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Search: Posts Made By: davidfee
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12-07-2007, 05:18 PM
Replies: 26
Views: 5,388
Posted By davidfee

RE: My vacuum bag layup has crinkles, any advice?

I think you'll be disappointed if you don't ensure that each ply is fully wet-out before you put it in the bag, as you're likely to get dry areas and puddled areas. How you get each ply wet out is a...
12-07-2007, 05:09 PM
Replies: 26
Views: 5,388
Posted By davidfee

RE: My vacuum bag layup has crinkles, any advice?

Yeah, I wasn't meaning to contradict you. I use the pink perforated stuff from CST myself... but my point was that if the release film goes in with wrinkles... those wrinkles aren't going to...
12-07-2007, 04:00 PM
Replies: 26
Views: 5,388
Posted By davidfee

RE: My vacuum bag layup has crinkles, any advice?

Any wrinkles in your drop cloth (or any release film... perforated or not) will result in these resin ridges. The resin fills the wrinkles and stays there. These resin ridges are kind of the nature...
03-09-2007, 05:27 PM
Replies: 10
Views: 1,602
Posted By davidfee

RE: heat shield ceramic

My point is, if the EGT is 600F at the point of the vectoring vanes, epoxy/fabric composites will not be suitable. Ceramic sheets may work fine, if you can find them. You need air between your...
03-09-2007, 05:22 PM
Replies: 10
Views: 1,602
Posted By davidfee

RE: heat shield ceramic

You need to define the temperatures before you can start looking for materials.
03-09-2007, 10:32 AM
Replies: 10
Views: 1,602
Posted By davidfee

RE: heat shield ceramic

What is the temperature of the exhaust gas at the location of the vectoring vanes?
03-09-2007, 01:45 AM
Replies: 10
Views: 1,602
Posted By davidfee

RE: heat shield ceramic

Use stainless steel for the exhaust ducting.
03-05-2007, 02:13 AM
Replies: 9
Views: 5,342
Posted By davidfee

RE: How do I make a plug from this heli canopy?

Wax and PVA are so cheap compared to the fiberglass and epoxy you'll be using for the mold and parts... so why cheap out? It's not that much work to do it right... and it will save you a lot of pain...
01-28-2007, 08:55 PM
Replies: 10
Views: 1,269
Posted By davidfee

RE: epoxy to epoxy?

Yes, that works fine. It's how molded wings are put together, for example. You should scuff the area to be bonded with sandpaper, and clean with acetone if possible. The bond will be fine.

It...
Forum: Aerodynamics
12-14-2006, 12:00 AM
Replies: 29
Views: 4,332
Posted By davidfee

RE: Best Prop. Wood? Why?

Not entirely true... you can re-pitch most plastic and composite props.
11-09-2006, 10:30 PM
Replies: 7
Views: 1,159
Posted By davidfee

RE: difficult to use Quicklock

No no no... no mallet.

First of all, what thickness is your bagging material? Obviously, that can make a big difference.

The easiest way I've found for getting the thing together is to...
11-09-2006, 09:48 PM
Replies: 6
Views: 1,185
Posted By davidfee

RE: Amount of epoxy to mix for skinning wings

If you want to build light models (they do fly better, after all), you look for ways to maximize the use of your materials, and minimize the amount of excess weight. Sealing balsa with a light coat...
11-09-2006, 09:38 PM
Replies: 22
Views: 3,580
Posted By davidfee

RE: Epoxy mixture?

Matt,
I'm pretty sure Randy is talking about joining the upper and lower skins of a hollow molded wing. The skin sandwich panels (balsa or foam sheet core) are bagged into their respective molds. ...
Forum: Aerodynamics
10-26-2006, 08:13 AM
Replies: 5
Views: 1,207
Posted By davidfee

RE: Alternate tail airfoil

You give the impression that this stab is very highly loaded and, thus, having sufficient spar height is critical. So, take the RAF30 and thicken up the 70-80% region to meet your requirements. ...
10-20-2006, 03:09 PM
Replies: 18
Views: 2,625
Posted By davidfee

RE: thinning epoxy

(covers ears) lalalala ;)

Yes, of course you can thin epoxy with alcohol (or acetone, MEK, etc.) Yes, the results can be quite satisfactory. It's just less than optimum and it's generally...
10-19-2006, 10:08 PM
Replies: 18
Views: 2,625
Posted By davidfee

RE: thinning epoxy

Just say no to thinning epoxy.

Warm the stuff up to make it flow. If you are doing a glass tape wrap of a dihedral break, use a heat gun to heat the epoxy and a credit card to work it into the...
10-12-2006, 12:13 AM
Replies: 23
Views: 7,215
Posted By davidfee

RE: Glass/balsa/glass laminate fuselage

Tom,
It is called a sandwich panel. It is many, many times stiffer for a given weight than a solid laminate panel. Thus, for a given design stiffness, the product can be made much lighter. Using...
Forum: Aerodynamics
09-17-2006, 03:04 AM
Replies: 10
Views: 984
Posted By davidfee

RE: Unequal winghalfs

I've definitely built some rubber-powered FF models with asymmetric wings, but these were indoor models with props that were about 1/2 - 3/4 of the wingspan. The asymmetry was required to react...
09-01-2006, 03:29 PM
Replies: 1
Views: 707
Posted By davidfee

RE: lap joint in molds

You generally make an additional piece (or set of pieces) for your joggle mold after the primary mold parts are built. The "joggle tool" is then removable and the parts can still be joined using the...
08-10-2006, 12:37 AM
Replies: 11
Views: 1,552
Posted By davidfee

RE: Composite Fin Layup

Those aren't done... time to start polishing! :)
07-25-2006, 08:08 PM
Replies: 6
Views: 2,557
Posted By davidfee

RE: Epoxy melting blue foam.

Yes, this is polyester resin. The catalyst is MEKP (not MEK), and the main ingredient is styrene monomer... which is what your blue polystyrene foam is made from. So... there's your problem. ...
07-11-2006, 10:48 PM
Replies: 7
Views: 785
Posted By davidfee

RE: K&B paint on plugs?

On Dolphin wax: Yes, it's a nice wax. Is it the end-all, be-all? I don't know. You'll read lots of praises... but my first part made with the stuff stuck in the mold. It was an old mold... with...
07-10-2006, 08:22 AM
Replies: 7
Views: 785
Posted By davidfee

RE: K&B paint on plugs?

Well, I've used a variety of products... all from the auto parts store. I've used No 7 White Polishing Compound, followed by a clearcoat-safe compound from 3M.

HTH,
-David
07-09-2006, 01:39 AM
Replies: 7
Views: 785
Posted By davidfee

RE: K&B paint on plugs?

I've had very good luck using automotive polishing products on my plugs. If you have a lot of orange peel, start with wet sanding.

WEST graphite powder will work fine in your tooling resin.
...
06-20-2006, 02:44 PM
Replies: 15
Views: 2,433
Posted By davidfee

RE: Want to do fiberglassing... what do I need?

Yes, MGS and Aeropoxy (in fact, virtually every epoxy type) are fully compatible with polystyrene foam (EPS).
Showing results 1 to 25 of 500
 


 
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