Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
December 17, 2017, 04:38:11 PM *
Welcome, Guest. Please login or register.
Did you miss your activation email?

Login with email, password and session length
 
Home Help Search Login Register
Pages: [1]   Go Down
Print
Author Topic: Loose Wing Post  (Read 785 times)
0 Members and 1 Guest are viewing this topic.
calgoddard
Gold Member
*****

Kudos: 13
Offline Offline

United States United States

Posts: 781


Topic starter
FAC Member



Ignore
« on: February 28, 2014, 07:53:58 PM »

My local flying club is having an indoor contest this Sunday. One of the events is Limited Penny Plane (LPP).

I have two LPPs that fly reasonably well. Both are near minimum weight.  I have four different props but one gives significantly better times on both of my planes. I think my best prop flares better and/or its pitch is optimum for the two airframes. LPP1 usually flies longer than LPP2. 

I was getting some rubber motors ready today and thought I should check LPP1 for any defects since I have not flown it in about a year.

The rear wing post of LPP1 is not snug in its tissue tube when that post is inserted to its correct incidence marking. In fact it is slightly loose and I fear it will not stay put during a flight, especially if the airplane kisses the ceiling.  We only have a flyable ceiling height (between beams and around light fixtures) of 25 feet and the beams themselves go down to about 22 feet. So I may not always be able to do the perfect "no-touch" flight even though I have extensive  motor size, rubber type, max winds, back-off winds, torque, max height, duration and turns-remaining data for each plane on the good prop.

I would like some input on the quickest and easiest fix.  I do not want to put on a new tissue tube, or shorten the wing posts, etc. because right now the wash in and incidence are just right for the longest duration (at least that was true the last time I flew LPP1). We have two other events Sunday that I am flying in and I don't have time to do a bunch of trim flights with a partially re-built LPP1.

The wing posts are probably 7-8# 1/16" square balsa, rounded on the lower 3/8 - 1/2". (Just guessing)

I know of several fixes but was wondering if there are better fixes.

1. Moisten the round part of the wing post so that it swells up.

2. Apply 3M Post It stick material to the rounded part of the wing post.

3. Apply a thin layer of a mixture of sawdust and glue to the round part of the wing post to provide a rough, slightly larger OD.

There are probably other quick fixes that I can't recall.

I can always fly LPP2 but it has a slightly smaller stab and LPP1 can fly around 10-15 seconds longer per flight in our small gym, which could easily affect where I place in the Limited Penny Plane contest.  I think that in our Limited Penny Plane contest your score is the total of the best three out of six official flights. 

BTW, I will check LPP2 tomorrow for any defects.

Many thanks to you experts out there for your advice.
Logged
Hepcat
Platinum Member
******

Kudos: 207
Offline Offline

United Kingdom United Kingdom

Posts: 1,679



Ignore
« Reply #1 on: February 28, 2014, 08:41:26 PM »

I shall be interested to hear the replies.  I am an inveterate bodger and always lick balsa bits to restore friction with paper tubes and I always feel guilty (for quite some minutes) afterwards.  Finding the correct, expert way of doing things will enable me to sleep more soundly.

John
Logged
Olbill
Titanium Member
*******

Kudos: 53
Offline Offline

United States United States

Posts: 2,228



Ignore
« Reply #2 on: February 28, 2014, 08:58:47 PM »

Licking works for me.

But seriously is it really such a big deal to either shorten the posts or replace the tube? If a real fix is out of the question then a piece of thread or a sliver of balsa inside the tube should do the trick.
Logged
ykleetx
Gold Member
*****

Kudos: 14
Offline Offline

United States United States

Posts: 640




Ignore
« Reply #3 on: February 28, 2014, 09:25:37 PM »

Try dipping the post in water and hope that it will swell.  Did you squish it?

I always re-trim my models every time I fly.  Certainly the previous markings is a good starting place, but I have found that all my models need slight re-trimming.
Logged
leop
Silver Member
****

Kudos: 5
Offline Offline

United States United States

Posts: 138



Ignore
« Reply #4 on: February 28, 2014, 09:52:49 PM »

I sometimes use a repositionable/restickable glue stick (not the more permanent kind) to tighten a loose post to tube joint.  Lately, I have had success using a wax based Chapstick for the same purpose.  I like the latter on the more delicate planes (F1D and F1L, etc.) as it is easier to more the joint but the joint still holds tight enough for flying.

If the wood has been squeezed rather than worn away, swelling with water will bring the post back to near the original size, as has been suggested.  I learned a good trick from an older flier.  This is to coat the ends of the posts with thinned (very thinned with acetone) Ambroid/Duco after/while fitting the post/tube joint when building the plane.  This coating (I use two thin coats) protects the post from damage and wear.

LeoP
Logged
calgoddard
Gold Member
*****

Kudos: 13
Offline Offline

United States United States

Posts: 781


Topic starter
FAC Member



Ignore
« Reply #5 on: February 28, 2014, 09:59:16 PM »

Good point about re-trimming each time the model is flown.

The wing post in question is not crushed or squished.  Both posts are plenty long enough to allow shortening.  Sounds like one solution might be to
shorten the posts and round them.  

I usually round the posts before they are attached to the spar by twirling between two sanding blocks until they are the right OD.  This does not seem practical once the wing is fully constructed.

Is there a way to round the new square ends of the posts without removing them from the spar?  Everything is glued with Duco so I can do this.  I was just trying to avoid too much re-work. I have the wash - in just right and I have had troubles getting this right in the past.  Sounds easy, just re-position the diagonal brace. Oh well.

Thanks for the suggestion of using Chapstick.
Logged
calgoddard
Gold Member
*****

Kudos: 13
Offline Offline

United States United States

Posts: 781


Topic starter
FAC Member



Ignore
« Reply #6 on: March 01, 2014, 10:58:31 AM »

Just remembered.  There are steel cutting dies that the end of the newly cut off square wing post can be pushed through to round the same to the desired OD.
Logged
Olbill
Titanium Member
*******

Kudos: 53
Offline Offline

United States United States

Posts: 2,228



Ignore
« Reply #7 on: March 01, 2014, 12:16:00 PM »

Most everyone I've been around since I started flying indoor puts tubes on the wing and posts on the motor stick. For an LPP there really isn't much point in using a wing brace b/c the minimum weight is high enough that you can use pretty sturdy spars. That's how I can use carbon rods on mine.

I think the best choice for posts for LPP is 1/16" bass dowels. Unfortunately I haven't been able to find them anywhere. Balsa USA has 1/16" square bass sticks that can be sanded round but it would be great to find round ones ready made.
Logged
calgoddard
Gold Member
*****

Kudos: 13
Offline Offline

United States United States

Posts: 781


Topic starter
FAC Member



Ignore
« Reply #8 on: March 01, 2014, 01:43:58 PM »

How do you control wash in when the tissue tubes are on the wing? There is no diagonal brace to pull down on the aft wing spar.

In the past I have used round tooth picks for wing posts.  They seem to be made of bass wood or other similar hard wood.  I just measured one and the OD is .087".  They are super rugged. I suppose you could sand the diameter down to .062" and they would still be plenty strong enough.

Two tooth pick wing posts are a bit heavy. However, I know you like to use short wing posts so you shouldn't have a problem getting under the LPP minimum weight using tooth pick wing posts.
Logged
Olbill
Titanium Member
*******

Kudos: 53
Offline Offline

United States United States

Posts: 2,228



Ignore
« Reply #9 on: March 01, 2014, 03:50:48 PM »

The official way is to soften the glue on the tissue tubes, reposition the wing and let dry. The unofficial way (mine) is to bend the posts as needed.

BTW - warps are bad for performance. I know that most people think you're supposed to have washin on the left wing but I've never understood why. All of my models have a small amount of washin on the RIGHT wing to counteract the twisting effect of the motor on the wing alignment. I try to adjust this so that in the cruise and letdown the wing is as flat as I can get it.
Logged
calgoddard
Gold Member
*****

Kudos: 13
Offline Offline

United States United States

Posts: 781


Topic starter
FAC Member



Ignore
« Reply #10 on: March 03, 2014, 10:33:23 AM »

I read about your LPP design that uses a pair of carbon fiber spars as the LE.  Is the TE balsa?  If it were carbon fiber it would be difficult to hold wash in on either wing panel.
Logged
Olbill
Titanium Member
*******

Kudos: 53
Offline Offline

United States United States

Posts: 2,228



Ignore
« Reply #11 on: March 03, 2014, 11:09:23 AM »

LE and TE spars are carbon rods for both wing and stab. I don't use warps.
Logged
cglynn
Gold Member
*****

Kudos: 7
Offline Offline

United States United States

Posts: 312



Ignore
« Reply #12 on: March 03, 2014, 02:55:35 PM »

Bill, have you thought about using a round toothpick for LPP wing posts?  I haven't mic'd one, but they seem really close to 1/16 and they are plenty strong.

Chris
Logged
Olbill
Titanium Member
*******

Kudos: 53
Offline Offline

United States United States

Posts: 2,228



Ignore
« Reply #13 on: March 03, 2014, 03:23:23 PM »

CalG suggested that above. I will investigate for sure.
Logged
Balsa-Buster
Bronze Member
***

Kudos: 2
Offline Offline

United States United States

Posts: 19



Ignore
« Reply #14 on: March 10, 2014, 11:24:49 PM »

I've also had this problem with wing posts.

My fix was to wrap a band of some isaki tissue around the post using white glue. Number of wraps depends on how loose your post is. If you find that your wrap is too tight is the tissue tube you can lightly sand until its fits correctly. 
 
Logged
mkirda
Gold Member
*****

Kudos: 12
Offline Offline

United States United States

Posts: 610

WWW

Ignore
« Reply #15 on: March 11, 2014, 12:06:16 AM »

I've also had this problem with wing posts.

My fix was to wrap a band of some isaki tissue around the post using white glue. Number of wraps depends on how loose your post is. If you find that your wrap is too tight is the tissue tube you can lightly sand until its fits correctly. 
 

Or just a tiny sliver of maybe 0.008/9" thick balsa can do the trick.
Logged

Pages: [1]   Go Up
Print
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.21 | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!