tomfiorentino

Oh right...I'm sorry Bob! When you asked about keeping it straight I thought you were talking about something else.

I have seen the link you provided on the reference lines....from the airfield site. I have been searching around on the internet (and my sense is I am getting close) for sheet steel with reference marks. I suppose it is easy enough to build, but time is at such a premium it drives me nuts. I am finding some fabricators that emboss metal, etch metal, acid mark metal etc. etc. and a lot of it is custom stuff, but it seems like there would be other commercial applications for sheet metal with precision reference marks etc. I dont know. But if I find something I'll be sure to pass the link along. In the end I may just make my own.

While I haven't worked with the magnets yet I had a thought to see how the magnet would hold through glass. Steel on the bottom, covered with plans, then covered with glass (or something really thinn and clear like mylar etc.) Then I can build with magnets but still over the reference lines provided by the plans. Just a thought!

Tom

JNorton

My Feedback: (2)

Hold the magnetic 1/4" away from the steel. Very liitle magnetism. I don't believe glass over metal will work. I use my magnetic board with a centerline then I reference rib spacing etc of the blueprints.
John

ser00

Just my two cents worth. I build using magnets, (exact same system found at www.airfieldmodels.com). My table is a 2'x6' steel plate (10 gauge) that sits on top of a HB work bench. I screwed in two 2"x4" boards flush with the surface of the work bench (along the front and back of the table) and placed the metal sheet on top of it and screwed the sheet down with 2" screws into the boards. Then, I placed a 6' level on the metal plate at a diagonal, darkened the room and placed a small flashlight behind the level and ran the light along the distance of the level, looking for any light that could be seen bleeding through between the level and the table's surface. I did this for the other diagonal and then straight down the two sides and center of the table. Since I did not see any light bleeding through from underneath the level, I assume that the plate is flat enough. If I had seen light, then I know that I would have found a low spot in the table. I hope this helps you.

Happy flying and soft landings!

tomfiorentino

Hey good point on flat enough! I like what you did...smart!

Do you care to share what you did for layout and/or reference lines on the steel? And while I'm at it, is it true that the Large Set package that airfield models sells is adequate for most building? I noticed the bridges etc. are special add-on fixtures but can't be so sure if I need those or not and should add it to the Large Set package.

Any thoughts and recommendations on the magnets from your personal experience would be great.

Thanks for sharing...

Tom

rgburrill

ser00

Hi Tom,

As far as in reference lines, I build on top of the plans so I do not see any lines. One thing that I do use is the Black and Decker laser level (the one that is shaped like a tape measure). I use it to place a line on the plans. When I get off work and later tonight, I will post some pictures of my setup so you can see what I use and what I do. It might give you a few ideas or generate a few questions. I have built planes using both the pinning on a ceiling tile method and using magnets. I have to say that it takes some time getting use to using magnets (or coming up with ways and creating new fixtures to get the job done.) The nice thing about magnets is I can build an entire wing, take it apart and rebuild it again without putting holes in the wood. It is really nice for test fitting parts before gluing and makes it easier to build a fuselage. As I said, I will post some pictures tonight.

Happy flying and soft landings!

ser00

Hey Tom, what size airplane do you plan on building? .40-.60 (2-stroke)? 1/4 to 1/3 scale? How good are you with working with wood? What type of wood working tools do you have? These are all questions that you need to ask before buying the large set (or any set). There used to be a template you could download and create the fixtures yourself (the old ones, not the new ones). 200 magnets would cost you $110 (enough for 50 fixtures - way too many). If you are handy, you can build a beginner set, sand it and stain it and add more pieces as needed. If you have loads of money, order away. The new style fixtures are extremely nice, practical and functional, and I know that you would get a high quality product.

Happy flying and soft landings!

tomfiorentino

ser00,

I have been building on and off for years; but always used pins on a piece of homosote. I see the limitations of that system though.

This particular project is a Giant Aeromaster; an old kit. Love the old stuff. I've been starring at the box for years, and threatening each year to build it. But I think I am going to have some time coming up so I'm getting my wheels going on it. I'll put either a G62 in it or perhaps a DA60 (it doesnt need all that power though). This is about as big as I go with airplanes.

I recently built a Tiger 60 (second one) with an OS 65AX with my son who is 11. It is his second airplane and he is starting with aerobatics.

I'm finishing a Champ that has a Saito 72 in it.

80" Extra 260 that flies great; but isnt always relaxing for me!

Couple pattern ships; trainers in the barn etc.

More than you probably wanted to know...but

Anyway, if you can get some pictures that would be great! Talk to you later.

Tom

bob_nj

My Feedback: (62)

What do you consider the limitations to the method of using pins on Homosote?

dadragon

Hey Guys;I do my building on a 32x80"hollow core door with a 1"thick sound board on top of it .if you pins that will work fine,I do not use pins,I like tape,rubber bands and weights like sand bags of coarse I like building big birds,like 120"to 150"stuff,mostly warbirds.and that size work platform stays flat and stable.

ser00

Good moring all,

First, to Tom, sorry I didn't get to post pictures last night. My 2.5 month old twin girls decided they needed my full attention and energies last night. Tonight, I will get the pictures posted as soon as I get home. Looking at the giant Aeromaster, is this a kit or an ARF? You are definately going for max power with the DA62, but that is what the throttle is for . It seems to me that you and your son are building planes that range from .60-1.20 size (2-stroke). I think that the large size might be more than you need, considering the largest fixtures are almost 12in tall. The standard size has the largest size at 9.5 inch tall. Remember that these tall ones are used more for the vertical presses than anything else. For me, the 3.5 and 5.5 inch fixtures are useful in building fuselages and various parts of the wings. The 1.5 inches are good for building the tail feathers (actually, the magnet themselves are better for this, as well as aligning the wing ribs to be 90° to the work surface). Now, I do not want to steer you wrong here, but I would give it some thought on getting the standard package instead. Actually, I suggest you make them yourself (it would be a good project for you and your son).
As far as in limitations to the pinning method, let me say that great results can be achieved with this method. My first couple of planes were done using it with great results. Also, it takes some getting use to using magnets after using pins (it requires designing new fixtures such as fixtures designed to hold down the spar to the plans - will include a picture of this tonight). One set of limitiations is that all your pin work occurs at the plan level on the ceiling tile. Any vertical work is very difficult. Also, it is difficult to build a fuselage with pins. With magnets + fixtures, you can build the fuselage with both sides standing up, put in each former standing up, and you can curve the sides of the fuselage as you move from front to back. How many times has somebody built a fuselage that was more straight on one side than the other. As you remove the pin and put it back into the orginal hole, the fit becomes looser and looser, until you have to put the pin somewhere else, creating more holes. Also, putting holes in the wood might be an issue for some (doesn't bother me unless I was using a transparent covering). It is much easier to take the structure apart and do some fine sanding to make the parts fit together better before gluing. Also, if you take some angled aluminum, cut it into 1.5 inch pieces, you can glue the magnet inside the angle and use them to make sure that your ribs are 90° (clamp the angle to the rib or use two angles, one on each side). There are additional irritiation, such as trying to push pins into hard balsa and how many people have jabbed a finger on a pin? Now, I have built using planes with both methods and as I said before, it takes some getting use to. One method does not make one a better builder than one who uses the other method. It is like the debate between using thumbs only or thumbs and forefingers on the control sticks. Which is better? The one that works for you (I use thumbs only but that was how I was taught to fly).

Happy flying and soft landings!

tomfiorentino

Bob,

Well there isn't anything you can't build with that method so it is not limiting in that sense. But I really like the idea of being able to dry fabricate parts with magnets where you can look at everthing all at once, remove, fit and re-fit certain pieces, get everything all lined up and then hit it all with CA while it is under pressure as a unit and all locked together. It seems quicker and more convenient too.

Sometimes when gluing and pinning as I go I may make small errors in the way parts fit that I don't really detect until subsequent parts are fit. Also, sometimes I find that various balsa parts are just not "compliant" and I can't get the right force out of pins to correct it. It's things like that basically.

Does a magnet build make an airplane that flies better? Heck I don't know...I haven't been there yet and I am not necessarily looking for that outcome! I just know what I have done over the years with pins, and from my reading, I can see that pins might not be the best system.

Great question...I was thinking about it last night while I was re-wiring some connections on a computer power supply conversion I did a while back. I was just tinkering with getting the supply in some kind of case with a panel and I got twisted around on the LED light. The thing was switched with on/off...now it's just on when I plug the darn thing in the wall and I can't get back to how I had it wired.

Oh well...

Thanks,

Tom

tomfiorentino

John,

Right on the 1/4" and you are probably right that glass wouldn't work...but a thin piece of transperent mylar? I have to experiement with that....

Tom

JNorton

My Feedback: (2)

Mylar - why didn't I think of that. Great idea. Although I'm so used to just transfering basic build lines and keeping my prints pristine that .... Still I think the idea has a lot of merit.
John

rgburrill

Gee, what happend to my 8 foot long level comment?  Can't build on it but can sure check if your surface is flat.

As for a surface twice now I have built one using birch cabinet grade plywood.  The first one was solid core and was much better than the standard core one I am using now.  And put hard foam insulation (1 inch thick) on top as a surface to stick pins in.  My first one was 12x60 but I now have both a 12x48 and a 24x48.  About $20 in parts.

Sport_Pilot

I had a home made work bench, it was not flat.  I went to Lowes and found some kitchen counter and glued that atop of my old work bench.  I tape a 4x2 ceiling tile to this counter top when I build.  The only problem is clearing off the work bench before starting a project, and not having its use during the project. 

ser00

Hey RG, that 8' level would definately be useful to see whether a door, table or plywood is flat. Was there a reason for buying the long level? As for me, I bought the 6' level for the sole purpose of making sure my tables are flat. I do not even try to level my table either. I know that people say to make sure your table is level, but if your building surface is completely flat and you build with respect to that surface, than everything works out. As far as in setting the wing incidence, I make sure that the horizontal stab is at 0° (or whatever is called for according to the plans) and then set my wing's incidence in relationship to the stab. So, even if my table is 2° higher on one end, I will prop up the tail so the incidence is 0°. Another word of advice, never set the wing incidence using the datum line as reference. Also adjust the the angle of the fuselage to make the stab 0°. I know this all seems long winded but I hope it helps somebody or generate conversation between people to maybe discover a better solution that we all can use. I think when it comes to hollow doors, your mileage will vary. The same is true for solid core doors. What makes one hollow door cost $20 brand new and another hollow door cost $60? It depends on the materials and the construction of the door. The same is true with solid core doors. I think the best workbench that is flat and stable is to create a torsion box. Even a simple torsion box consisting of two high quality plywood pieces with a basic planed 2'x4' structure between them is going to stay flat for many years and take some abuse. I have a 2'x14' workbench along side one wall of my workshop that used hollow doors, covered in hard board, attached to a 2'x4' grid with 2'x'4' legs with a bottom shelf and that table is still flat (and leveled - this I wanted level - do not want things rolling away). I feel that the beauty of this hobby is that there are so many ideas out there to meet whatever needs each of us might have and other people out there to help come up with new solutions to help their fellow modelers. For me, the many build threads that I see here on this site help to not only build my planes better, but whether I want to build a particular plane. For example, the Ultrasport. Minnflyer and RCKen has said so much about it, have threads on it and the following of these threads had me so convinced that I have US1000, US 60 and US 40 that are flying, with 1 US1000, 2 US60 and 2 US40 new in boxes for future builds when needed (okay, I admit it, I am a kit hoarder!)
Also, look around for used items when you build. For example, the steel plate that I have weighs about 50-60 lbs. I got it for $10 at a steel fabrication shop because the customer ordered it and change his mind on the size. Because it was 2 feet wide, the shop had no use for it and was going to scrap it. Their loss, my gain.
Finally, remember that not only do you need a strong magnet (a large magnetic field around it), but you also need to have some thick metal for it to attract to. For example, lets say a magnet has a magnetic field that extends .5 inches from its edge. You place this magnet on a 1/16 in piece of steel. The magnetic field extends 7/8in beyond the metal and pulls on nothing but air. Now, if you put that same magnet on a 1/4in piece of steel, it only extends 1/4in beyond the metal, meaning that more of the field is attracting itself to the steel, hence, the stronger the attraction. This is a very simplified example but if you wanted to build a table with a steel top and cover it with glass, use strongs magnets and make sure your steel top is thick enough.

Happy flying and soft landings!

tomfiorentino

Really? I don't remember hearing about this when guys make mention of what gauge steel is sufficient for magnets. 10 gauge, 16 gauge etc. Have you measured this, read this....details and/or authoritative source would be great (not that you don't know what you are talking about)!

Outside of the obvious, the reason I ask is this. Just the other day I called a precision steel fabrication company out of state based on some website research. I explained to the guy what I was looking to do with a painted, reference line etc. piece of sheet steel. Get this....the guy was a huge RC'er! His first question was..."Why don't you just build with pins?"

Anyway, they specialized in much bigger projects and had an assortment of steel machine table tops made our of various thicknesses from 1/4" to 3" with really small tolerances end to end for flatness...I totally discounted that as way overkill. Besides, shipping cost on a piece of steel that heavy is crazy.

But if the magnetic field statement above has merit, I may be able to get a used steel table somewhere locally (swap sheet etc.) and ditch the pool table slate altogether.

I'm going to do some researching on what you said!

Tom

ser00

Hi Tom,

I remember reading this somewhere a long time ago. I did a quick search and found this article on magnetic flux lines and metal thickness / air thickness. ( http://www.newton.dep.anl.gov/askasc...9/eng99338.htm). I hope it helps a little bit. Also, I did not want to make it seem that you must use a thick piece of metal to get good results. 16 guage, 18 and 20 guage will work just as well for building an airplane. I got lucky (right place at the right time) and got a thick piece of metal which is so heavy that it is not going to warp (as long as it is properlly supported). I have used 18 and 20 gauge metal and attached them to MDF boards and built tail feathers while I am building the wing on the big table. As far as in measuring it, I can tell you that from just feel alone, It is more difficult to pull a fixture off the big table than it is on the smaller boards with the thinner metal. If I had a fishing scale, I could do a comparison on how many pounds of pull I needed to make the fixture come off each. Also, the above reference to the thickness and strength of the magnet was in reference to putting glass over the metal table and having enough attaction for the magnet to be of use. Now of course, I could be wrong, I could have misheard or I could have misunderstood so as with everything on the internet, take it with a grain of salt. If you do find something to prove I am right or wrong, let me know.

P.S. I have found another article on magnetic saturation of steel, the thinner the material, the faster the saturation and thus less the pull. The thicker the material, the longer it takes to get magnetic saturation and the stronger the pull. After a certain thickness, the pull does not get stronger and stays the same, no matter how thick you go. See articel http://www.kjmagnetics.com/blog.asp?...ess-calculator

Here is another article on magnetic saturation http://www.allaboutcircuits.com/vol_1/chpt_14/4.html

Happy flying and soft landings!

MTK

Bob,

I'd use exterior if it's flat enuff. Should be less susciptible to humidity variations.

One thing I tried recently to get a perfect flat surface was to float flooring 2 part acrylic epoxy on a bench. Had to make sure the bench was level of course which was a challenge in the Gay-rage. All kinds of wedges on the feet to get the sucker level. But the epoxy floated well and after about a week of curing in this cold, produced a rather nice product. Just an idea

Firepower R/C

My Feedback: (10)

Just a thought, you could get a thin sheet of clear PETG, put dark graduation marks (grid) on that, paint over the marks with a light colored paint, flip it over and lay it on top of your metal magnet surface. Easily replaceable, too.

I do like the idea of floating floor epoxy... should be perfectly level... right?

bob_nj

My Feedback: (62)

MTK

Elaborate on floating the epoxy on the table.

BDZ65

I built a magnetic building table, using 16ga. galvanized steel sheet on top of particle board. To provide a flat surface I fabricated a frame out of 1.5" steel EZ strut, C-Channel used for construction. I also ordered the magnets suggested on Airfield Models and fabricated several of the jigs shown on the same site. I then build over my plans using a sheet of clear mylar for protection. This is the best building system I have ever used. I believe I paid about $30 for the steel sheet, around $20 for the 1.5" strut, with the price of magnets and particle board I probably have aroung $120 in my system.

Brian

rgburrill

Brand new house falling apart! Needed the level to show that the floor in the kitchen was wavy, the outside wall in the back was bowed and the ceiling in the entry at the main load bearing beam was dropping. But that's another story. The level, however, has come in very handy as a straight edge when checking things like how straight the fuse is and wing warp. A 6 foot would work unless I want to build that 95 inch A-26 Invader. But, of course, I would need a bigger building board

[email protected]

My Feedback: (6)

Hi Tom,
That's funny! I bought my ajusto jig on ebay also. And... it didn't come with the rib alignment tool so I had to make one. Here's some pictures of how I did it. I had the same concern as you about learning how in the process of ruining my first wing (grin). So, I built a smaller plane (an old BF109 kit) first that I wouldn't be as upset about meesing up... but it came out perfect!

I built my zero's stab on the jig first, and then dove into the wing. I'm *very* pleased with the results.

One thing that worked out well, but I'll admit was a total accident, was that the forward rod holes ended up being exactly where I needed to locate the aileron controll rods. I made a mental note to keep this in mind next time when I'm placing the a-just-jig rod holes!

-Skip