Warbird Racer Trinity-build
 

This thread will detail my composite building methods duringa simultaneous lay-up of 3different fuselages for the purpose of scale air racing.

This begins in response totrying toensure I have plenty of race planes in the hanger to get me through therace season,and to make the most of my3 weeks of Spring break, I decided to try laying up 3 fiberglass fuselages and cowls simultaneously. Since re-appearing on therace scenewith my composite P-47 a couple weeks ago, I have had a few of my friends ask if they could watch how I lay-up a composite fuse, but some of them are working while I am trying to complete this project, and I have a really small workshop anyway, so I thought I'd take pictures and share the process in this forum, instead. This way, any and allwho might be interested can follow along.

Please realize that I am self-taught. I am a schoolteacher by-trade, not a fabricator. I certainly do<u>NOT</u> claim that this is the best way tocomplete this process.These aremerely methods, that through trial and error (an there has been alot of error!),and<u>NO</u> specialized equipment,give me relatively good results and mostwho see thework view it as successful.While I appreciate feedback on my methods, that is not my intentin this thread. I am merely sharing my methods with my fellow club members and several friends I've made from out of town that are nice enough to regularly attend S.A.M.'s warbird races,that have asked me to do so.These are the reasonswhy I am posting in this forum, rather than in the Composites Fabrication and Repair forum.

There is a "learning curve" to the compositefabricationprocess. Ihave only made 8 fuses, at this point;so I am still learning each time I make a fuse. And yes, IDO have an alterior motive: My hope is that if I share what knowledge I have acquired thus far, perhaps I can shorten that learning curve for others a little, and more of my friends will feel that they can be successful too. The more of us that try this form of modeling, the more our skill sets grow,the more we can all learn from each other, and the bigger the variety of modeling/racing subjects we will see out there. So while I apologize in-advance for my P-51 (Tommy Gun), my intent is to see less ARF P-51s at those races!

So Casey, Dick, Spencer, Steve, and a few others, and Jake who was asking if there were any more of these models coming out
. . . here we go!

I will be attempting the lay-up a P-39, a P-47, and a race-modified P-51 and their respective cowls and other details, all at the same time. I intend to race each of these planesin the Silver class of S.A.M. Warbird Racing events, but they would also be capable of Gold speeds with the right combination of pilot and nitro. (In fact, Dave Sullivan flew my last P-51 to a Gold class victory in the 2008 President's Cup V race.)

RE: Warbird Racer Trinity-build
 

Okay, I learned one lessonalready in this process. . .

Remember to turn the camera from thehighest resolution settings used when taking pictures of planes in-flight, to a lower resolution in order to be able to post them here without having to edit each and every one, first! (So now I'm off toa slow start, already!) http://www.rcuniverse.com/forum/js/f...spinnyeyes.gif

I dusted off my 3 molds, and am already wondering which one to finish first to fill in the hole on my charging rack.

RE: Warbird Racer Trinity-build
 

<u>Step 1</u>: Clean the molds. I take them out to the back yard and spray them down with a hose, then wipe them dry with blue Scott Shop Towels being careful to remove any PVA (Polyvinyl Alcohol) &amp;/or resin left behind from the previous lay-up, without scratching the molds. (I find that CAREFUL use of my fingernail, a popsicle stick, or similar semi-soft material, works relatively well for this.)

<u>Step 2</u>: I'm doin' Mr. Miagi proud! "Wax on . . . Wax off!"
I put a coat of Rexall mold release wax on each of the molds. The directions say only one coatis necessary, but until now I've always done two or three. We'll see in the end if one truly is all that is needed . .. are your fingers crossed, too?!

RE: Warbird Racer Trinity-build
 

<u>Step 3</u>:
After wax is applied, removed, and molds are buffed, allwith the same blue Scotts Shop Towels, it is time to put the molds on my spraying rack and apply a mist coat of PVA. Normally I use the Rexall, pictured below, but have also used TAP Plastics version. Steve Brownjust gave me an 8 oz. bottle (thanks Steve!), and I have a couple ounces left in an old 16 ouncer, too, so will kill off all the TAP Plastics PVA and getthese extra bottles out of my cupboards.

RE: Warbird Racer Trinity-build
 

Gotta wait for the mist coat to dry, so I check on the dogs. Just got a new puppy, and what can I say, I am a proud "PuppyPapa" and "Doggy Dad."

Well . . . until I see the mess they've made in the backyard. The new Great Pyr. puppy has shreddedthe mat outside the door, gutted a stuffed toy, and shredded my whippet's fancysilk collar. It seems that anytime I do something for myself, I end up paying for it, one way or another. I'm a little worried about what else she will havein store for me duringthe course ofthis build.

RE: Warbird Racer Trinity-build
 

Almost forgot to donew cowls. Had to rush and "Mr. Miagi" them quickly, so I can do the rest of the steps with them at the same time as the fuses.</p>

RE: Warbird Racer Trinity-build
 

<u>Step 4</u>:
Apply a little heavier coat of PVA. Let it dry thoroughly (about a half hour in warmer weather). Together, the wax and the PVA form a parting layer between the mold and the fiberglass lay-up of the newly fabricated parts, so they can be removed, and not permanently adhere to the mold.


<u>Step 5</u>:
Apply a heavy "flow coat" of PVA. You want it wet enough that it flows together and forms a continuous and even film. Butbe careful . . . there is a fine line between this, and causing runs. Any runs will show in your final product and will need to be filled and sanded. However, I find that the PVA makes any defects so smooth and gradualthat most spot fillers have nothing to "grab" onto, and end up coming offwhen trying to sand the imperfection out. So,if runs do happen, instead, I find it better to just start over, beings I am still at arelatively early point in the process.

RE: Warbird Racer Trinity-build
 

Great Thread so far Ollie:

How did you aquire the molds, or should that be saved for an entirely new thread?

3 weeks for spring break, man I am teaching at the wrong high school!

RE: Warbird Racer Trinity-build
 

Nice Job I.D.!!! I always admire how precise and clean your work is!

RE: Warbird Racer Trinity-build
 

Thanks guys!

Yes Jake, being a year-round elementary school teacher does have certain advantages!

To answer your question, the molds are each made from a plug that must be fabricated first. Generally, these represent original designs:

The P-47 was my first, and was a scratch build. It uses the same airfoil as the former Air-Kill kit, but the fuselagewas a complete re-design. After drawing out my plans, I constructed the fuse by cutting sections in white foam. The sections were sheeted and then glued together. Seams were filled and sanded, so that each section blended smoothly to the next. Then the plug was fiberglassed, sanded, primed . . . filled, sanded, primed . . . filled, sanded . . . (you get the idea).I wish I couldsay that whenIwashappy with the results, I used the plug to make a 2-piece, clamshell-type mold . . . But the reality is that the more I work on trying to getthat last imperfection out,it tend toaccidentally bang the mold against thearm of the chairI'm sitting on. Or,catch the corner of the sanding block on it. At one point, my wife kicked me out of the garage because she was tired of the fumes from the primer, so I had to take it outside in the July heat and sun. BIG MISTAKE! The foam inside the darkly primered plug expaned in the heat of the direct summer sun. JustasI thought it was perfect andtook it back to the garage and broke forlunch, I returned to find every seam between each section visiblefrom different rates of expansion and cooling off. This meant filling and refinishing all over again. (I toldyou there was alot of trial and error . . . with WAYto much error in this learning curve.)At this point, I inevitably ended up puting another ding in the plug, while trying to fix that last imperfection. So, at some point I just have to say, "I can't get too greedy, that's as good as it is going to get", and move on. No one ever seems to notice those slight "boo-boos" anyway; we always tend to be our own worst critics.

The plug for the P-51originated from a crashed and shattered Dago Red fuse that one of the racers that visited us from Concord wrecked at one of the SAM warbird races in 2006. I was intriqued by the U-shaped design, and the resulting ease I saw of laying out all the internals and wanted to trythis method of constructionout, without having to start from scratch. I told him that I thought I could fix it and use it to make a plug. I told him that if he'd let me try, I'd give him the first fuse from the mold. I changed some things about it in order to make it a "Red Baron" P-51. I see why that manufacturer covers their fuses in plastic covering, the finish quality of the fiberglass work was horrible! It took alot more work than I thought it would to make a usable plug, and gave me confidence in my own abilities seeing that my work was of a better quality than that of a "professional". The 2-piece cowl is from a plug I made that was intended to replace the oldKyosho Spitfire .40 so that it would be long enough to house 91 - 110 engines. It just happened to fit perfectly, and look more likethe Red Baron's cowl, anyway. After it was completed, all that season, I brought the prototype fuse to the races, but the guy never returned to pick it up. Eventually, I gave up and finally decided to finish it myself, and race it in the Silver class during the first heat of the Spring Fling race in 2007. I suffered a dead-stickat the end of the very first heat,and a visitingpilot refused toabort his landing approach,so I was forced to put it down in the rough. Damage was relatively minor, but I did not trust the repaired wing mount blocks to hold long-term under the stresses, so I gave the fuse away. That is the red, yellow, and blue P-51 pictured below.

The P-39 plans were drawn from Paul Matt's scale drawings. This time I used open-celled foam without balsa formers in the middle (I learned from the mistakes of the P-47). This particular type of open-celled foam (called "Polyisocyanurate") can not be cut with a hot-wire, but it sands easily. However, a high-quality filtering mask must be worn while sanding, and the dust gets EVERYWHERE and can be ratheritchy andirritating.* But I thinkthe results are wellworth the inconveniences!This time, I tried incorporating hatches to make fusing the halves together and internal linkages and radio installation easier. (I always try something different each timeso I can continue to learn and evolve my techniques.) I detailed much of the process under the "P-39 Anything Thread", and will attempt to post a link (I haven't done this before, so it may not work). These details begin on pg. #7 of the thread, if you are interested in the specifics.
http://www.rcuniverse.com/forum/fb.a...747365&amp;key=

* <u>Note</u>: My friend Steve Nickerson found a blue foam called "Schedule 40" that he is very happy with. It can be cut with a hot-wire and sands relatively easily. It is also dense enough that it does not get dinged up quite as severely. I am going to give this stuff a try, next time.

RE: Warbird Racer Trinity-build
 

<u>Step 5</u> (continued):

When spraying on the PVA make sure that there is not too much air in the mix of the spray gun settings. If the PVA goes on dry, without forming a flowcoat, it will leave a rough, pitted finish on the final product.Getting it right takes some practice, but if you are conservative, you will likely have good results from the beginning.Rather thanspray it on too heavy and get runs, spray repeated light coats untilit is just slightly wetand begins to flow together.

After the PVA has thoroughly dried for at least 45 mins., it is time to start the actual lay-up.


<u>Step 6</u>:

I like to start byapplying a thinned-down layer of epoxy over the entire surface of themold(except the flat flanges); and, letting that partially cure out (usually overnight, as it has usuallytaken me all of my first day to get to this point anyway). While many might view this as extra weight (as epoxy, by itself, does not add strength), as explained below, I think the penalty is worth it:
1. The layer of PVA is extremely fragile.Even aslight touch can frequently scratch, remove,or pull the PVA away from the mold surface. This THIN layer of epoxy protects the PVA.This extra protection is especially important when filling the radius of sharp corners with microballoons in the next step, wiping up drips, etc.
2.Without this initial layer, I find that there are too many pinholes. Priming, filling, and sanding to fix these pinholes end up adding most of any weight savings back on, anyway; plus, then you have extra steps to complete which adds extra time, mess and expense to the project, as well.
3. This layer also gives me just a little something to sand to help even/smooth things out when needed, without immediately sanding into the cloth.

As stated previously, I always have to try something different. This time, I tried spraying on my thinned epoxy layer using my compressor and an old detail gun. I thought this might make it go on smoother, eliminate air bubbles that I am always trying to brush out otherwise, and speed up the process beings I am foolishly doing 3 at a time. In my opinion, it wasn't worth it:
1. It was too hard to clean the epoxy out of the detail gun, so time saved resulted in extra time cleaning up.
2. I forgot to take off my new glasses (Man!, getting older really sucks!) The overspray coated everything, including my new glasses.
3. It didn't flow together quite as well as I had hoped.
4.Now I have epoxy on the flanges, too! Oops, I didn't think about that outcome before I did it. http://www.rcuniverse.com/forum/js/f.../msn/71_71.gif That may come back to bite me big-time when I need to clean up the molds prior to their next use. I have found that epoxy alone, without fiberglass backing It up, tends to not come off of the mold surface very easily.

<u>So, bottom line</u>: my normal method of merely brushing the initial layer of epoxy is the better method of the two.

The pictures below are the molds completed up to this point:
1. First is the P-47 (the round, stubbyfuse with no incorporation of a vertical fin make it easy to identlfy)
2. Second is the P-51 (the open bottom and 2-piece cowl make it easy to identify)
3. Third is the P-39 (this is a round fuse, like the P-47, but incorporates a vertical fin and hatches into the structure)
Pictures 4 &amp; 5 are all the molds lined up.

RE: Warbird Racer Trinity-build
 

Life is already getting in the way, and my progress is slower than I had hoped. In composite work, life revolves around cure rates. I need to have a good 3 - 4 days to complete from start to finish. It is hard enough doing one, when family has their needs to be met, too. Now I am doing 3, AND spending alot of time to write this all up and document the process.

So, I guess this means I get to try something else new this time too . . . "Will I still get a good chemical bond between layers if I am later getting to each progressivestep, beyond what I would consider optimal cure rates?"

Well, we are about to find out.

Jake, you asked about how I aquired the molds. I told you about designing the P-39 from Paul Matt's scale drawings. This is the book that the drawings originated from. (pics 1 &amp; 2)

Also included are some pictures of the materials I am using in this build.

RE: Warbird Racer Trinity-build
 

Were I just laying up one fuse, I'd use the "Slow" (West System #206) hardener. But during hot weather, or in this case with 3 fuses, I need extra work time (or "pot life"), so I'm using the "Extra Slow" (#209) hardener.

I also found the cups for cheap at Smart and Final. I find that using wide, shallow containers, rather than tall,narrow ones,keeps the epoxy from "firing off" too quickly, and will also give me those crucial extra few minutes of working time.

The blue Scotts Workshop Towels are pictured. I tend to cut each sheet in quarters and use these quarter-sheets for wiping, waxing, and buffing my molds.

I use a combination of flux brushes and the 1" brushes (pictured above) to apply resin. I generally use the flux brushes for fabrication of smaller parts like cowls and hatches, and getting into tighter spaces of the mold (wing fillets, corners, etc.). The 1" brushes are great for applying larger amounts of epoxy and quickly wetting-out the cloth when applying layers of cloth to the entire mold surface.

I believe that pinholes are most commonly caused by not sufficiently filling the weave of the cloth with epoxy. I eliminate alot of this with the initial thinned coat that I detailed previously. But, I almost forgot to mention that when you mix the initial, thinnedlayer of epoxy, you need to VERY GENTLY stir parts A and B together. If you stir to quickly, you will mix in aslough of air bubbles that will take considerable time to brush out and hopefully be able to pop so you don't end up with these bubbles causing pinholes that were supposed to be eliminated by this step. Pictured below is a cup that I stirred quickly. Note all the air bubbles that are visible if you look carefully. (Don't worry, this batch is the 2nd batch and is about to get microballoons mixed into it for the next step, anyway. You don't have to be so careful mixing after the initial layer.)

RE: Warbird Racer Trinity-build
 

Sorry,

I've gotten a little behind in posting my progress. I'll try not to get too far behind.

<u>Step 7</u>:

Once the initial thinned layer of epoxy has set up, we can get to the fun stuff. Next, mix microballoons into the resin and use this filler material to fill in and smooth out sharp edges in the mold. Each type of cloth has its own idiosyncracies, but most fiberglass cloth will conform pretty well to compound curves (this is why it is such a popular choice for scale construction these days), but it definitely has its limitations. It does notconform tosharp corners well. Especiallywith the type of "hand-layup" construction methods I am detailing in this thread. It would do better under the pressure of vacuum bagging, but that requires specialized equipment and a whole other learning curve that I haven't gotten to, yet; and, some that I have talked to state that they still have serious problems with the cloth laying down in the corners. I've learned to stop fighting it and just radius the corners and fill in (at least partially) other details with microballoons and resin.

As microballoons are added to the resin, it becomes more opaque. The higher the microballoons to resin ratio the: 1) lighterthe filler material becomes, 2) the easier to sand it becomes, 3) the thicker the mixture becomes, 4) the more delicate it becomes. (And vice-versa.) Different ratios have different uses in the process. More viscous mixes are better for flowing easier into- andfilling in- sharp edges (such as the thinnest parts of a wing fillet), but the mold must be supported such that the mixture stays where you want it until it jsut starts to cure. Somewhat thicker mixes are better for holding the shape of radiused corners. I've read that a ketchup consistency is good, but have found that if you want the mix to stay where you put it reasonably well, while having the filler still be workable, (It is going to settle on you somewhat. Just accept it. You are never going to totally override gravity!) get itto a consistency where it behavesalmost more like merangue(I hope you guys are cooks out there, or that analagy won't help at all). http://www.rcuniverse.com/forum/js/f...eeth_smile.gif In other words, it will almost tend to hold stiff peaks, only very slowly settling under its own weight slightly. I included a picture to demonstrate what this might look like. Realize that some applications will require thinner mixes that this. You just have to play around with it and see what happens. If it is too thin for your application, slowlymix inmore microballoons. If it is too thick, add more resin.

. . . OH yeah,did I mention that:
1. I recommend that you always wear gloves when working with epoxy. Research has shown that excessive skin contact leads to an allergic reaction to epoxy (I believe that this is withworking professionalswho have much more exposure to these chemicals that most of us hobbyists; but why take the chance when clean up is so much faster and convenient. Like whenyouhave to answer the phone continuously because: thewifekeeps calling to remind you about stuff on the "honey-do" list .. .and all your friends keep calling to find out how the project is going, and want to know when you are going to get more posted on the fabrication process. . . and you have to keep taking pictures and don't want to get epoxy all over your expensive camera . . . trust me and just wear the gloves, already! http://www.rcuniverse.com/forum/js/f...wink_smile.gif

2.It is a good idea to thoroughly mix your resin first, before adding any other fillers.

3. Then pour a little of the resinin another cup. This has two benefits. First,the shallower the resin level, thelonger the pot life (working time); and, second, this wayyou have extra resin to thin down your mix ifyou get to aggressivewith the ratio of microballoons.

RE: Warbird Racer Trinity-build
 

<u>Step 8</u>:

Use your microballoons mixture to start filling in areas with sharp, compound curves; narrow, hard to get to areas; and to radius those corners.

Pictured first, below, is the cowl mold for the P-47. Most radial engined planes have cowls with a sharplyradiused,compound curve. It is easier just to fill most of this in and soften the curve enough that the cloth will conform and lay down nicely.


One suggestion to avoid one of my rookie mistakes:

To avoid air bubbles getting trapped underneath and thenshowing up on whatwill end up being on the exterior of your finished cowl, do not pour blobs of filler at various places around the curve. Use gravity and the weight of the mixture to your advantage by pouring slowlyin one spot, directly over the epoxy that is already there. Angle the mold sothe expoxy spreads out. As it does,it will automatically displace the air without any getting trapped below the weight and thickness of the epoxy, unable to escape.

RE: Warbird Racer Trinity-build
 

<u>Step 8</u>: (continued)

Use your microballoons mixture to start filling in areas with sharp, compound curves; narrow, hard to get to areas; and to radius those corners.

Pictured below, is my P-39 cowl. Here, I am using a flux brush to "paint" the filler materialin the corner and up the sides just a little. Remember, even if it is relatively thick, gravity will want to make this stuff settle in the bottom, somewhat.

One of the things I learned to do is to paint it up the sides a little (don't get too carried awayoryou are just adding dead weight), so that when it does settle to the bottom slowly, it will pool a most at the bottom,and a little less and less the higher you go up the sides. In other words, itends up withthat gentle curve to radius the corner, just as I wanted.

RE: Warbird Racer Trinity-build
 

<u>Step 8</u>: (continued)

Use your microballoons mixture to start filling in areas with sharp, compound curves; narrow, hard to get to areas; and to radius those corners.

Pictured below, is me radiusing the corner of the leading edge (spinner backplate area) of my Spitfire/"Red Baron" P-51 2-part cowl, using a flux brush.

RE: Warbird Racer Trinity-build
 

<u>Step 8</u>: (continued)

Use your microballoons mixture to start filling in areas with sharp, compound curves; narrow, hard to get to areas; and to radius those corners.

Now I'm begining to work on the fuses. Pictured below, is me filling in the sharp angles around the tail section of my P-39.

The first picture shows both halves of the mold. Note the sharp angles and compound curves around the recessed stab in my mold on the left side, and how I am able to fill in and smooth them out on the right side.

The second picture shows how I use the curvature of the end of a popsicle stick to form a smooth radius in the corners. If you want a bigger radius, use a tongue depresser, rounded rubber squeegee, or similar relatively soft material. Note that I am gently scraping the sides of the mold. Had I not putthat thinnedlayer of epoxy down, I'd be scraping up my PVA now. See, there <u>IS</u> a method to my madness!

The third picture shows the "trail" of filler left at each side of the radius that will need to be cleaned up or smoothed out; or this could cause trouble with getting the F.G. (fiberglass) cloth to lie down cleanly.

RE: Warbird Racer Trinity-build
 

<u>Step 8</u>: (continued)

Use your microballoons mixture to start filling in areas with sharp, compound curves; narrow, hard to get to areas; and to radius those corners.

More pictures ofme filling in the sharp angles around the tail section of my P-39:

The first picture shows what it looks like after I used the flux brush to gently push the excess material back into the radius, the brushed smooth any remaining residue. I repeatedly run the popsicle stick over this area to ensure the entire corner is completely filled-in smoothly, while occasionally cleaning off the excess material that builds up on the stick, before it accumulates enough to deposit material in a new "trail" outside of the area I want it. Notice that the side of the fuse (bottom of the pic) is cleaned up, but the T.E. of the fuse (rudder post area) still needs to be cleaned up, too.

The second picture shows both areas cleaned up; and now this one area of this mold half is complete. However, there is still a lot left tofinish up. . .

RE: Warbird Racer Trinity-build
 

<u>Step 8</u>: (continued)

Use your microballoons mixture to start filling in areas with sharp, compound curves; narrow, hard to get to areas; and to radius those corners.

Now it is time to beginfilling in thewing filletsof my P-39.

Notice I poured a thinner, runnier, batch of microballoons and resin for this application. I start to pour it in on a higher spot and let it slowly creep into the crevice and displace the air so that I get a nice SHARP finish quality line on my fillet when it is popped out of the mold. There is NO WAY I have figured out to get the cloth to accurately and completelyfill in such a tight space.

And "yes", that is an accidentaldrip of filler materialon the curvewherethefillet meets theside ofthe fuse. Notice in the second picture that the filler is spreading out and filling in the fillet. Also the drip has been wiped up so that the cloth will lay down nice and smooth. Again, had I not put a thinned layer of epoxy first,and let that start to cure out, I would have pulledup my PVA and ruined all the work up to this point;or, I'd have to leave the drip and likely have problems withgetting theupcoming layers of FG cloth to conform around it nicely and hurting thequality of the finished product.

RE: Warbird Racer Trinity-build
 

<u>Step 8</u>: (continued)

Use your microballoons mixture to start filling in areas with sharp, compound curves; narrow, hard to get to areas; and to radius those corners.

Finally, I am donefilling in thewing filletsof the left half ofmy P-39.

RE: Warbird Racer Trinity-build
 

<u>Step 8</u>: (continued)

Use your microballoons mixture to start filling in areas with sharp, compound curves; narrow, hard to get to areas; and to radius those corners.

Now the righthalf ofmy P-39 is underway (picture 1), and done (picture 2). Finally!

Note that the mold halvesneed to be angled andbraced so that the material does not flow right back out of the area you want it to fill in.

RE: Warbird Racer Trinity-build
 

Here's the P-39 all ready for the application of cloth. The microballoons and resin filler have "set" enough that I can now lay the mold halves out flaton my work table.

RE: Warbird Racer Trinity-build
 

I followed similar processes to complete my other two fuses.

Here's the P-51 mold halves all prepped andready for the application of FG cloth.

Being less scale, it has simpler lines and is easier to get to this stage. (The microballoons and resin filler have "set" enough that I can now lay the mold halves out flaton my work table.)

RE: Warbird Racer Trinity-build
 

Here's the P-47 mold halves all prepped andready for the application of FG cloth.