invertmast

My Feedback: (23)

if the area's aren't structural, you could probly get away w/ 1/32 or 1/64 ply or even balsa with a layer of glass on the exterior and interior.

Props4ever

Yep it's not structural area at all, I just have to sit back and think how i am going to do this. Your suggestion is a good one also that i'll consider it.

ergocentric

Why doesn't anyone suggest 1/32 or 1/64 FRP plates as used for Printed Circuit Boards?

Props4ever

Reconstruction commenced...


Last night after talking to another friend i decided to re construct this section with ol foam and glass method. I went out and got myself few pieces of blue insulation from from near by housing construction site.

For the first piece i used old former that i took out from rear section and as template to mark and cut the foam piece. Since this former was glued in on an angle is was slightly bigger in size needed, I had to trim it down to fit in side the fuselage opening. This took bit of time testing it's fit back an forth but in then end it nicely fitted now.

Now for my second piece i used same technique as above with with the former as template and then had to place right against exhaust nozzles and marked its outline from inside the burners with help if 1/16" piano wire. Pulled it out and marked the pattern with ball pen and went on to my scroll saw and cut it out in right shape. To test it i placed it against the nozzles once again to find out the for the middle section i can use blue foam as i would need thinner piece there then 2". Now for that i am going to use white foam.

Props4ever

Since i couldn't use 2" blue foam piece for the center, i used a trick to take off 1/4" from all around the outline of the burners marked earlier, this helped in making bit more room for 1-1/4" white foam piece as can be seen in pictures below.

Props4ever

Question:

Can i use Aeropoxy resin to make this section as original fuselage is made with polyester resin of some type!, i am not sure if even after 10 years plus these chemicals with react to each other or not in long run. The only reason i ask this is coz i have Aeropoxy on hand atm that i used on my S Connie model.

Props4ever

Little bit more done, mostly sand and bringing bottom fuselage engine cones in to shape.

I anchored the foam pieces with two 1/4" dowels so they stay together as i did my sanding. You will notice there is a step created in between fuselage and foam mould, i did this so when i lay up the cloth and add resin to it, it will come our smooth in level to the present fuselage, i also intend to lay light 2oz cloth on the foam mold which would be larger on sides then the opening and then lay heavier cloth 40z or 6oz cloth on top of it to fill the step. once this gets dried up, i am thinking to lay up another layer of light cloth which would be again slightly more then required opening to blend in with rest of the fuselage and nozzles once i sand it.

invertmast

My Feedback: (23)

IMO i think your cloth layout will be a little over the top. i think the 2oz over foam overlapping the edges w/ a fine weave cloth would be fine. then i'd remove "most" of the foam from the inside leaving a thin 'foam" pad to keep the rigidity of the fiberglass, and then lay 2 layers on a 45* bias of each other on the inside. I think this would be plenty strong enough for the area you working and would be lighter as well.

Props4ever

Invertmast,

I see what you are saying but my only concern with using heavier cloth sandwiched with lighter is to fill the 1/16" step so the rebuilt section would come out smooth and nicely blended in with rest of the fuselage. Other thing i had in mind was to burn off the foam once fiberglass is fully cured.

I am still open to opinions...

ergocentric

From the boat repairs I've done and read about, the best way to go is to spread out the interface between old and new through grinding in a taper and to try to match the existing composite structure as much as possible (e.i. same weights/weaves/resin) to minimize the stress at the interface between the patch and the hull. I also know it is possible to create stable composite structures over something with as little stability as a doughnut or slice of toast provided it is well engineered. The form material really doesn't matter; the finished composite structure does.

Mike Emilio

Apart from finances, , ,
Since it's the lower section that's affected, the whole thing could be put back into the lower mould half, and layed up from the inside.

Props4ever

Again it can surely be done no doubt about it, but cost has become a major roll player on this once again. That is why i decided to take it upon myself to do it....

ergocentric

So, do I understand this correctly to mean you are repairing your own aircraft because someone else won't invest their money in it?

This is getting really confusing.

Props4ever

There is no confusion at all, if you go back and read the thread you will understand it better. I asked Mike to make couple parts that i require to fix this model from his newer lower fuselage mold. He quoted me $400 bucks to make these parts which in my opinion is too high of a price as i was thinking on lines of $100-$150. So in the end i decided to repair it myself which i am doing now.

Mike Emilio

Not to worry Sam. Your doing fine, keep it going.

Props4ever

Mold building is almost complete now, bit of sanding and Spackle filling is all there is to do and it's ready for layup of fiberglass.

I made filler fuselage piece using 9" square. First i had to mark the reference lines and curves on it. After the lines were drawn i started to carve out the curved areas on both sides which simulates engine compartments on the fuselage with #11 blade. At this time i wished for hot wire set up but my scroll saw and hands worked pretty good.

Had to add side extensions on the nozzle piece as i had sanded more then i should have initially. Some filler was also needed on the main piece to fill and smooth out the surface.

Props4ever

Last pictures for tonight while Spackle dries....

Good night to all....[sm=redface.gif][sm=redface.gif]

Props4ever

As of now 10th November 08 we have our first snow fall coming down here in Mississauga, Ontario. Don't know if it's wet snow or would be staying with us. Will post pictures soon...[][]

Back to the build..

I spent last 20 minutes trying to successfully realign the filler mold piece but for some reason i wasn't being able to. As it turned out i had to flip the model and replace it on it's belly and found that there is this slat strip molded into fuselage at the top inside of angular cut!, now it seems to be a sort of flat base but there is nothing there or was there either except a filler fiberglass panel that shouldn't be there on first place. Now i am trying to sand it off so mold could properly sit against the inner curves of engine compartment.

Props4ever

Sanded that step/ridge/base strip whatever you wanna call it as much as i can then did same on other side as there was little there and on top flap part.

Now i have perfect filler mold ready for lay up of fiberglass cloth!. Alignment is perfect also as there are no gaps between the belly and foam mold.

Once again i want to ask same question again as couple post ^if i can use epoxy resin for glassing or not since original fuse was built with polyester resin!. Once i get to this i will either start glassing this section with next couple of hours or wait till i get Poly resin. In case poly resin is needed then what is the good brand for it that i can purchase from LHS (Local Hardware Store)....

ergocentric

To avoid causing stress you want to use as close a resin and glass as the original.
Anything stiffer or softer will crack and break along the seams during flight.
You should clean and prime the old resin as well for better adhesion, then lay some
cloth against the seams on the inside.

Props4ever

Ok i got my answer from the shop i usually buy my composite materials, they said epoxy resin will work great with poly resin as this way they are compatible. They also said if it was other way around then that would have been a problem. So now that this is out of way i will use my Aeropoxy resin with cloth i have to repair this section.

ergocentric

Oops, I was in Messy-Soggy today and I wanted to give to some glass mat I had found in my cleanings-up. [sm=spinnyeyes.gif]

sunnybreeze-inactive

Props4ever,
Sunnybreeze here! You requested I take a look at your project which I did. To be honest there are quite a few ways to tackle this project and if I had to do it I would do it exactly the way you are. I'm big on vacuum bagging and west epoxy with all the various fillers you can get. I have done one off models using Blue foam as a plug then wrapped cloth and epoxy and vacuum bagged to 8"hg. Then after it's hard I simply burn the foam out by pouring acetone in the nose opening. The blue foam just melts away in a few seconds thus leaving a shell.

My advice to you is finish the foam plug the best you can and use epoxy and 2oz cloth. If you have 2oz satin weave it would be better. The next part is your choice but you can lay up two different ways. One way is lay up 2 layers of 2 oz cloth on the outside and then remove all the foam from the inside leaving a uniform 1/8" to 3/16" wall thickness of foam and lay up a single layer of 2oz on he inside. The wall thickness will greatly increase your strength without adding to much weight. The hard part here is getting the uniform wall thickness. the second hard part is laying up on the inside. It looks like a big part which helps but unless you have done some glassing before and made all the mistakes like me in the past it can be hard.

The second lay up schedule which can be easier is three 2 oz layers on the outside of your foam plug and them remove all the foam from the inside. The trick is to be close to existing fuse size. Then is you get a good lay up you are happy with I would simply glass the new section to the old fuse using 0.75oz cloth and epoxy. I have done this quite a few times so trust me here. You must use at least 3 layers with each layer getting smaller to help with the blending in process. Remember you can sand the crap out if the old and new and keep adding cloth and epoxy to blend in. If you sand into the cloth it's no big thing. Just layer on more epoxy and sand some more. When you are getting close you will want to mix fairing compound with the epoxy to make a thick mixture like peanut butter and completely cover everything. Then sand and sand until it looks good. You will have to add more compound and sand quite a fer times to get it looking good.

Good luck and don't hesitate to ask questions. Thanks how you learn.
Steve

Props4ever

Hey Sunnybreeze Tempast maker...hehe

Thanks for taking few minutes to post your suggestions on my thread here and also to provide your support. First i have to say that i don't have vacuum bagging equipment. Secondly I have done lots of glassing before specially glassing my whole S Connie model with is 8' in length and 9' in wingspan!, it's a big one for me and it's foam structure!. I did it all by hand and didn't needed to vacuum bag it, i am sure others would have but it all worked out for me with out it. Now for this i liked your second option better and specially the way you explained it is quite nice and easy to understand. My only problem is i want to use material on hand atm!, so can i lay up single 4oz or 6oz cloth instead of laying up 3 layers of 2oz cloth!, if i can do it that would really help. Once i have layed up the cloth with resin, i am thinking to make a thick past with resin and fumed silica mixed together and spread it as peanut butter like you suggested it. I know i did same on one fuselage's side of my Constellation to fill imperfections and then add Spackle on top of it too smooth it all out.

Super Constellation build thread
http://www.rcuniverse.com/forum/m_4538333/tm.htm

Model is all ready to start glassing this section, it's just matter of time i actually start working on it.

Sam

sunnybreeze-inactive

There is really no problem using 4oz cloth. The reason for 2oz is weight savings. Flying C/L stunt weight is everything and not quite so important in Jet R/C. I would lay up the single 4oz and let it kick off hard. Then man handle it somewhat and try to get a feel if it's strong enough. If not lay up a second layer of 4oz. Only you will be able to tell where you need to be for stableness. Simply keep adding layers until you are happy. Not having vacuum bagging gear just means you have to do more hand work and get messy. Making up a paste is fine but DO NOT use something which is going to be hard to sand. Sounds like you have some prior glass skills so you should have a handle on it.

Go ahead and get-er-done and let's see how it comes out. If not well simply make a new foam mold and start over. I should be posting new pics of my Tempest project by the weekend. Its's coming out well and exciting to see the fruits of my hard work.

Stay in touch.
Steve