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1.4 oz vs .75 oz Fiberglass Cloth For Balsa Finishing

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Old 08-24-2013, 07:26 PM
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Default 1.4 oz vs .75 oz Fiberglass Cloth For Balsa Finishing

Can you use 1.4 oz fiberglass cloth for balsa finishing with out getting weave pattern that is hard to fill. I would use epoxy resin for application and Klass Kote primer and paint for finish. I have used .75 oz before but never 1.4oz for outside surface finish.

What would be the difference in surface hardness and surface strength between .75 oz and 1.4oz cloth? The slight increase in weight is not a factor in this application but surface hardness and strength would be.

Thanks for your ideas and suggestions.

Gary
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Old 08-24-2013, 08:13 PM
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The truth is you will only add the weight, the surface will still dent easily and the strength will be negligible.

Bob
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Old 08-26-2013, 07:25 AM
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Quote:
Originally Posted by Viper1GJ View Post
Can you use 1.4 oz fiberglass cloth for balsa finishing with out getting weave pattern that is hard to fill. I would use epoxy resin for application and Klass Kote primer and paint for finish. I have used .75 oz before but never 1.4oz for outside surface finish.

What would be the difference in surface hardness and surface strength between .75 oz and 1.4oz cloth? The slight increase in weight is not a factor in this application but surface hardness and strength would be.

Thanks for your ideas and suggestions.

Gary
Surface hardness and/or toughness depend a lot on coating thickness as well as type of glass and epoxy used. Hanger rash depends alot on these things too.

1.4 oz glass and finishing epoxy resin is about twice the thickness of .7 oz glass / resin. But since .7 oz and epoxy finish very thin, (about 2 thousandths of an inch), going to 1.4 oz won't buy you much more surface hardness. To be fairly tough and resistant to dents and dings, thickness should be a minimum of 10 thou and 15 is almost bullet proof. But weight builds up very quickly. If you are finishing a cabinet or a boat for example, it's possibly a good way to go. Not so much if you are finishing a plane....
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Old 08-26-2013, 08:57 AM
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Ok, I guess the best plan is to just stick with .7oz cloth for the best surface for fill and finishing and not smack the surface with anything.

Here is another question.

How would a 1/8" balsa sheet fuse side laminated on both sides with .7 oz cloth and epoxy resin compare with the same fuse side made from poplar light ply in weight and strength?

Is there any advantage to using the laminated balsa sandwich to plain light ply for strength and weight?
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Old 08-26-2013, 10:38 AM
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A sandwich constructed 1 ply balsa 1ply is very strong and light indeed. I don't use 1/8" thick light ply in any of my design or builds I use 3/32" thick basswood plywood from Aircraft Spruce & Specialty, it is almost as light as light ply with just about the same strength as Birch plywood, this allows me to place all kinds of lightening holes throughout the fuse and achieve the lightest construction of all.

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Old 08-26-2013, 12:25 PM
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Quote:
Originally Posted by Viper1GJ View Post
Ok, I guess the best plan is to just stick with .7oz cloth for the best surface for fill and finishing and not smack the surface with anything.

Here is another question.

How would a 1/8" balsa sheet fuse side laminated on both sides with .7 oz cloth and epoxy resin compare with the same fuse side made from poplar light ply in weight and strength?

Is there any advantage to using the laminated balsa sandwich to plain light ply for strength and weight?
The better compromise between strength, stiffness, minimal hanger rash and minimal weight build up for moderate sized planes (2 meter size) is either a balsa/glass sandwich (slightly heavier) or an airex/herex foam / glass sandwich (lighter). The glass layers that work well for this size plane are 2 - 2 1/2 ounce on the outside and 1 1/2 on the inside. The balsa we use is sealed 1/32" 6 - 8 ounce stock; the Herex we use is 1-2 mm 2 pound density stock for an extremely light yet durable construction. Ding resistant but not ding proof
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Old 08-27-2013, 03:43 AM
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If we may ask, what is it you are building specifically so we may optimize our replies to your questions?

Bob
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Old 08-27-2013, 05:04 AM
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Bob, Matt, Thanks for your help.

I am building a 110" turbine powered tail-less flying wing with thrust vectoring called Sabre XLT (Extra Large Turbine). This is strictly a sport jet, non UAV project for fun. Estimated weight is 30 lbs empty and 40 lbs take off with fuel and smoke, with 40 lbs thrust available. The wings are standard balsa covered foam cores attached with two 2" diameter x 48" fore and aft aluminum tubes. 1/2" balsa vertical sheer web runs from wing skins to the tube sockets on top and bottom and inside the aluminum tubes in the center 48". Uni-carbon tape runs over and under the sheer web from root to tip. The root has 42" chord, 3 1/2" thick, tip has 24" chord and the fuse is about 96" long. It is a plain box fuse with flat bottom and rounded corners. The top has a canopy hatch and aft hatch of balsa covered foam.

Here is a photo of the .60 glow sized 2nd prototype called Lancer. The design is Mike Oser's from Texas. It flies great. He has designed the airfoil and sweep such that the wing does not require reflex in the elevons. It will turn up its tail and is extremely stable at high AOA when slow. It should be a great flyer with a thrust vectored turbine.

So my questions are how to build the fuse sides, doublers, and formers for a larger turbine powered one. What materials to use. The build has to be simple, flat with straight lines, constructed on a flat table. Curves are from carved balsa or foam, and mostly wood. My nose cone and canopy are stolen from an old Eurosport. I have built sport jets before with 1/8" light ply sides, IMAC style, with lightening holes and covered with Ultracote, but was looking for a better way. I was thinking of laminating 1/8" balsa with glass and making the sides, doublers, and formers from it and using some plywood in stress areas. I have 1" wide uni-carbon tape for uses as needed. Finish this time will be Klass Kote paint over .7 oz glass.

Cheap, fast, and simple are considerations. The whole idea is to have a unique sport jet for grass runways, with an airframe that can be finished for a few hundred dollars vs a few thousand in my workshop using basic tools. I can cut foam, wood, vacuum bag, and spray paint but no exotic composite processes or molds or expensive materials.

Hope this helps you visualize the project. I really appreciate your ideas and suggestions.

Thanks Gary


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Old 08-27-2013, 07:37 AM
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Very cool project, check this stuff out, I have been playing with the 3/16" thick Gator Board in conjunction with balsa for a couple of years now and it may be right up your alley, it glues very well, it is light, strong, paints well, takes glass well, and the cost is very reasonable.

Bob

http://www.google.com/aclk?sa=L&ai=CGHb7eMMcUs7nMO73yAGKtoGQCbLAuOgDuuaT4FCG8ZBPCA AQASC2VCgCUOPP-NoEYMnGiI3kpIgUyAEBqgQhT9AfeFNPgzIozYklLRcAlzyl7Jg qUJnuEPFm34wZFo5tgAWQTroFEwiL5KOt9p25AhVobrYKHaE3A J_KBQCAB5WKRg&ei=eMMcUovILOjc2QWh74D4CQ&sig=AOD64_24wsqWj21nLZlMdMBETaSWM9_kxQ&rct=j&q=gator+board&sqi=2&ved=0CCsQ0Qw&adurl=http://clickserve.dartsearch.net/link/click%3Flid%3D43000000119007266%26ds_s_kwgid%3D580 00000002165521%26ds_e_adid%3D21587456242%26ds_e_ma tchtype%3Dsearch%26ds_url_v%3D2&cad=rjaI



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Old 08-27-2013, 08:03 AM
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Quote:
Originally Posted by Viper1GJ View Post
Bob, Matt, Thanks for your help.

I am building a 110" turbine powered tail-less flying wing with thrust vectoring called Sabre XLT (Extra Large Turbine). This is strictly a sport jet, non UAV project for fun. Estimated weight is 30 lbs empty and 40 lbs take off with fuel and smoke, with 40 lbs thrust available. The wings are standard balsa covered foam cores attached with two 2" diameter x 48" fore and aft aluminum tubes. 1/2" balsa vertical sheer web runs from wing skins to the tube sockets on top and bottom and inside the aluminum tubes in the center 48". Uni-carbon tape runs over and under the sheer web from root to tip. The root has 42" chord, 3 1/2" thick, tip has 24" chord and the fuse is about 96" long. It is a plain box fuse with flat bottom and rounded corners. The top has a canopy hatch and aft hatch of balsa covered foam.

Here is a photo of the .60 glow sized 2nd prototype called Lancer. The design is Mike Oser's from Texas. It flies great. He has designed the airfoil and sweep such that the wing does not require reflex in the elevons. It will turn up its tail and is extremely stable at high AOA when slow. It should be a great flyer with a thrust vectored turbine.

So my questions are how to build the fuse sides, doublers, and formers for a larger turbine powered one. What materials to use. The build has to be simple, flat with straight lines, constructed on a flat table. Curves are from carved balsa or foam, and mostly wood. My nose cone and canopy are stolen from an old Eurosport. I have built sport jets before with 1/8" light ply sides, IMAC style, with lightening holes and covered with Ultracote, but was looking for a better way. I was thinking of laminating 1/8" balsa with glass and making the sides, doublers, and formers from it and using some plywood in stress areas. I have 1" wide uni-carbon tape for uses as needed. Finish this time will be Klass Kote paint over .7 oz glass.

Cheap, fast, and simple are considerations. The whole idea is to have a unique sport jet for grass runways, with an airframe that can be finished for a few hundred dollars vs a few thousand in my workshop using basic tools. I can cut foam, wood, vacuum bag, and spray paint but no exotic composite processes or molds or expensive materials.

Hope this helps you visualize the project. I really appreciate your ideas and suggestions.

Thanks Gary


Gary, a nice project. Based on the available thrust, I believe some of the discussion applies yet some is likely overkill. A model this large and with only 40 pounds of thrust will fly rather slowly; I'd hazrd a guess and say less than 100 mph.

Recently I outfitted an Extreme Flight balsa and ply 78" Extra with a piped DLE55. The model is intended for medium sized electric power or 35cc gas or YS175 4 stroke power, but the DLE55 was an experiment worthy of my effort. The model was extremely lightly built, weighing a scant 12 1/2 pounds with the DLE up front delivering around 6 HP and 35 pounds of thrust. It flew great.....BTW- the carbon tubing connecting the two halves was a 7/8" OD size x 1mm wall x 30" long. Plenty of strength for the project. Your project only adds about 16" to each side so one 2" carbon tube x 40" in length should be plenty of strength for a 30 lb airplane

The point is balsa-ply structures are amazing engineering materials in terms of strength because they are flexible enough to give when necessary. Add some glass or carbon cloth and these become incredibly strong and light. It also is that 40 pounds of thrust is not that much thrust and doesn't require extravagant or exotic materials of construction even for a 30 lb airplane. Medium density of 6-10 lb 3/32" balsa stock or holed basswood as Bob mentioned, laminated with maybe 3 oz on the outside and 2 oz on the inside will provide more than enough strength but be light. Let me suggest that the sides should be vacuum laminated on the bench first before starting fuse assembly for optimal strength. Doublers (again I'd use the same thickness, 3/32" balsa) in the high stress areas can be built in at this time under the glass. Let me also suggest that carbon tubing should be used as longerons.

Your wing as explained is around 3600 square inches and your loading will be around 14 ounces per sq ft. A floater!!! The foam will not need any more than 1/16" balsa veneer. For a little more insurance and stifness, you might consider 0.2 oz carbon veil under the skins. I apply mine with nitrate dope (2-3 coats) directly on the inside sheeting surfaces. After that flashes for a couple days, I epoxy laminate the skins on the foam. Very light but strong construction.

The carbon tube spar I use has sockets embedded in the foam of course. These are simple tubes I build from 2 oz glass and epoxy. The carbon spar joiner is installed into the socket while the socket is being gorilla glued into the foam, to hold the form. The socket is supported in my constructions in similar fashion as your described....basically I use a shear web extending from socket to foam surface. I use 1/8" balsa web 6-8 pound density, and extend the web (false spar if you will), out beyond the end of the socket 3-4" to remove the stress riser away from the socket's end. I also apply a layer of 2oz glass on the foam maybe 4" square on biasat this socket end area, then apply the skins. The shear web false rib forms an "I" beam from top skin to bottom skin, and through the socket. Wing panels are removable of course. Very strong but light, for a 5 kg model. For a 15 kg model such as yours. the larger joiner and larger shear web are the right moves.

Good luck
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Old 08-27-2013, 06:18 PM
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Hey guys, thanks for the ideas.

Bob, I have used foam board before but not for any jet stuff. Im a little afraid of the heat in the rear for it. However it may be just the ticket for the vertical fin. I'll have to check it out. What is the difference between Gator Board and regular foam board?

Matt, Vacuum lamination of the fuse sides before building was what I was thinking of. I was wondering why you use larger weave and heavier weight cloth on the outside vs inside. I wanted to skin the whole thing with .7 oz cloth for finishing so wonder if the large 3 oz weave would be harder to fill and paint. Also I was going to make the doublers and formers from the same material as the fuse sides. I would just cut out the doublers and formers from pre laminated planks. Then I could bag the larger fuse side and doublers at the same time under the glass on the inside. It seems this would be very strong. I was thinking of running some 1" uni-carbon tape on the top and bottom of the fuse sides but not sure if this would produce any extra strength.

Your wing skinning and tube joiner ideas are similar to what I was going to use. I like the idea of putting the glass on the foam over and under the end of the wing tube to spread out the stress at the tube socket end. I was planning 1/8" wing skins but based on your suggestions I may go back to 3/32". Also I was wondering if glassing the inside of the skins was worth it. .7oz was my thought. Would carbon veil be better? If so how does it ad to the strength. It seems that the carbon fibers are short and run in all directions from what I have used. How does it work on the inside of the wing skin?

I was interested in how you use carbon tubes for longhorns. What size tubes do you use for this size fuse? Also not shown in the Lancer photo above, the Sabre will have NACA air inlets behind the wing TE to get air inside to the engine. See attached photo below for similar intake. This will leave just a narrow area of the fuse sides above and below the widest part of the inlet hole to hold the entire back end on with the weight of the engine and TV nozzle. I wanted to use some kind of carbon in these narrow areas to make sure the back end does not fall off under G load or hard landing. Any suggestions there?



I hope to start construction in late fall for next spring test flights. I still have some time to decide how to build the thing. I have the retracts, fuel/smoke tanks, canopy, wing tubes and sleeves, and Kingtech 180G engine on hand so far. I still need to get wood, glass, and foam. My questions and you guys suggestions are helping me understand what type and how much glass cloth I need to get.

I came up with 19-25 oz/sq ft using the same numbers, 3600 sq in or 25 sq ft. Still very light for this size wing. My experience says speed will be somewhat higher, however it will not be fast, which is what I want. A slow jet. I have been flying my AcroJet since 2003 and have never seen it above 130mph. It is an IMAC jet, built from an old Aeroworks G-202 foam wing and tail, fixed gear, and light ply and balsa fuse with external engine between the tails . Span 104" and weight 31lbs empty 41lbs full fuel and smoke with 34 lbs of thrust. After 8-10 min of aerobatics I download an average 65-85mph with a max of 100-110mph nearly every fight. I feel I could easily snap or bend the 1 1/2" aluminum spar tube if I yanked it when going fast. That is why I planned on using 2 x 2" tubes on the Sabre XLT since it can generate a very fast turn rate. The Sabre will also have retracts so will not have the fixed gear drag. I will try to attach some AcroJet photos. Thrust vectoring at post stall airspeed is really fun and with smoke on makes some cool smoke patterns.

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Old 08-27-2013, 06:27 PM
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Bob,

I just reread the the thread. I noticed you said "3/32" thick basswood plywood from Aircraft Spruce & Specialty".

I have never seen basswood plywood.

Do you use it by itself or laminated
with balsa or glass? How would it work in a large fuse like the Sabre XLT project?

Gary
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Old 08-28-2013, 03:26 AM
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It would be great material to use on an airframe that large, Basswood plywood It is really great stuff to work with in conjunction with balsa wood and I have never laminated over Basswood with glass and resin, there just hasn't been a need too. Last time I looked it was in the $130.00 range for a 4' X 8' sheet and I think you can purchase it in 4' X 4' sheets as well. I am one of those guys that is fanatical on keeping every oz. off the airframe, I have done many giant scale airframe build threads talking about the use of that plywood and lightening techniques throughout the structures. Here are just couple of pics from 1 or 2 of those threads showing engine boxes, fuselage construction, and wing core lightening application. By the way, the finished fuselage in these photos is 144" long.

Bob
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Old 08-28-2013, 03:58 AM
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Bob,

Thanks for the photos and info. I got some good ideas from them and have a few more questions to ask you but no time this morning. I will try to get back to you tonight to get your thoughts.

Thanks
Gary
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Old 08-28-2013, 06:57 PM
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Bob,

Where do you get a 4x8' sheet of basswood plywood without paying a fortune for shipping?

How does it compare with 1/8" light ply and 3/32" birch ply?

When you are using basswood ply for fuse sides are you using the plywood for doublers under balsa or just as a stand alone fuse side? Since I will not be using iron covering on the fuse this time I wanted a solid side. How would you recommend building a solid fuse side, stringers, longerons, and formers for my project described above?

What technique do you use to cut the lightening holes in the foam cores. I see no holes in the foam shuck beds. Are they cut after the airfoil is cut?

How do you cut the sheer web slot over the wing tube and outboard of the end of the tube?

How do you construct the sheer web over the tube and out? Is that a carbon strip over the sheer web?

On the foam cores shown are the ailerons already cut out. Do you cut them off before sheeting? If so how do you cut them out. If after sheeting how do you cut the out? I had always sheeted first and then cut the ailerons off and then capped the edges with balsa at the hinge line.

What type of wing sheeting are you using. What type of glue do you use to adhere to the foam.

Thanks for your building tips.

Gary
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Old 08-29-2013, 04:17 AM
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Hello Gary,

I buy direct from from Aircraft Spruce & Specialty, when I order, I always purchase two or three sheet at a time because the shipping is almost the same for one to three sheets. 3/32" thick basswood plywood will be much stronger than 1/8" light ply and almost the same weight as the 1/8 light ply. When I am using the basswood plywood for the fuse sides, I do not place plywood doublers, as you would see in many kits, I run 3/8" X 3/8" medium density balsa longerons, the same for diagonals and fuse bulkhead formers. Cores, first I cut the cores then I make lightening hole templates for both sides of the core from the cheapest paneling I can find at Lowe's or Home Depot, next I screw them to the sides of the core with course thread drywall screws ( just a few will do), I then us a soldering iron and make holes in the core in each area of the of template, after that I just take my time and cut out each area with a hot wire. This is actually very easy to do, it just takes a little time. The slot over the tube I cut with a router and a strait edge screwed to the core, and yes that is a carbon tube I place in my core as wing tube extenders both on top and bottom of the cores, at the point the wing tube stops the carbon tube extenders are placed extending toward the tip to around 65% of the wing panel and back towards the root around 20%. Now for the wing skins, I use medium density 1/16 balsa 3" X 48" sheets, I true the edges and tape them together, next I cut 3/4 oz. fiberglass cloth strips 1" wide and place them on the opposite side of the tape directly centered over the seems and utilizing EZ POXY 10 epoxy laminate system purchased again from Aircraft Spruce & Specialty I laminate 2 plies and allow to cure. After cure I lightly scuff over the laminated areas with 320 grit abrasive and clean all the dust away. Using the same epoxy system I sparingly roll the epoxy onto the cores and skins place in the shucks, and into a vacuum bag not exceeding 5 hg throughout the cure cycle (overnight). The nice things about this epoxy system are you have plenty of time to perform your layups with out fear of it going into thermal runaway, it has a low viscosity. I hope this helps. By the way, I glue everything wood together on my fuselages with thin and medium CA only but that is another story.

Bob

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Old 08-29-2013, 08:57 AM
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Quote:
A model this large and with only 40 pounds of thrust will fly rather slowly; I'd hazrd a guess and say less than 100 mph.
You are only thinking about the 40 pounds of static thrust.....not the 500 - 600 MPH exhaust velocity.
The jet below is 102" span with 36 pounds of thrust, weighing 52.5 pounds with fuel and flies at speeds well over 100 mph.


Nice project, Gary!


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Old 08-30-2013, 06:32 PM
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Gary,

Is that one of the 125% Turbinators? I really like that idea and considered building one last year.

Gary
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Old 08-30-2013, 06:42 PM
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Bob,

Does the paneling bend and curve enough to wrap around the airfoil ok. The stuff I see at Lowe/HomeDepot is at least 1/4" thick and would seem very stiff for making the hole cutting templates from.

Also the foam cores in the photos seem to have a thick trailing edge. How do you finish the trailing edge of the wing?

Gary
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Old 08-30-2013, 07:07 PM
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Hello Gary,

If you look at all the paneling real good you will find some stuff closer to 1\/8" thick, that is what you want to use, it bends real nice for you. The trailing edges of my airplanes are very thick, because my control surfaces are huge for 3D and a thick T/E remains loaded in flight at neutral much better then a sharp trailing edge. I cap them with 1/16" medium density balsa wood sheeting and Gorilla glue.

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Old 08-30-2013, 10:26 PM
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I believe that 1/4" carbon tubing x 1/32" wall has plenty of strength as longeron stock and is very light and stiff, but bends enough to conform. I think the longest I've seen is 4 feet tho. The lonerons will need splicing, A 1/4" ID carbon tube that the pieces are inserted into will work fine. Six inch splices are long enough.

At the duct areas of the fuse, I'd suggest doubling up the 1/4" longerons.

On wing loading, yes true enough, IF the model weight comes in at 30 pounds. i was guessing that you were going to shave 5 lbs off the total dry weight. Of course with jets I forget that take off weight is about 1/3 higher than dry weight. Talking shaving weight, have you considered the tank types yet? Let me suggest clear PET plastic types rather than the epoxy-kevlar-glass. Fittings can be obtained at Eldon James (internet search). I sell the 1/8" size but you may need larger ones that I don't carry.

PET is polyester and is impervious to kero, avgas and auto gas. Many drinks come in 64 oz bottles so finding that size should be straight forward. These tanks are bound to save you as much as a pound of dry weight.

Thust versus speed versus load....that's a rather large wing. I hear what you're saying about the two 2" aluminum tubes. I was thinking one 2" carbon tube with a thicker wall, around 2mm or so. If a 7/8 x 1/32" x 36" carbon tube can hold two full grown men (at least 350 pounds) then a 2" x 2mm x 40" carbon tube should hold at least 600 lbs or 20+ G's of loading. The weight savings would be significant too....Of course 2 7075 ally tubes will cost maybe 40 dollars where the carbon probably at least 3X that.....Just trying to inform you of other possibilities....cost would go up of course but might be manageable

Re: wings, ailerons, TE's etc. The foam wings i prefer are cut with the TE down to the desired thickness, usually no more than 1/16". Sheeting adds another 1/8". I usually cap off the TE with med-firm balsa and feather the balsa accordingly. The foam TE usually will have some 3K carbon rovings, top and bottom, laid flat with epoxy. I cut the ailerons out of the wing. Aileron and wing facings are usually 1/4" medium balsa. Hinges are spaced every 6" or around 5 per side for my meter spanned wing. On your wing, add some hinges. I use and really like the Radio South CA types, but there are others that work well too

Oh yeah almost forgot retracts holes and servo cut outs. I tend to not use anything extra here in my 2 meter models but on your jet, you may want to add 2 oz cloth on the skins before veneering, with considerable overlap of 3-4" all around

Good luck. It sounds like a real fun project....
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Old 09-01-2013, 05:57 PM
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Matt,

Thank for your reply and ideas.

Where do you get your carbon tubes that will telescope inside each other? How do you glue them to the fuse sides? I assume to the top and bottom of the side. What material do you make your fuse formers from?

I had planned on using plain Dubro tanks since they are cheap and available. I'm using a 100 oz and 80 oz for fuel and an 80 oz for smoke. The same for the aluminum wing tubes, they are much cheaper than carbon and available with pre-made sleeves. I have looked at PET bottles before but never figured out how to close them up and put fittings in.

I also use Radio South heavy duty hinges. I like them since they are easy to slot, use lots of them, 2-4" apart, and allow great gap seals just by ironing covering material in the hinge line.

Gary
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Old 09-01-2013, 10:00 PM
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Quote:
Originally Posted by Viper1GJ View Post
Matt,

Thank for your reply and ideas.

Where do you get your carbon tubes that will telescope inside each other? How do you glue them to the fuse sides? I assume to the top and bottom of the side. What material do you make your fuse formers from?

I had planned on using plain Dubro tanks since they are cheap and available. I'm using a 100 oz and 80 oz for fuel and an 80 oz for smoke. The same for the aluminum wing tubes, they are much cheaper than carbon and available with pre-made sleeves. I have looked at PET bottles before but never figured out how to close them up and put fittings in.

I also use Radio South heavy duty hinges. I like them since they are easy to slot, use lots of them, 2-4" apart, and allow great gap seals just by ironing covering material in the hinge line.

Gary
Carbon tubes can be purchased from CST Sales and/or ACP. A quick on line search will reveal several sources. Kite makers also.

For my models, balsa formers work fine. On occasion, I will laminate glass and honeycomb stock where extra lightness and stiffness are needed. I control strength by the glass I use. Nothing wrong with your approach tho....glassed balsa is a fine engineering material. Strong, stiff and light enough.

Setting up PET bottles is so elementary you'd kick yourself once you see it done. My fittings are not permanent installs...serviceable. Bulkhead type fittings require a plastic washer with a neoprene seal washer outside the tank and a plastic nut inside the tank. Holes are burned in the tank with a soldering iron. Fittings are installed from outside..... Nut is fished on inside with a length of cable. Snug down with fingers. Tools not necessary. Caps are lined with viton (best) or teflon lined neoprene. Once the cap is on snug, I add a strip of Fusion Mastic tape which holds firm but is serviceable. McMaster Carr probably has everything you need except for large PET bottles
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Old 09-02-2013, 05:50 PM
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Matt,

Thanks, I looked at ACP and CST but was not able to determine exactly what sizes would work due to the tolerances indicated for the ID. I can call to get that info.

Can you post a photo of one of your PET tanks and fittings.

Thanks, Gary
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Old 09-03-2013, 03:17 AM
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As Matt stated, they are very simple to make. Here are just a couple of soda pop tanks I put in my 35 and 40% birds back in 2006-2008, Same tanks and airplanes are working great today.

Bob


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