You will probably find as time goes by that a lot in sport aircraft
design is very empirical, ie a bit like building old sailing ships, ( of
whihc I have a bit of an interest in ), line up a few planks on the river
bank with a plumb bob and a thumb, and away you go, undercarrige for
instance, there is not a lot of design information available, its a case of
this works, so everyone uses this, then follows over the years a process of
empirical development, I am surprised that thngs happen this way, I would
have thought that a more engineering approach would be more appropriate, but
anyhow, the system seems to work so what can I say???? And because you are
a plummer, bears no relationship to your intelligence or creative ability. I
know guys who are aeronautical engineers and they are absolute dolts, they
get their degree because they have a very very good memory, but cannot put a
nut to a bolt, I'm the other way round, have no memory capacity at all.
Flying boat hulls were also manufactured by wooden strips laminated
together diagonally and bonded with wood glue, they were quite light and
very strong, but labour intensive, so they went to metal hulls, much quicker
to put together, and easier to repair.Just a bit of history.
Anyway, you are in the right part of the world for innovative ideas,
Australia is a very backward place for technology, science and aviation,
most ideas worth anything have to go overseas to do any good.
The platten press sounds like the way to go. The glider guy I knew was
very emphatic about the water problem in teh balsa wood, its absorbs the
water like a sponge and then the rot sets in and its was impossible to get
rid of it, in a one off design like the kr where teh builder is the owner,
and much care is taken in looking after teh airplane, then damage to the
skin is not a problem as these machines get looked after very well, but in a
prodcution environment where the airframes are distributed to glider clubs
the world over where the aeroplanes are made to work quite hard , ie
constant club use day in and day out, and not much care was taken of the
airframe, then the balsa core gave problems. Gliders carry water in teh
wings as ballast, it improves teh performance curve by shifting everything
to a higher airspeed, you get the same glide angle, but faster, the down
side is you do not climb as fast in the thermals, untill the thermal
strength gets quite strong, then the loss in climb is only marginal, on a kr
you probably would be pretty safe untill some kid comes along and thinks,
"Gee, what is this stuff," and pokes a hole in it somewhere you don't see,
and .......................
Chris Johnston
North Richmond
NSW Australia.
----- Original Message -----
From: "Mike johnson" <[email protected]>
To: "krnet" <[email protected]>
Sent: Monday, October 30, 2006 1:19 PM
Subject: Re: KR> boatless fuselage?
> Chris,
> You have some very good thoughts. I will run it by some of the guys and
> see what they think.
> I will try to keep this conversation about KR's so knowone gets upset.
>
> I can't give much of an opinion because I am a plumber and just don't have
> that type of knowledge.
> You do have a clever ways of thinking. Regardless of where you live you
> can still be creative.
>
> Here is something to think about. For many years my father has owned a
> large manufacturing company producing phenolic panels for the medical
> industry. Anyhoo, I have been with him on many adventures around the globe
> and have seen some companies produce some very unique products. One of the
> products that was unique was a company that made wood molded dash panels
> for BMW.Imagine three sheets of veneer put in a stack, each having a
> thickness of about .030 thick. Similar to how phenolic is made, very thin
> sheets of phenolic coated rice paper is put between them, this is the
> glue.
>
> Next, this stack is put into a machine called a platten press. It is just
> a simple mold of the part, similar
> to a plastic injection machine. The top and bottom each have hot oil
> running through them to heat the
> glue up and melt the glue sheets between them. After about 3 minutes the
> oil is evacuated and the
> part cools. Open up the press and bingo.Take a knife and remove the
> flashing. Not only is the part perfectly molded, but no finishing is
> required because the glue is also a phenolic resin which when cured is a
> rock hard gloss that a simple buffer cleans up. The phenolic is
> impregnated into the wood
> because of tons of pressure and heat. Handling the glue is easy because it
> is dry and in the form of
> a thin sheet of paper. The glue type paper product is made by my father as
> well. You would be amazed how strong that part is.
>
> Imagine what you could do with that kind of process. Another product that
> is similar to the BMW
> dash is the wood bowls you find in a restaurant or bar. You may have seen
> them before, they
> usually have chips or salsa in them. This product is even stronger because
> it is made from strips
> of veneer weaved together to make a type of cloth like Rutan glass.It
> comes out smooth
> because of the heat and pressure. The word strong is an understatement.
> The company that makes
> it is located in Minesota, USA.
>
> Well, as interesting as it is I should stop here because we should keep it
> about KR's.
> At any rate, I have made a bunch of tail springs for airplanes this way,
> utilizing a prototype press
> my father has. I am about 5 or 6 springs away from perfection. They cost
> nothing and weigh nothing.
> And if I make it work I will send you one for nothing. Mike Johnson :)
>
>
> ----- Original Message ----
> From: Chris Johnston <[email protected]>
> To: [email protected]
> Sent: Sunday, October 29, 2006 5:47:28 PM
> Subject: Re: KR> boatless fuselage?
>
>
> Hi Mike,
> Re: Balsa composite
> I used to do a lot of gliding and the glider guy who was very
> experienced used to tell me that some of the earlier gliders, ASW 15B etc,
> were exactly this type of construction, the only problem with this idea is
> that of water ingestion, more so with gliders as they carry water ballast,
> and if the fibreglass skin leaks, for any manner/number of reasons, and
> not
> just on gliders, then the balsa gets wet and rots, this rot is sometimes
> very difficult, if not impossible to detect, thats why they then went to
> using foam, does not rot and stops the water getting in to start with.
> I always thought that a good way to make aeroplane fuselages was with a
> molded ply skin, put a sheet into an autoclave with the appropriate cut
> outs, apply heat and pressure and when it comes out, a pressed 3d ply skin
> with beautiful compound curves, the compund curves are good for
> aerodynamics
> and increase the stiffness of the skin. You can then add a minimal
> internal
> structure, and with modern CNC machines you can cut your parts to a
> perfect
> fit, giving a wood monocoque structure, save hours of time over sheet
> metal
> and rivets, and hours of messy layups with fibreglass. If you need more
> strength then use a double skin, on the inside as well as the outside, or
> even fill in the void with foam for even more strength, try gluing a piece
> of ply with some foam and then another peice of ply together with some
> T-88
> and try to pull it apart, its incredibly strong. This is what I am going
> to
> do on the floor of my KR2, the foam ply sandwich is already there, all you
> have to do is add glue, so there is no serious weight penalty. You could
> make the two fuselage halves separately, fit all internal fittings and
> then
> glue together. I would love to be involves in this type of project but
> have
> not not the higher engineering or opportunites in this country, I woul be
> interested to know what your engineer freinds have to say on this idea,
> its
> a very backward part of the world for good ideas this place. You may have
> to
> build up the skin by layers of veneer or you may be able to use one sheet
> of ply, I don't know enough to know what is the best way to tackle this
> problem. The advantage of wood is that it has no fatigue life in
> aeronautical use, unlike metal, and to a lesser extent, composites.
>
>
> Chris Johnston
>
> North Richmond
>
> NSW Australia.
> ----- Original Message -----
> From: "Mike johnson" <[email protected]>
> To: <[email protected]>
> Sent: Sunday, October 22, 2006 3:21 PM
> Subject: KR> boatless fuselage?
>
>
>> I'm sure I will be crucified but here goes.
>> I am very fortunate to be surrounded by a bunch of smart engineers. Three
>> of them are aeronautical.
>> Most of them have numerous patents.
>> Myself, heck i'm just a plumber. Anyhoo, I was talking to them about the
>> kr2s plans I have and was asking them for any input about them. They said
>> it sounded like a nice plane, and should be real
>> nice to fly, etc,etc.
>> We started talking about the boat or main structure. On a whim I asked
>> this question, " why couldn't
>> you just build it like a long-ez but use balsa wood instead of the foam?"
>> Boy what a question! It was like kids in a candy store. At any rate, they
>> became real excited and thought I should try and do it.
>> By the way I was thinking of balsa wood because my father ownes one of
>> the
>> largest phenolic mfg.
>> companies in the U.S. and has a premium supplier of top grade balsa wood
>> that he uses for some type of substrate for General Electric.
>> Now I have this problem of these guys calling me and pushing me to do
>> this.
>> At first I regretted bringing this up, now it almost sounds like a good
>> idea.
>> I really am quite lucky to have friends like this. Maybe I should try and
>> do it, what do you guys think?
>> Most of these guys are in there 60's and 70's, and own some type of
>> composite airplane.
>> They said they would do the engineering data for fun. Then build a
>> fuselage, and destroy it for something called destructive testing.
>> The catch is I pay for the materials. They seem to think, that doing the
>> math is fine but we should also destroy it and analize the failure. After
>> it is destroyed I would then start to built my own plane. It's not the
>> money, I can swing it, it would just take alot of time.
>> I must say I am a little nervous about it, But it would be sweet. Please
>> give me your'e input, it would
>> really mean alot to me. If I did do this, I could post the photos and
>> info. to the group.
>> What do ya think? Mike Johnson
>>
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>
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