Logo
Builders' Plan Gallery  |  Hip Pocket Web Site  |  Contact Forum Admin  |  Contact Global Moderator
July 21, 2019, 09:38:44 AM *
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] 2 3 4   Go Down
Print
Author Topic: Another Boston Cub  (Read 5775 times)
0 Members and 1 Guest are viewing this topic.
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« on: January 08, 2012, 06:13:56 AM »

This is my build of Scigs30's Boston Cub design. It's a really cute little bostonian.

I started by laminating the outlines for the tail surfaces and wing tips - my first attempt at this method. It was done around a form cut from 1/8 balsa sheet. The strips were cut and soaked in warm water for an hour or two. Then laminated with thinned PVA (Speedbond). After an hour or two I released the lamination from the form then taped it back on to dry thoroughly overnight. There was very little springback.

I found that PVA sticks quite well to Sellotape  Roll Eyes but brown 'Parcel Tape' is awesome - the laminations just fell off when released.

The outlines were then pinned down on the plan and the other structure was added.


Jon
Attached files Thumbnail(s):
Another Boston Cub
Another Boston Cub
Another Boston Cub
Another Boston Cub
« Last Edit: January 08, 2012, 07:28:16 AM by Yak52 » Logged
Dave Andreski
Titanium Member
*******

Kudos: 82
Offline Offline

United States United States

Posts: 3,052




Ignore
« Reply #1 on: January 08, 2012, 09:21:32 AM »

Jon,
Those laminations look very nice.
Dave Andreski
Logged

Aspire to inspire before you expire.
crashcaley
Palladium Member
********

Kudos: 238
Offline Offline

United States United States

Posts: 5,161




Ignore
« Reply #2 on: January 08, 2012, 09:46:26 AM »

Jon, Very nice work.  Caley
Logged

What's stall speed?  Undecided
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #3 on: January 10, 2012, 06:31:41 AM »

Thanks Dave, Caley... it's a start anyway.  Smiley
Logged
OZPAF
Palladium Member
********

Kudos: 177
Offline Offline

Australia Australia

Posts: 4,983



Ignore
« Reply #4 on: January 10, 2012, 07:36:19 AM »

Your laminated shapes came out well Jon. I was also impressed by the glued joints on the finished tail and fin.

John
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #5 on: January 12, 2012, 08:08:26 AM »

Thanks John, I do try to pay attention to the dry fit before I glue. I've also started to thin the PVA a bit and apply it with a small brush. That helps, as well as having the right clamping pressure applied.


I've now built the wing.

I first sanded the laminated tips flat, sticking them down on some masking tape on my bench. This holds the piece nicely and avoids breaking it. Getting it off again can be tricky! (You can always cut it off with a knife then remove the tape) The outer profile was sanded after the wing construction when it was better supported.

The tips were then pinned down on the plan and the LE and TE shaped for a close fit. Then the ribs were trimmed to fit. The LE is quite hard balsa. The panels were built as two seperate entities, spars and all, glued up but only joined by the trailing edge. This was cracked and the correct dihedral set. The centre pieces were then added.

Sanding the LE and TE is always a bit of a heart stopper for me. I find it makes it much easier and reduces the stresses on the structure if it is stuck down to the desk. Also the ribs are covered with a patch of tape to prevent damage. This means you can concentrate on the shape and worry less about unintentional 'cross sanding'.

The finished wing weighs 2.3g at this point. I also compared the Cub tail plane to my Cloudster dimer build and weight for size, the laminated structure is quite a bit lighter.


Jon
Attached files Thumbnail(s):
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Logged
abyssdncr
Bronze Member
***

Kudos: 7
Offline Offline

United States United States

Posts: 99




Ignore
« Reply #6 on: January 12, 2012, 09:46:04 AM »

Jon,

That's looking great!  I really like your method of using tape to aid in the sanding process.  I was doing LE & TE last night on one of my builds and that would have definitely helped!
 
Cool
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #7 on: January 12, 2012, 05:34:39 PM »

Cheers Brian, I was just trying out an idea but it worked pretty well. By sticking it down, all the loads are directly on the piece of wood you are sanding and there is no real flex in the structure, like when you hold it by the rest of the wing. That means very little stress on the glue joints.

The tape is single-sided wide masking tape - its just taped down the 'wrong way up' with smaller pieces.


Jon
Logged
OZPAF
Palladium Member
********

Kudos: 177
Offline Offline

Australia Australia

Posts: 4,983



Ignore
« Reply #8 on: January 13, 2012, 06:41:57 PM »

I like the use of the masking tape to hold the wing down and protect the ribs, as well, Jon. It would have helped considerably on some recent Hanger Rat LE's.
I imagine you are using a small sanding block for the LE and TE's. I found that a paddle pop (ICE?) stick with some 80grit was great as very little pressure was needed and the finish sanding could be done with a emery tape nail file, but it was still a pain to hold them still.
John
Logged
Pit
Palladium Member
********

Kudos: 127
Offline Offline

Germany Germany

Posts: 5,507


aka staubkorb


WWW

Ignore
« Reply #9 on: January 14, 2012, 09:20:55 AM »

I found a double-sided tape used by interior house painters to secure plastic tarps.  It's fairly low-tack, but I haven't tried it yet for holding parts for sanding (SHOULD work OK)
Logged

A Dedicated Convert to:
WWWoFF (Wonderfull Wacky World of Free Flight)

Comparing Spammers to a pile of organic waste is an insult to the organic waste!
Tmat
Titanium Member
*******

Kudos: 67
Offline Offline

Canada Canada

Posts: 2,928




Ignore
« Reply #10 on: January 14, 2012, 09:44:57 AM »

I've been using Scotch brand Wallsaver removable Poster Tape to hold balsa down to my board whilst sanding.
http://www.officedepot.com/a/products/508218/Scotch-Wallsaver-Removable-Poster-Tape-34/

Works a treat!
Ordinary double sided carpet tape works well if you remove some of the tack first.

Tmat
Logged

F1B guy...
But don't hold that against me!
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #11 on: January 14, 2012, 10:22:03 AM »

Thanks guys, I normally have some double-sided tape about the place but I'd run out. The reversed masking tape is low-tech and low tack Grin  but cheap as chips too! It works as long as the reversed piece of tape is stretched out properly to imobilize it... double sided is better of course.

My sanding block for this was largish - about 10" by 1" - I used around 400 grit but have been known to use 80 for larger bits. The LE/TE is only 1/8" by 1/16" so I wasn't intending to remove much material.


By the way, Scigs original build thread for this design is here at: http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=5018.0 It's a lovely little model!

Jon
Logged
scigs30
Gold Member
*****

Kudos: 65
Offline Offline

United States United States

Posts: 593



Ignore
« Reply #12 on: January 15, 2012, 06:39:16 PM »

Jon, Your build is looking great, she is a great flyer.
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #13 on: January 27, 2012, 06:55:20 PM »

Thanks Scigs! I'm having fun with it  Grin

I've slowed down a bit as I've started drawing up a new Bostonian plan. Just a little more progress over the last few days... I've built up the fuselage sides. I did wet the top longerons slightly and there was no issue with spring back when the sides were released.

I've opened up the tail plane slot to allow me to trim with shims if neccesary.
This is not a lightweight by any means, but I'm aiming for the 14g target.

Apologies for the poor quality pics  Undecided

Jon
Attached files Thumbnail(s):
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Logged
crashcaley
Palladium Member
********

Kudos: 238
Offline Offline

United States United States

Posts: 5,161




Ignore
« Reply #14 on: January 27, 2012, 07:30:08 PM »

Jon, The pics look good to me.  And you do very nice work.  Caley
Logged

What's stall speed?  Undecided
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #15 on: February 03, 2012, 08:52:56 AM »

Thanks Caley  Smiley

The fuselage is coming together bit by bit. I've made a slight modification by adding a full nose former. As usual I've ended up with a bit of banana in the forward end - but I'll just call it "intentional built in side thrust"  Undecided

I haven't gone to town on the weight with this model - the sticks are quite firm. I'm aiming for the 14g rule but we shall see...
Attached files Thumbnail(s):
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Logged
OZPAF
Palladium Member
********

Kudos: 177
Offline Offline

Australia Australia

Posts: 4,983



Ignore
« Reply #16 on: February 03, 2012, 09:56:00 PM »

Very neat Jon. You mean it wasn't intentional built in side thrust Grin
John
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #17 on: February 04, 2012, 06:59:51 PM »

Thanks John  Grin At least it goes the right way this time!
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #18 on: February 09, 2012, 08:10:43 AM »

I've now added the cowl, chin and nose blocks. It's almost complete, just wheels and the UC fairing to do.

I found that there was a bit of a 'stress riser' where the cowl block joined the fuselage (I broke it!) I think this is because a very thick rigid part joins straight to a thin part and when there is stress (my sanding  Roll Eyes) or an impact, it will break at the join. I've added a couple of gussets to spread the load.

The weight so far is 8.5g. I haven't been using particularly light wood so I'm not suprised. I've also started building in noseweight - the nose block is quite dense wood. Scigs reported needing noseweight for his prototype build.

I think the nose is a bit bulbous (my sanding not the plan) but hey, it's semi-scale... At least this one has a long tail moment!


Jon
Attached files Thumbnail(s):
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Logged
tross
Gold Member
*****

Kudos: 43
Offline Offline

United States United States

Posts: 704




Ignore
« Reply #19 on: February 09, 2012, 09:07:44 AM »

Jon,
You're doing a great job on this one. I really like it.
The nose looks good also.
Is that snow I see? Burrr!

Tony
Logged

Instructions: Step One...Assemble the pile of sticks shown in pic "A" to look like the model airplane shown in pic "B"........
OZPAF
Palladium Member
********

Kudos: 177
Offline Offline

Australia Australia

Posts: 4,983



Ignore
« Reply #20 on: February 09, 2012, 06:07:12 PM »

You have the perfect soft test flying area there Jon Grin except for the fact that its wet.
Loads of character and I like that nice tail moment.
John
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #21 on: February 09, 2012, 06:46:02 PM »

Thanks John, Tony. Yeah, ironically we are now having the coldest weather of the winter so far. Some have it a lot worse though...

Loads of character and I like that nice tail moment.

I agree! Kudos due to Scigs for that  Wink
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #22 on: February 20, 2012, 05:51:39 AM »

Started covering the Cub... The tail surfaces were quite straight forward but covering the bulbous nose block has been a pain. I'm on attempt five or six now, using dope with wet tissue. Attempt 5 was almost acceptable but not quite there yet... I was getting double thickness wrinkles around the edges.
Attached files Thumbnail(s):
Re: Another Boston Cub
Logged
Yak 52
Titanium Member
*******

Kudos: 61
Offline Offline

United Kingdom United Kingdom

Posts: 2,429


Topic starter
Free Flight Vagrant



Ignore
« Reply #23 on: February 22, 2012, 04:54:24 PM »

I've finally given up on the nose block  Undecided What I have is reasonable but I still have a few wrinkles.

The UC wire was attached today, using... you guessed it a special jig  Grin Basically it just ensures that the model is level, the wing tips are level and the axles are level.

I've also added a diagonal brace to the forward fuselage. It just seemed that in an impact with the wall (rather likely  Roll Eyes) that the lower longeron would be the place it would 'go'. So the brace is an attempt to spread that load. It does help a lot, but I seem to have ended up chasing stresses around the model, adding weight and just moving the weaknesses somewhere else. C'est la vie...  Undecided
Attached files Thumbnail(s):
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
Re: Another Boston Cub
« Last Edit: February 22, 2012, 06:21:20 PM by Yak52 » Logged
FreeFlightModeller
Russ Lister
Titanium Member
*******

Kudos: 65
Offline Offline

United Kingdom United Kingdom

Posts: 3,631


Russ Lister



Ignore
« Reply #24 on: February 22, 2012, 05:35:53 PM »

That has really made me smile Jon .... how you have highlighted your wrinkles  Smiley
Your build standard is very high .... combine this with your 'self checking criticism' and I know that we are going to see some great models coming from your direction.
I think the nose block looks a hard prospect to cover in one piece without wrinkles.

Will your UC jig be a Leg-O-liner?  Roll Eyes
Logged
Pages: [1] 2 3 4   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!