Build Log Hkm 1:2.5 Asw 28

[scalebldr]

The following photos show the process of making plugs and molds for the seat pan and seat back. This process is much the same as the ASH 26 I did on the ISSA Tech Tips page only here I decided to use polyester resin insted of epoxy.

[SteveR]

Rick, is the final molded product a single combined seat and pan or two separate pieces? Also, where do you get 3# foam?

TIA,

Steve

[scalebldr]

Originally Posted by SteveR

Rick, is the final molded product a single combined seat and pan or two separate pieces? Also, where do you get 3# foam?

TIA,

Steve

HI Steve, it's two parts, the pan will be mounted with 4 screws and the seat with the pilot mounted in it will have a single screw to hold it in place, I will have more shots to show how.

Check with building supplys for the foam, or an online sorce where you are located. Use a 3 or 4# foam.

[SteveR]

Thanks Rick, info greatly appreciated. That foam sure shapes beautifully. Do you fill the pores of the foam with spackle or similar before you apply glass cloth and resin?

I'm working on a new tow plane...the same 4 meter PA-18 that Pete Goldsmith towed us with at the JR Aerotow. I want to add a lower air scoop to the cowl, like the one in the attached photo and thought using your foam technique might be the way to go e.g. make a plug, then glass over it. Any comments or ideas?

Regards,

Steve

[Big Nuts 181]

Hi there steve can I suggest an easier way would be to wax up in some pvc waterpipe or mylar with a couple layers of 3oz glass and epoxy/resin and simply cut the scoop accross its length to make the scoop, make a matching cut out in the cowl zap the new scoop onto the cowl and glass it on from the inside.

[SteveR]

Thanks Big Nuts, won't that produce a semi-circular shape? I'd like to duplicate the shape of the squared off scoop shape in the photo above (below the prop).

Sorry, don't mean to hijack the ASW thread,

Steve

[scalebldr]

Originally Posted by SteveR

Thanks Rick, info greatly appreciated. That foam sure shapes beautifully. Do you fill the pores of the foam with spackle or similar before you apply glass cloth and resin?

I'm working on a new tow plane...the same 4 meter PA-18 that Pete Goldsmith towed us with at the JR Aerotow. I want to add a lower air scoop to the cowl, like the one in the attached photo and thought using your foam technique might be the way to go e.g. make a plug, then glass over it. Any comments or ideas?

Regards,

Steve

HI Steve, you can do what we call a lost mold, make your shape, glass it with 3 layers of 3oz glass, sand it smooth like you were going to paint it.

You can use epoxy but let it cure for 2 days to get good and hard. Or you could use Polyester that gets harder in one day. With eather keep it in a warm dry place they don't like cold and humidity.

Then remove the foam with a dremel, then sand the inside and finish install to the cowl, prime and paint. This way you don"t have to make a mold for just one part

Regards Rick

[scalebldr]

Here is the final assembly less install and painting.
BFN Rick

[SteveR]

Rick, you is one velly clever flyboy. Thanks very much for the great tips. Just curious...was it easier to make a separate seat pan and seat or was there another reason for making them as separate pieces?

TIA,

Steve

[scalebldr]

Originally Posted by SteveR

Rick, you is one velly clever flyboy. Thanks very much for the great tips. Just curious...was it easier to make a separate seat pan and seat or was there another reason for making them as separate pieces?

TIA,

Steve

Steve, It is easier to remove the pilot to access the rear of the model.
That way you can get to the R/C equipment. Some models have it all in one piece, I wanted to have more scale detailing. You will see once I build the side combings.

BFN

[SteveR]

Thanks Rick. I'm going to try your approach for the Cub air scoop. Some questions: do you finish the surface of the 3# foam in some way before you apply the glass cloth e.g. spackle, etc.? Also, do you allow each of the 3 layers of cloth to completely set up before you apply the next layer? Finally, I assume you have apply some body putty or filler after the 3rd layer to fill the weave and other imperfections...yes?

TIA,

Steve

[scalebldr]

Originally Posted by SteveR

Thanks Rick. I'm going to try your approach for the Cub air scoop. Some questions: do you finish the surface of the 3# foam in some way before you apply the glass cloth e.g. spackle, etc.? Also, do you allow each of the 3 layers of cloth to completely set up before you apply the next layer? Finally, I assume you have apply some body putty or filler after the 3rd layer to fill the weave and other imperfections...yes?

TIA,

Steve

Steve

OK sooooo you want to be a glassman, If you don't have the right materials you won't have much fun! People wonder why this kind of work can be a little pricey, Ya gata do it to see why. Sounds like you need to find a store that handles fiberglass and resins, they will have the rest. OH ya, get a good air mask, fiberglass dust and the smells will get ya big time. Oh and one more thing, disposable Nitrile 5 mill gloves, you can get a box of 100 for $14.00
I use them all the time, keeps epoxy and junk off you hands.

You could fill the foam with a cote of Z Epoxy finishing resin. Then lightly sand with 320 wet sandpaper it doesn’t have to be baby smooth, it’s the inside. Then get a pint PVA liquid mold release ( it's Green) and spray the plug with it before you lay-up, I use my airbrush, any small spray gun will do. It's water soluble, it will wash of the inside of your part when you remove the plug.

Next cut your cloth on a diagonal with extra waist to cut off when its hard.
The reason is so the cloth will bend on hard corners.
Place your plug on wax paper.
Use a laminating resin and lay-up all three layers, and I would also lay-up the
extra cloth about 1" from the plug on all three sides to form a flange for mounting to the cowl. When hard you can cut off the extra waist of the flange down to 3/8" wide. The flange would mount from the inside of the cowl not the out side.

Don't remove the plug yet, go a head and sand the out side with wet 320.
Fill any minor holes with a body filler, do not prime yet.

Remove the plug, wash off the mold release, cut and fit the scoop to the cowl and bound it. You can use epoxy on polyester, rough up the surfaces to be bonded.

Now do any priming and filling, then paint. Assuming your are going to repaint the cowl.

Keep me posted skywalker!

Yoda

[Big Nuts 181]

Sorry about that Steve didn't look closely enough, ok take two just use either 1mm ply and glass inside and out or sheet glass and glass on the inside and the balance of above or score the inside of your glass end benh it to shape once there lay an extra layer of glass on the inside you can cyano it together to hold its shape!! Too Easy.

[SteveR]

Guys, thanks very much for all the tips. I'll let you know how it all turns out. This Cub is turning out to be a way bigger project than I first envisioned. For starters, because of tight noise restrictions at our field, I'm running two huge cannister mufflers inside the fuse which requires creating an internal "tunnel" from the firewall back past the landing gear. As soon as it's completed, I'll launch my new occupation as the glassman.

Steve

[scalebldr]

Originally Posted by SteveR

Guys, thanks very much for all the tips. I'll let you know how it all turns out. This Cub is turning out to be a way bigger project than I first envisioned. For starters, because of tight noise restrictions at our field, I'm running two huge cannister mufflers inside the fuse which requires creating an internal "tunnel" from the firewall back past the landing gear. As soon as it's completed, I'll launch my new occupation as the glassman.

Steve

Steve, I think 181 has the better idea for making the scoop, after looking at the photo of your cub . But for future projects that have curves and round shapes, the lost mold idea will work.
Rick