Seaplanes Aircraft that typically take off and land on water...radio control seaplane discussions are in here.

Waterproofing Balsa?

Reply

Old 06-08-2004, 07:24 AM
  #1  
pjwright
Thread Starter
 
Join Date: Aug 2002
Location: Chattanooga, TN
Posts: 244
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Waterproofing Balsa?

Hi, guys - I'm starting a Sealane this week, and was wondering if it is prudent to waterproof parts of the hull that may experience water penetration?

For example, I was considering applying dope or Balsarite to the exterior hull sides and bottom, as well as the interior hull bottom (aka "the bilge" ) prior to Monokoting.

Please let me know if this slight addition of weight adds to the longevity of the plane (assuming some fool doesn't smash the thing to bits).

Thanks!

pjw
pjwright is offline  
Reply With Quote
Old 06-08-2004, 09:25 AM
  #2  
MinnFlyer
Senior Member
My Feedback: (4)
 
MinnFlyer's Avatar
 
Join Date: Apr 2002
Location: Willmar, MN
Posts: 28,519
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Waterproofing Balsa?

I usually coat the radio compartment with polyurethane, but that's about all.
MinnFlyer is offline  
Reply With Quote
Old 06-09-2004, 08:17 PM
  #3  
Fast Freddy
 
Join Date: Jun 2003
Location: Madison, WI
Posts: 172
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Waterproofing Balsa?

PJW,

I would recommend glassing the bottom of the hull to strengthen and waterproof the wood. The hull is going to take a lot of abuse and you want to make sure you get some use out of this plane. It's well worth the effort and it will not add all that much weight. Many flying boats have glassed bottoms or the fuselage/hulls are made entirely out of fiberglass. Good luck!

Fast Freddy
Fast Freddy is offline  
Reply With Quote
Old 06-09-2004, 08:27 PM
  #4  
JimCasey
Senior Member
My Feedback: (1)
 
JimCasey's Avatar
 
Join Date: Mar 2002
Location: Lutz, FL
Posts: 1,957
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Waterproofing Balsa?

Sealing any balsa or particularly light-ply (Which I think is made from stale saltines) is a good idea.

Polyurethane varnish has been mentioned. Thinned epoxy (epoxy+denatured alcohol) is also good, as are fuel proof dope and balsarite.

Seal the inside of the tank compartment, as well as the radio compartment. Anywhere water or fuel might lurk.

Glassing the floats or hull with a layer or 2 of 3/4 oz glass cloth does not add much weight but does add a great amount of strength. The cloth can be applied with the polyurethane varnish. Doesn't have to be epoxy.
JimCasey is offline  
Reply With Quote
Old 06-10-2004, 08:51 AM
  #5  
pjwright
Thread Starter
 
Join Date: Aug 2002
Location: Chattanooga, TN
Posts: 244
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Waterproofing Balsa?

Thanks, guys!
I appreciate and value your advice...and will proceed as you've recommended.

PJ Wright
Chattanooga
pjwright is offline  
Reply With Quote
Old 07-06-2004, 09:23 PM
  #6  
moesair
Junior Member
 
Join Date: Jan 2002
Location: royston, BC, CANADA
Posts: 13
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Waterproofing Balsa?

As mentioned, glassing the exterior below the waterline is an excellent ideas, while that processs is in progress, some resin on the interior bottom parts is an excellent sealer and stiffener as well, Moe -good luck.
moesair is offline  
Reply With Quote
Old 07-07-2004, 12:19 AM
  #7  
Turbobeaver
Senior Member
 
Join Date: Dec 2003
Location: Ottawa, ON, CANADA
Posts: 306
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Waterproofing Balsa?

Any where there is a hint of a chance of water possibly coming into contact with wood,seal it........and I mean back to front.Finishing resin thinned with denatured alcohol(rubbing alcohol) works best for this application.It will actually soak partially into the wood and seal it.I've built around 7 different flying boat models over the years and let me tell you, irregardless of how well sealed you may think you have your plane,water will still find a way of getting in.The wing seal is the biggest culprit of water penetration on a flying boat usually.Make sure you seal the wing saddle area well by making a silicone gasket using the silicone /saran wrap method.The saran wrap prevents the wing from permanently sticking to the fuselage and acts like a mould release.Jusy make sure the silicone is well cured before trying to separate or peel off the saran wrap.You will be rewarded with a very water tight seal when you are done.

I've seen flying boats literally fall out of the sky because of a altered C of G due to water wicking into the wooden structure at the back of the airplane.If you have open bulkheads which lead to the rear of the plane ,this is a definite possibility.Even if they are not,you can still have a small pin hole somewhere in the covering(built up structure) which water can migrate into.If water gets into the rear of the plane whether it's sealed or not,it will change your C of G very drastically.The difference being,if it is sealed,the wooden structure will not soak up the water like a sponge and you will visually see the water puddling inside the hull upon inspection.The plane can be easily mopped and dried out and no chance of warping to the structure.If it is left unsealed,the water will simply soak into all of the wood.This increases the weight of the plane,throws off the CG,raises the grain of all exposed balsa,and you run the risk of having a warped structure when and if it ever dries out again.This will lead to weakened glue joints eventually also.I wouldn't just limit the bottom part of the model to sealing either.Unless you never plan on flying inverted or performing any aileron rolls,water can reach just about any where inside the hull,up or down.

When flying off water,inspect the inside of your model very frequently to check for early signs of water penetrtation.This is especially true when flying a new model for the first time,but it is a good habit to get into any time you are flying off of water..It may save your plane from a disasterous ending.I've seen this ugly scenario play out many a time over the years and most could have been prevented if they had only periodically checked there models for signs of water penetration. Corrective action could have been taken to rectify the problem and prevent the inevitable crash.

I have done a lot of water flying both with float planes and flying boats(the latter being my favorite) over my 30 years in this hobby and these observations,recommendations are based on my own personal experiences.I have never lost a plane due to water getting in.Brain fade and arsing around?............Well that's a whole other story!Hope this helps you some.Always glad to share ideas with a fellow modeler.
Turbobeaver is offline  
Reply With Quote
Old 07-07-2004, 07:44 AM
  #8  
tpstorey
Senior Member
 
tpstorey's Avatar
 
Join Date: Nov 2002
Location: Saint Louis, MO
Posts: 257
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Waterproofing Balsa?

I use a can of spray polyurethane to do it the easy way.
tpstorey is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy