The Hours of the Arrow

[kittyfritters]

HOUR ONE

The Black Sheep Squadron had several Arrow kits in the club stock so it was decided, a few meetings back, to have a "Doughback" contest last Sunday. A Doughback contest is where when a member who buys a kit from club stock shows up at a designated contest with the model built from the kit he gets his money back. Thinking this was a good idea, I bought one, and since the Arrow is also eligible for this year's "G" Challenge I could kill two birds with one stone, so to speak. Unfortunately, I procrastinated, with other projects pending, and managed to get sick the week before the contest and so managed not to get my money back.

Anyway, I did get started on it and since the "G" Challenge runs to October 31, I am not procrastinating with that entry. It does not take too long to build an Arrow so I thought to do an hour by hour report on the build.

I opened the factory sealed kit and examined the contents. It was a die-cut kit. From the style of the catalog included, and confirmed by the date stamp on the back of the decal sheet, the kit probably left the factory in December of 2009. (Kits were usually produced about three months after the decals were printed.) It has wooden, not plastic, wheels, and the wood in the kit was a mixed bag. The 1/20" sheets were about 8 pound stock. The 3/32" sheets were 17 pound per cubic foot oak. Strip wood was about 10 pound stock. On the whole this is not bad, since the Arrow has a lot of wing area, having a few heavy parts in it should not affect the flying much.



I reviewed both sides of the plan to decide on my method of attack before pinning it to my building board. The fuselage width at the motor peg is a bit constricted in this design and many builders widen the back end of the fuselage. My decision was to move the motor peg forward a bit. I started with bending the landing gear wire before pinning the plan to the board. The next task was to free the parts from the sheets. I usually sand the back side of die cut sheets with 225 grit production paper (I use 3M.) until the die-cut lines are quite visible. Usually, this works well and the parts mostly fall from the sheets. This worked well on the 1/20" stock, but required too much effort on the 3/32" sheets and I had to use 120 grit. Even then, enough wood fiber remained in the die cuts that I had to use a hobby knife to free the parts.



So, after the first hour's work I was ready to start building.

[kittyfritters]

HOUR TWO

Just in case anyone wondered, I actually do keep a timer on my building table.



Having looked over the plans and decided on some slight modifications; moving the motor peg forward, adding a dethermalizer (In a moment of optimism.) and adding a removable nose plug (Which may be a Gizmo Geezer front end) I finally pinned (thumbtacked) the plans to the board.



I covered the plans with waxed paper and went to work on the tail feathers. Since I don't like to put pins through the parts, if I can avoid it, I use some long push pins that I found at Office Depot. They are longer than the usual office supply push pins, and while not as long as the Czech pins made just for model building, work rather well. Obviously, I don't follow the pin positions indicated on the plan.



Assembling this die-cut kit pointed out another difference between engineering for die cutting and laser cutting. Laying out parts for laser cutting makes it easier to keep the part numbers on every part facing the builder when the parts are pinned to the board. It's a minor point but something I consider when doing my own designs. Anyway, I got the tail feathers rough frames by the 30 minute mark when I had to take a break to feed the cats.



The break ended up being a bit longer than I anticipated but I finally got back to work and started the timer again. In the next half hour I got the wing to the point where I was about to add the top spars. It was tempting to go ahead and finish the wing but I'm sticking to the one hour per day building schedule.



Obviously, that hour does not include posting about it.

[zoomie]

Howard, is Schrodinger helping you with this build? Seems that this project will go faster than normal with two working on it .


zoomie

[kittyfritters]

Zoomie,

Schrodinger and I had a bit of a disagreement over who was going to install the wing spars during hour three of the build, but he ended up seeing it my way.

Howard

[kittyfritters]

HOUR THREE

Starting the third hour, I had a slight disagreement with my cat, Schrodinger, over who was going to install the top spars. After a brief paw swatting exercise at the edge of the building board he saw it my way. After that, I got the spars installed.



Then I set the dihedral angle. The Arrow was intended to be a beginners model, but I think they took it a little far here. I couldn't find anyplace on the plan where they specified the actual dihedral dimension. Instead, they show a dimension on the plan to cut a piece of 1/16" square stock to length and use it to prop up the wing tip to the correct angle.



The also show cutting another piece to length to set the center section dihedral. I measured the two pieces shown on the plan and found that they are exactly the same length! I don't know if you have ever tried to set a dihedral dimension this way using a piece of 1/16" square stock, but it's a bit shaky. My suspicion is that they wanted to do it with material that was already available in the kit. My solution would have been to include a dihedral gage in the 3/32" parts sheet. Since I have an extensive supply of balsa stock I was able to do it in a more stable manner.






I did cut one of the sticks, as shown on the plans, to measure the angle. After the wing dried, immediately since I am working with CA and kicker, I removed the wing and tail feathers from the plans, moved the plans up on the board, (They are just a bit large for this board.) pinned them down again, and covered them with plastic wrap. (I prefer it to waxed paper and had been grocery shopping since I started the build.) The design calls for wing hold down pegs of 1/8" dowel, the same stock as the motor peg. I use 1/8" aluminum tube for motor pegs so I can put the pin on my stooge trough it. I would have used aluminum tube for the wing hold downs also. The holes for the pegs are only suggested by indentations in the wood and I would have used a 1/8", brad point, drill bit to open them up before pinning the parts to the plan, but I decided to use opposing rare earth magnets to hold the wing down. Two 1/8 inch diameter rare earth magnets, facing each other, have a pull of three pounds. Three pairs are more than powerful enough to handle any flight loads on a model this size and will still allow the wing to come off in a bad landing. Besides, not having the rubber band holding the wing on looks so much cleaner.



This is as far as I got in the third hour. Since I am moving the motor peg forward one bay, the next task will be to cut a new motor peg anchor to fit in that spot.

[davidchoate]

I like the magnet idea. I have a RTF Rc trainere that uses magnets to hold the wing on. It works well. Where do you buy those little magnets? I have only been able too find ones that are too big.

[kittyfritters]

I like the magnet idea. I have a RTF Rc trainere that uses magnets to hold the wing on. It works well. Where do you buy those little magnets? I have only been able too find ones that are too big.

I can usually find them at Michael's. They have the quarter inch and eighth inch rare earth magnets on the rack sealed onto cards. Careful that you get the shiny rare earth magnets. The black ones are for craft projects, are heavier and have nowhere near the strength. I have also found them at Radio Shack, if you still have one open near you. There are various sources for them on the Internet also.

Howard

[kittyfritters]

HOUR FOUR

The pattern for the new motor peg mount was made by slipping an index card under the frame at the position it was to go and simply tracing the inside of the frame onto the card with a pen. I cut the traced pattern from the card and used it as a pattern to cut the mounts from 1/16" sheet balsa. They fit exactly.



Now it was time to take the frame off the board. You don't realize how many pins you use until you take them off and line them up on one edge of the board. The pins in the photo were used to hold down one side of the fuselage frame.



A feature of Guillow's kits with box fuselages since the 1930's has been the alignment former. I have found this to be a very good idea since it makes it easy to square up a box fuselage. In this particular case it would have worked much better in the laser cut version since the die cutting on the former was not accurate from side to side and needed some adjusting. I use alignment formers in my own designs with box fuselages.



Before I installed the B2 former I opened it up for better access to the rubber and reinforced the opening. The slightly trapezoidal shape of the hole is deliberate to provide one directional keying for the removable nose plate.






I still haven't decided if I am going to use a Gizmo Geezer front end or simply make an adjustable nose plate for the supplied prop, but either way I made a cross laminated part for the removable nose plate. The face of it will be hardened with 1/64" birch plywood. I've been told that the plywood is a waste of time since the models will not last that long, but I'm still flying a couple that I built eight years ago, so... The B1 former will have the same hole as the B2 former and plywood facing. The key will be on the back of the nose plate. If this had been a scale model I would have shortened the nose of the fuselage by the thickness of the nose plate to keep the dimensions straight, but in this case having the nose an 1/8" longer is not an issue.



My hour is up so I will have to complete the nose plate in the next hour. At least I got the leading and trailing edges of the wing and tail feathers cut to shape and I can put enough of the parts together so that it looks like a plane. Yes, I know that the B3 former is in the wrong place, but it's not glued in, just sitting there. Which brings up another peculiarity in this design. There are formers and cross members the positions of which have to be measured, there are no locating notches and they do not line up with vertical members of the side frames. The plans show the positions, but you have to notice this and take the dimensions off the plan. This is rather peculiar for a beginner's model, but not much of a problem when compared to some of the pre-war designs. Many of them left critical details to the imagination of the builder.

[davidchoate]

I just bought an Arrow. I got A Javelin, but I'm think i'm gonna make the Arrow a RC.

[kittyfritters]

HOUR FIVE

The plan says to sand the rib tails down at the edge of the workbench. I keep a scrap of plywood to put at the edge of my work bench when sanding the edge of parts, like dihedral angles in sheet wings, leading edge rounding, trailing edge tapers, and rib tails.



I didn't really sand the rib tails all the way down to the edge. My hands are still steady enough that I could cut the rib tails extensions off using a hobby knife with a fresh blade and finish with sanding. There are other things to note when you sand one of these. The die cutting is not so accurate that the some of the ribs do not overlap the leading edge. The front of the ribs have to be sanded to match also. Another thing to consider is the "transitions", the points where the 1/16" thick leading and trailing edges meet the 1/20" thick wing and stabilizer tips. A little trimming with a sharp blade followed by sanding makes sure that these awkward points do on show through the covering.



When surface sanding flat parts, such as the tail on this model, I find that putting a piece of sand paper on the bench to rest the part on while sanding keeps it from squirming under the sanding block and breaking joints. I use a circular motion when sanding parts like this since the grain of the components in the part run at different angles.



When you build a 600, 700 or 900 series kit, don't throw away the extra 1/20" parts or the scrap from the 1/20" sheets until the frame is covered. You may break out a part during sanding or handling and have to scab in a piece of scrap to fix it.



As I mentioned before, all the formers and cross members on this fuselage do not meet at the intersections of the verticals on the frame. You have to take the positions of formers B3, B4, B7, and B8 off the side view on the plan. Another thing is that not all the cross members are called out the the section of the plan dealing with the dimensions of the cross members. You have to examine the full side view on the plan very carefully to find where all the cross members are located. The cross member at the bottom of the frame below B9 is not mentioned in the dimensions section and you have to take the dimension off the bottom of the former. Don't get me wrong, Guillow's plans and instructions from this period were about the best available, and the current ones still are, but they have gotten better with the test building and editing since this set of plans was done.



Well, the hour's up, (This is a bit like being in therapy...)and I didn't quite get all the parts on the fuselage. I did get the wings and tail surfaces sanded and ready for covering. When I slip the wing in, where it is supposed to go, it fits with just enough clearance for the covering. This is a good sign!



I have two other models on the bench for the remainder of the day and I have to do some cooking for dinner tonight so more later.

[Mitch]

Howard,

I built one of these a while back. I need to modify my front end as it is impossible to stretch wind the amount of rubber I want to load. And my rear peg position (as per plans) there is not much room back there, I may need to move that as did you. I have one question for you... I can not seem to find the FAC rules for P-30 flyers. Do you know what they are? I have been told that the Arrow meets the criteria of P-30.

Mitch

[Steve Blanchard]

Hey Mitch,

P-30 is an AMA event not FAC. That's why you can't find the rules.

Steve

[kittyfritters]

Howard,

I built one of these a while back. I need to modify my front end as it is impossible to stretch wind the amount of rubber I want to load. And my rear peg position (as per plans) there is not much room back there, I may need to move that as did you. I have one question for you... I can not seem to find the FAC rules for P-30 flyers. Do you know what they are? I have been told that the Arrow meets the criteria of P-30.

Mitch

Just Google "P-30 Rules". Basically, it's 9" plastic prop, cannot exceed 30 inches in any projected dimension, minimum weight 40 grams without rubber, and maximum rubber 10 grams. I was actually considering flying one of my prototype Pilatus Porters as a P-30. (Not the one you saw.) I have a P-30 design converted from my indoor towline glider design with the motor tube of a "Vector" attached, called "Unintended". Have not competed with it yet. Photo is glider before conversion.



It's all balsa and the wing projects to 29.75 inches. The glider weighed 14 grams, and even with adding the rolled motor stick and prop from the Vector, and a dethermalizer, I had to ballast it to get to 40 grams. Probably will be flying it this summer.

[Mitch]

Thanks Guys... Found it. At my 2nd meet I took my Arrow along for fun. I took with me EVERY model I had that was flight ready. People asked me is that a P-30? Now I know! I increased my wingspan as the leading and trailing edge balsa allowed. My ws is just under 30 inches. Longer than my fuselage. My weight is 43 grams. I need to adjust the nose block and pack in 10 grams of rubber and swing a 9 incher. Next Time I am at an FAC/AMA event I will be looking for P-30 challenge! Got to go back to my ship now... sailing to Alaska and I have my Stuka plans laid out on my desk already!

Mitch

PS. I have kits for an Embryo and a Half Awake (1/2 Wakefield) My next endurance models... I might need to learn how to make a DT...

[kittyfritters]

HOUR SIX

The gap in this build made it a bit hard to find where I left off. Anyway, I'm back on track. This has to be finished and flown before October 31 to be entered in the "G" Challenge. I also have a #601 Cessna 180 on my portable board, but that's another thread.

I finally got all the cross pieces and stringers in. If you have a laser cut kit, rather than this die cut one, I'll bet the stringers fit more precisely. I had already bent the landing gear wire so it was a matter of slipping it in place, binding it with thread and gluing it into place.

Somehow, this all took an hour. Part of that was because I was working at the dining room table, not my bench. There is no air conditioning in my garage and the temperature was 102 (F) so I was hiding from the heat.

The next step is to put the magnets in the fuselage and center section of the wing to hold the wing on. After that it's a "simple" matter of sanding, covering , finishing, assembly, trimming and flying. (Right!) I've been taking a considerable ribbing from other guys in the club..."It's just and Arrow. What's taking you so long?"