pics I then mounted them in a scrap piece of boom. This was done because I was planning to mold a little wing saddle. In retro-spect this was not the best approach. A better method is to simply mount the posts straight to the boom with some tow and thin epoxy. The wing angle is adjusted with thin balsa blocks on the back post.

I will put the posts in the wing, CA the wing to the boom. Remove the wing and then wrap the posts to the boom with a little tow. Put some packing tape on the bomm of the wing and re-mount it. Now a very clean and light weight saddle can be formed with epoxy and micro balloons. That over built fairing I did weighed only 3 grams.

If you think this through it is very simple, and strong. It also allows you to use any of the nice pods available. I am sure there are a bunch of folks with SGII type pod molds who would be happy to dust them off and make a pod for you.

The plane I just did has a few things I will change in the next build and it is still sitting at 7.54oz. with just the push rods left to do. The wing is a littler narrower than some at 165mm but I did not cut any corners in the build. The wing has a full strength lay-up as does the boom and pod.

I rolled the boom using 2 layers of 4.1 uni and 2 layers of 1.6 glass. If someone were to roll a boom with HM carbon and had some other high end materials a plane built this way could easily be even lighter.

Obviously with a standard Katana wing the weight would go up slightly but so would the wing area and I sure it would still be right at or below 8oz. It seems clear to me that with any of thenice wings available from folks like Brian, Sam, Tom and others a person could easily have an 8oz DLG that is still robust enough to take ballast.

The key is how you spend your weight budget. There is a certain amount of weight that must be there but where you put it is up to you. Please share ideas you may have and feel free to ask how to do stuff. I will try to be an open book.

Paul
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Jun 06, 2012, 04:45 PM
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Final flying weight is 7.7oz!!!!
Jun 06, 2012, 07:04 PM
the icbm of pilots
skylerraver's Avatar
amazing where are the pics of the entire air frame
Jun 06, 2012, 07:20 PM
Registered User
Very cool Paul! I'd love to hear more about how the narrow wing performs! If all goes well, my high AR wing will be in the air by the end of the week. I wish I'd thought of putting the wing mounts in the boom like that. I tried to form a lost foam pod to fit a wing and it turned out only so-so. I'm not sure where you are wrapping the tow, though. The T-nuts are inside the boom, so how do you wrap them?

Also, did you mold the horizontal mount?

Brandon
Last edited by bwill6; Jun 06, 2012 at 07:50 PM.
Jun 06, 2012, 07:38 PM
Registered User
Paul,

You could wrap the posts directly onto the boom, as was done with the SG I. That would save a bit.

If a person was going to the trouble of wrapping a boom, then consider doing a long one and just use fairing for the electronics, as per the Blaster 3. That has to be a minimalist pod and so easy to work on.

Gary
Jun 06, 2012, 09:10 PM
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Brandon, I was saying I will wrap the next one. They are inside a piece of boom not the true boom. I got to play with it some this evening and thus far I am very pleased with the handling. Yah I molded that little tail bracket. it is made from resin, micro balloons and I tinted thge resin.

Gary, Nate and I discussed doing just as you describe and making a really long boom and molding a faring. I think the B3 fuse is brilliant. The mold for doing that would be much more complicated and I really wanted this to be something anyone could build at home. I actually had a fuse drawn up but chose this direction for the ease of building it. I almost ordered mandrels longb enough to make a 45" boom. The ones I ordered will allow me to roll about a 39" boom.

I really hope this inspires some people to take on a project like this an discover the "older" ideas were really pretty good. This plane is very much inspired by the SGII. If anyone wants to build something like this I will help where I can.

Tomm in the day light I will shoot some pics of the whole plane.

Paul
Jun 06, 2012, 10:32 PM
Aurora Builder
Paul,

Nice creativity. I think the key to weight is getting all the servos in the pod, reducing or eliminating the need for nose weight, especially with your nice modification to get the wing out over the boom, further reducing nose weight.

Certainly with a carbon d-box 120g wing (certainly buildable), and 3-4 servos in the pod with a nice pylon mounting scheme, you'd have yourself a nice sub 230g airplane. I am going to try this with Adam's one piece fuselage, I think it can be done and it disgusts me to think how insane Tom's or my wing would be flying in super light air at this weight. I still need the ballast to move out, my ship seems to love 300g+..think B3 or Sirius wing with thinner, higher L/D foils.

I'm curious to hear your thoughts on the high AR wing. At this weight does it still do OK in float? I flew one at ~270g (one of the first Zone v2 wings ever) and distinctly remember Kyle outworking light air that I found just for him, rather annoying. I'll say pilot skill and wind build quality were deciding factors but lack of wing area didn't help.
Jun 07, 2012, 09:45 AM
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Sam, I am not sure an under 8oz full size all molded plane can be done. My wing is still over 300 sq inches. I didn't intend to discuss wings and such as much as I wanted to show some building methods that really save weight would allow a home builder to put together a very nice plane.

I got to 8.2 last year with a very light fuse Adam made for me. Ther fuse on this plane is 33grams with the bulky saddle and it is still pretty much full length. A nice 1pc like Adam's fuse is going to be stiffer but I would never suggest a Gorilla type launcher (Gavin) try flying a sub 8oz plane.

I guess I was trying to point out that with solid building methods and basic components a very nice flying plane can be built.

Basically get an older SG or SGII type fuse, I believe Sporter is still making them, a nice boom, wing and tail set. Hit the harware store, and build a nice plane.

The wing I have on this plane is 315 sq inches, the tails are full size katana tails, so there is nothing really exotic in this build. Somene with some patience and attention to detail could easily build a very solid flying plane on a pretty small budget. There are so many nice wings available that building an SGII type plane with a newer style wing is pretty easy and well worth the effort.

On the next one I will move my wing mounts forward because right now the majority of the wing mount is behind the CG

Here are a couple of pics of the finished plane.
Jun 07, 2012, 10:58 AM
Aurora Builder
Very nice looking ship Paul! 315 in^2 is smaller but not radically so, similar to the MIB in area by the looks.

How is the aileron linkage stiffness? I don't have much experience with the larger carbon rods, and those look pretty beefy, but 2" is a lot of unsupported pushrod length.

Wish I was coming to York to check it out for myself, but I'll be 200 miles offshore
Jun 07, 2012, 11:33 AM
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Thanks Sam, I did not want to get as radical in size as some have gone. It is simply a narrower katana wing. I kept the general plan form the same and narrowed the wing by 15mm.

If anyone wants to build something like this let me know. I have some of the hardware handy and can send some out. I got in the aluminum posts today. The 8-32 nylon screws are coming from diff warehouseso hopefully they will be here tomm.

I will be aiming for an AUW of 7.5 with the next one I do.

Paul
Jun 07, 2012, 12:03 PM
Will fly for food
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I have one of these wings from Paul and it is stiffer and the surface quality is good. The weight of the two pannels was 118g and peg only added 2g. The ailerons on this one are only 1" deep and taper to nothing at the tip. It will be interesting to see how much braking (if any) the flaps will produce. I'm going to do an experiment and build this wing with HS5035 servos in the wing and the fuse and use the 11g Topsky tails with spring/string. I will have rudder as no rudder=no fun. My goal is to get it under 9 oz. (255g). Doable???? we will see.
Last edited by davidjensen; Jun 07, 2012 at 01:43 PM.
Jun 07, 2012, 12:38 PM
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The textured look on the wing is awesome! How'd you do that?
Jun 07, 2012, 01:44 PM
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David, I believe you can get down to 8.5 with the gear you are using. If you are going to mount the elevator on thbe top, run the string down the boom, over a turn around and then back to the horn. This will give you elevator for up and spring for down.

I got that look by stretching some mesh over the wing when I airbrushed it. On my rockets where weight is less of an issue I spray a bright color, stretch the mesh and then shoot a darker color. That gives a very wild scally look.

Paul
Jun 08, 2012, 07:25 AM
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Had the opportunity to get some air time last night and I must say it was a lot of fun!!!

It was fun to float around the sky again and I did it on a very small budget and with basic materials. It was a lot of fun to build a one off with no production thoughts influencing the outcome.

Here is a little video we shot last night,http://rcgroups.com/forums/showthrea...0#post21837947

Paul
Last edited by The_Builder; Jun 08, 2012 at 07:53 AM.
Jun 08, 2012, 10:55 AM
Transplant Chey WY from Reno
Thermaln2's Avatar
Quote:
Originally Posted by The_Builder
If you are going to mount the elevator on thbe top, run the string down the boom, over a turn around and then back to the horn. This will give you elevator for up and spring for down.

Paul
Paul,

I think the pull for up is a nice idea and I would prefer it, however many of the current competitive models like the Stobel, Concepts, and more have the spring for up and pull for down and work as well. It might be due to the spring size. I have it that way on one ship and it appears OK.

What is the root chord on the ship? 6"? It looks great in the air, I like the AR. BTW, you, however, are ugly. I was going to say b**t ugly but that would be a complement! LOLOLOL

Keep up the good work.

Chris


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