ML Boatworks: GP 335 - P sport hydro

[Jesse J]

I have her done, but thought I would get a build thread going so we can keep all our input in one place and not dispersed throughout the site.

Overall comments:
instructions are great - if you read them and as Mike warns, read ahead multiple times. I did a couple things I could have done better had I followed this advice.

kit quality was excellent.
- wood was all high quality, no knots or warps and pieces fit snugly but not too tightly.
EDIT!!!- there were several lengths of stringers (1/4" stock) and it was a little vague as if this was on purpose or not - USE THE SHORT ONES ON BOTTOM AND THE LONG ONES ON TOP!!! be sure you have the full length on top that make it all the way to the nose piece. since the bottom of the tunnel has the air dam, you wanna be sure to go shorties down there. Todd just learned this the hard way
- Since the tunnel is kinda complex with all the bulkheads and stringers above and below - I will also re-emphasize the strategy of tacking everything in place then - be sure to thin your west systems. I did not, and know that the model would be all that much stronger if I had.
- the sponsons are always the most challenging, but only because we are bending things that want to be straight. This works much better if you can recruit another pair of hands.

The build.
I had my computer next to me so I could have instructions handy and not waste paper/ink with a 20 page printout.
I laid everything out, opened a beer and started fitting things together. after several trips to the garage for tools, I had my clamps (narrow arms is best - and be sure not to glue them into the frame! I know cause I did it), my 2.5 and 5 lb flat weights, a piece of 90deg angle to make sure my bulk heads were as straight as possible, and my tape to hold the parts. Even though I did like the CA kicker, it only really nails the outside so I wanted to give some time for set up. after a few beers and 2-3 hours I had my sponsons framed up.
Next morning I did some skinning and after a couple cups of coffee and 2-3 hours or so I had the sponsons pretty much done. I cut some time off the shaping of the overhanging side and bottom by using a utility knife to carve it down. BE VERY CAREFUL WITH THE KNIFE!!!! it would be very easy to slip and cause a serious injury - getting blood all over your nice new kit. The other way is to use your belt sander and grind it down like Mike suggests.
I worked off and on Friday through Sunday and by the end of the weekend I had the hull done save for the upper decking.

[Jesse J]

Part II: sealing the hull

Luckily there is a place in Houston that sells West Systems (actually 4-5 in all!) so I picked up some Sunday afternoon on a break.

Throughout the week, I kept cranking. I coated the inside with the Epoxy using a 1 1/2" trim paint brush and cleaning it out with a jar full of acetone. I should have thinned it but I didn't and only me and you guys know that
As Mike states, the Epoxy is to seal and more importantly bond up all the parts, so be sure to get all the nooks and crannies, but not leave pools. I was glad I put mine on a flat table with a layer of wax paper because it leaked out through the pegs that lock the bulkheads to the bottom. In the tunnel, I laid heavy fiberglass strips and because I was paranoid of a cup in my hull, I placed some flat squares of scrap wood (flat mind you) weighted down with the 2.5lb weights on top of some pieces of thick plastic (sandwich bag thickness) to keep the weights from sticking to the epoxy. DO NOT USE WAX PAPER FOR THIS. I did once, and the heat from the kick when the epoxy goes melted the wax and gave me a nice layer of wax on the inside of my hull that I spent hours cleaning off so glue would stick again. I used Kevlar/carbon fiber in the sponsons - messy looking, but only me and you guys know that too. for the skid fin, I set some blind nuts in 24hr JB weld so I could remove for painting and not have problems with loose or lost nuts.

Then my US composits 2 part foam came. I went 2lb density and gave it several days to totally finish curing. When I was sure it was done expanding, I took my shark tooth saw (hand saw) and cut off the excess, being careful not to cut the framing, but evidently not worried enough about cutting my finger - it went to the bone in a split second.
I didn't get a picture, but I also filled the two chambers along the outside of the tub. This really adds to strength and gives plenty of flotation!!

the final step was to Epoxy the outside. Here I don't think thinning is necessary. I painted on 2-3 thin coats since I learned on my last build that the stuff will run and make very obnoxious droozles along the side that take for ever to sand off. You want just enough so you don't see the wood grain; any more is just unnecessary weight. I then sanded with 150, 220, 320 sand paper - ALWAYS USE A SANDING BLOCK MADE FROM FLAT, HARD WOOD. I used some scrap oak pieces, but just make sure there are no cavities or protuberances, or you will have a difficult time getting a smooth surface.

[Jesse J]

Part III: hardware and prep for painting

I played with my electronics for days testing all the possibilities and was concerned about my 4S 5000 mah packs I wanted to use... turns out way too much battery - and weight!!! This boat likes CG around 3" (I found out yesterday). Unfortunately, I did not document my assembly.

I made me a motor mount from 1.5" aluminum angle flashing and the front mount part this I had laying around. I ran 6 screws through the bottom of the hull into a 1/8" piece of ply filling the second chamber and through the mount. then I cut a piece of hardwood as a motor rest.

The back of the motor mount was set just at the middle bulkhead and the flex tube entering just behind it. This gave me maximum amount of battery positioning flexibility. I put the servo in the hole in the side that Mike designed. I did set the motor/strut 0.25" starboard of centerline to combat propwalk. I got me a long speedmaster rudder with two water intakes and cut it down - still need to take some off. Target depth is 3.25" below base of transom.

Then I took everything out and prepped for paint. I cleaned all with paint thinner then alcohol. I know there is a thread debating primer, but my dad is a carpenter and believes in primer on treated wood, so I primed it. Since I like how wood boats looked, I masked off all the bottom behind the air dam, to leave as unpainted wood.

I used two cans, since primer also acts as a subtle gap filler, it helps to develop a nice smooth finish. I did use bondo on the places where I had gaps in the decking. This was because my stringers were emerging slightly above the skin on the tub and did not get sanded flush - gap could have been avoided. Also, there were a good number of pin holes in the cowl. These could have been filled with something softer than bondo, but I was not about to go out shopping instead of building!!

[Jesse J]

part IV: paint scheme

I love the Oh Boy! Oberto theme, so that was a no brainer. After I had a good opaque white primer base coat lightly sanded and buffed out, I got me some good quality edge-lock masking tape and got my inspiration photos of the 2004 Oberto paint scheme in hand. To make the paint edge, I cut my 1" tape into 1/4" strips so they would make the curves better without wrinkling. I was aware of the humidity and made sure it was sufficiently below the 80% recommended on the Krylon can. I did 2-3 light coats and then a couple heavy ones over the course of an hour or so. WEAR YOUR HAZARDOUS PARTICLES MASK FOR THIS, not just a felt mouth cover, but a real on that makes you sound like Darth Vader when you breath. Since I was painting 4 days before our race, I was not a perfectionist and will be recoating in the near future. I did dress her up for now with some graphics I had laying around. O TWO (for Oberto II)

You will notice a slight gap at the front of the cowl; I had the cowl cut down perfectly, but then I did not account for the 1/8" piece of plywood I put between the hull and the motor mount... So when you are getting ready to mark where to trim your cowl, be sure you have your motor in place and all your gear inside, so you can be sure where the cowl must be for best fit. I did put a layer of expanding foam in the cowl also for added strength and flotation.

[Jesse J]

part V: tuning

As for tuning, it has taken me a nearly a dozen runs to get the hops out, the nose up and the boat freed up. She definitely has plenty of down force on the nose and this allows for a very forgiving free flying ride.
Here is yesterdays success!

33.5" kit running 4S2P - 8000 may total
1521 1.5D motor, CC 240 LV, Speedmaster hardware, 3/16" flex drive, ABC 1916 prop
COG 3" behind sponsons
9.4lbs running weight

strut 17mm from transom base to center of drive line,
0.5deg positive angle (back higher than front) when measured from line drawn between base of sponson and base of strut
0.25" starboard of centerline

[detox]

Thanks for sharing your build. I see some burnt wood along inside of tub. What happened? BTW I like Marshal Tucker

[oscarel]

I see some burnt wood along inside of tub. What happened?

Ouch, is that where the controller burned up?

[ray schrauwen]

Nice build.

That foam exposed on the inside will absorb a fair bit of water if any enters, that is if it is cut or sanded.

[oscarel]

Doesn't that depend on the foam? This is from the stuff I got from US Composites.

"This two-part liquid, expanding rigid urethane foam is a closed cell, pourable foam, which will resist the absorption of water."
"The lightweight foam is commonly used for filling voids, filling under decks and practically any other flotation or insulation application. "

"14. Is this foam water resistant?

Yes, but with the following caveat. The foams that we sell are considered closed-cell, which means that each cell that makes up the foam structure is completely closed off from surrounding cells which prevents it from acting like a sponge. It is completely safe for this foam to be in contact with water for hours/days/weeks and even months with no adverse effects. However, it should never be submerged in contact with water permanently. "

[Jesse J]

Nice build.

That foam exposed on the inside will absorb a fair bit of water if any enters, that is if it is cut or sanded.

Thanks!
nope. read up on US composites foam, that's why I included the name.
You might want to know more about what you are telling people before you say something that is not accurate.

[ray schrauwen]

I've read it, it has this Caveat:

Pinhole sized openings would essentially have no effect on the foam since the amount of exposure is so minimal but you should always make repairs as soon as possible to keep the foam effectiveness as good as possible. This will be the case with all after market closed-cell polyurethane foams and even manufacturer installed foams.

Meaning if it is cut or damaged from it's original skin except in cases of pin holes it needs to be repaired for its full effectiveness.

My english is pretty good and I meant no harm.

Do an experiment, take a piece of waste and cut it open and then submerge it for a minute or two as if your boat was upside down before retreval.

You will notice it sucks water up like a sponge and takes a long time to dry out.

I use the stuff, just once I expose the inside, I coat it with epoxy to re-seal it.

BTW, pool foamies are the same, once cut, very sponge like, more so..

[Jesse J]

Right on, thanks for sharing - what is the reference to this, I would like to read more myself.

Experiments are good, as are thick skins! Fair enough, I have a bunch of the little blocks layin' around and can do such an experiment.
I will take a chunk, weigh it, put it in some water - held down with some weight and weigh it in a day - that ought to give us some data to compare with the claims.

[Grazacind]

Hi Jesse the boat is starting to look like a winner. Great job mate.

With mine I am going to run 5000mah as per our rules. If you were to run that would you change your cog at all.

Cheers
Andrew

[jaike5]

The boat is wood, should float...... cheers, Jay.

[Fluid]

Nope, wood will only support a certain amount of weight per cubic inch of volume. The typical wood in an FE boat is very dense (plywood) so it 1) has very little volume in the total build, and 2) supports less weight per unit volume. To paraphrase an actor in Titanic: "I assure you, she can sink... and she will. It is a mathematical certainty." Additional floatation is required for a nine-pound boat. Trust me. Especially the fiberglass hatch....



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