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        Build Log 1/4 Schreder HP-18

#1 bobthenuke Jun 04, 2009 12:03 PM

1/4 Schreder HP-18
8 Attachment(s)
Hi, all

I'm going to be working on my scale 1/4 HP-18 and will continue to post in this thread if anyone is interested.

Some background...I have a love for this particular sailplane after having owned (half-owned, actually - my buddy, now deceased, was the other half of the partnership) and flown one for several years. To say it was an exciting plane to fly would be an understatement as it had a Vne of 150 MPH Which we pushed to 180 more than once with no problems) and with full 90 degree flaps could land as slowly as 35-40 mph in a very small space.

It was different in several ways from most other gliders of its class (15 meter) in that elevator and aileron control was via a truncated stick that was mounted on the side of the fuse just below the canopy. This stick also engaged the elevator trim and was integral with the wheel brake. The flaps were coupled to the ailerons and were controlled via a crank on the left side of the fuse. The parachute included a blow up bladder to provide a cushion as the pilot flew in a full supine position with the head propped up by a small cushion. Overall, it was a very comfortable position and with the full length canopy visibility was excellent. The only tricky thing was that to dump water ballast one had to reach behind to engage the pull valve attached to the spar where the water was carried. Flying with ruddervators was no issue at all and didn't appear to be any different than flying a standard tailed ship.

Tony Eliott of www.laserflight.com (I'm sure most of you here are familiar with him and his projects) offered to build me the components for this project and I jumped on it. The quality is second to none, and although I haven't bothered to weigh it, at this point it's very light, more so than most other sailplanes I have of this size. The wings and tail feathers are obechi covered foam and the gel coated fuse is a work of art and conforms to the original in almost all ways with the exception of the wing roots. The full size utilized a Wortmann FX 67-150 airfoil which would not be appropriate for this model, so Tony provided an airfoil that would work well for what we, as modelers, would desire to exhibit good flying characteristics. The truncated tail section is not what ours was (it tapered to a nice rounded point) but will be easy enough to modify to the scale outline. No big deal at all and most people would probably not bother with it.

Included are a couple of initial pics I took of it after receiving the giant super well packed box (who can wait to see what it may look like, right?) and a couple of old pics I dug up of our HP-18 N17DW. I intend to finish this as our HP-18 existed prior to it's sale back in the late 80's...white with red lettering and trim, and Schreder spec'd winglets. Also are a couple of pics showing some of the landing attitudes of this little guy...it was a blast!

Of course, any additional pictures will be of the "build". I have a lot of things on my plate at this time so the build will go relatively slowly, but if you're interested hang in there...this will be fun.


#2 Shaper Dave Jun 05, 2009 04:00 AM

Awsome Bob! bet you wish you still had the real one. The model looks like an easy build. Good luck, I'll be watching.


#3 Ranfred Radius Jun 05, 2009 09:49 AM

1 Attachment(s)
Glider? Heck! Tell us about that sound system of your's! ;)

#4 bobthenuke Jun 05, 2009 10:42 AM


Originally Posted by rocketman47
Glider? Heck! Tell us about that sound system of your's! ;)

I'm trying to type while I'm laughing... :) I sort of hate to post pics of this room since it's not related to the subject, but it's the only place I have where I can spread out these planes.

Without meaning to hijack my own thread, it's an Exposure based system, tri-amped Spendor SP9/1 speakers, Merrill Heirloom turntable, cables, etc. etc., total craziness. I wish I had now in the bank what I spent on this...I could easily afford a very nice used full size sailplane.


#5 bobthenuke Jun 05, 2009 05:45 PM

Retract Install
4 Attachment(s)
I'm trying to do a little each day or whenever with the hope that this model will be completed in a reasonable time. The major components have been supplied by Tony and the one installation that I have to perform without screwing up is the retract install.

I'm using the original aircraft construction details for some of this model although It's really not neccessary. I'm a bit anal (I heard that snickering - cut it out!) regarding details and since I have the info available why not?

I printed out a worksheet of the area I'm dealing with and drew a few lines, made a few measurements to determine the scale so to transfer relative dimensions to the model fuse. No surprise, the front of the wheel is just a touch aft of the wing LE.

The full size used a 5.00-5 tire which equates very closely to a 3.5" diameter tire for the model. The I-care 1/4 scale retract unit I had in a box just happens to have a 3.5" diameter tire, although the wheel itself is small and a bit funky. Maybe someday I'll find a better, more scale looking wheel, but this will do for now.

After some careful measurements based on the mold lines of the fuse I came up with some centerline marks for the fuse side and streched a piece of tape down it in order to have a reference point. Following that I dropped another piece of tape at a right angle just ahead of the LE and thus determined the point that the most forward point of the tire will be. This was, IMO, the hardest thing I'll have to do to fabricate this model.

#6 bobthenuke Jun 06, 2009 04:36 PM

6 Attachment(s)
I couldn't leave it like it was without seeing how it would look up on the wheel.

I took some basic measurements and layed out the opening outline in masking tape. After scribing the outline with an Xacto knife I took out the trusty Dremel and cutting wheel and had at it. It came out just right and I'm happy that this part is over!

One thing I hadn't thought about was the wheel extension of the full size compared to that of the model. The commercially available retracts (at least the ones I have) simply swing the wheel down and are thus limited in throw. The full size actually folds the wheel up into the fuselage and when extended the wheel ends up fully outside the fuse. To get the wheel out further I had to lose the supplied mounting plate for the retract which reduced the distance of the retract assembly from the fuse bottom. You can see the difference in the two photos below. It's not exactly what I'd like, but should be good enough (I hate using the term "good enough") for this model. Maybe someday when I have nothing else to do I'll either build a scale retract for this plane or commission someone else to.

So now I've got the retract assembly just tacked in with a couple spots of CA gel while I work up some nice ply mounting brackets as well as adding some glass and/or carbon cloth to the area for extra strength.

As far as doors go, I'm going to make these from aluminum. The full size fuse consists of a fiberglas pod that goes back a bit past the wing TE with the rest of the fuse consisting of several truncated aluminum cones. The doors on the full size are metal (I think I read somewhere that they're magnesium but that seems to be a bit much) but I like working with aluminum printing plate of which I have a sheet or two left from the days that newspapers used to give these away.


#7 mosquito303 Jun 06, 2009 08:29 PM

You might like the center stick conversion. grins

#8 bobthenuke Jun 06, 2009 10:35 PM


Originally Posted by mosquito303
You might like the center stick conversion. grins

I'm sorry - this went over my head.


#9 bobthenuke Jun 07, 2009 07:50 AM


Originally Posted by Shaper Dave
Awsome Bob! bet you wish you still had the real one. The model looks like an easy build. Good luck, I'll be watching.


Hey, dave

The more I get into this the more I miss the big one. I'm keeping my eyes open for one that's not too far away or something similar. The toys are great but there's nothing like being up there in body as well as mind. ;)


#10 romanl Jun 07, 2009 05:34 PM

Very cool, Bob; I will be following along.

#11 shhhhh! Jun 25, 2009 08:57 AM

Awesome Bob!!!!!!!!!!!!!!!!!!!!!! very inspiring!!!! keep up the great work!!

#12 schrederman Jun 26, 2009 12:15 PM

AAAWWWW!!!!! Dang... Now I have to start on my PIK-20B... See what you've done! The real one landed the same way... nose WAY down, and just ease off the forward stick to flair for touchdown.

She's definitely a beauty! So was your real one. I sold my PIK in a fit of idiocy. I now actually have time to fly it.

Keep us posted. Interested? I'm in!


#13 Pheasant Jun 26, 2009 01:04 PM

Looks like an awesome project, the HP-18 is a sweet airplane.

And for those with some time to kill, check out Bob Kuykendal's site here: http://www.hpaircraft.com/

He has some HP stuff (plans and parts) including for the -18, but be sure and check out the HP-24 build log.

#14 bobthenuke Jun 26, 2009 03:35 PM

5 Attachment(s)
Hey, Jack

I thought you'd find this thread sooner or later! A friend had a PIK 20 and we used to bet on who could come in the shortest...real nice plane and I know you miss it as much as I miss the -18. Just gotta love those 90 degree flaps.

Back to the build, I finally found some time to continue along. The pics will explain everything but I want to say that if you can get ahold of some newspaper or printing aluminum sheet (lithoplate), do so. I got mine a number of years ago and perhaps with the computer printing done today it's no longer available. I guard my stash jealously but am known to share if someone really has a good use for it. ;) What's so nice about it is that it's easy to work with (can be cut with household sissors) and has a spring to it so when it's formed it stays that way. I use it in lots of places in scale building and it makes great hatches, cowl parts, etc. etc. An added bonus is that one side has a coating that's similar to a prime coat and is easy to mark with a pen.

#15 Libelle201B Jun 26, 2009 04:31 PM


Originally Posted by bobthenuke
Hey, Jack

I thought you'd find this thread sooner or later! A friend had a PIK 20 and we used to bet on who could come in the shortest...real nice plane and I know you miss it as much as I miss the -18. Just gotta love those 90 degree flaps.

And who won ? an X HP-11 owner . :)

P.S. I really like your r/c project :)

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