North West Hobby Technologies (Now Jack Devine Models)
P51-D Mustang
Updated can be seen at rcscalebuilder.com
I purchase this model from a man on Rcuniverse. The plane was almost completely sheeted when it arrived. Most of the work I am doing to the model is to make a few modifications. I have a new in the box kit of the NWHT p51-B and I wanted to get some experience on the D model before I started building the B. This is what I started with:
Wings:
Here you can see that the original owner wanted to use Robart mustang retracts. I'm choosing to use a set of SHINDIN MACHINE retracts with an 85 degree pivot block. I had to make a few modifactions to the wing to get the required mounts. Much stronger now though.
I used expanding foam to fill in the blank areas. It really just a poly glue so it should hang on to the existing foam pretty good.
Above: On the left you can see a real mustang leg. Picture taken at the 2003 Boshears fly in. On the right you can see the one of a kind SHINDIN MACHINE leg. Lenny doesn't want to produce these because he doesn't think they look good. He is so busy making 109 and 190 gear he doesn't have time for the American stuff yet. I'm planning on doing some filing on the lower leg to round off the corners and them I'm going to paint them. They'll look awesome. Not to mention they are machined out of solid stock and not cast aluminum.
This is a side view of the left wing panel. I have decided to glass the entire fuselage with .75 or 1.0oz cloth. Then, cover it with chrome monokote and duct tape to simulate the aluminum finish. I will be masking and scratching to simulate panels.
Here is a closer view of the flap/aileron. I installed a TE that extends over the aileron to simulate a more realistic hinge line. Not perfectly scale but much cleaner looking. I tested the monokote to ensure it would stick to the glass/zpoxy and so far so good.
Aileron mpeg (Shows the action)
The wing is glued together now. I've glassed the center section and I'm waiting to finish the control surfaces and servo pockets until I glass the wing. So far the construction has been straight forward and simple. I was confused about the wing attachment method but Jack Devine sent me this email:
"The two hollowed dowels that are used to secure the wing go directly through the bottom of the wing. One is about three inches behind the leading edge and the rear one is about the same distance three inches in front of the trailing edge. You need to measure three times and make sure you have the positions right for the fuselage plates. I use a very long 1/8" drill bit to do the pilot hole and drill through the wing. Before you drill those holes set the fuselage in a cradle upside down and place your drill in the center of the plywood plate in the fuselage and make the angle of the bit as close to 90 degrees as possible. I use a little shop square to do it. Once you have a reference angle for the frill bit have someone hold the drill bit and use a piece of masking tape to put a stripe straight down the side of the fuselage from the wing saddle up toward the cockpit. Eyeballing this will put you right in the ball park because you need a reference line one you set the wing in the saddle because the airfoil shape of the wing takes away your reference to the plate inside the fuselage. With the wing set in the saddle line the bit up in the center of the wing. Measure the wing and draw a reference center line from leading edge to trailing edge or use the tape again. Both dowels need to be in the center of the wing. Once you have the drill bit sitting on the center line of the wing and have a partner hold a weighted string and keep the bit aligned left to right. I just use a big hex nut tied to a piece of string and use it like a plumb bob. It sounds kind of nuts but it works and you will have nice straight holes that accept the wing bolts into the blind nuts very easily. Once your assistant has the line up right viewing it from the front looking back at the tail feathers then you line it up on your tape from a side view and you should be centered on the fuselage plate and level with it too. If you have a drill with the level bubble on the back of it you can use it but the fuselage has to be set up level or you will be off with that method too. Two pair of eyes watching the two important angles takes only a few seconds to line up and drill the pilot hole. If your side tape mark was centered on the plate you should get a nice straight hole right through the middle of the plate. Adjust slightly if you are off but if you are within 1/8" it is plenty close enough and will work just fine. Most people that have problems here have them because they don't take into account that adding the wing to the fuselage totally screws up your level perception and they end up drilling at an angle that is level to the bottom of the wing where they are drilling and the wing is not level because of the airfoil shape and they drill a hole that totally misses the plate. This method sounds a bit corny I know but I have never missed with it and had to drill another hole.
Once you get the pilot hole drilled go up to 1/4" and then up to 1/2". You won't get a real smooth hole but you need to keep the speed on the drill as high as possible. Running it slow rips the foam out and going fast actually shears it. Cover the ends of the dowels with a small piece of scotch tape to keep the epoxy out and fit the dowels onto the wing. Use the slowest curing epoxy you can find (45 Min) to glue them in and rough the outside edge of the dowel with a saw blade so the epoxy gets a good bite on the dowel. I use a little throw away acid brush to make sure plenty of the epoxy gets painted into the hole in the wing.
Push the dowel down into the hole and wipe away any excess epoxy. Tape the dowel in place top and bottom and set the wing aside in a flat level position so that any excess epoxy runs out the bottom and does not get on the model, Trim the dowel flush with the bottom of the wing and I leave about 1/4" sticking out on the top of the wing. Do not round the dowel with the bottom shape of the wing leave it square so it supports the flat washer that is used with the wing bolt. This system works very well and I don't recommend modifying it. The wing will be securely mounted but it will give a bit in the case of a hard landing and it minimizes damage. This has been proven over and over again. Those two steel bolts are very strong. "
Thanks Jack!
Here we see one of the flap. I added balsa to the flap where the robart hinge points will be glued in to add strength. I would have done this before sheeting but I bought this plane partially built and the sheeting was allready added. You can also see the hardwood block I added for the control horn attachment. (Recommended by Jack Devine) The blue stuff is a two part polyester finishing and blending putty. It sands great when it's soft and is light. You can see the can in the upper right hand corner of the picture.
Here you can see the first wing section being glassed. I used zpoxy resin and 1 oz cloth from Ziroli. I still plan on using chrome monokote. Glassing it seems like a waste of time but it makes me feel more secure in the covering. Not to mention warm and fuzzy inside. Notice how much better the retract area looks!
The entire wing is now glassed. I drilled the wing mounting bolts as Jack stated above. It sounds complex but it was real easy.
FUSELAGE:
I started working on the fuse as soon as the wing mounting blocks were done. Immediately I wondered how the I would get the correct location for the tail and cowl. The fuse seemed a little long in the front and I wanted my mustang to look realistic. I used an overhead projector and a three view to get all the distances close.
2/13/04 updates!
I found it difficult to move the cowl over the fuselage the required 2 inches in order to place the spinner in the correct position. If I placed the cowl up against the firewall the nose would be too long. I modified the cowl by cutting it in two pieces. The top piece is permanantly mounted onto the fuselage. The bottom piece can easily be removed in order to make engine adjustments. This is a very similar arrangement to the top flite mustang kits.
In order to blend the fuselage and cowl together I had to use a bit of evercoat glazing putty. This stuff works great even if you use it directly on balsa wood.
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Questions?
More to come:
