Thoughts on construction materials - Balsa?

Anything to do with mechanical, construction etc

Thoughts on construction materials - Balsa?

Postby pralfred » Sun Aug 20, 2017 6:52 pm

I've been reading threads on this forum non-stop for about two weeks now, and I've learned a lot from the discussions here. I'd like to first say thanks to everyone's sharing of experience and opinions.

Because weight is a major issue for me since I'm going to be pulling my tear with a motorcycle, I've been hard-pressed to find a building material that will let me build a 4x8 that is light enough to pull with the bike. I was planning on using 1/8" ply as a primary construction material until my mentor, a construction worker and woodworking craftsman, suggested that perhaps we could use balsa.

After researching balsa's properties, I think we can skip the thin ply and use 1/2" balsa for the wall/floor panels with 1"x2" balsa framing and 1" insulation foam. We're planning on going with a torsion box design using gorilla glue and liquid nails to laminate the layers together, and a shiplap to join each balsa board to the next. The two walls, the floor, and ceiling will weigh about 30lbs each, or a little less.

The cost of the balsa for the walls, floor, and ceiling will come to about $500 each, which is fine by me since the curb weight of the trailer when it is done should be about 250-275lbs. Well worth the cost for me and my application, and giving me an estimated total project cost of about $2500 to $3000 (possible discounts, deals, and sales not included). This means I can build the trailer I want for about 1/4 to 1/3 the cost of buying one pre-made, and I get to have the fun and enjoyment of learning a bunch of new skills along the way.

NOTE: I am always open to suggestions for build ideas and weight-saving materials. I am, however, trying to go for a classic woodie teardrop or as close as possible.
Last edited by pralfred on Tue Aug 22, 2017 2:02 am, edited 2 times in total.
User avatar
pralfred
Teardrop Inspector
 
Posts: 17
Images: 6
Joined: Sat Aug 12, 2017 10:41 am
Location: San Antonio, Texas

Re: Thoughts on construction materials - Balsa?

Postby Pmullen503 » Sun Aug 20, 2017 7:04 pm

I would suggest sheeting 1" foam with 1/8 balsa on both sides rather than solid 1/2". It will be about the same weight and MUCH stiffer. I would do the walls and roof the same way.

For a woodie, balsa doesn't look great but you could cover it with a nice wood veneer it you were willing to spend the money and weight.
Pmullen503
Teardrop Master
 
Posts: 232
Images: 57
Joined: Sun Nov 23, 2014 1:33 pm

Re: Thoughts on construction materials - Balsa?

Postby pralfred » Sun Aug 20, 2017 7:11 pm

Pmullen503 wrote:I would suggest sheeting 1" foam with 1/8 balsa on both sides rather than solid 1/2". It will be about the same weight and MUCH stiffer. I would do the walls and roof the same way.

For a woodie, balsa doesn't look great but you could cover it with a nice wood veneer it you were willing to spend the money and weight.


I was wondering just how thin I could go with the balsa, especially on the flooring since I'm not building on top of a trailer frame. And the idea (as it is in my head now) was to use the 1/2" balsa sandwiched on either side of 1" foam, for a 2" thick wall and floor, and use 1/4" or 1/8" sandwiched on 1" foam for the roof. If I can go thinner, that would give me a little extra space inside, which would be cool. Also, if I were using 1/8" balsa for everything I could afford (weight-wise) to add a veneer to the outside for a nicer finished look, I think.
User avatar
pralfred
Teardrop Inspector
 
Posts: 17
Images: 6
Joined: Sat Aug 12, 2017 10:41 am
Location: San Antonio, Texas
Top

Re: Thoughts on construction materials - Balsa?

Postby Atomic77 » Sun Aug 20, 2017 10:50 pm

Are you bolting the torsion axle to the balsa?
Michael

"The Strength is in the Sum of the Parts..."

The Astroliner

Follow The Astroliner Blog Here!

Check out our YouTube video
User avatar
Atomic77
500 Club
 
Posts: 957
Images: 308
Joined: Tue Oct 08, 2013 5:29 pm
Location: Fort Wayne Indiana
Top

Re: Thoughts on construction materials - Balsa?

Postby elcam84 » Mon Aug 21, 2017 8:52 am

Have built allot of planes with balsa. Also a woodworker. I would look into paulownia or however it's spelled. It's a fast growing wood with similar properties to balsa and is grown in the us. Jimmy Carter tried to get everyone to grow them many years ago. Interesting tree as it grows fast and if you lop it off at the stump it will regrow from the stump.

I would also look into fiberglass as you can easily make your own spars etc to whatever shape and length you need. That coupled with a lightweight wood is a good combo.
You might also consider veneering the outside when done for a better look. However this is a big undertaking and likely to fail sue to the sheer size and curves.

Sent from my SM-T320 using Tapatalk
elcam84
Teardrop Master
 
Posts: 121
Joined: Thu Oct 30, 2008 2:59 pm
Top

Re: Thoughts on construction materials - Balsa?

Postby pralfred » Mon Aug 21, 2017 1:38 pm

@Atomic77 I was planning on bolting the torsion axle to a hardwood board screwed into the underside of the floor, so not directly onto the balsa.

@elcam84 I'm still researching what material is best to use for my build as I realize that building nearly entirely out of balsa is a bit of a massive undertaking that might/will be frought with problems. It's actually why I started this thread, to see what others thought of the idea and what other super-lightweight options there might be. While I would prefer to have a woodie of some sort when I'm done I am still very open to ideas that will have a very different look when finished. I've also been reading up on veneers and canvas/paint outer layers...there's some great ideas with those.

I appreciate the input so far, and I would love to hear more. I'm planning on taking the tear on the road and living out of it for at least several months, so I want to make sure I get this right. Everyone's input and ideas a very welcome, and I'll be sure to make a good build thread (and possibly a blog too) when it comes time to build.
User avatar
pralfred
Teardrop Inspector
 
Posts: 17
Images: 6
Joined: Sat Aug 12, 2017 10:41 am
Location: San Antonio, Texas
Top

Re: Thoughts on construction materials - Balsa?

Postby QueticoBill » Mon Aug 21, 2017 7:04 pm

IMHO there are simpler ways to get ultra light weight. Foam and fiberglass has to be one. The ultra light frame in design resources but with aluminum. Basic stressed skin deck. I think much simpler and tried than balsa.
QB
A tear with no name: viewtopic.php?f=50&t=67624
QueticoBill
Silver Donating Member
 
Posts: 520
Images: 22
Joined: Sun Apr 14, 2013 7:22 am
Location: Oak Park Illinois
Top

Continuing the research of lightweight building materials...

Postby pralfred » Tue Aug 22, 2017 1:41 am

So, I have continued researching building materials since it seems that the balsa idea is likely to be more trouble than it's worth...especially considering its expense.

I am probably going to end up using the ultralight A-frame undercarriage it seems, unless someone thinks I can bolt the axle directly to the floor of the trailer (haven't gotten many comments on that yet).

I'd rather not use fiberglass, though I am liking the idea of possibly using the heavy canvas and paint idea (love the retro/vintage concept there) for the external veneer. I called and talked to a local lumber supplier and they suggested I look into marine and/or aircraft grade plywood, which I've been doing most of the day. If I were to use a 1" thick framework and hard insulation foam as the core for my walls and floor, could I get away with using 1/8" Okoume ply as the outer layers? If so, that would be far cheaper than my (silly newb) idea of using balsa, and nearly as light...estimates come to about 30-40lbs per wall/floor with 1/8" ply/1" frame-core which would leave me enough wiggle room for the shelves and cabinets for the galley still.

As always, I appreciate the comments and suggestions. I am also still reading through the plethora of back-posts in hopes of learning more.

EDIT: I am also considering spruce as the material for the internal framework...it seems to be the most popular among wooden aircraft builders since time immemorial (ok, since the 20s & 30s) and is still popular today due to its strength and lightweight characteristics. Any thoughts on this as well?
User avatar
pralfred
Teardrop Inspector
 
Posts: 17
Images: 6
Joined: Sat Aug 12, 2017 10:41 am
Location: San Antonio, Texas
Top

Re: Thoughts on construction materials - Balsa?

Postby QueticoBill » Tue Aug 22, 2017 6:46 am

I believe 1/8" ply on foam properly adhered and pmf or fiberglass skin would allow you to omit most framing. Without any framing or blivking, attachments would rely on adhedive, which with pmf or fiberglass would probably be fine.

Registration aside, i think you could attach an acle to a stressed skin deck directly but what about the tongue? Not sure its worth the enginering when just a little more frame would solve both. I have pondered and sm concerned by the axle to tongue being only plywood, and if it is, the exrea thickness of the ply probably offsets the weight of a lityle more frame.

Interesting. I likevyour thinking.
QB
A tear with no name: viewtopic.php?f=50&t=67624
QueticoBill
Silver Donating Member
 
Posts: 520
Images: 22
Joined: Sun Apr 14, 2013 7:22 am
Location: Oak Park Illinois
Top

Re: Thoughts on construction materials - Balsa?

Postby Pmullen503 » Tue Aug 22, 2017 7:11 am

If you are not committed to a woody, foam and canvas will be the lightest. My 4x4x10' foamy weighs 600 lbs. And I was not trying to keep to weight down.
Pmullen503
Teardrop Master
 
Posts: 232
Images: 57
Joined: Sun Nov 23, 2014 1:33 pm
Top

Thoughts on construction materials - Balsa?

Postby kramergwt » Tue Aug 22, 2017 3:36 pm

pralfred wrote:EDIT: I am also considering spruce as the material for the internal framework...it seems to be the most popular among wooden aircraft builders since time immemorial (ok, since the 20s & 30s) and is still popular today due to its strength and lightweight characteristics. Any thoughts on this as well?


I'm building a Pietenpol Air Camper and using Sitka Spruce. Sitka is becoming rare and therefore expensive. Not all spruces have the strength and lightness characteristics of Sitka. Western Red Cedar is cheaper and so is Douglas fir (also used in airplanes). There is a list of suitable aircraft woods out on the internet. I would just check which one is the cheapest and go with that.

https://www.faa.gov/regulations_policie ... a_Ch06.pdf


Sent from my iPad using Tapatalk Pro
kramergwt
Teardrop Advisor
 
Posts: 53
Joined: Sun Feb 26, 2012 9:24 am
Location: Austin, TX
Top

Re: Thoughts on construction materials - Balsa?

Postby pralfred » Tue Aug 22, 2017 5:13 pm

@QuiticoBill, I am going to talk with my mentor tonight and likely we will settle on the ultralight A-frame design posted to this forum. The more I think about it, the little bit of extra weight is worth the added stability.

@Pmullen503, I am fairly set on a woodie of sorts, lol...but I'm reading up on foamies as well. My concern is that a foam-only design wouldn't stand up to the abuse of being lived out of for months on end. I could be wrong there, however, which is why I'm researching them still. They certainly would make the weight issue pretty much null.

@kramergwt, I have read many tmies over on this forum, "Think airplane, not tank." Between that comment and the suggestion of the guys at my local hardwood supplier, I have been researching what types of wood are light enough, yet strong enough, for aircraft and then figuring out if my budget can afford those materials. You're correct that Sitka is the preferred spruce varient, and that it is getting harder to come by and more expensive. The suggestion of douglas fir is a good one, and I am looking into that for a framing option as well now.

I am liking the idea of using a combination of light wood framing and skinning with an outer veneer of painted canvas. The "homage" to not only the original teardrop builds but also the aircraft of the same era is a nice touch for me. I may even try to paint it in a military aircraft type scheme just to add to the theme.I even considered a wooden tongue at first to go as vintage as possible, but scrapped that idea before I even made my first post here...too many issues related to stresses and weight. I'm probably going to go with an aircraft aluminum (6061) I-beam or rectangular stock for the A-frame and tongue. It will be about as lightweight as I can go and still have a structurally sound setup.

As an aside, I'm planning on having the motorcycle re-painted eventually to look like an old army Harley and sidecar. If my tear turns out at all the way my ideas are headed, it will fit the theme of the (eventual) new paintjob nicely. It may not be how I envisioned it at the start, but I'm liking where this is headed more and more.
User avatar
pralfred
Teardrop Inspector
 
Posts: 17
Images: 6
Joined: Sat Aug 12, 2017 10:41 am
Location: San Antonio, Texas
Top


Return to Teardrop Construction Tips & Techniques

Who is online

Users browsing this forum: No registered users and 1 guest