1/4 thick, 4x8sheet = 20 pounds, thin aluminium on both sides.Stronger than regular plywood.
If it doesn't say aircraft on it somewhere, it isn't legal in a certificated aircraft. Be careful you don't spend tons of time cutting and fitting something that your mechanic then has a fit about.
Boeing supposedly has some honeycomb material available surplus that is legal aircraft grade, that a friend of mine thinks might make good floorboards.
I`m posting in experimental and i `m building experimental, this product is not certified, but i think homebuilders should have a look at it.
Did you have to buy a 4x8 sheet? What is the thickness? Have you compared its weight to a normal Cub plywood floorboard?
Yes i had to buy a 4x8 x1/4 thick sheet,paid $ 132.00 cdn. I will use it to build my floorboard,bagage floor,rear seat bottom and back. My main concern was the weight and rigidity. If my memory is correct, ECONOLITE was 2/3 the weight of the plywood i was supposed to use ``without any protection on`` .Econolite doesn`t really need protection,it look like cardboard with a plastic core sandwich between to thin aluminium sheets ,it`s stronger than my plywood. i figure i can save 1.8 pounds on the floor alone.I found a 3x5 ins sample of the stuff in a RONA hardware store. If you are building exp. floorboard i think you should have a look at it before you buy plywood. After all that`s what exp. aircraft are all about.
If anyone is able to see the product,let me know what you think.
Keep in mind that honeycomb needs a bushing of some sort to carry the crush loads, wherever a through bolt is installed.
Looks like good stuff. Paintable too. I wonder where I could get a 3x5 sample in my area? Will have to research.
Well my research was less successful. I had a number of composite materials sent my way. In each case to get the same strength as the ply it was as heavy or heaver, except for the kevlar stuff. At 700 dollars a sheet, roughly 4 x 8, I decided the cost was not worth it at this time. I can always go back and replace the floorboards later if I find a product I am happy with. Sigh.
What is the weight difference between floors & baggage area made from Plywood, Aluminum, or Econolite????
I had it in my mind that Aluminum was lighter than wood, however I haven't done an apples-to-apples weight comparision. Anybody else?
If some has made this weight comparison, or has weights of Aluminum floor & baggage area, what thickness did you use on the front floor, rear floor, main baggage area, extended baggage area? Total weight?
Another consideration for my application, using Aluminum, is the ease of cleaning.
Weighed 1/4 marine plywood floor boards 7.6 lbs.
I was told that there is a very lightweight honeycomb material available from Boeing surplus as excess pieces for a nominal price. This stuff is supposedly very strong, and aircraft approved. Anyone know any more?
Nomex core Gillfab is used for cargo floors in Boeings and other cargo aircraft. Comes in different thicknesses and is very light. Made by McGill, if I remember correctly. Googling Gillfab will bring it up.
I have a design for a light weight floorboard using some techniques you guys have not yet thought about. Who wants to try one for their PA-18 project?
Gillfab 4809, developed for the Boeing 787 Dreamliner looks promising.
I know he has the brains to figure carbon, for instance, would be structured to have an upper skin seperated from a lower skin with foam, honeycomb, etc. This would be very much less in density than simply a hunk of solid carbon fiber thick enough to do the job of a floorboard.
Josh, why did you put just the density of each material? It makes plywood look like a champion on all counts, which it is not.
Also, anyone thinking marine plywood would be better or worse than some other type of plywood should think again. The 'plywood manufacturers association' has changed the spec on marine plywood and it now has a comparable 'void allowance' to most any AB sheet you'd go out to buy. For our application, more voids would be desirable, I just wanted to get out the bit of information about the loosening of the specs.
I wonder what a sheet of that stuff runs....?
Dave, what's your method of preventing crushing? I'm thinking in terms of a thinwall aluminum bushing topped by a stainless countersunk washer and bottomed with a fender washer or equivilent.
More info. I found a sheet of composite material at a reduced price. I replaced my cargo floors, forward and aft. Here are the weights.
Less than half the weight of plywood. Because it will not have the lateral forces applied to it from feet like the cockpit area floorboards I am not as concerned about wallowing out the attachment holes. You must use inserts as Crash mentioned if you use it where there will be stress and or movement. There are a lot of composites out there but many will exceed the weight of plywood. I don't find the weight in cubic feet to be very helpful so I have converted things to weight per sq foot for a given thickness.
There is enough sq feet in interior panels to save close to five pounds using .016 Vs .020. I have yet to find ANY composite that is lighter than .016 AL.
Your 1/4 inch composite needs to be .6 ppsf or less to make it worth the trouble. Plywood has a much higher modulas of elasticity so it will flex and return to shape without any permanent deformation. The composites will flex some but often they will go plastic and show permanent deformation at a lower stress level than plywood. Thus composite use on floors under the seats and or for the seat bottoms, (seatbacks may be OK) may not necessarily work out as you will need a really strong composite which may end up being heavier than the comparable plywood.
There are a lot of different types of materials, like Al, nomex, kevlar, fiberglass, etc. Each with different properties and weights. The stuff that is lighter than the ply is usually EXPENSIVE.
This is my upper baggage compartment using composites. Smithcub.
.023 thickness 48"x96" CARBON FIBER sheet 4.066lbs per sheet weight, a little expensive. This is what I am using for my side panels.
Took some time before work and then some more at lunch to see what my design would weigh.
Stock design came out at 3.04 pounds for the front floorboard.
My revised design came out at 1.976 pounds.
So with my method getting 30% of the weight out would not be too hard.
Im not sure if it is worth the extra hassle. The cost is about 3-4 times what a normal 2'x4'x1/4" piece of wood would cost.....just for ballpark.
Homemade composite floorboards are within the realm of any of us who are willing to mix epoxy accurately and follow a few instructions.
Making test pieces for destruction to compare to other materials choices takes the guessing out of what to use. Also, composites retailers (Plaschem Supply in Anch.) have competent persons willing to assist in design.
A foam core with fiberglass cloth or carbon fiber cloth applied to both sides with epoxy resin wetting the cloth can be built on your workbench.
After drilling the bolt/screw holes thru the material, the core material is 'gouged-out' in the area within, say, 5/16 inch radius of the hole centers without changing the size of the hole in the top and bottom skins. Then a 'Putty' of epoxy mixed with a thickener (a thixotropic agent such as cabosil) at a ratio providing a putty thickness like peanut butter is placed in each gouged-out hole. After curing, each hole is redrilled and localized crushing is impossible due to the putty.
This method is simple, does not require precision tools, and has the advantage that the 'hardened' (putty-reinforced area) is adhered to the structure of the floorboard.
I've seen a fabric interior and baggage floors and sides that appeared to work very well. I'm thinking a zip-in cordura interior would be nice, and provide easy access. And the stuff is pretty tuff. (trading weight for tuffness and tuffness for weight) everything is a compromise.
Dave, I've been using fabric upper baggage floors in J-3's for years. Works great. I run them back to just short of the trim jackscrew. Good for holding fishing poles and other such stuff.
Your stiffening technique works fine as well.
I've been thinking that a guy could get away with partial floorboards if he wanted to.
Floorboards in the area of the rear stick are needed so your passenger has a place to put a foot when they get in, and the pilot and passenger need a place to put their heels. Everything else is superfluous.
Stock floorboards don't keep stuff from falling down in the belly, so that's not a good reason to have a complete set.
If light weight is king why not eliminate most of the floorboards?
If you are taking the floorboards out you can take the brakes off!!
Will work like this Car's brakes..
discussing the 'sans-floorboard' Cub yesterday in the hangar, Fred's car brakes were mentioned.
Funny how ideas can be developed in parallel, without any communication.
Had a friend fly in yesterday in his Legend Cub with honeycomb floorboards. Seems he had to jab a brake to avoid a helicopter at his home airport and pulled the two bolt brake pedal mount doubler right through the floorboard. This part looks identical to the stock Piper part. Needs more area to distribute the load. Seen this on plenty of 30-40 year old wood floorboards. Easy fix was a large stainless steel plate. Just something to consider.
Steve, the lightest way ive seen to stregthen that up is to ad a tab on top the floorboards that goes from the brake pedal attach clamp bolt up to the rudder attach clamp bolt. I did that in mine but i have plywood, but it transfers the load right to the frame. I think i could break the back pedal off before the front would ever wiggle. On something lighter than plywood it probably wouldnt hurt to put a little wider washer underneath on the brake brace channel bolts also with the tabs. Spread the load some? The brackets can be made for under 25 cents.
How does a (new to planes guy) like me know what types of floor board / side board materials can be used in certified cubs?
444LZ give Phil, Steve or Jim a call at CAC Plastics.. they have light (certified) honeycomb material that is paint-able. For re-enforcement of bolt holes they simply cut the hole large, plug with resin and re-drill to size. They are just waiting to get some more orders to save on freight.
Several weights and thickness but 1/4" two ply (HD) is 8 OZ/Sq Ft and tough!
Use what Piper used, 3/8" plywood and aluminum. Tried and true in certified.
Ha, yes Mike 1/4". I think some sort of composite iver the honeycomb would help, something beside the stock attach plates to spread out the loads.
I used very stiff 6mm (1/4 in) 12 ply all Birch plywood from B&D International Inc. in Tacoma, WA. It is imported from Finland. Weight stated by the supplier is 0.92 lb/ft sq. After one spray of Epoxy Varnish I weighed a sheet at 0.98 lb/ft sq.
I don't see the purpose of putting floor boards under the front seat and so on... When I drop something small in my Cub it usually falls in the fabric belly anyway. Would make cleaning easier.
A lot of warbirds only have a strip of aluminum as wide as a human foot under and aft of the rudder pedal. Just something to rest your foot on. Just bend some corrugation strips in it to stiffen.
I am currently working on getting a honeycomb carbon fiber material for the floorboards and baggage. You can save 8 to 10 pounds by using this stuff. It is quite difficult to get. Everyone advertises one thing and delivers another. 8 week lead time is the norm. And they usually have minimum orders that make it impractical for individuals. They also do not want to talk to you unless your name is Boeing, Gulfstream, or Airbus Industries. If and when I get all this sorted out Javron will be carrying it and selling it. If you are interested give him a call as he does not have any feel for what the demand will be.
I've used Boeing's alum honeycomb for other purposes but not on my Cub. I remember a story about flight attendants spike heels denting the stuff, whereas a fully outfitted marine did not. And as others have pointed out it needs reinforcing inserts where bolts and other hardware might be located. Different cell sizes and thicker top skins might solve some of these problems, but custom production is expensive. Which probably makes other materials (Gillfab) worth looking at.
The place where I get some of my guitar-making stuff has DuPont Nomex in 16" x 22" pieces; 1/4 x .080", 1/8 x .080" and 1/8 x .060. Some folks are using it for soundboards on guitars. Boeing uses the stuff, so I'll assume it's approved materials. I'm willing to bet it doesn't burn as well as aircraft plywood does. It will need some layers of carbon fiber or fiberglass cloth, or both, and the appropriate resin. It's probably not hard to find videos or other media articles dealing with construction techniques.
I'm sure there are other places to get it, bigger sheets, etc.
I know I should lose about two complete floorboards.
I have a board with Nomex core on it. It´s about 5x5" so it´s hard to judge how it flexes but it is really solid.
Here is the source (http://www.nauticexpo.com/prod/bellotti-spa/sandwich-panels-plywood-honeycomb-30295-197074.html) for it.
And you will note that to get more info on this product you have to fill out an info sheet and they will contact you. Finding and procuring this type of stuff is a PAIN. I have invested more hours on this one topic (and part) than any other part of the ENTIRE airplane. It works and it saves weight but you would think you were buying a nuclear reactor to get the stuff. So to help others, once I get this stuff sourced, I will make sure it is EASILY available to others. Probably through Javron, as I am not a cub kit manufacturer.
Has anyone tried making their own from a veneer (your choice of material) with a balsa wood core? Be sure to place a crush resistant material where all fasteners pass through. Or, how about the process that some of the plastic homebuilts use for primary structure with a foam core. I have seen samples of this which was cut out of a Glassair (like a window hole). Really tuff stuff.
Anybody ever try end grain balsa core? Kind of old school in todays composite market but it is really easy to work with. I have used it in boat decks... easy to work with simple to reinforce point load areas, lay glass over (vacuum bag if you like).
The issue with foam and or balsa core is that it is relatively easy to get it as heavy as plywood. The lightest core material is the nomex core 1/8 inch hex cell. The light plywood weighs .85 ppsf and a good honeycomb material will be .45ppsf or less, thus half the weight of plywood.
Small business located in Minneapolis. Usually keeps it all in stock and also carries vacuum bagging supplies. Ask for Jim.
To provide a "block" in the honeycomb for a fastener, drill a small hole in one face and chuck a small allen wrench in a drill, push the top (short leg) through the hole and spin it. Fill the cavity with an epoxy/microballoon or colloidal silica mix and let it set.
A possible plywood to use would be Lite Ply which is an Italian poplar. Very light weight but not too stiff or rot resistant. The 6mm is 5 ply. Next lightest is Occoume , then Meranti and Khaya or Sapele all in marine grades, 6mm 5 ply. GLII birch 6mm is usually 12 ply and would be about the same weight as the Sapele and also very stiff.
Wow, it's been a while since I was at their site. Probably hired a marketing intern or something :) (I hope I don't offend anyone!:P) but if you click on the X of the pop-up, then you get to the right window. I forgot it was all in Italian!
54205421I make a floor board laminate from the top side (finish side ) down, acrylic gel-coat on the top side, 5.8 OZ E glass, 5.8 OZ carbon,5mm PVC 4# density, 5.8 OZ carbon all layed up with a class I fire retardant vinalester resin. Comes out right at 8 OZ a square foot any color you want. I have had them installed in my cub since "98" approx. 900 flight time and still look great. I have not been able to find anything lighter that is finished and this finish is tough. I saved just over 4# on my cub with the two front boards rear seat bottom and standard baggage floor. I am just getting ready to send out samples for a burn test!
It certainly does make it easier to retrieve dropped hardware. Not to mention control inspections and lubrication. But I'm always paranoid I'm going to put a foot through the fabric, or bend a control rod getting in an out.
I made carbon fiber floorboards with 1/32 plywood center and carbon fiber cloth on both sides using epoxy and a vacuum bag with peelply and absorbent pad. I radiused the corner for increased stiffness and an attach area for the side panels. The surface comes out with a tough finish, is waterproof, and weighed less than .032 aluminum. It was a fun process to learn. Pictures are in my photos but I can't seem to upload them to here.
If one was able to get some "FAA approved" Boeing floor board or cargo bay scraps, is there an advisory circular that would allow for a legal install in a certified cub?
Sounds like a 'minor' mod to me - - I used some surplus honeycomb for rear seat base and back, with no paperwork and no disagreement from my IA.
I've heard it's been field approved before.
I have been working on floorboards for my experimental PA14 made with Carbon fiber-end grain balsa-carbon fiber construction. I placed 1/4 inch plywood in the balsa in desired locations before processing in the vacuum bag to provide crush resistance in the area of bolts. I used West System epoxy, peel ply, and absorbent pad to absorb the extra resin and decrease weight. The end result was better than expected. The structure is very stiff, waterproof, well sealed, and light weight. The weight turned out to be 0.53 pounds per square foot which is 56% the weight of 1/4" plywood alone and also less than .040 aluminum. Besides it is kind of fun to do. Almost magic.
Looks good, mind saying what that total job is going to run.
Just a few places for balsa core material (and others). Express Composites is in the Minneapolis/St. Paul area if you make it into the Cities frequently.
I finished the floor board set for the PA14 replica. They are made in three sections because of angulations to the floor and convenience for installation and removal as needed. They are a total of 88"long and 29" wide. They have a turned up lip on the edge to help with side wall anchorage and stiffness. They are 1/4" thick endgrain balsa as I previously described. There are 3 layers of carbon fiber cloth bonded together with West System Epoxy. Total weight is 11.1 lbs and 17.72 square feet for a total of .626 lbs/sq ft. finished on both sides. They are very stiff. I included plywood on the ends and in the middle where needed for anchorage points. Joewoodworker.com was a helpful site to learn how to do this process.
Total weight is 11.1 lbs and 17.72 square feet for a total of .626 lbs/sq ft.
pretty, but did that work out how you hoped??? weight and cost wise???
Yes, I am pleased. The rear section came in between .032 and .040. The forward section was heavier because of the reinforcements for the rudder pedals and the control blocks. The angled sides also added a slight amount of weight but should give a nice surface for the Kydex to snuggle up to. When all is said and done it is lighter than plywood and should be more durable. Is it cost effective and time efficient to do? No, but it was fun and educational.
Well done Jim, I expect that the sound dampening qualities will out weigh the small weight penalty.
Very nice. CF is something I would like to lurn.
Jim, Way cool. Thanks for the post, something I want to play with now.