# Balsa Fins: Plastic Wood Wood Filler?

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#### eduncan911

##### Active Member
Needing to seal up some balsa fins on a few new rockets we are building. I last tried papering and it turned out o-k; but, it was a lot of sanding and resealing as I goofed on the papering (too much glue, wavy lines, nothing on rounded edge, etc). This time around she wants to try thinned wood paste/filler, and sanding.

Our local Home Depot only has Plastic Wood - Wood Filler, and Minwax Wood Filler. The Minwax comes with a hardener, so I don't think I want to use that.

Our local hobby store doesn't stock (nor heard of) "CWF" or Carpenter's Wood Filler. And I missed ordering it from Apogee when I just placed my last order.

My daughter and I have just finished making 16 fins to seal up from scratch (a 3-stage Comanche and 2-stage scratch built). So you know story, keep it going! Went down to the local Home Depot and that's all that had.

Could I use this Plastic Wood stuff, thinned out with some water per instructions I see online?

If I come across it at Lowes or Michael's or something, what are some other options? Maybe something like this?

Thanks!

#### Flyfalcons

##### Well-Known Member
If I come across it at Lowes or Michael's or something, what are some other options? Maybe something like this?

Thanks!
Yes, that one.

#### Overeasy123

##### Well-Known Member
I'm pretty sure I scored mine at Lowe's.

#### Woody's Workshop

##### Well-Known Member
TRF Supporter
You don't want to use a dense filler on balsa. You will end up sanding away more fin than filler.
Most Big Box stores including superstors, and hardware stores carry it. Also lumber companies.
You can even get it in colors in tubes if you so desire...

#### eduncan911

##### Active Member

Thank you all for the quick replies! We've already done her 6. Will move onto mine later in the week after I see how her's turn out.

#### HandsomeRob

##### Well-Known Member
Make sure to buy the Elmer's Wood Filler for Interior use. The Exterior's texture's too grainy, and it gives me heartburn.
heh.

I will second this. I got a tub of the Elmers Probond (pretty sure that's the name) Woodfiller and it's super grainy and takes forever to sand. Unfortunately, I refuse to let the whole tub go to waste so I'll continue on with it until it's gone....

#### Micromeister

##### Micro Craftman/ClusterNut
TRF Supporter
I haven't filled a single fin in more then 12 years.
Why spend all that time filling and sanding any "filler" product when they can be replaced with any CHEAP rattle can sandable primer. If you like spending money go with High Build primer. but seriously any Cheap as you can find grey , brown or black sandable auto primer works like a dream.

Apply 3 wet heavy coats about 5minutes apart, then let the rocket sit overnight. use the "sniff Test" (Nose on the rocket surface- if you can smell paint - it isn't cured). When the primer is cured, dry sand with 240 -320 sandpaper. if you hit bare wood or cardboard repeat the 3 coat process. I've never had it take more the 5 coats to completely fill the deepest wood grain or spiral body tube seams. You are left with a babies butt smooth primed finish ready for base and color coating. with FAR less sanding time involved and super fine rocket finish. The System Works!

#### Flyfalcons

##### Well-Known Member
Probably not a big deal on micro models but that's a whole lotta primer to waste on large fins.

#### AfterBurners

##### Well-Known Member

http://modelrocketbuilding.blogspot.com/2010/09/carpenters-wood-filler-mix-ratios.html

Make sure to buy the Elmer's Wood Filler for Interior use. The Exterior's texture's too grainy, and it gives me heartburn.
I agree 100% but where can you find the old CWF. I'm not sure if it's still on the shelves at the local hardware stores like Home Depot and Lowes. They have the color changing stuff.

#### AfterBurners

##### Well-Known Member
I haven't filled a single fin in more then 12 years.
Why spend all that time filling and sanding any "filler" product when they can be replaced with any CHEAP rattle can sandable primer. If you like spending money go with High Build primer. but seriously any Cheap as you can find grey , brown or black sandable auto primer works like a dream.

Apply 3 wet heavy coats about 5minutes apart, then let the rocket sit overnight. use the "sniff Test" (Nose on the rocket surface- if you can smell paint - it isn't cured). When the primer is cured, dry sand with 240 -320 sandpaper. if you hit bare wood or cardboard repeat the 3 coat process. I've never had it take more the 5 coats to completely fill the deepest wood grain or spiral body tube seams. You are left with a babies butt smooth primed finish ready for base and color coating. with FAR less sanding time involved and super fine rocket finish. The System Works!
Because at $7 a can for good high build primer can cost more especially if your rockets are bigger than a pencil. This is why a lot of people on here use a filler on their spirals and fins. They want good results without dumping a lot of money into it. #### maccordabc ##### Member I haven't filled a single fin in more then 12 years. Why spend all that time filling and sanding any "filler" product when they can be replaced with any CHEAP rattle can sandable primer. If you like spending money go with High Build primer. but seriously any Cheap as you can find grey , brown or black sandable auto primer works like a dream. Apply 3 wet heavy coats about 5minutes apart, then let the rocket sit overnight. use the "sniff Test" (Nose on the rocket surface- if you can smell paint - it isn't cured). When the primer is cured, dry sand with 240 -320 sandpaper. if you hit bare wood or cardboard repeat the 3 coat process. I've never had it take more the 5 coats to completely fill the deepest wood grain or spiral body tube seams. You are left with a babies butt smooth primed finish ready for base and color coating. with FAR less sanding time involved and super fine rocket finish. The System Works! but after 3 heavy coats, sanding then 3 more heavy coats those little micro models must weigh a ton! And you do 3 heavy coats up to 5 times? Id rather be launching the rocket then sanding all that goop off. #### AfterBurners ##### Well-Known Member but after 3 heavy coats, sanding then 3 more heavy coats those little micro models must weigh a ton! And you do 3 heavy coats up to 5 times? Id rather be launching the rocket then sanding all that goop off. Agreed. I like using the AEROGLOSS dope or something similar if you can find it? Bottom line everyone has their own of getting the results they need when it comes to filling balsa or other parts pf the rocket. There's more than one way to skin a clown. #### Micromeister ##### Micro Craftman/ClusterNut TRF Lifetime Supporter TRF Supporter Because at$7 a can for good high build primer can cost more especially if your rockets are bigger than a pencil. This is why a lot of people on here use a filler on their spirals and fins. They want good results without dumping a lot of money into it.
All of the Rockets pictured in my previous post are full size Rockets. The Inerceptor is the E-interceptor, some of the others are BT-80 in size with Large Balsa and or Basswood fins, transitions and Nose cones. All of my 3X Up-Scale Rockets have been finished in the same way. NO filler other then Cheap grey brown or black sandable auto primer. The stuff I'm currently using is Walmart Color place Grey Auto primer. I buy it this primer in 3 - 6 can cases at a time. Last time I paid .89/per 12oz can. Generally I get one or two full size rockets from a single can. I get 8 to10 Micros from a single can.
Paying 7 bucks a can for high build primer is ridiculous on anything under HPR rockets. Yes; it sometimes takes a second set of 3 coats to fill really deep wood grain but it's still quicker and easier then any wood filler I've ever heard of.
As usual; It your choice and Your rocket but if your looking for outstanding Finishing this primer only technique is an outstanding process.

with the 3 coat process most of the primer is sanded off anyway. That is exactly why it makes very little sense to spend high dollars for high build sandable primer. since we are sanding off almost all of it. Most of my Micro models with Babies Butt smooth finish weigh less the 10g. Paint is the heaviest coating!

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#### Nytrunner

##### Pop lugs, not drugs
TRF Supporter
I agree 100% but where can you find the old CWF. I'm not sure if it's still on the shelves at the local hardware stores like Home Depot and Lowes. They have the color changing stuff.
Still walmart. They have the Orange wood filler in tubes and tubs. Check behind/around the paint horseshoe.

#### AfterBurners

##### Well-Known Member
Still walmart. They have the Orange wood filler in tubes and tubs. Check behind/around the paint horseshoe.
Is this the correct CWF? It looks to be correct?

https://www.walmart.com/ip/Elmer-s-Carpenter-s-Wood-Filler-Interior-Use-Natural-Color-3-25oz/17011272

I also found this too....same stuff it looks like, but not sure?

https://www.walmart.com/ip/Elmer-s-Products-E847-Carpenter-s-Interior-Wood-Filler-1-4-Pint/147190152

For me I'd rather buy online because you have a better chance off getting, whereas in the store, which I already looked for it never seems to have it on the shelves. At least where I'm at. I figure the amount I spend on gas and also my time I'd rather spend a few dollars to have half dozen tubes shipped out.

#### Scott_650

##### Well-Known Member
Yup, same stuff. Follow the link in Overeazy's post to Chris's blog - he gets some consistently great results. I've used the multi coats of primer technique like Micromeister does and that works well too. Bottomline, I like getting a reasonably smooth finish on my rockets but since I do this strictly for the entertainment value I try not to obsess over balsa grain and tube spirals - the performance difference is negligible and after a couple of launches a good rocket is a slightly beat up rocket!

#### Overeasy123

##### Well-Known Member
I agree 100% but where can you find the old CWF. I'm not sure if it's still on the shelves at the local hardware stores like Home Depot and Lowes. They have the color changing stuff.
I even cross-checked the Elmer's Part Number to the product I'm using currently, E842. Orders under $35 ship for$5.99. Myself, I'd order 7 Quarts, shipped Free, and look into leading a Fin-Finishing Symposium at the local Bowling Alley.

#### Sooner Boomer

##### Well-Known Member
When I was in my early heyday of rocket building, one of our group discovered that if you used Plastic Wood putty and rubbed it into the bare grain very thoroughly, when dried and properly sanded, it would give a surface like glass. You had to take a pea-sized lump and rub it into the balsa until only crumbs fell off, without leaving and putty behind on the wood. I was using either SIG sanding sealer or clear dope mixed with baby powder, which gave decent results, but took time for the dope to dry enough to be sanded, and took multiple coats. Plastic Wood has a lot of nasty solvents (toluene, acetone, etc), and of course we rubbed it in with out bare fingers. If I had a can I might try it again on my next project, but there are lots of good alternative now.

#### HandsomeRob

##### Well-Known Member
One of the reasons I use wood filler is to strengthen the balsa, as well as create a smooth finish. I can't imagine coats of primer offer the same benefit.

(For what it's worth, I'm less concerned about things like fin flutter at high speeds, and more just wanting a durable rocket that doesn't get dinged up on landings or other household hazards.)

#### neil_w

##### Marginally Stable
TRF Supporter
One of the reasons I use wood filler is to strengthen the balsa, as well as create a smooth finish. I can't imagine coats of primer offer the same benefit.

(For what it's worth, I'm less concerned about things like fin flutter at high speeds, and more just wanting a durable rocket that doesn't get dinged up on landings or other household hazards.)
I'm not convinced CWF adds any strength to fins.

#### BABAR

##### Builds Rockets for NASA
TRF Supporter
One of the reasons I use wood filler is to strengthen the balsa, as well as create a smooth finish. I can't imagine coats of primer offer the same benefit.

(For what it's worth, I'm less concerned about things like fin flutter at high speeds, and more just wanting a durable rocket that doesn't get dinged up on landings or other household hazards.)
If strength is your goal, papering the fins might prove a better option (I guess there is also glassing, but that is a BIG step up.)

#### dpower

##### Well-Known Member
Agreed. I like using the AEROGLOSS dope or something similar if you can find it?
Brodak makes good old fashioned dope based sanding sealer. I still have a small supply of Aerogloss, but when it's done, I'll switch to this. SCIGS30 uses it, and he reports its as good as, or better than aerogloss, which went out of production recently.

http://brodak.com/finishing-products/dope.html?limit=20

#### AfterBurners

##### Well-Known Member
Brodak makes good old fashioned dope based sanding sealer. I still have a small supply of Aerogloss, but when it's done, I'll switch to this. SCIGS30 uses it, and he reports its as good as, or better than aerogloss, which went out of production recently.

http://brodak.com/finishing-products/dope.html?limit=20
I wa actually able to locate a supplier that still has Aerogloss sanding sealer with Balsa filler primer. I'm pretty well stocked up, but when I do run out I'll make the switch.