jinzo

Looking sweet! [sm=thumbs_up.gif][sm=biggrin.gif] The hinge design is really cool. I'll have to keep it in mind and maybe try modding a plane one day using that.

Relating to what Sparhawk said, I too would like to be on the pre-order list, once you start making one that is. The project is still far from completion, I'm sure, since you still have to prototype it and likely change a few things.

Keep up the awesome work!

Mods-R-Me

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Thanks guys. I am starting a "pre-order" list but please understand that it will be at least Jan 07 before I can start production. The engine will not be here for another two weeks [:@], but this is actually good because it gives me time to evaluate the wing design and make corrections. Most of the exterior CAD work is done and I'm waiting on the engine to complete the fuse. Talking with some Solidworks drivers at work, I've learned quite a few new building techniques. These techniques will greatly increase the clarity and CPU efficiency of the file. Presently, the the wing file is so large that it takes 20-30 sec to load [X(]. I incorporated the new techniques in the stab and elevator and it drastically reduced the build time (5 days vs 1 month for the wing). I'm going to redraw the wing as well in the mean time.

Mods

tuskegee pilot

My Feedback: (37)

Hey Mod:

I am highly interested. Add me to your pre-order list. My 2 emails are: [email protected] and [email protected]

I am in Connecticut. Let me know what is needed. Hey, I have a degree in Mechnical Engineering (Bachelor's). You have pretty imressive skills! I like the fine art of designing your own airplane. I love ARFs but it is something about a beautifully designed kit!

Mods-R-Me

My Feedback: (1)

Hey thanks! How are your Solidworks skills? Also, you might want to PM me your email addresses from now on unless you want a whole bunch of spam.

You're on the list,

Mods

Mods-R-Me

My Feedback: (1)

The new wing model is coming out great. The plans are looking much sharper and the curves are a lot cleaner (figures 1 & 2). Also made one major improvement: removed all washout from the wingtips! Fear not, I found a better alternative. I found it very difficult to keep the same degrees of washout at the wingtip because of the way the wing is constructed (figure 3). I had to cut off the wing tip only to glue it on back on to the wing trailing edge after the aileron is completed and hope it remained the same . Once the tip was glued on there would be no way of accurately checking if the degree of washout. The solution was to use a progressive airfoil.

The way it is assembled will be identical and the wing root will have the same symmetrical (SYM) airfoil as before, but the wingtip will be a semi-symetical (SSYM) airfoil of my own design (figure 4-wingtip airfoil). The shape of the airfoil will geometrically progress from SYM to SSYM the full length of the wing (figure 5). The SSYM airfoil will create more lift than the SYM airfoil, thus causing it to stall later. This will produce the same results as the traditional !QUOT!twisted wing!QUOT! washout method (the controls will become mushy when the wing root stalls, alerting the pilot to add power) but without the headache of using jigs or twisting. Everything is built flat in the building board and when it comes off it's ready to glass and paint (or cover). Should be done with this within the week and the engine should be here this week . Then I can start Phase 2; making the .dxf laser cutter files.

More to come,

Mods

jinzo

That is a very unique way to substitute for washout. Good job!

Speaking of covering the plane, are you designing it with one method more in mind than another? If so, which? I have never done a fabric covering on a plane, though I can't imagine it being too difficult. However, I would think that it would be heavier than a plastic film covering. Now that I'm thinking about covering, I'm already starting to scheme up ideas for a covering pattern/paint job, and I haven't even settled on the scheme for the plane I'm currently building!

Anyways, keep up the awesome work. It will be nice to see a full 3D rendering once you have the SolidWorks modeling complete.

Mods-R-Me

My Feedback: (1)

Good question. I'm going the glassing and paint route myself. The booms and fuse are made out of fiberglass already. The wings will be fully sheeted with balsa. I've seen a few threads on covering fiberglass with monokote and even tried it once.....once [:@]. It can be done, just not by me. To answer your question, either will suffice. Painting would only add 1-2oz by a skilled painter/glasser like yourself. Paint looks far superior to monokote anyway IMHO.

If you think about it, this aircraft is being designed around a 0.90 size Jett engine. The ARF models of this plane fly on 0.46-0.75 engines and are of comparable size and weight to the Modkat. What's a few extra ouces?


LOL [sm=lol.gif] I've been racking my brains on that as well. Just can't seem to "see" it yet. I figured the paint scheme will appear once the plane is built in front of me. To assist the builder, I'm including a clear 2D rendering if the model in the instruction manual to aide in this process.


That will definetly happen! Only reason I have not done it yet is I don't have the hardware layout for the booms and fuse. If I assemble all the parts now I'd probably start moving things around only to have to do it again to make room for a former of something. I find it easier to CAD from the inside out. External problems can be fixed easily. Internal misalignments require an entire redesign [&:].

Mods

Razor-RCU

My Feedback: (50)

Mods- How goes it? Just wanted to keep this thread at the top-

I am a fan

Now get that thing finished already ---- [8D]

Mods-R-Me

My Feedback: (1)

I'm stuck waiting on the engine [:@]. Can't continue until it gets here. Once it does, I can send it off to the kit cutter.

bob27s

My Feedback: (19)

Your patience shall soon be very well rewarded

Mods-R-Me

My Feedback: (1)

Roger that! Talked to Dub today and my engine is being sent out tomorrow! I can start making airplane noises now [sm=shades_smile.gif]

!YEA!

patterndreamer

My Feedback: (1)

Good to hear that everything is falling into place on this plane. I can't wait to see it built and flying.

patternd

Mods-R-Me

My Feedback: (1)

Me Either
__________________________________________________ __________________________________________________ _____________________

The engine will be here tomorrow and I will take plenty of pics

I expect that once the engine gets here the Modkat will be off to the kit cutter in two weeks. Once the design phase is complete, I have to format it into a laser friendly .dxf file. Adhering to the laws of statistics, it will take at least three trips to the kit cutter before I have it in a production quality form.

The design is nearly complete with the exception of the wing servos and control linkages (figure 1). The aileron and flaps use the same "gap-less hinge" technique as the elevator (figure 2-hinge point plan view). The aileron will have a travel of +/- 17 degrees and the flaps will be ~10-20 degrees (figure 3-aileron travel, figure 4-Crow Set Up).

I began estimating the prop ground clearance and was surprised to find that I still have +1 inch even with a 11x7 prop. This translates to about 10 degrees of rotation before the prop smacks the ground on take-off/landing (figure 5). With this in mind, I'm probably going to jerry rig some kind of prop saver to the bottom of the plane. I've managed to get most of the wheel into the wing when the gear is up so I'm happy about that (figure 6).

The project as at the point where I can start thinking of covering options. I was going to use the traditional fiberglass and klass kote combo but I will experiment with another alternative......A friend of mine recommended the Poly Fiber method from [link=http://www.stits.com/]Stits Covering[/link]. I bought the step by step instruction video for evaluation and was thoroughly impressed. It dries quick and all layers are chemically bonded (resists chipping/cracking) rather than mechanically bonded as in fiberglass & paint. The reason for my transition is that the humidity here is +70% at all times of the year and this causes the "fuzz" on all of my paint jobs. Usually, I paint a cowl outside and quickly run inside the house before the fuzz develops. I've resisted painting an entire plane for this very reason []. The Stits system is not affected by humidity or temperature and is about the same price as fiberglassing/klass kote [sm=thumbup.gif]. If the Stits system works as advertised, I'll never go back to Monokote or "shaker cans" again .

Tomorrow the engine arrives!

Mods

Mods-R-Me

My Feedback: (1)

Engine's Here![sm=shades_smile.gif]

The road has some twists and turns on the way here and it turns out I almost didn't have an engine [sm=what_smile.gif]. First lucky coincidence: this engine has a counter rotating crankshaft, which he doesn't make a whole lot of. It just so happens when I first called to order it he had his last two on hand. Second lucky coincidence: the day before the engine was to ship out he placed the crankshafts on the counter and went to lunch. When he came back they were gone. He searched for them the entire day and was just about to call me and cancel the order when he passed a box of regular crankshafts..... On a whim he turned over the box and began sorting them out 1 by 1. After an hour or so, he found them at the bottom of the pile. Turns out that one of is workers was cleaning up, saw the crankshafts, and tossed them in the box [:@]. Third lucky coincidence: he missed the UPS driver on Friday so I would have to wait until the following Friday to get the engine, but on a whim he took the box with him while going to lunch just in case he met a UPS driver on his route, which he did.

Here's some quick pics of the engine, accessories, and a 3D CAD rendition. Since the engine plays such a critical role in the design process, I dusted off the digital caliper and got everything within 0.0001 inches. Also, the throttle arm is fully functional so I can check the linkage for binding. The engine came with the muffler, remote needle valve, cleaning cloth, and spinner. All hand made & pre-tuned for $475 out-the-door. Dub was great on customer service and I would highly recommend buying a Jett engine for yourself.

Mods

bob27s

My Feedback: (19)

some story huh

wait till you get that puppy on the test stand

Mods-R-Me

My Feedback: (1)

Progress So Far....

Phase 2

1. Join the fuse with the wing and making the appropriate mounting cuts- Complete
2. Modifying the shape to accommodate the Jett 90- Complete
3. Finalize fiberglass type and thickness- In Progress

The wing is done (figure 1). Visually, not much has changed from the last version I did except that all the measurements are within 0.0001 in. I got a chance to fit the flap & aileron servo and found that there is not a lot of room in between the ribs (figure 2). This is why I'm going with the [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=000614822&I=LM0950&P=K]Hitec HS-125MG Wing Servo[/link] (figure 3). It has a very small volume, dual ball bearings, and metal gears. I had some doubts about using such a small servo on these surfaces, but after some research I found that the turbine guys use them in their wings as well. Just in case, I will be using a 6.0V power supply to get an extra 10oz of torque out of each servo.

Now comes the assembly of the engine, fuse, and wing. The plan is to use a standard [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&W=000614822&I=LXJ773&P=K]GP 0.60-1.20 engine mount[/link] and cut 2 inch sections off of each arm (figure 4), tap, and bolt them onto the engine mount ribs (figure 5). I left 0.10 in of space on each side of the crankcase to compensate if bigger engine is used. Plywood shims can be epoxied in to snug the fit if desired.

What's Next?

1. The Fuse!

Mods-R-Me

My Feedback: (1)

Mounted the fuse to the wing and cut out space for muffler. Now it's on to the bulkheads. This is going to take a little longer than I thought [&:].

Strykaas

I am impressed each time I check your progress. Even the "professionals" don't go that far in the CAD process I guess... Are you training before moving on to another job ??

I have two questions :

- How will you prevent the rear part of the fuse (around the pipe) from getting burnt ? Exhaust is very hot there... My understanding is that it will be made of fiberglass... not good [&:]

- Are you going to fit a 90 degrees rubber pipe to the rear end of the pipe to get the exhaust under the belly ? I can see no other easy route to avoid a messy rear end fuse ...

Keep up the good work

Mods-R-Me

My Feedback: (1)

Hey thanks,

The fiberglass fuse will be have at least a 1/8" of dead airspace between it and the pipe. The muffler and fuse are closest at the opening. I've mounted a few mufflers the were 1/8" away from the fiberglass cowl without any problems. Here's a pic of the set up (figure 1). The fuse isn't hollowed out yet, but it should give an idea of what I'm talking about.

Good eye! That is exactly what I plan to do. The rubber tubbing will connect to the muffler and through a hole cut in the sheeting that exits out the bottom. I could have modeled that pretty quickly but I'm still in the process of engineering the placement all the hardware. Not a lot of room in there so most of the formers will be pulling double duty supporting the fuse and housing hardware (gear, servos, fuel tank, etc).

Right now I'm fitting the fuel tank. For reliability I'm using a 18 oz tetra bubbles tank. The unknown is can the engine still have constant fuel flow with the tank 8" away from the engine [&:]. There isn't room for a header tank []. I'll set up a the actual engine on the test stand this weekend to find out. If not, I have a few Perry Oscillating Pumps on hand.

Mods

bob27s

My Feedback: (19)

Project is looking great !

You should not have a problem with the tetra tank 8" away. Plus you have the advantage here that nose-up means 'tank high'. Try to avoid the pump. They tend not to work well at higher rpms.

I recommend using an metal tube for the exhaust routing - thin wall aluminum. Ends up much less restrictive than rubber tube for various reasons.

Mods-R-Me

My Feedback: (1)

I was planning on updating the thread when I had the fuse finished but just found out that I'm going out of town for the weekend [sm=frown.gif].

The fuel tank is installed as well as most of the fuse formers (figure 1). The bubbless tank 12 in from the engine and secured with four rubberbands on it's own platform which is epoxied to the fuse (figure 2). Later I'll make a former to sit right in front of the tank to keep it from sliding aft. Been talking with bob27 and should still feed fuel to the engine when the aircraft is in the nose up attitude (when it really counts). I place the steering, retract, and throttle servos in a modular setup (figure 2). This will allow me move the entire assembly for and aft to adjust for CG rather than moving one piece at a time. The tray is secured with three screws and is removable so to access the nose gear and steering servo (figure 3).

Mods

Mods-R-Me

My Feedback: (1)

I'm Back!

The fuse is 95% done with only the canopy formers remaining (figures 1 & 2).

I decided to keep all of the electronics and hardware (i.e. retract fill valve, on/off switch, etc.) internally to keep the aerodynamic shape of the fuse [sm=shades_smile.gif] (figures 3 & 4). I have always favored the MPI power switch over all others since it has a quick charger port, voltmeter, and switch all in one package. The retract actuator is attached to a three panel ply mount that is constructed using one way build tabs.

The muffler mount was a little tricky.... It's a [link=http://www2.towerhobbies.com/cgi-bin/WTI0001P?&I=LXB864]Dave Brown Tuned Pipe Cradle[/link] screwed onto a .5in x .5in x .75in basswood block (colored blue in figure 5). I wanted to keep the "one way only" building process so the mount has a tab that is epoxied into the center wing rib and is secured in between the two 1/8 ply rib doublers. You'll have to cut the slot into the basswood muffler block so I'll include a template of it in the plans.

What's Next?

1. Make formers for canopy
2. Make formers for twin booms
3. Check fit of all parts and pieces
4. Create .DXF files for laser cutter

Be on the look out for the new MRM RC-Models website launching next month. You'll be able to purchase the Modcat there through paypal, receive tech support, and catch updates on future kits that will be available to the public. I'm starting to see daylight!

Mods

Strykaas

Good job !

Still no idea about the "introductory" price ?

Mods-R-Me

My Feedback: (1)

Thanks, but it all depends on the prototype. I can't even give out an estimate (for fear of mis-information) until I at least order the parts [sm=wink_smile.gif]. I will keep the price down as far as possible. I'm not really out to make a bunch of money, just want to produce a quality kit to gain cool points at the field .

jettlag

wow wow wow

nice work