Props4ever

This cowl plug is for my S Connie model, now after waiting for 2 years, i had enough and want to take on this challenge myself with some help and guidance from you guys.
I want to make epoxy mold as i like using epoxy resins over polys. There will be 6 cowls to be made from this mold, so it could be light molds vs commercial type heavy mold. It's not the easiest cowl to be molded but this is what i made and want to use it. 3 part It's more like a part then a plug as i have been told before but i have good idea where to make separations as main cowl will be 4 piece, aft cowl will 1 pce and not sure if lower air scoop fairing should be 2 pce or 3.

I'm posting pictures of this plug for you to see and post ur suggestions how you think is the easiest and fast way to mold this up. I don't want to break this plug as this is all i have!. I will use mold release agent before initial layup but not sure if i need PVA or one i have on hand will do the job. One i have is rubber mold release in a spray bomb...

Props4ever

Back of the main plug, you can see how cowl flaps will be, so these might where undercut situation may arise.

Back part of the main cowl plug
Aft cowl plug (Like a doughnut)
Lower air scoop

ARUP

Relieve foam from the inside and install a smooth disc faired into the nose ring. Plug has to be slick. Paint it, wax it, stick it to a parting board, Klean-Klay the plug to board junction, apply mold release, lay on the resin and cloth, wait for proper cure, remove parting board and then pop plug from mold. The plug looks like it may have to be made in at least two parts for it appears the mid section circumference is slightly larger than the aft end's circumference. Even if it is a perfect cylinder it would need to be made in two parts. You need a certain amount of 'relief angle' from the parting board in order to create a one piece mold.I have a tutorial on RCScalebuilder. I made a cowl for a 1/4 DH-5 which is in 'scratchbuilds'.

Props4ever

So ur are suggesting that i burn the foam from inside first and the block the lip from inside and start from there.
Another thing i should mention here is that, i didn't used fiberglass cloth on this plug, what you see is few layers of epoxy resin only, so if i go with your suggestion, will resin alone will hold it's shape or will it get distorted as i will burn the foam
with gasoline....

Other thing is, i'm not on rcscalebuilders site anymore, so how can your tutorial be seen with paying for that site.

ARUP

Just manually remove the chunks of foam with resin overlay to expose uncoated foam then get a conically shaped wire brush in a hand drill or, preferably in a drill press, to do the rest. To protect the inside lip of the nose ring for this operation lay on a lot of masking tape. I have made molds without sealing the end but you have to be careful to not get glass and resin in that area or it makes it extremely difficult for plug removal.

Props4ever

Main cowl plug piece has been hollowed out, while doing that and breaking off the flash from the inside of the intake lip, one section got slightly damaged that now needs fixing.
Also going to review to see if i still need to keep the exhaust outlet bases or not for the dummy scale exhaust stacks. Also i need to figure out if i still need small support edges behind the flap doors or not. I don't think actual cowl flaps are supported this way. Pictures in second line are of exhaust port bases on which i would stick scale dummy exhaust stacks.

ARUP

After you have slicked up, painted and waxed the cowl measure across the nose of the cowl where a balsa disc can be eased into the inside lip, approaching from the front. The smaller the disc the deeper it will lay into the cowl. Make sense? Remove balsa disc and put a nice Monokote job (it's a great 'release' agent) on it leaving the edges clear. The edges will get glued to cowl nose ring. Klean Klay can be used to fillet the intersection of disc and nose ring. Your plug has some cutouts for leading edge of wing??? If you make cowl full depth you can relieve it to clear the wing after a part is pulled from mold. Do you have a drawing for the parts you need? You may need to make multiple and or split molds. Hope this info is helpful.

Props4ever

I understood first part of your reply but this above is sorta going above me....lol

Pls explain it again, cowl Vs LE of the wing.....hmmm

This cowl goes on the nacelle, so where does wing comes in between....

Well what you see in the pics above parts are what i need to make copies off, yes i do have drawing of actual aircraft's cowls but why those for..

Yes this main cowl's body will be molded in split sections no doubt about it, that i know and i also know how i would split the sections of it to make separate molds. Now this dosen't mean by cutting the plug at all, i meant by placing parting boards.

invertmast

My Feedback: (23)

Not the way i would have done it, but ill be watching to see how it turns out..

ARUP

I'm not familiar w Connies so can't picture the whole cowl. I don't understand the trailing edge or rear of cowl as your plug is with those open spaces and all. A 3-view of the cowl etc helps me visualize what is needed to make the part. You will have to make a plug for the cowl and a plug for the firewall nose bowl if that is what is sitting behind the cowl. That would be the easiest way instead of trying to mold the whole irregular plug. Just think how the full scale parts were made. Have you gone over the tutorial I have in the 'scratchbuilds' thread on RCScalebuilder for my DH-5? It shows everything about this process except I used polyester resin. It is very easy to make the plugs with this process. There are some different ways to do this but this works well for me and I have made many nose bowls and cowls. If I was going to make this, as I see it, I would turn the cowl on my homemade 'lathe', make it perfect with resin and sanding then add the intake. A mold would be pulled from this plug. The rear firewall nose bowl (?) would be its own separate plug. This cowl WILL get done!

Props4ever

I'll post pics of real aircraft's cowls no biggie there for you to understand. Yes firewall nose bowl will separate piece to be molded and that's why i made it separate from the front main cowl part.

Yes i would make make a mold of intake lip and leading edge of the cowl ring as one mold by placing parting board on first green line which will include front part of top air scoop.

I would then place parting board in the top center of this plug from front to back and to 2 molds of both left and right side. Only thing that bothers me are the exhaust port bases, two of left side and one on right side. If the the mold would seprate from the plug with out damaging the plug in those areas, then i'd be very happy to do it in 2 halfs.

Props4ever

Thomas get int there and suggest how you would go around it, just keep in mind this is only plug i have and this all i want to make molds from.
It's done all by hand and took long time, so not willing to do another plug...

http://www.rcuniverse.com/forum/m_45...17/key_/tm.htm

Props4ever

Pictures of actual aircraft cowls and my plug on my model's nacelles to illustrate how they are suppose to be.

Props4ever

Another set of pictures...

invertmast

My Feedback: (23)

I would of glassed the foam plugged, then primed sanded, filled, paint, etc to where it was as perfect as possible, you could of even put in rivet and panel line details.
then the nose bowl area could of been 1 portion of the mold, then split the cowl down the center. The aft ring would ha e to be done separatley, and the lower scoop separate as well. For the exhaust cutouts, you can fill those in with none drying modeeling clay so the plug can stand up vertically on a parting plane base.

There are many different ways to do it, and you just gotta figure out how to go about doing it.

ARUP

I see now. The cowl flaps have clearances for the exhaust outlets. The scoop on top and bottom is an addition. Your plug will require 'dams' around the cutouts. Kinda like a parting board but there is no way it can be flat unless you fill in the cutouts to be cut back later as cowls fabbed from molds to be installed on nacelles. The firewall nose bowl will have to be separate item.

Can you separate the firewall nose bowl from the rest? Can you add foam to the rear portion once you separate the two? If you can add to the rear portion the parting board is a piece of cake. If this can't be done then send to me a full sized paper 3-view and I'll spin a new cowl plug for you. I'll have it painted and everything by around February. I don't put panel lines or rivet details on them because they look cartoonish molded into the part. That detail, to me, is best left at the 'final primer just before painting' stage. I can't do this right now because I'm building a pedal plane as a Christmas present. However, you never know!

Props4ever

Look at the initial pics i posted in the post 1, cowl bowl is a separate piece and yes it will be molded separate from the main cowl piece. Same goes for the lower scoop.

If you want me to fill the exhaust cutouts, i can do that and then if you want to place cowl vertically on a piece of foam and then on parting board, that i can do also. Now what material can i use as parting boards?

invertmast

My Feedback: (23)

Melamine shelving boards. The parrticle board with the white plastic coating on it.

ARUP

The shelving boards work great. If you don't have them then tape Monokote to cardboard or blue foam board. Monokote is very slippery for this app. Build up your plug long enough for the scoops to be fashioned, eventually. You can always cut the finished cowl back for length and exhaust cutouts. You will have to create an account on RCScalebuilder in order to lurk, for free. I can post here but will have to be later in the evening.

Props4ever

Arup, just sent you a detailed pm, it will better if you post ur tutorial on here too that is if don't mind, i have in past tried to log into my account on RCSB but it was no go even to see and read.....

Update is that i have come up with a plan of action here with my bud Frank who has a lot of experience and knowledge about composite mold making, i twisted his arm today to get me through this as i have been waiting on him for last 2-1/2 years for this to happen, he has agreed to do it on coming Sunday but i have to do clay fill up in exhaust cutouts and space between flap doors and cowl's dome.

I will as usual keep posting my progress on here and seek your help and suggestions and opinions.

Props4ever

Plan is to do main cowl piece in 2 sections, first 1/4 and then remaining 3/4, then cowl dome and lower scoop both will be done separately after the main part.

To do lower 3/4s of the cowl, i have filled all the exhaust cutout pockets and space between flap doors with modeling clay. This way whole lower part can easily be molded. I will make border line all around edges of the flap doors and exhaust cutouts as reference so after part is made, i can then use that line to cut off the flash from the part and get these cutouts and flap doors on the part. I will also make outlines for the flap doors on the mold so, when part come out, it will have doors outlined and marked. A clay flange will be made all around and on the first green reference line plus i will add some sort of keys on it, so when i will do lower part mold, keys will be there to lock in both molds.

Here are pictures of the cutout and flap door space filled with the modeling clay. I still need to clean up the plug area on which bit of clay is visible before glecote is applied to the plug's surface.

Props4ever

Flange has been made. We did it with material on hand, first rin was made with 1/8" balsa sheet, it was very light, so i reinforced it with 1/2" thick foam flange ring.

Facing side of the flange was covered with monocote. Fit of the flange around the outer body of the cowl is pretty good and snug, gaps will be filled with modeling clay.

A flat disk to blase cover was made to block the main intake opening. This disk was also covered with monocote. It's gaps will be filled with clay also.

Plan is to make clay keys. Plus i will get mold release spray and and gelcote in this week, this way next weekend first intake mold will be made.

As for rest of the lower mold, it will be done in 2 halfs...left and right side, i will make those flanges in this week. So now it's established how we are proceeding towards making this mold.

Props4ever

Pictures to illustrate today's' progress...

Props4ever

Finally found my hot glue gun n glue sticks, glued the flange to the plug with this glue all around the plug at few spots.

Props4ever

Well here is the update of mold making if this cowl, method used to make the mold of this plug is very much as invertmast aka Thomas said, i looked at it with my friend n we came up with same plan of action too due to shape and
undercuts of the cowl lip and how top intake fairing tapers down towards at the back.

Take a look please n thanks...

http://www.rcuniverse.com/forum/m_45...page_51/tm.htm