Large Scale Foamboard Cessna 180

[Planiac01]

Okay, So after seeing the two Flex Innovaiton 170's at FFE17, I have decided I want to do a foamboard version. I chose 180 because I couldn't find suitable 170 blueprints. Anyways, I was wondering if I could get a few tips.

I have built a few large scale planes in the past. My favorite by far has been my 7.5 ft. wingspan glider, the Galaxy V2. I brought it to this last FliteFest; some of you might have seen it. Lots of people asked about it. Also, I built a 1/2 scale Cri-Cri, and I also brought that to FliteFest. In addition, for FF16, I built a 200% version of my Galaxy, a fifteen foot wingspan. It flew great then, but when I tried to fly it again at FFE17, I used a cheap receiver since I was rushing and it crashed horribly due to a brown out. I also built the very large rectangle plane there, but lets not discuss that one.

So, I was wondering if there is anything I need to know before I build it. I have a 5045 500kv motor left from the 200% Galaxy, along with the necessary ESC and batteries for 4kg of thrust. I have tons of 40+ gram servos, an 8 ft aluminum spar (Is that overkill??), and STL files for a 3d Printed Thrust Vector.

Oh, and lots of foam.

So, hit me. What should I be prepared for? Would it be capable of performing similar aerobatics? I would appreciate any help. Also, I will be documenting all progress in this thread. I will try to post quite often. Thanks!

 

[Kunphushun]

In cause I like big ole planes! I offer no insight as I have not yet built anything cool or near that size.

 

[Hai-Lee]

You have not specified anything to aid in design apart from description of the project plane and the thrust available.

Depending on what performance you are expecting your target weight should not exceed about 6 Kilos with 4 kilos being a better performance target.

The actual structural design elements will require setting the wing span and the LOA, (Length Over All).

The main areas for concern are the high stress areas of the wing and fuselage. They are the central wing area, engine mounting area, the landing gear supports and the tail forces generated. OH! Do not forget the battery mounting and the CG point.

Give a few dimensions and I may give a little better guidance or test methods to ensure that your design will fly and fly well.

As for maneuverability, As the size increases the wing gets more efficient BUT the increased span and inertia of the increased plane weight normally mean that the maneuvers become more "Real World", that means slower in response and rate.

I will help if I can!

Have fun!

 

[Planiac01]

You have not specified anything to aid in design apart from description of the project plane and the thrust available.

Depending on what performance you are expecting your target weight should not exceed about 6 Kilos with 4 kilos being a better performance target.

The actual structural design elements will require setting the wing span and the LOA, (Length Over All).

The main areas for concern are the high stress areas of the wing and fuselage. They are the central wing area, engine mounting area, the landing gear supports and the tail forces generated. OH! Do not forget the battery mounting and the CG point.

Give a few dimensions and I may give a little better guidance or test methods to ensure that your design will fly and fly well.

As for maneuverability, As the size increases the wing gets more efficient BUT the increased span and inertia of the increased plane weight normally mean that the maneuvers become more "Real World", that means slower in response and rate.

I will help if I can!

Have fun!

I don't really have any dimensions yet, just a rough outlook. One thing I might ask, how do you suppose I mount the wing? It will be a two piece wing, but I'm not sure how I want to mount it to the fuselage. Thanks!

 

[Timmy P]

I beat ya to it a few years ago. You could very easily scale up my 50" design. Here is a link

http://forum.flitetest.com/showthre...0-Swappable-with-plans-50-quot-inch-wing-span

 

[Hai-Lee]

I don't really have any dimensions yet, just a rough outlook. One thing I might ask, how do you suppose I mount the wing? It will be a two piece wing, but I'm not sure how I want to mount it to the fuselage. Thanks!

For a shoulder wing prototype of large span I would use a removable spar tube which slides into each wing and possibly a smaller sub spar to align the TEs, (also a slide in).

As for joining and securing to the fuselage, (For a prototype), I would use locating blocks of FB glued to the wing underside and sized to fit snugly in the fuselage top. That is half on each wing root underside.

When the wing has the spar/s fitted and the wing is placed atop the fuselage so that the locating blocks hold the wing roots together I would use the old rubber bands, (in sufficient number), to hold the wing in place.

This method is normally for the prototype only and is upgraded after the test program is nearing completion and hopefully the crashing program has finished.

The reason is simple. In a crash the wing will want to separate from the fuselage and often rotate to be inline with the fuselage. The locating blocks are easily destroyed in such an event and can save a total loss of prototype if I make a mistake or have a build/design issue.

For an aesthetic finish I do like the wooden dowel in the LE or a support cage under the wing and a TE screw down arrangement to a wing hold-down platform with captive nuts.

I hope this helps.

Have fun!

 

[Planiac01]

Thanks a ton. I will definitely keep this on mind. Although, what do you mean by locating blocks?

 

[Planiac01]

I can't really though, because mine is twice the size and therefore needs to withstand four times the flrces

 

[Hai-Lee]

I am not sure what you cannot do because of the weight but I will give another or secondary quick disconnect method for the 2 wings.

In the bottom of the each wing root and aligned with the inside of the fuselage you glue in or otherwise attach a piece of Aluminium angle at the rear of the wing and a piece of flat Aluminium for each wing through which the tubular wing spar passes.

At the ends of the Aluminium pieces that protrude into the fuselage drill a 3mm hole. to fit the wings just position in the proper location and slide a barbecue skewer through each pair of hold down Aluminium pieces. The skewers can be fixed temporarily using a sleeve of surgical over the exposed ends of the skewers.

To reinforce the inside of the fuselage where the skewers are to be fitted glue in a piece of 2mm ply with a 3mm hole of course.

It is a bit of measuring and drilling but it will be extremely strong. Later if the project gets even heavier the skewers can be replaced with music wire or even with screws.

Chances are that you will bend the aluminium spar before you snap a skewer.

Have fun!

 

[Planiac01]

I am not sure what you cannot do because of the weight but I will give another or secondary quick disconnect method for the 2 wings.

In the bottom of the each wing root and aligned with the inside of the fuselage you glue in or otherwise attach a piece of Aluminium angle at the rear of the wing and a piece of flat Aluminium for each wing through which the tubular wing spar passes.

At the ends of the Aluminium pieces that protrude into the fuselage drill a 3mm hole. to fit the wings just position in the proper location and slide a barbecue skewer through each pair of hold down Aluminium pieces. The skewers can be fixed temporarily using a sleeve of surgical over the exposed ends of the skewers.

To reinforce the inside of the fuselage where the skewers are to be fitted glue in a piece of 2mm ply with a 3mm hole of course.

It is a bit of measuring and drilling but it will be extremely strong. Later if the project gets even heavier the skewers can be replaced with music wire or even with screws.

Chances are that you will bend the aluminium spar before you snap a skewer.

Have fun!

Wow-awesome idea. I'll go with that. Thank you

 

[Hai-Lee]

Just a little added info to aid you. The locating blocks mentioned earlier are just a few scraps of FB that are cut to just fit into the top of the fuselage and mounted centrally on the wing underside in the required locations.

Their function is to ensure that the wing only fits EXACTLY in the correct position EVERY time. Nothing worse than a wing that is possibly fitted asymmetrically on the fuselage it makes trimming useless.

Have a good build!

Have fun!

 

[Planiac01]

Just a little added info to aid you. The locating blocks mentioned earlier are just a few scraps of FB that are cut to just fit into the top of the fuselage and mounted centrally on the wing underside in the required locations.

Their function is to ensure that the wing only fits EXACTLY in the correct position EVERY time. Nothing worse than a wing that is possibly fitted asymmetrically on the fuselage it makes trimming useless.

Have a good build!

Have fun!

I understand now. Thanks a ton!