fullofenergy

Hello, this is my first post and my first plane and I am asking for help.

I removed the spar from its panel and noticed one of them is very warp/curved upward, if I remember well, that spar was already broken out of its panel and curved inside the box already.

If you look at the pic, the top one is curved up significantly.
Can I curve it back down?

Thanks.

Walt Thyng

My Feedback: (9)

Couple of ways to straighten that spar. One way is to steam it until it is soft then pin it against a straight edge until it is completely dry. The other is to soak it in an ammonia/water solution (10%) until soft then pin it against the straight edge until dry.
Walt

karolh

I have had very good results using the ammonia method.

Karol

fullofenergy

What would be the best way to acquire ammonia? Is windex ok or do I need to mix myself?re">

karolh

Possibly the pharmacy .

Karol

sebo

I'd go to the LHS and buy a piece of balsa that most nearly meets the same density, width, and thickness as the one that has the curve in it.
Cost maybe a couple of dollars. make a copy of the spar that is straight and cut it out replacing the bowed one.
I never had luck trying to straighten out a curved piece of wood. I've been building since the mid 1970'sYou'll spend more money on buying the stuff to correct it and waste more time than cutting a new piece..It may not even straighten out all the way once the pins are removed......Ron

Walt Thyng

My Feedback: (9)

Windex is fine. Make sure you slightly overcorrect the bend and when the pins are pulled it should be straight. It may take mre than one attempt.

You can buy ammonia in any store that sells household cleaning supplies (like Windex).

The idea of cutting a new spar is a third way to go (unless your LHS is a long distance away)
Walt

Lnewqban

I may be wrong, but I think that the other parts and the cover will straighten this one.

The only material resisting re-shaping is each little section of wood by the notches.

Besides, those are no spars, but wing webs that get sandwiched between the real spars.

karolh

This is his first model and quite possible his first attempt at building, so we should keep whatever options we suggest as simple as possible. Having him tracing and cutting new sections might be a bit daunting just now, so working with what he has keeps it as simple as possible, and as Lnewqban suggested the member in question might just straighten when all the notched ribs are in place.

Karol

Jonathan Ott

My Feedback: (25)

Send an e-mail to Great Planes: [email protected] and tell them you need a new spar for your PT60 as it was warped in the kit (e-mail that pic too) and they just might send you a new spar for free...can't hurt to ask.

Jon

smithcreek

My Feedback: (25)

I built this plane as my trainer a few years back and until you posted that picture I couldn't remember how that went together, now it comes back to me. Yeah, probably not a big deal with the warp. Try dry fitting the spars and that piece and see if it makes the whole assembly warp. I'll bet it doesn't.

Lnewqban

I agree with Jon.

Also note that the deformation seems to be around one notch, if you decide trying the ammonia method.
You can use one or two straight edges and verify if the attached schematic is correct.

I would cut the web right there, since the part does not need to be continuous.
Its function is only connecting both upper and lower spars and avoid any relative movement between them.

fullofenergy

Thanks for all the suggestions, I'll try them and report back!

karolh

Welcome on board to the greatest hobby there is. Take your time and feel free to ask questions of anything that you are not sure about, as we are always here to give a helping hand, and the very best of luck on your first build.

Karol

Poffit

My Feedback: (4)

That warped piece would not bother me at all. I looked at the building manual for your PT 60 and the warped piece is the webbing that gets glued to top and bottom spars. The spars will hold the webbing perfectly staight after they are glued.

That is why it is so important to have a very flat building surface. Make sure the bottom spar is pinned down flat and staight to your building surface, be sure the webbing is bottomed out in the groove the full length of the spar, and keep the top spar flat when gluing. After the glue sets, the spars will hold everything staight.

Also make sure to keep the wing perfectly flat while sheeting, so you don't build in any permanent warps.

I have been a carpenter for more than 25 years, and if I didn't learn how to work with a little warped lumber through the years I wouldn't have gotten much accomplished these past 25 years.