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NACELLE

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For the people who wish to know 4+ hours with files to rough out these sections, a few more to go

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NACELLE PLAN VIEW

Lessons learned
* Make more sections than needed
*Print a plan view of the Nacelle & verify thickness prior to shaping


Job Log 10-23-2007
Right hand sections in clamps (done).
Left side sections that need replaced in clamps (done).
Sections planed to thicknes & edge jointed square (done).
Profiles glued to Nacelle slices with datum ref (done).

Things to do list
1) Shape Left & Right nacelle slices
2) Glue up fuselage left hand side utilizing (eps) expanded polystyrene foam for shaping
3) Cut Spinner plugs

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Fuselage plan view
FS 0.00- FS245
Ruler is a standard "12 rule"

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Spinner plug 1/8th scale

Plug pre lathe turn & post turn

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left hand side Nacelle starting to look like something, 6 slices to go
Partical board is a great material to form


2007-10-26
LESSONS LEARNED
1) segment/s transition areas should have a high degree of match so as to minimize sanding after glue up
2) do not crown segments as this increases the sanding time after glue up

I am very happy with the results


Here is the Simi finished product; I am truly amazed at the fidelity that I have achieved. My patterns were very good
I made the decision to do the chin cowl (intake & oil cooler passage) separately as the engine intake slopes back at an angle
Off to get some body filler for the low spots and a little work left on the gear blister

Enjoy

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Looking for guidance on vacuum bagging/forming,
There seems to be several different opinions on vacuum forming.
What is a good medium to use for the bag, I have seen posts by several people utilizing "3 mil+ plastic" & RTV as the bag sealing agent, will this give satisfactory results?
What is the rule of thumb for in Hg & flow volume?
I believe the pump I have can pull 30 in Hg?

Ref material/links
http://www.mackrc.net/patternwings2/index.htm

http://www.rcuniverse.com/forum/m_43...tm.htm#4341072

http://home.online.no/~ofremmi/HowTo/

http://www.pilotsguide.com/rc/vacbag.shtml

http://www.rcgroups.com/forums/showthread.php?t=411348

http://www.rcgroups.com/forums/showt...ng#post8418858

http://www.bertram31.com/proj/tips/vaccuum.htm

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Fuselage shaping
scrapped the foam prototype

g-rock

My Feedback: (1)

Ho-229,

It looks to me that one of your illustrations is for vacuum forming and the second is for vacuum bagging. When vacuum forming (pre-heating the material), the material when pulled down on the plug (or female mold) acts as the 'bag'. I usually use a couple of layers of masking tape on the perimeter of the base that the plug is mounted to or in case of a female, it's lip. The vacuum can often be supplied by a vacuum cleaner. The important thing is to pull the vacuum quickly. What I have done in the past is to use a compressor tank as the vacuum accumulator. This arrangement provides the quickest and highest vacuum.

Vacuum bagging is usually used for placing a fiberglass lay-up into for holding the lay-up in place and removing any air and excess resin. the bag will hold things in place until the lay-up is cured. The amount of vacuum required is often as much as you can pull with your vacuum pump but you usually have time to pull the vacuum.

Gene

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Gene,
I was (still am) unsure about vacuum forming the spinner or vacuum bagging it.

I have never made an airplane using either of these two techniques so I am on the learning curve.

Your accumulator Idea is a good one; I have an old portable tire storage tank that I could evacuate.

Job log 2007-10-29
1) Glued up some foam for the fuselage
2) Shaped 40% of the RH side of the Nacelle
(sanded the left side of the Nacelle

Lessons learned
3M 77 is an aggressive glue if applied incorrectly (excess)

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WING/LANDING GEAR Ref material/links

http://www.rcuniverse.com/forum/m_19...tm.htm#1966079

http://www.rcuniverse.com/forum/m_86.../tm.htm#862529

http://www.rcgroups.com/forums/showt...ts#post5487389

http://www.rcgroups.com/forums/attac...hmentid=319193

http://www.pages.drexel.edu/~garfinkm/Spar.html

http://composite.about.com/od/aboutc...l/aa000109.htm

http://www.fibreglast.com/contentpag...tions-230.html

http://www.info-central.org/construc...mbagging.shtml

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WING BLANK JIG

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To Error is human & I am no exception. I mistakenly cut into my reverse image outline.
The quality of a fine cabinet maker is his ability to hide his mistakes.
MDF has no grain so scabbing a repair is easy & does not cause shaping issues.
Upon drying the scab is sanded true on the sanding station & shaped

2007-11-09

Well, here is 40 min of sanding…. I was WOW struck… the fidelity is awesome.
I still have to shape the window area but that should be about 2-3 hours of work

2007-11-11
Fuselage 170 aft waiting for the next data dump
Aprox 40% of the segments are drops (cut-offs from other projects)
The drops can be end glued & reused; nothing is wasted when using MDF


Enjoy
Dave

BMatthews

Vacu forming a spinner implies a fairly soft plastic. How big a diameter and how many revs are you planning on? Any thickness of plastic that will vacuform is not going to be that strong. Far better to work out a male and female mold pair and mold them from cloth and resin and rely on the male-female pair to hopefully provide enough thickness control so it's not way out of balance.

For vac bagging the skins you won't need to pull anything at all like 30 inches of Hg. I played with some very rudimentary vacbagging a few years back and found that an aquarium pump converted to suck instead of blow would pull about 2 psi. That was enough to literally crush white bead styrofoam cores. I had to add an engine's needle valve as a controlled leak to reduce the pull to around 1 psi. On some blue foam experiments I was able to let it "run wild" with the whole whopping 2.something psi vacuum and it was fine. If you think about it if you could push fiberglass and resin down evenly with 1 to 2 lbs of pressure over a single square inch that would squish the cloth and resin around pretty darn well.

However I never got into the whole peel ply thing. Just used some drafting mylar as a skin finish and hardware store construction plastic as the bag. I got some rolled vac bag seal strip the guy called "elephant snot" that forms a nice and reusable bag seal for the fold and to go around the suction tube. It's best to run the tube right in and under or into a little cavity in the side or end of the form. Otherwise the plastic sucks down and cuts off the suction before the whole bag is pulled down.

IT's quite the job you've done so far. I hope my brief experience and the lessons I've learned helps in some small way. This is definetly a build to watch!

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Bruce,
I do not honestly know what the RPM of the motor will be at this time, I am very sorry but I do not have the depth of knowledge to accurately predict the weight of this aircraft at the present time, with that being said motor selection will have to wait until I start firming up some things.

The spinner diameter is aprox 3.5 in at the big end, as of today I am planning to use my male spinner plug as the starting point to cast a female mold from composite

Also, I intend to cast the fuselage the same way.

I have a long way to go before I can start making molds from my plugs but I must confess that medium density fiberboard (MDF) is a dream to shape.

I have a few items that concern me, one of which is the girth/weight of the fuselage plug. Have you read or seen any data on fuselage splicing?

I have not made any decisions on splicing the fuselage sections at this time but I have not removed the idea from the table.

If you have ever worked with MDF you know that it is not a light medium to work with

Attached is a concept drawing of my proposed fuselage splice

Regards,
Dave

2007-11-19
Wing glue-up & shaping

LOFTING made easy
Lofting command not needed
Lofting can be done with simple commands

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GEAR Pprototype
(WORK IN PROGRESS)

BMatthews

With the size of model you're making the centerline joint won't be an issue. Just crawl in with some glass tape and a bucket of resin and a roller...

Obviously you'll need some access large enough to get the tools into the fuselage to allow you to work the glass tape and apply it. You'll need to practice outside with tricks, tools and techniques before tackling the final deal.

One trick I've read about is presoaking the tape with resin and rolling it up around a roller. Then you start the tape end and just push and rollout the presoaked tape along the inside of the joint. Working through the wing opening would give lots of working room. The joint taping doesn't need to be all in one single length either. 1 to 2 feet at a time is fine.

If this is to be electric powered then weight is important. Not as important as it USED to be with the earlier electric motors and such but your flying time will be extended by a lighter weight. You may want to look at using a cored structure of two much lighter skins with a core of foam of some sort. It'll be just as stiff or stiffer and far lighter than a single layup of resin and cloth that is thick enough to be self supporting. It would mean using some sort of pressure bag or compessed in foam rubber in the mold but if you can figure out how to do such a shell you may be able to avoid needing at least 1/2 of your internal structure.

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motivation

http://www.youtube.com/watch?v=5F86ART6R-g

ptxman

My Feedback: (2)

Go over to the composites section & you can research all the questions you've asked (and some you are about to) regarding plugs, molds & layups. Here is a specific post regarding seaming composite fuselages.

http://www.rcuniverse.com/forum/m_13...tm.htm#1411434

are better in small tight confined spaces where there is no other option. One trick I use to do with seaming tape is 3M spray it, then stick half its width on one layup side, close the mold, press it down on teh adjoining half (now its completely stuck & correctly positioned) then resin it down with a brush/roller/whatever it takes. Of course the closed fuse mold is now a dark tunel so you need some light in there. Ahhh.. the memories.

Your MDF is a lot of shaping grunt work but its coming along great, you will be rewarded with a very rigid & dimensionally stable plug. It will accept all varieties of finish (I recommend epoxy & 2-stage catalysed auto primer & paint) polished to as good as you can do. Then you are ready for layup of female molds.

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composite ref data

Integrated Design & manufacturing
Using
Fiber-reinforced
Polymeric
composites

http://books.google.com/books?id=81G...P7o0ig#PPP1,M1

material selection
http://www.netcomposites.com/education.asp?sequence=41

FIBER TERMS/DEF
DRAPE the ability of a fabric to conform to a complex surface

WARP are the lengthwise threads attached to a loom before weaving begins.

The WEFT is woven back and forth through the warp to make fabric. Warp means "that which is thrown across" (Old English wearp, from weorpan, to throw, cf. German werfen, Dutch werpen).

CRIMP is the natural wave formation of the fiber and is expressed as waves or crimps per unit of length

POROSITY the property of being porous, having pores; the ratio of minute channels or open spaces (pores) to the volume of solid matter

S-GLASS Structural glass; a magnesia/alumina/silicate glass reinforcement designed to provide very high tensile strength

E-GLASS A family of glasses with a calcium aluminoborosilicate composition and a maximum alkali content of 2.0%. A general purpose fiber that is most often used in reinforced plastics and is suitable for electrical laminates because of its high resistivity
"Standard fiberglass cloth used in surfboard manufacturing. it is also the weakest, least expensive cloth avaiable"


2/4 layup weighs 12 ounces per square yard, or .0092592 ounces per square inch.
2/6 layup weighs 16 ounces per square yard, or .0123456 ounces per square inch
4/6 layup weighs 20 ounces per square yard, or .0154321 ounces per square inch

joining methods
http://www.fao.org/docrep/003/t0530e/T0530E08.htm

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Wing jig is complete, it was easy to make, less then two hours.
I had to make the router compass to be able to make the articulation slot.
I am very pleased with the results.

The wing jig theory is basically as follows:
a) Screw the work item/plug to the jig (do not use screws that pass thru the area to be cut)
b) Attach the first wing section profile to the work piece.*
c) Attach the second wing profile to the opposing end*

*Each wing profile has equally spaced vertical division lines (pass lines) on it

Example:
Wing root has some number of equally spaced vertical division lines on it (50 for example) (router pass lines).
Wing tip or outer wing rib has 50 equally spaced vertical division lines on it (router pass lines).

By following these equally spaced pass lines symmetry & wash out/in is insured

NOTE:
The fence should always be positioned on the side of the work piece that is sacrificial. Doing this insures that the router cannot advance into the work piece accidentally.

(Basically the router is advancing towards the thicker portion of the wing profile)

Router bit
Hogging .75 in straight flute
Pass lines .375 radii bit

2007-11-25
Router table & insert are complete, was going to use 1/8” aluminum but at 150.00 a sheet MDF will work just fine
The router compass makes quick work of the MDF
Steps are basically counter bore & bore thru
Next step is to square up the wing blank & fasten it to the jig for cutting

2007-11-27 the wing jig is done

2007-12-05
Router guide/milling jig finished
Wing profiles with pass lines done
Look forward to cutting some MDF next week

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Twin engine/motor thrust affect
Counter rotating versus non counter rotating