How to reduce plane weight

freed2003
Member
Member
Posts: 135
Joined: Tue Nov 03, 2015 11:00 pm
Division: B
State: CA
Contact:

How to reduce plane weight

Postby freed2003 » Sat Mar 18, 2017 7:00 am

Right now my planes are averaging around 11 grams and are getting around 30 seconds. I think that if I can reduce the weight to around 7.6 grams the time will hopefully increase.
Also on a side note should a 0.65 rubber normally get to 1800 winds?
Kraemer/Regionals/state
Microbe Mission 30/ /
Wright stuff 16/6/11
Dynamic planet 10/8/20(wot)
Road scholar 12/2/22(wot)
Wind power 31/1/4(wot)
Fast Facts 44//

User avatar
bernard
Administrator
Administrator
Posts: 1856
Joined: Sun Jan 05, 2014 11:12 pm
Division: Grad
State: WA
Location: Seattle, WA
Contact:

Re: How to reduce plane weight

Postby bernard » Sat Mar 18, 2017 7:13 am

Use less glue. You hardly need any 3M Super 77 to attach mylar, just a mist a foot above the wing frame is enough. Less glue for joints, enough to be rigid but not covered in glue. Sand the motor stick and tail boom if they contribute significant weight.
"One of the ways that I believe people express their appreciation to the rest of humanity is to make something wonderful and put it out there."

freed2003
Member
Member
Posts: 135
Joined: Tue Nov 03, 2015 11:00 pm
Division: B
State: CA
Contact:

Re: How to reduce plane weight

Postby freed2003 » Sat Mar 18, 2017 7:23 am

If the hole the glue comes out of is a considerable size(like duco cement) How should I apply the glue
Kraemer/Regionals/state
Microbe Mission 30/ /
Wright stuff 16/6/11
Dynamic planet 10/8/20(wot)
Road scholar 12/2/22(wot)
Wind power 31/1/4(wot)
Fast Facts 44//

User avatar
JasperKota
Exalted Member
Exalted Member
Posts: 158
Joined: Fri Oct 23, 2015 3:01 am
Division: C
State: NY
Location: WEHS
Contact:

Re: How to reduce plane weight

Postby JasperKota » Sat Mar 18, 2017 2:13 pm

.65 rubber should be able to wind beyond 1800.

Don't apply glue directly from the bottle, whether the bottle has a large opening or small. Put it in like a petri dish or just put a small blob on a tissue, and then use a toothpick and dab it onto where you need the glue. Here's a detailed document on minimizing weight gain while maximizing glue strength that I suggest you read: https://www.soinc.org/sites/default/fil ... weight.pdf
2018 Events: Helicopters, Mousetrap Vehicle, Parasitology, WIDI
2017 Events: Invasives, Wright Stuff, Ecology
2016 Events: Invasives, Dynamic Planet, Crave the Wave

kevin_vs_the_world
Member
Member
Posts: 1
Joined: Thu Feb 23, 2017 10:10 pm
Division: B
State: MA
Contact:

Re: How to reduce plane weight

Postby kevin_vs_the_world » Sat Mar 18, 2017 2:55 pm

Sanding might seem to be the obvious choice, but don't do too much of it. With mylar, the light stuff that seems very breakable can work if you crinkle it and stretch it back, which will make it much more resistant and it will not lose its shape once air gets under it, unlike a traditional lay over and glue, where the mylar will cause bad things to happen if a single flaw comes about. Other ways to reduce weight are to cut off excess, because you can care about your CG later if you have an adjustable wing, find or build a lighter propeller and if all else fails, use a lighter rubber motor, because that numbs the weight that is added with the motor, but this should only be done if the aerodynamics are good enough to work with the lower amount of power you put into it. 1800 turns on a motor of that size is adequate, but if I were in competition, I would kick it up to 2100, or somewhere in that range. On my planes, I usually go up to 1650, but that is because the height and size of my school's gymnasium is fairly low in height. I hope this helped! :) :) :) :) :) :)
kevin_vs_the_world

States:
2015, 2016, 2017 - 1st
Road Scholar, 2015, 2017 - 1st
Simple Machines, 2015 - 1st
WIDI, 2015, 2016 - 2nd
Bottle Rockets 2016 - 2nd
Dynamic Planet 2016, 2017 - 1st
Wright Stuff 2017 - 1st
Nationals:
2015 - 36th
2016 - 26th
Geocaching, 2016 - 9th

freed2003
Member
Member
Posts: 135
Joined: Tue Nov 03, 2015 11:00 pm
Division: B
State: CA
Contact:

Re: How to reduce plane weight

Postby freed2003 » Sat Mar 18, 2017 5:04 pm

JasperKota wrote:.65 rubber should be able to wind beyond 1800.

Don't apply glue directly from the bottle, whether the bottle has a large opening or small. Put it in like a petri dish or just put a small blob on a tissue, and then use a toothpick and dab it onto where you need the glue. Here's a detailed document on minimizing weight gain while maximizing glue strength that I suggest you read: https://www.soinc.org/sites/default/fil ... weight.pdf


How to I think the glue? Should I just pour it into the dish and add acetone everytime I'm using it?
Kraemer/Regionals/state
Microbe Mission 30/ /
Wright stuff 16/6/11
Dynamic planet 10/8/20(wot)
Road scholar 12/2/22(wot)
Wind power 31/1/4(wot)
Fast Facts 44//

User avatar
JasperKota
Exalted Member
Exalted Member
Posts: 158
Joined: Fri Oct 23, 2015 3:01 am
Division: C
State: NY
Location: WEHS
Contact:

Re: How to reduce plane weight

Postby JasperKota » Sat Mar 18, 2017 6:32 pm

freed2003 wrote: How to I think the glue? Should I just pour it into the dish and add acetone everytime I'm using it?

I personally never thinned the model cement I was using (duco cement), but I believe you might want to get a different bottle and then thin the glue and store it in the bottle so you don't have to keep adding acetone.
2018 Events: Helicopters, Mousetrap Vehicle, Parasitology, WIDI
2017 Events: Invasives, Wright Stuff, Ecology
2016 Events: Invasives, Dynamic Planet, Crave the Wave

jander14indoor
Member
Member
Posts: 1466
Joined: Mon Apr 30, 2007 2:54 pm
State: -
Contact:

Re: How to reduce plane weight

Postby jander14indoor » Sun Mar 19, 2017 6:41 am

Weight is CRITICAL in the flying events. If you are flying an 11 gram plane 30 seconds you pick up TONS of time with a 7.5 gram plane.

BUT, it's VERY difficult to lose significant weight on an already built airplane. The best solution is to build light to start with. How do you do that? Build with a plan called a Bill of Materials.

- List EVERY part in your plane in a spreadsheet.
-- Describe the quantity, size (length, thickness, width) to figure volume and an estimated density.
-- Figure out the weight of each part.
-- Make an allowance for glue and hard to calculate stuff like tissue reinforcement. How much depends a little on experience and skill, but you should be shooting for less than 0.5 gm.
-- Don't forget the covering and the prop assembly. You'll need to weight your prop assembly. Probably need to weight covering samples to get weight per unit area info.
- Now, add them all up, if you aren't under the max by say .25 to .5 gm, adjust density/sizes until you are.
-- You don't need to be consistent density in the wood, in fact it isn't wise. Wing spars and posts need strength so should be higher density. Ribs and tail components don't need the strength, use lower density there.

With this, you can start to build. Weigh the wood parts, or at least ensure you start with stock at the target density you used. If you aren't building with a scale next to you, you will have difficulty consistently building to a target weight.

Here are some real killer's I'm seeing often this year for weight.
- those red molded props with the attached plastic prop hangers are HEAVY AS SIN! A couple of grams alone, 25 to 50% of your weight budget.
-- This used to be common knowledge, but if you are using molded props you HAVE to scrap them thinner to lose weight
-- Ditch the plastic prop hanger and that WAY oversize prop wire. I saw some today that were probably 0.032 inch diameter or thicker, you don't need more than 0.020 thick wire for your prop. Sleeve the prop hole to that size so it doesn't flop on the wire.
-- Look around the web to see how to make your own prop hanger.
- Coverings.
--You should only be covering on one side! Saw a many double covered wings, top and bottom the last couple of weeks.
-- Watch the covering weight, you can't use just any material! Anything that isn't easy to tear is too heavy! Saran wrap is too heavy! Any decorative wrapping paper is too heavy. Try produce bags from your local grocery store. Dry cleaning bags tend to be light. SOME grocery bags are light. I've found the local Home Depot bags to be fairly light, some pet store bags. Look around, weigh samples. Your weight budget for cover TOTAL should be less than a 0.5 gram with a fairly heavy covering. 0.3 is a better target.
- Stick sizes
-- Except for the motor stick, you should have no sticks over 1/16 square, and for many parts you can go thinner! Control strength by managing density.
-- Again, I saw planes with huge sticks. 1/18 for wing and tail spars.
-- Motor sticks are the most stressed part of the plane and they have to be stiff/strong enough not to bend significantly for consistent flight. However, you shouldn't get there by using dense strong wood. You have a weight budget for your motorstick, all up, including any prop hangers, motor hooks, etc of about 1 to 1.5 gm, 2.0 at the VERY most. If you use dense wood, it will have to be thin in cross section and be very bendy. Instead, use very LOW density wood and increase the size up to what your weight budget will allow. OR, learn how to make hollow motor sticks (discussed in previous threads if you look).

I hope those are some helpful suggestions, again, weight is CRITICAL in the flying events.

Jeff Anderson
Livonia, MI


Return to “Wright Stuff B”

Who is online

Users browsing this forum: No registered users and 1 guest