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Lightening the load

Hai-Lee

Old and Bold RC PILOT
Mentor
#1
During my time on the FT forum I have seen some fantastic builds and aircraft and some so elaborate I could only aspire to build such a model. Unfortunately I have also observed many builds, (some marathon builds) and great designs either fail to leave the ground or crash immediately upon becoming airborne. Whilst there are a myriad of different reasons for the failures and crashes there was an overall issue with most and that was the AUW, (All Up Weight).

Some builders dismiss a heavy build as being good and having great wind penetration but the truth is that increased weight equates to increased drag, higher wing loading, greater in-flight stresses on structure, more severe crashes, lower top speed. higher landing speed, and reduced handling agility. Sure some designs are great and strong but some have extra strength where the strength is not needed and from observing the progress of some members the extra strong and heavy areas are never subject to the stresses as the plane invariably is written off and replaced after a heavy crash due to the damage incurred.

Building in extra strength and extra weight can have an adverse effect upon every aspect of the aircraft's performance and life span.

Almost anyone can draw an outline and quickly fold up a silhouette for a plane and add a similar style wing and tail set. Then add a motor and battery and go flying. I should know as I have done it often but have not always been happy with the results even though the flight performance was adequate it was somewhat less than I had expected in most cases.

As a result of the failures posted on the forum and of course my own failures I started looking into weight issues and with this came structural issues. Recently the FT crew took a quantum leap in the use and application of FB in model aircraft design with the release of the "Master Series". I wholeheartedly applaud their extensive work in developing the series and curse the lack of an FT outlet in my country, (that I know of). As you might expect I immediately started practicing with their techniques in relation the locally available FB.

Anyway for those interested this thread will soon have a build using as much of the new techniques as possible used in its construction as well as a serious emphasis upon keeping the build light using techniques I have been using in my own designs locally.

The build subject:

Pic to be supplied when the project starts.

Have fun!
 

mayan

Well-known member
#3
I watching this thread. Many times you mentioned to me the influence of the paper to the weight of the airframe and I didn’t pay much attention to it as I didn’t need to build light. Only recently when I started my Mini Edge project did I actually realize the importance of the weight and how something like one side of paper can make a huge weight difference when removed from multiple parts. I want to learn more about this for future builds and projects.
 

FastCrash45

Well-known member
#4
During my time on the FT forum I have seen some fantastic builds and aircraft and some so elaborate I could only aspire to build such a model. Unfortunately I have also observed many builds, (some marathon builds) and great designs either fail to leave the ground or crash immediately upon becoming airborne. Whilst there are a myriad of different reasons for the failures and crashes there was an overall issue with most and that was the AUW, (All Up Weight).

Some builders dismiss a heavy build as being good and having great wind penetration but the truth is that increased weight equates to increased drag, higher wing loading, greater in-flight stresses on structure, more severe crashes, lower top speed. higher landing speed, and reduced handling agility. Sure some designs are great and strong but some have extra strength where the strength is not needed and from observing the progress of some members the extra strong and heavy areas are never subject to the stresses as the plane invariably is written off and replaced after a heavy crash due to the damage incurred.

Building in extra strength and extra weight can have an adverse effect upon every aspect of the aircraft's performance and life span.

Almost anyone can draw an outline and quickly fold up a silhouette for a plane and add a similar style wing and tail set. Then add a motor and battery and go flying. I should know as I have done it often but have not always been happy with the results even though the flight performance was adequate it was somewhat less than I had expected in most cases.

As a result of the failures posted on the forum and of course my own failures I started looking into weight issues and with this came structural issues. Recently the FT crew took a quantum leap in the use and application of FB in model aircraft design with the release of the "Master Series". I wholeheartedly applaud their extensive work in developing the series and curse the lack of an FT outlet in my country, (that I know of). As you might expect I immediately started practicing with their techniques in relation the locally available FB.

Anyway for those interested this thread will soon have a build using as much of the new techniques as possible used in its construction as well as a serious emphasis upon keeping the build light using techniques I have been using in my own designs locally.

The build subject:

Pic to be supplied when the project starts.

Have fun!
Excellent post!! Right on the spot and informative to us newer people.
 

FastCrash45

Well-known member
#5
I watching this thread. Many times you mentioned to me the influence of the paper to the weight of the airframe and I didn’t pay much attention to it as I didn’t need to build light. Only recently when I started my Mini Edge project did I actually realize the importance of the weight and how something like one side of paper can make a huge weight difference when removed from multiple parts. I want to learn more about this for future builds and projects.
I am slapping together a profiler right now and paying close attention the the weight. I've noticed that taking off even one side of the paper shaves grams off the total weight. Grams may not sound like much but it WILL make the difference from it being able to hover or not. An 1806 can produce only so much thrust no matter what prop you use.
 

Kendalf

Well-known member
#6
Following this thread! Very interested in your techniques! I've been very weight conscious with my models (esp with my recent Mini Scout build for the newbie challenge) and I'm testing to see how much paper I can remove from the Sportster build I'm working on without compromising structural integrity. For example, I've peeled off the inside layer of paper from the foldover wings.
 

bracesport

Well-known member
#7
this will be a great thread as we are always looking forward to more tips and guidance from the Pros!

Incidentally, I use the 'Adams Ready Board' here in NZ (which is very light and actually quite fragile). I find it helps my builds to tape the surface to maintain more integrity when folded and glued - then with little or no internal structures, the fuse remains light and strong. removing the internal card surface lightens the fuse incrementally but the strength can reduce quite a lot - all things need to be in balance I suppose!
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#9
You may have already drawn from the preamble this is the design and build of the plane I had mentioned in a PM we shared.

Today I finally am able to start replenishing my FB stock so the work can commence though for this project I want to produce the finished product first and then post the build. If you are following or building at the same time I will share progress via PM!

have fun!
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#10
this will be a great thread as we are always looking forward to more tips and guidance from the Pros!

Incidentally, I use the 'Adams Ready Board' here in NZ (which is very light and actually quite fragile). I find it helps my builds to tape the surface to maintain more integrity when folded and glued - then with little or no internal structures, the fuse remains light and strong. removing the internal card surface lightens the fuse incrementally but the strength can reduce quite a lot - all things need to be in balance I suppose!
I agree the Adams FB is somewhat soft and fragile but the local FB here, (Across the Ditch), is heavier and stronger. It is the using of the heavier FB that lead me to the lightening approach I use and also to the strengthening of the bare FB when the structural strength is just a little insufficient.

I used to use tape, but I now use minwax and paint to harden/strengthen the FB. Sadly water gets under the tape easily but the sealed paper doesn't "Wick" like taped FB.

Have fun!
 

DamoRC

Well-known member
Mentor
#11
As someone who has built a couple (at least a couple) of heavy-ish builds, some which worked, some not so much, I am looking forward to seeing what you will be doing here. I am not neccessarily inclined to move to the masters series approach of removing paper and using formers mostly because of my inability (or perhaps its just reluctance / laziness) to cut formers. I'm pretty good with straight lines though!

If you can also share your insights on adhesives, that would be great. I have tried a couple of the PVA based liquid glues over the last couple of months and they just can't match gorilla glue for strength in various applications, although they are lighter. Maybe I'm just trying the wrong ones.

Let the games begin!
 

DamoRC

Well-known member
Mentor
#13
Titebond Translucent has worked pretty good for me. It's stronger than the BSI Foam Cure that I used for two earlier planes, both of which had tails come loose. That said, I fly rather slow and gentle, so I haven't really exposed my planes to much stress. I've heard good things about Titebond Quick and Thick and that's what I want to try next. Supposedly it sets faster than other PVA glues.
Thanks. I've tried Titebond II and III and although they work, they are not as strong as the GG, at least in my hands. I looked for the Quick and Thick when I picked up the Titebond III but they didn't have any. Soon I am going to have to take up woodworking with all the glues I am collecting! ;)
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#14
Sadly my climate means that in mid summer hotmelt does just that! So I use a clear liquid glue mostly and the closest I can find listed in the US is made or sold as Sullivans clear craft glue. Mind you I also use PVA for sealing, cupping, reinforcing, and when laminating in some applications. I addition I use a polyurethane glue when laminating for extreme strength.

The Sullivans actually really bonds to the foam as well as the paper and often I find, (post crash), that the join/seam is still in perfect shape and unbroken but the FB either side has exploded! The weight saving in glue Sullivans Vs Hotmelt is noticable but the sullivans is not good at joining parts that are not properly cut out or shaped.

Have fun!
 

Bricks

Well-known member
#17
For glue that I like it tacks very quick and dries pretty darn fast but yet stays a little pliable which is great when working with foam. It is Beacon Fabri-Tac permanent adhesive usually any craft store or Walmart carries it.

Saving weight adding extra glue does NOT add to extra strength.
 

Hai-Lee

Old and Bold RC PILOT
Mentor
#18
Saving weight adding extra glue does NOT add to extra strength.
As a general statement you are correct but extra glue applied for the correct reason can improve strength with very little weight penalty.

FB has a weakness in compression as the paper fibres are not well bonded to each other. To improve compression resistance you can use doublers or more rigid material as a laminate which is a standard approach. I was worried about the adding of extra weight and even did structural experiments using thin balsa as a laminate.

By applying a thin layer of glue to the paper, (just enough to bind all of the paper fibres into a solid mass), improved its resistance to compression considerably. I first used the process on a FB copy of a Depron BiPlane design, (internet search for "Otto Vs Eddie"),Whilst my final build weighed many times the original I found that applying a thin PVA glue layer to both sides of the wings made the sheet FB wings not only rigid enough to support the plane in flight but to also withstand the numerous accidents the plane suffered from at the hands of a newbie.

I addition when laminating FB together you can either put down a few lines of glue or, as I do, remove all hidden paper from the lamination and replace all of the hidden paper with a thin and uniform layer of glue.

More glue does not make a glued joint stronger! But the use of a thin layer of glue to replace a layer of paper or even a FB doubler can make a plane lighter and stronger!

I invite you to do your own testing!

Have fun!
 

Michael763

Active member
#19
I still have my DTF Otto, built using white Gorilla Glue, hanging on my bedroom wall. It was such a fun biplane to fly. I added ailerons and lowered the dihedral by half if I remember correctly.