Mods-R-Me

My Feedback: (1)

This is an ongoing debate between modelers. I'll give you the "Mods" point of view on the subject.

Fiberglass & Paint

Pros
1. Long lasting finish
2. Will not sag with time & lasts as long as the airplane does
3. Adds more durability to paint job

Cons
1. Adds more weight than shrink covering (the amount depends greatly on the experience of the modeler)
2. Requires a bit of practice to get desired results

Monokote (shrink wrap)

Pros
1. Easy to apply
2. Adds minimal weight to aircraft
3. Easy to repair

Cons
1. Sags and requires reheating
2. May/will come off eventually

coolitdown40

I kept fogetting to mention this about cornering the market but here it is. There has been anouther kit like this one on the market for a little bit.

http://www.avia-richmodel.com/englis...iew.asp?ID=771

mmattockx

I agree with Mods views, but I would say that the fiberglass adds significantly to the durability of the model and makes it much more hangar rash resistant in my experience. And MK WILL come off, it's mostly a matter of time...

I will add a third option (in the interest of mass confusion ) - Sig Koverall and paint/dope. It is a polyester fabric that you apply with dope or Balsarite adhesive and is sealed with dope, then painted. It heat shrinks beautifully and does not sag or wrinkle - EVER. If you are willing to paint, it is an excellent option. Finished weight is about the same to 10% more than film if you are careful, it is far tougher than film (but not as tough as 'glass) and very easy to work with. If you have only applied film before, you will be amazed at how nice the Koverall goes on.


Mark

Mods-R-Me

My Feedback: (1)

True, there are other ARFs, but only one KIT. A few people have been drooling over that one for quite some time. I almost bought one but it's an ARF [:'(]. That's one of the main reasons why I started designing my own.



Thanks Mark, I forgot to add Koverall to the equation. I have not tried it yet, but from your discription I will test it out.

coolitdown40

Opps I'm sorry, I was cleaning out my bookmarks and found that, I misstakenly remembered it is a kit without looking at it.

Mods-R-Me

My Feedback: (1)

The build has slowed down a bit due to me constructing the fuse plug, wing, and tail booms simultaneously. I usually update at least once on the weekends but the Modkat is a point where all the components are dependant on each other causing me to multi-task.

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Fuse Plug 4

I'm done sanding [sm=shades_smile.gif] (figure 1)! The fuse is not perfect, but it's good enough to fiberglass. To really fine tune the plug, it must be coated with primer to see all the hi/low spots and divots. Then, fill & sand, fill & sand, fill & sand all over again [sm=drowning.gif]. I will admit that the toughest part of the plug was to get the tail end symmetrical (figure 2). The color difference between the white spackle and grey primer kept playing tricks on my mind or maybe I was going crazy for all the effort, take your pick [sm=bananahead.gif].


Figures 1 & 2


I knew it was time to glass because the Bondo cracked along the edges every time the plug was repositioned. To combat this I beveled all the seams with a sanding block (figure 3). The edges will be built up using a hard mixture of tooling resin after the plug is glassed. This way the seams will be almost as hard as the plug. When fiber glassing, the most important consideration is weather. Epoxy needs to be at 70 degrees and above to cure properly. Also, the humidity needs to be as low as possible (~50% and below). To get a real time reading of the weather, I went to Lowes and purchased a thermometer/humidity gauge for $12 (figure 4). As you can see from the readings, this is not the best day for fiber glassing.


Figures 3 & 4


Solution? A space heater and dehumidifier (figure 5). These units do not need to be very big since I work in a very small area. I got the temp up to 75 degrees and the humidity down to 30% after a few hours- TIME FOR GLASSING! First, I wiped down the plug with alcohol to remove all contaminates (figure 6).


Figures 5 & 6


Next, I covered the top of plug in one layer of 5oz fiberglass cloth (figures 7 & 8). After it became tacky, I flipped the plug over and feathered the edges with an 80 grit sanding block (figure 9). Then, the bottom was glassed (figure 10). I stopped this process here because the wing needs to be completed before the plug sanding begins. There is a large fairing between the fuse and wing. I plan on molding the bottom of the fuse with epoxy and filler to achieve a gapless wing saddle area. This is much easier to do once the wing is sheeted.


Figures 7 & 8


Figures 9 & 10



Wing Construction 2

The outer wing construction is pretty straight forward (figures 1 & 2). One thing that will be instituted in the production model is a self aligning leading edge (LE)/trailing edge (TE). The ribs will slide into notches cut into the LE and TE. This will negate the need to a bunch of "T" pins and 90 degree squares. I guess I forgot to put in that feature while my rushing to get a plane in the air . I did find that the hinge point holes were right on though [sm=thumbs_up.gif] (figure 3).


Figures 1 & 2


Figure 3


What’s Next?

1. Finish left wing panel

2. Install final fuse details


More to come,

Mods

jinzo

I love me some good fiberglassing action. Just checking in. New job is keeping me pretty occupied and all. Very nice so far Mods. [sm=thumbup.gif]

speed lover

Does any one have any info on wing design as I want to design my own plane but have got to the wing root and do not have a clue on what size I should make it is there a guide some where to get more info

Mods-R-Me

My Feedback: (1)

Hello speed lover and welcome to RCU!

Try: [link=http://www.airfieldmodels.com/information_source/index.htm]www.airfieldmodels.com[/link] or [link=http://webpages.charter.net/rcfu/HelpsHints/ModDgn.html]A qiuck "cliff notes" look at rc design[/link]

I highly recommend airfieldmodels. A large chunk of my r/c knowledge was gained from there.

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Wing Construction 3


Summary

The holidays have been busy. This is the first real shop day I've had all week, but it was productive. The other wing is nearly complete. Starting to see daylight.


Construction

The other wing is framed and ready for sheeting (figure 1). The production model will have the wing sheeting pre-cut so I made a template to trace and load the dimensions into CAD using wax paper (figure 2).


Figures 1 & 2


Next, I joined three pieces of 3/32 balsa to match the approximate dimensions of the template and cut out the basic shape (figures 3 & 4). For a step by step tutorial on this process [link=http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/construction/edge_join_balsa_sheet_skins/index.htm]CLICK HERE[/link].


Figures 3 & 4


To attach the sheeting to the wing I used Titebond Alphatic Resin (figure 5). The sheeting is then held in place with clamps and weights until the glue cures (figure 6). In the past I used CA but it does not give enough time to adjust the sheeting for the best fit. The alphatic resin gives you at least 30 min until it sets and creates a very strong bond.


Figures 5 & 6


What's Next?

1. Finish sheeting the wings

2. Attach the wing leading edge

3. Blend the fuse plug with the wing.


More to come,

Mods

speed lover

Cheers got all the info I need I seen the engine and wing area chart and I was planning to put in an engine that was twice the size it should be according to the chart. But the wing loading would work out good at 21oz/ft for a 49" span at 4lbs the engine would be a .46 Irvine just wondering if you could give me your thoughts about this.

Mods-R-Me

My Feedback: (1)

I'm glad you got the information you needed. 21oz sounds o.k. for a sport plane, but that really depands on the wing shape: delta, straight, swept back/forward. Send me a PM and I'll refernece you to some good reading material. Designing a plane is easy once you do the necessary research.
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Wing Construction 4

Summary

Wings Done! There is one low point it in the wing tip sheeting where the build tab didn't come off cleanly, but this is easily repairable.


Construction

First, I removed the build tabs and routed the servo extension wires through the lightening holes in the wing ribs (figure 1). To keep track of what goes where I labeled th eends of each servo extention (figure 2). This makes putting the plane together and connecting all the electronics at the field much easier.


Figures 1 & 2


Second, I constructed the sheeting for the wing top using the same methods demonstrated in the above posts and glued it to the wing ribs using Aliphatic Resin (figures 3 & 4).


Figures 3 & 4


Third, the servo hatches were blended in with the wing sheeting using 60 grit sand paper and the servo heads were taped to the wing sheeting to keep them from damaging the finish (figures 5 & 6).


Figures 5 & 6

Lastly, here are shots of the wing root anf wing tip ribs. You can clearly see how the root is fully symetrical and the tip is semi-symetrical. Looks like all that CAD-ing paid off [sm=shades_smile.gif].


Figures 7 & 8


More to come,

Mods

Mods-R-Me

My Feedback: (1)

Wing Construction 5

Summary

I decided to work on the wing trailing edge and see if the "hidden hinge" technique was do-able. It is possible, but takes a little patience and careful attention to detail. I started a new thread over in the tips and techniques section demonstrating how to install hidden hinges on any wing. Check it out if you want to see how to do it: [link=http://www.rcuniverse.com/forum/m_5125610/anchors_5125610/mpage_1/key_/anchor/tm.htm#5125610]Hidden Hinges Made Easy Thread[/link].


Construction

Since the wing was 90% complete, I decided to build the control surfaces and leading edge. The laser cut 1/32" ply control surface sheeting was held down with weights while the ribs were glued in with CA (figures 1 & 2).


Figures 1 & 2


Second, the control surfaces were separated with scrap 1/16" ply spacers (figure 3). Then, the hinge blocks and leading edge caps were installed and the entire assembly was beveled with a 60 grit sanding block (figure 4). After this the laser cut control surface top was glued on with Aliphatic Resin and held down with weights.


Figures 3 & 4


Third, the wing tip was carefully separated from the control surface assembly with a razor saw and attached to the wing trailing edge using a template generated from Soldiworks (figures 5 & 6). The production plans will have quite a few templates like this to aid in shaping. I found them to be very useful and easy to attach to any surface using 3M Super Spray Adhesive.


Figures 5 & 6


Fourth, the control surface leading edge was attached and sanded to shape (figure 7). Then, the hinge points were installed in the laser cut holes (figure 8).


Figures 7 & 8


Lastly, the flap and aileron were separated using a razor saw and test fit to the wing (figures 9 & 10). Finally, the wing leading edge was attached and sanded to shape using a razor plane.


Figures 9 & 10


Completed Wing




Now that the wing is complete, it's time to sheet the wing center. I used the same technique to sheet the center as I did to sheet the wing (figures 11 & 12).


Figures 11 & 12


What's Next?

1. Route the servo extensions through the center. May dry install the retracts now or wait until the fuse is done.

2. Sheet the top of wing center

3. Fit the fuse plug to the wing


More to come,

Mods

krossk

My Feedback: (27)

Mods,
All I can say to this point is "PHENOMINAL!!!!"
I'm not sure how likely it will be that I venture into this type of aircraft - or even kit design, but I have learned more than I thought possible from follwing this thread. The level of craftsmanship and attention to detail is simply awe-inspiring and should be beneficial to any modeler. And I can see that when you get the prototype finished, you won't even have to worry about an assembly manual - you will already have one of the best ever produced residing right here on RCU! I'm certain you have a real winner in the Modkat.

Mods-R-Me

My Feedback: (1)

You caught me [sm=lol.gif]. That was my plan all along. I was going to copy/paste all the posts and have the manual available for download on the MRM homepage.


Thanks, that's why I do it. It's my way of givign back to RCU. The thread is far from over . Wait until I get to the plugs [&:].

Mods

Mods-R-Me

My Feedback: (1)

Wing Construction 6

Another fulfilling shop day has come to a close with the completion of the wing center. I just realized that it will take (8) 36" servo extensions to link up all the control surfaces and all these wires run through the wing center [X(].


Construction

First, I ran all the servo extension wires through the fuse and secured them in place until the top sheeting is installed (figures 1 & 2).


Figures 1 & 2


Second, the wing bolt pilot holes were drilled into the bottom sheeting (figure 3). My biggest problem with drilling through balsa is that it never leaves a clean hole. This can be countered by finishing the hole with a conical head grinding stone Dremel attachment (figure 4). It leaves the cleanest holes I've ever seen in balsa with minimal effort.


Figures 3 & 4


Third, the top sheeting was applied using the technique in the above posts (figures 5 & 6).


Figures 5 & 6


Fourth, the leading edge was attached and shaped using CAD derived templates (figure 7). I'm so loving the templates. Takes out all the guesswork and makes it so easy to achieve the perfect shape LE. Don't know why I didn't start using them sooner [sm=confused.gif]. Shot of the finished wing center (figure 8).


Figures 7 & 8


Just for grins I had to fit the plug up to the wing center and get some shots. Starting to look like an airplane!






What's Next?

1. Finish the other wing

2. Finish the fuse plug


More to come,

Mods

coolitdown40

Mods,

I'm trying to put a list together of parts needed for this plane to buy them now and so far I've got the BSE FIRE .90L, Robart 520 Tri Gear 90 Deg Rail Mount Nose, (8) 36" servo extensions, and Hitec HS-125MG 2BB Wing Servo U. Also, how many of the flat hitec servos will be needed and will other hardware be included such as control horns, push rods, etc...?

A little off topic but I've been looking it anyone makes (not sure what they are called) rudder/elevator supports. Rods that link the elevator and rudder together. I've searched the internet but with no avail. I have a Sig Fazer and have jimmy rigged my own but it really needs more support with what I do with the plane. It’s been clocked at 70mph level flight ground speed and as it goes by you will see the rudder vibrating violently.

coolitdown40

Oops forgot pics...

Mods-R-Me

My Feedback: (1)

I'll get a Modkat parts list together for you.

Oh, you're talking about flying wires [sm=idea.gif]. Used some of the kevlar type with my beater plane. Here's the link [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXFV30&P=ML]Flying wires[/link].

Hope this helps,

Mods

coolitdown40

Yes that perfect thank you!

Mods-R-Me

My Feedback: (1)

I've been trying to put together a parts list for the Modkat and decided to only list the items that have a 95% or higher chance of being used in the production model. I will add to and complete the list once the protoype has been tested.

Parts List

Servos

1. HS-125MG 2BB: (4)
2. GWS Micro 2BBMG (6)
3. Standard 50oz or greater servo (1)

Servo Extensions

1. 36" servo extensions (8)
2. 24" servo extensions (4*)

* This number will change once I fiber glass the boom sections


Miscellaneous

1. Control Horns* (8)
2. 4-40 Control Rods (?)
3. Flexible Throttle Control Rod (1)
4. 18oz Tetra Bubbless Tank (1)
5. Dave Brown Muffler Cradle (1)
6. Robart 1/8" hinge points (18)

* If you intend on flying beyond 90mph I recommend using the steel control horns linked on page 5.


Landing Gear

1. Robart 520 Tri Gear 90 Deg Rail Mount Nose or Spring Air 701 with Firewall Mounted Nose (1 set)


Engine

1. 0.75-90cc Glow Engine* (1)

*Engine brands vary greatly. I personally fly with Jett engines. The Modkat performs best with 0.90 FIRE with Counter Rotating Crankshaft and exhaust routed through the fuse.

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Made some progress on the color scheme. I was going for; "easily distinguishable at the field" .





More to come,

Mods

coolitdown40

Thanks for the list.

Do you have a better qualtiy blank profile of the ModKat. The one you posted bedfore becomes distored when I try to open it up in any type of photo editing software.

Mods-R-Me

My Feedback: (1)

Strange [sm=confused.gif]. That's the same file I used to create the above paint scheme. I'll try and clean up the profile and email it to you directly. Maybe loading the pic on RCU distorts it slightly?

Mods

bob27s

My Feedback: (19)

Word of note to those perhaps considering the Jett 90 reverse-rotation configuration. Crankshafts for the left hand engines are out of stock. They will remain unavailable for a few months into the new year.

Mods-R-Me

My Feedback: (1)

Thank for the info Bob. A conventional 0.90 FIRE also works, but the prop selection would be limited.

Mods-R-Me

My Feedback: (1)

Moderator please delete: Repost [sm=bananahead.gif]