Scale 112” - Taylorcraft by HeyLuc & Snoopy.

[Snoopy1]

Ok have a question. Once all is done and the plug is ready how much cloth is required to make a cowl. Ie how many layers and what weights to use. I was thinking right or wrong. First layer in 3/4 oz, second layer 2 1/4 oz cloth and final layer 4 oz cloth. Would that be enough and strong enough for 120cc cowl. Your input will be appreciated.

 

[TonyHallo]

Well first you will need to make a mold, two piece of one piece? When I laid up the canopy for the Cherokee, I used one 4 ounce layer and one 6 ounce layer of glass on the final version. The first one I made was 4 ounce and two layers of 6 ounce cloth, it was a little heavy. I am doing some studying now and testing several options for the Cherokee fuselage, just got some 1/8" Nomex honeycomb to play with. In the past all the parts I made were at least two layers of 6 ounce cloth, one layer is just too flimsy. Your suggested layers may work, made a few test pieces. The other thing to consider is what resin will you use? I think vinyl ester resin is as strong as epoxy but much stiffer that will allow less glass cloth to achieve the desired stiffness
I bought the Kelvar scissors on Amazon, about $30, the scissors I use to cut glass clth would not touch the Kevlar, the Kevlar scissors cut the cloth like butter.

 

[Snoopy1]

Well first you will need to make a mold, two piece of one piece? When I laid up the canopy for the Cherokee, I used one 4 ounce layer and one 6 ounce layer of glass on the final version. The first one I made was 4 ounce and two layers of 6 ounce cloth, it was a little heavy. I am doing some studying now and testing several options for the Cherokee fuselage, just got some 1/8" Nomex honeycomb to play with. In the past all the parts I made were at least two layers of 6 ounce cloth, one layer is just too flimsy. Your suggested layers may work, made a few test pieces. The other thing to consider is what resin will you use? I think vinyl ester resin is as strong as epoxy but much stiffer that will allow less glass cloth to achieve the desired stiffness
I bought the Kelvar scissors on Amazon, about $30, the scissors I use to cut glass clth would not touch the Kevlar, the Kevlar scissors cut the cloth like butter.

Thanks for taking the time to help me. Appreciate that. So so I will add just a extra layer in of 3/4 oz that is just to get the cloth to conform to all the small things like the spinner hole and the 2 air intakes , just makes a little easier and also the lighter cloth is smoother less sanding and filling. Then as you have advised one layer of 4 oz and one layer of 6 oz.
I will be using epoxy from West systems.
Interesting how one scissors can cut one item and not the next. Will have look in to a pair of scissors depending on your results when using the Kevlar.

 

[heyluc]

Hi All, thinking along the lines of a three piece mold, to be confirmed. Once I get the nice work of Snoopy1 the frontal dimensions will be checked and the nose piece will be 3D Printed. Drawing and stl file of the nose piece are ready. Then getting it all smooth and prepped for molding. Parting boards can be cut on the CNC.

For the cowl itself two layers of 6oz will be fine with a lighter one, like 1/2oz -3/4oz, and fiberglass cuttings to conform to the air inlets and the spinner opening. Still long way to go before we are there.

On the CNC 6 sheets have cut with 28 more to go. Since it is flying season it all goes at a slow pace.

Next time, when I can show something interesting, I will post pictures.

Best, Luc

 

[BalsaDust]

Ok have a question. Once all is done and the plug is ready how much cloth is required to make a cowl. Ie how many layers and what weights to use. I was thinking right or wrong. First layer in 3/4 oz, second layer 2 1/4 oz cloth and final layer 4 oz cloth. Would that be enough and strong enough for 120cc cowl. Your input will be appreciated.

Per talking with Ben Fisher from Extreme Flight about the cowl of a plane I designed. He suggest 5 layers for 2-3oz cloth. Lay a layer in the mold and wet it out. Allow 30ish minutes setup time then layup another layer. Use paper towels to blot out excess resin.

 

[TonyHallo]

As recommended by others on the web that I consider knowledgeable I purchased this laminating epoxy and slow hardener. It wets out real nice and gives you plenty of working time. It is cheaper than West Systems as well.

 

[BalsaDust]

Hi All, thinking along the lines of a three piece mold, to be confirmed. Once I get the nice work of Snoopy1 the frontal dimensions will be checked and the nose piece will be 3D Printed. Drawing and stl file of the nose piece are ready. Then getting it all smooth and prepped for molding. Parting boards can be cut on the CNC.

For the cowl itself two layers of 6oz will be fine with a lighter one, like 1/2oz -3/4oz, and fiberglass cuttings to conform to the air inlets and the spinner opening. Still long way to go before we are there.

On the CNC 6 sheets have cut with 28 more to go. Since it is flying season it all goes at a slow pace.

Next time, when I can show something interesting, I will post pictures.

Best, Luc

Also per Ben on 3D printed molds. Unless you plan to mass produce its not worth the time to prep the mold to a super smooth finish. Instead do the following.
1. Wax the mold 5-6 times. Lots of the residue will be left in the texture of the printed part and that's fine.
2. Next do 4 or 5 coats of a good PVA mold release.
3. spray on several light layers of a high build sandable primer.
4. now you can clamp the mold halves together and do the layup.
5. Once cured you can separate the part from the mold and sand the part smooth. Between the wax left over in the printed layers and the primer build up you will be able to sand it smooth without ever sanding down into the cloth.

 

[TonyHallo]

More data to add. I have two cowls unfinished from Fibertech-n-More, the Cherokee cowl measures .021" thick in four places, the Chipmunk cowl measures .018" to .020" in four places. The unfinished cowl for the BUSA 33% Super Cub measures .030" to .034" thick, this was laid up by Steven at Aeroglass in Canada. Two cowls laid up by Fiberglass Specialties, 33% laser and 30% WH Cessna 150 measure .030" to .040" thick closer to .040" in most spots. And finally a blast from the past I have a Bill Effinger's W. E. Technical Services 33% Piper Tri Pace cowl laid up by Fiberglass Masters, you remember the blue colored resin, it measures between .050" to .070", rather heavy
I have a test piece laid up with 2 ounce and 4 ounce cloth, measures .010" thick, not thick enough for a cowl in my estimation, vert flimsy . 6 ounce E glass is just under 010" thick, I would shot for 10 to 12 ounces of cloth.

 

[Snoopy1]

Ok all I can say is thanks for all your help and numbers . So it looks like 10 to 12 oz of cloth should do the job. So just depends on what fibreglass cloth is available around us we will buy but as long as we get between 10 and 12.oz in total thickness.

 

[AKNick]

That's some great layup data guys, I'm going to have to jot that down in my notebook!