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View Full Version : Roachwerks wood issues.


sandman
07-26-2010, 11:50 AM
Well, nothing major accept for one particularly fussy customer. Although I'm not blaming him for my issue.

Here is the problem, I was asked to turn some scale BT-80 parts for a Black Brant II (nose cone, tail cone and motor section) out of basswood. Simple right.

The parts were turned as close to spec as I could. I thought they were perfect. I always check the final fit of parts with sections of body tube to verify fit.

The fit was perfect and the parts were shipped.

A few days later I get an irate email from this customer telling me the parts are way too small, unacceptable and he demanded a refund.

A few email later he calmed down and returned the parts.

Sure enough they were too small. After scratching my head a bit I just bit the bullet and turned some more parts.

I took twice as long to make these just to make sure they fit properly and matched his specifications. They were absolutely perfect!

I finished the parts and placed them in a box in my office late Saturday morning so I could pack them over the weekend and ship them out Monday morning.

Just as a side note, my house is air conditioned my shop is not, humidity has been around 90%.

I started to pack up the parts this morning but I though I should check the size again before I box everything up.

Originally I turned them to 2.610" O.D. as instructed by the customer. the O.D. of a BT-80 is 2.600". Yes, he gave me dimensions and specification in 0.001"!

When I remeasured the parts the dimensions were now 2.590" to 2.597" on the tail cone and motor section.

They shrunk! Not a lot but significantly!

In the meantime the original parts that I and the customer measured had been in my shop and when I remeasured them they were not 2.610" O.D.

They grew!

Granted the difference in size probably amounts to less than an extra coat of primer but I'm afraid I have more parts that I can't sell.

As a final note the nose cone did not shrink significantly at all. I think the reason the tail cone and motor parts shrunk so much was probably due to the fact that there is a hole drilled in each for a 29mm motor tube.

Any ideas? Or should I just make more oversize parts bring each one in the house, let them stabilize then take them back out to the shop and finish them.

The customer lives in Colorado and the air is much dryer there so he will probably get even more shrinkage.

Doug Sams
07-26-2010, 12:05 PM
They shrunk! Not a lot but significantly!
<snip>
Any ideas? I had the same problem with my replacement Cherokee-3D nosecone. I turned one out of cedar and later discovered it was too loose on the tube. I could have wrapped it with some tape and gotten a good fit, but wanted the wood right against the tube wall. I use shear pins on this bird and need the snug fit [to ensure the pins get sheared and not just bent].

Other cedar pieces also shrunk. I intially thought the wood wasn't adequately cured, and hoped it having aged a year in my garage would have helped, but pieces still fell out of spec a few days after turning.

So now I've gotten in the habit of priming them right after turning. This helps lock in the moisture content and thus stabilize them against shriinking/swelling.

It's not perfect, but it significantly reduces the amount of swearing :D

Doug

.

CPMcGraw
07-26-2010, 12:34 PM
Even Estes (and Centuri) had similar problems. You mention how the Colorado atmosphere is drier than other areas. I'm down on the Gulf Coast, where we breathe water. Balsa has a bad habit of growing once it gets down here, soaking up that humidity like a sponge.

BMS parts grow measurably from Illinois, and even Carl's parts grow a little between North Carolina and Alabama... :(

Without expensive climate-control workrooms and shipping, I don't know if there is a 'perfect' solution. I suspect even with such conditions, once the end user starts working with them, the environment they wind up in is going to affect them regardless.

Addendum: Some kind of disclaimer may need to be added, saying you have no control over the end-user's environmental conditions, and that wood by its nature grows and shrinks over time. Depending on how long it takes to travel from your shop to the customer, it may shrink and grow before it arrives. You do your best, but the customer has to accept his responsibility do his part in the finishing.

Solomoriah
07-26-2010, 12:49 PM
Even Estes (and Centuri) had similar problems. You mention how the Colorado atmosphere is drier than other areas. I'm down on the Gulf Coast, where we breathe water.
Gulf coast? I thought you breathed oil down there... :D

CPMcGraw
07-26-2010, 12:51 PM
Gulf coast? I thought you breathed oil down there... :D

Nah, we just bathe in it... :eek:

ghrocketman
07-26-2010, 01:12 PM
Breathe/Bathe; What's the diff? OIL is what moves this country and will remain so for a LOOOOOOONNGGGGG time. It's amazing that a disaster of this magnitude has not happened until now. That being said, from a liability standpoint, I do not understand why the oil companies perform their drilling within soverign territorial waters. Seems to me their liability would be SERIOUSLY curtailed if they did so OUTSIDE of the soverign territorial line.

sandman
07-26-2010, 01:19 PM
So, I guess the question is...is anybody interested in some BT-80 Black Brant II parts?

I suppose all I can do with a fussy customer is refund his money.

But now I'm kinda stuck with two sets of parts...slightly undersized but more than usable!.

Of course if you live where it's humid then they're perfect!

sandman
07-26-2010, 02:08 PM
I can sell the parts for $60. That's $20 less than the original price. The nose cone although it is designed for a BT-80 the customer requested that the shoulder fit a BT-80 coupler. I'll include the coupler section.

Although the nose cone is basswood the last 4" is hard maple for extra strength.

I also have decals for the Black Brant II in this size. No roll pattern, that's way to big so you have to paint that.

I can cut some plywood fins for it but no guarantee they won't warp before you get them. ;)

Just a note on the nose cone. Although it is basswood, the last 4" is hard maple for strength.

MarkB.
07-26-2010, 02:32 PM
Gordon,

I had been meaning to ask you about that. El Paso is also high and (really) dry like Colorado and there is some shrinkage. For instance, the Pershing I nose you made for me shrunk a lot, but the Pershing II nose you sent in the same order didn't, so go figure. What I do is lightly sand the already-too-small nose cone and slip a coupler over the shoulder. Taa Daa! Instant perfect fit. Maybe someone can make a Black Brant out of BT-80 coupler stock. If nobody steps up, PM me and I'll order some coupler stock from BMS. Those parts will fly.

I've never had a part from you that needed to be sent back.

sandman
07-26-2010, 03:46 PM
Gordon,

I had been meaning to ask you about that. El Paso is also high and (really) dry like Colorado and there is some shrinkage. For instance, the Pershing I nose you made for me shrunk a lot, but the Pershing II nose you sent in the same order didn't, so go figure. What I do is lightly sand the already-too-small nose cone and slip a coupler over the shoulder. Taa Daa! Instant perfect fit. Maybe someone can make a Black Brant out of BT-80 coupler stock. If nobody steps up, PM me and I'll order some coupler stock from BMS. Those parts will fly.

I've never had a part from you that needed to be sent back.

Actually this guy wanted them to fit coupler stock. The problem was exaggerated by the fact that he was using Apogee Components coupler stock. That coupler is thinner than the stuff from BMS. I have coupler stock and will include it with the cone.