Mods-R-Me

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You know that feeling when your present project is 95% done and you see the most attractive aircraft that you just have to build. Right then you have to make a decision, finish the one you're on or follow your hearts desire and start the new one. I choose the latter. This is my new project....



This pic is of a Kingcat, but the problems are:

1. It's an ARF (don't do ARFs)
2. It's a turbine (would like to do it, but way too much $$$$)
3. BVM does not produce it in kit form

This (coupled with my insatiable need to build) inspired me to design my own and like my handle implies heavily modify it. First and foremost I plan to turn it into a 0.90 size cowled pusher prop. If all goes well I will kit the plane and make it available to the public. To keep everything fair and honest I called BVM to ask if I could design and sell a similar design to the Kingcat. Their only requirement is that I do not use "cat" in the name. Awesome guys [sm=thumbup.gif].

Here are the design specs so far:

1. Power Plant: BSE Jett 90L Rear Exhaust (muffler routed through the fuse)
2. Weight: 8-9lbs
3. Wingspan: 50", fuse length: 60"
4. Spring Air 100 Retracts
5. 6 channels (standard four, retracts, and flaps)
6. Airfoil: NACA 0010 root to tip with 1 degree of washout
7. Balsa build-up wings with fiberglass fuse and twin booms
8. The engine will have a custom molded fiberglass cowl
9. The fuel cells will be mounted in the wings

Mods-R-Me

My Feedback: (1)

It's still in the early CAD stages but I have the basic wing designed in Compufoil (figure 1) and exported the rib sketches to Soildworks 2005 (figure 2) to complete the final touches (landing gear, joiners, servos, etc).


Figure 1

Solidworks is a very powerful 3-D design program in which I can design everything down to the very last detail and once that is complete Solidworks can format all the parts in a laser cutter friendly format. It even can transform the 3-D design into 2-D drawings (for plans).


Figure 2

Mods-R-Me

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More progress

Started adding the ply doublers, wing joiner tubes, and spars.

Blade47

Sign me up ...love the idea

krossk

My Feedback: (27)

You guys seen this yet?

[link=http://www.rcuniverse.com/market/item.cfm?itemId=212297]Bobcat .46[/link]

Mods-R-Me

My Feedback: (1)

There's already a thread about it over in the speed planes forum: [link=http://www.rcuniverse.com/forum/m_4580021/tm.htm]CLICK HERE[/link]

Originally, I was going to buy one and make a bunch of modifications to it (listed below), but after a while I figured that it would be better to design a version of this great bird that meets my specifications. In other words; I want to raise the bar a little. It would take quite a few mods to get it the way I'm designing mine now. Particularly the way the exhaust is mounted. My friend has a pusher like that and oil just soaked that side of the aircraft. That's one reason why I'm routing the muffler through the fuse and out the bottom. Also, the engine will be cowled and out of the air stream (much less drag). Don't get me wrong, for the price it's a steal and you better buy two before BVM's lawyers hear about it......

Mods

Mods-R-Me

My Feedback: (1)

Solidworks is a great platform to design in because it allows you to multitask by building different parts at the same time then drag and drop them into the same assembly. Got all of the ply rib doublers (red) and spars attached. Most of the easy stuff is done. Now I have to create virtual renditions of all the parts I want to use (servos, landing gear, engine). The only draw back when starting out in CAD design is having to build up your parts library, but once you have a good one built up designing goes really fast.

Today I tried and focus on the engine mount. DLyons built a pusher a lot like mine (Pic 4) and I'm going to immulate his set up (Pic 3).

Mods

Mods-R-Me

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I'm slowly, but surely, building my Solidworks part library. Just completed the main gear retracts. The plan is to use the Spring Air 701 gear with oleo struts depending on how much clearance there is. Cool thing is that they are fully functional so I can test the clearance when installing them into the wing assembly. Here's a shot of the gear up and gear down.

Mods


Gear Down




Gear Up

Mods-R-Me

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Note: I've decided to build the wing with the top side down to ease the installation of the hardware (the pics aren't upside down).

Just about done with the wing. Finally got the landing gear installed along with the mounting brackets. Decided to go with the offset due to the limited space issues between the spars. Tried really hard to incorporate gear doors in this design but space is a at a premium. Did manage to get the strut totally enclosed in the wing body though. Only have slightly more than 1/3 of the wheel remaining in the airstream but it still looks pretty good . Only things to do now is design the aileron and flap linkage then mirror the other side. The fuse and booms will be molded out of fiberglass so they'll go pretty quick.

More to come,

Mods

Mods-R-Me

My Feedback: (1)

Just had the thread moved over from the scratch builders forum.

Mods

Strykaas

Hi Mods,

The Solidworks screenshots you've posted exemplify your skills... What about the learning curve with this software ? Some of them are rather tricky ... How much does it cost for a home user just like you ? And what is the "laser cutter friendly" format you are referring to ? DXF ?
Do you have any kind of setup to turn your nice Solidworks drawings into CNC milled / laser cut wood ? Or do you plan using some expensive laser cutting service ?
The Su27 is waitiiiiiiiiiiiiiiiiing

Mods-R-Me

My Feedback: (1)

Thanks, but there was not no learning curve with Solidworks. It's very intuitive. To create a part is easy. Just draw a sketch then set the thickness. Tankes 5 min. After making minor changes group them all in a assembly by dragging and dropping the parts in one screen. Then tell the computer which surfaces you want in contact with other surfaces. Think of it like if you were building a plane in reality. You would apply glue to certain places to keep it from moving, do the same thing in Solidworks. The glue points are where the attachements should be. The export format is DXF and I will sent it fro laser cutting to AK-Models. It is not expensive at all. Only draw back with Solidoworks is that a full license costs $4000 BUT a 2 year license only costs $250. It's worth the price IMHO.

I know but this plane got me hooked [sm=bananahead.gif]!

Mods-R-Me

My Feedback: (1)

I went ahead and ordered the BSE Jett 90L for $375. It was a pleasant surprise to find out that Dub can make a counter rotating crank shaft (the prop runs backwards) for only $25.00 extra! Previously, it was necessary to design the entire aircraft around what prop you were using. For pusher props this is ideal because you can now use any regular prop with the engine.

Still on schedule and the wing is about 90% done. Added the leading edge spar (figure 1) and wing bolt tabs (figures 2 & 3). Also began experimenting with the plan maker in Solidworks (figure 4). I had no idea it was this easy. Just hit "make a drawing out of assembly" and presto you have plans. Next select paper size and what views to input. You can even scale the drawings to whatever ratio to make the model bigger or smaller. This is too cool.

Mods

Strykaas

Mods,

Wow I did not know Dub provided that kind of option, that's indeed the best you can do. Poor pusher prop selection really made me give up some really cool designs I just couldn't get to work because of that, not only pusher airframes, but also twin engined a/c for which I wanted counter rotating engines... There existed a pretty good alternative though. Some time ago, engines had a two piece crankcase, and there you coul rotate the front case by 90 deg and voila you had a counter rotating engine... I think these were K&Bs, and Enya. Today, nearly no engine allows that ...

What about the exhaust setup ? Any full length tuned pipe running inside the fuselage ?

Mods-R-Me

My Feedback: (1)

Now that you mention it, I've be doing a few preliminary designs an found that a regular Jett Fire 8" exhaust (figure 1) would be perfect for this bird. It will attach the back of the engine and route through the fuse and exit out the bottom of the wing. I'll CAD it in about a week to better explain what I'm talking about. For the production model, it will probably have the same engine set up as the Keecat and have the one I'm using as an mod option. I have also found that with the short pipe I can mount a 16 oz. fuel tank on top of the wing in-line with the engine and muffler instead of having multiple tanks in the wings as described earlier. Should have about 3" of space between the tip of the muffler and the front of the tank. Shouldn't need to insulate it but I'll know more once testing begins.

More to come,

Mods

Hawk21

My Feedback: (7)

nice work I will like a kit also of this one
very good

Strykaas

Yes very professional approach / work. By the way, Mods, how much time did you spend designing that wing with Solidworks ? Just to give me an idea of the amount of time one should spend ...

Mods-R-Me

My Feedback: (1)

Well that is directly proportional to how much engineering you want to put into the project [sm=angel_smile.gif]. I spend vast amounts time studying kit manuals, aircraft design techniques, airfoil analysis, and alternative materials for a knowledge breath. Then I evaluate building techniques from similar models. I find that the best place to do this is Towerhobbies because they post the manuals (be it limited) for for all of their kits. If I don't find anything useful there: the web is your friend. I can count at least 20 hobby design references in the "favorites" section of my web browser. Finally I put the design ideas into Solidworks to test them out. To answer your question: I spend about 4 hours a day doing research and about 1-2 hours a day actually drawing in Solidworks until the project is done. To give give you an idea why I do this; I graduated college with a Mechanical Engineering degree with an emphasis in design (CAD) only to find a job that requires me to do 0 designing [sm=punching.gif]. This is how I get my creative frustrations out . To answer you question: spend as much time designing to meet your own standards. I'm never satisfied hence the 6 hour a day schedule .

Hope this helps,

Mods

Strykaas

I was starting to think CAD is now dead easy ... I wish you the best with all that dedication [X(] ... and I wish you won't be hooked by another one before you finally maiden it [&:] !

Mods-R-Me

My Feedback: (1)

I have a two project max. I don't have the space to start another one so I'll have to get these two done before even thinking about it [sm=bananahead.gif]. Thanks.

Mods

Mods-R-Me

My Feedback: (1)

The aileron and flap are installed (figures 1 & 2) and fully functional. I worked it so the flight surfaces have a 1/16" gap on both sides to eliminate binding. Tested the full range of movement by having both surfaces in the "crow" configuration: flaps full down and ailerons acting as speed brakes (figures 3 & 4) and they work pretty well. I'm actually running out of stuff to do on the wing.

What's Next?

1. Add hinge blocks
2. Add one more wing tube retention rib


More to come,

Mods

Sparhawk

Looking good Mods.
In the second pcc, you can see all of the ribs lined up, and their building tabs. Are you going to add any washout on the wing, as it looks pretty straight on the TE? Just curious.

BTW - get that Flanker done! You are missing out on a great flying jet. If you saw pics of mine, that Mig29OVT scheme is the best, and has great orientation and visibility in the air. You will kick yourself for not finishing sooner.

Cheers,
Spar

Mods-R-Me

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I only have about 1 degree of washout now. The plan is to stick a low reyolds number airfoil on the wingtip to create aerodynamic washout. This is the same set up on the full size BVM model.

I will finish the Flanker . Should get back into it when I send this one to the kit cutter. Yours does look awesome though.

Mods

Mods-R-Me

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Wing is 99% done and it would be 100% done if it wasn't 2am [sm=what_smile.gif]. Just a few odds and ends left then it's off the start the fuselage! At this rate I should have an operational prototype by Oct. Also talked the Dub and my engine should be ready in 3 weeks. This might be the short pole in my plan because I don't want to get too deep into designing the cowl and fuse until I get detailed measurements off it and into CAD [].

More to come,

Mods

Mods-R-Me

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ANDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD......DONE!

I am happy to report that the wing is complete with all lightening holes, servo compartments, and wing mounting hardware attached. This design will probably go through multiple stages of fine tuning but the bulk of the designing is done (figures 1 & 2). I have only modeled the right wing and center section due my limited 60 inch building table. I will provide plans of the other side as well as the fuse for construction. First thing you'll notice is the amount of light ply (colored red) used in it's construction. In this design there are quite a few high stress area associated with control surfaces, engine mount, and wing mount. To mitigate the additional weight I concentrated most of the lightening holes on the light ply components without sacrificing strength.

For the landing gear mounts, I wanted to design something that would be incorporated into the overall rib design rather than using the standard "block of .25 inch ply and screws" method. It's only six components (figure 3) but incorporated with the gear housing yields a very strong set up. It has to be because I had to remove a small piece of the lower main spar to fit the strut into the fuse [&:] (figure 4).

I've been debating whether to use phenolic (cardboard) or fiberglass wing tubes (figure 5). I decided to use fibergalss tubes from [link=http://www.acp-composites.com/acp-tube.htm]ACP Composites[/link] on the prototype (mine) and leave it as an option for the production model. The wing mounting set up is pretty standard consisting of two .25 in wooden dowels encased in a 3/32 in light ply "box" (figure 5). The conical shaped floor adds lateral strength.

For the crucial components I tried in incorporate build tabs as much as possible. They will ensure precise assembly and can only be attached one way so it will speed assembly. I first learned of this technique building the AKM SU-27 and gleamed a great deal of R/C design knowledge off that kit. This has been a very fulfilling project so far and I recommend designing your own R/C aircraft at least once. I like it so much that it will be hard to go back to kits........


What's Next?

1. The fuselage


More to come,

Mods