HMD 19 Scaling Plans

Power Boats only. Please include the boat type in your question.
User avatar
Evan_Gatehouse
Very Active Poster
Very Active Poster
Posts: 3210
Joined: Tue Aug 27, 2002 1:00 am
Location: Vancouver, BC, Canada

Re: HMD 19 Scaling Plans

Post by Evan_Gatehouse »

All small boats will change their trim significantly as the crew moves around. If you're carrying the family in the cockpit for a day's fishing, then it will be stern down. If you're carrying a bunch of groceries and clothes aboard further forward, and you have 2 people sitting in the seats, it's going to be much closer to level. My weight estimate assumed 2 persons + food + clothing + basic gear + full tanks for a week or so long cruise. If you don't have all that stuff aboard, which is mostly stowed forward it sits stern down more.

Actually the boat sitting in the first picture looks very nice. Transom is out of the water.
designer: FB11/GV10,11,13/ HMD18/
SK17,MM21/MT24

User avatar
chicagoross
* Bateau Builder *
* Bateau Builder *
Posts: 1927
Joined: Wed Aug 29, 2007 3:42 am
Location: Guam, USA, middle of the Pacific Ocean

Re: HMD 19 Scaling Plans

Post by chicagoross »

The second pic was mine on launch day. I didn't install the optional water tank. In the forward compartment under the berths, I stowed a couple cases of bottled water, which I want on board anyway on an ocean-going small boat from a smal speck of an island in the middle of the pacific. The trim problem was pretty much solved.

With seven people on board, the boat layout pretty much solves the weight distribution - a couple of folks are always in the berths catching a nap (remember that at 7 mph you're always going to be out for a long day!), one or two in the cockpit tending the trolling spread, and the rest centered in the pilothouse.

Of course when you anchor for a swim, and everybody wants to use the bow as a diving board, "small boats will change their trim significantly " :D

alex2293
Frequent Poster
Frequent Poster
Posts: 10
Joined: Mon May 03, 2021 12:40 pm
Location: Quebec, Canada

Re: HMD 19 Scaling Plans

Post by alex2293 »

I understand that scaling this displacement hull in every directions will increase its displacement at power of 3. However, is it acceptable to use some lead ballast in the bilge to make it float at or near its line?

I would like to stretch 8% to make it 20ft long with a 8ft 6in beam.

I would use this boat on the St-Lawrence river in Quebec, mostly on Lake Saint-Pierre. Between Montreal and Quebec, the St-Lawrence river widens to the Lake Saint-Pierre. It's almost 20 miles long by 9 miles wide. It's a shallow lake (average depth around 10ft, a maximum depth of 33ft in the seaway) and can get quite choppy when the wind is against the current.

How would this boat do in these conditions? Anyone have a video of this boat?

Thanks
Alex

Cowbro
Frequent Poster
Frequent Poster
Posts: 159
Joined: Fri Aug 14, 2020 1:06 am
Location: Northern California

Re: HMD 19 Scaling Plans

Post by Cowbro »

alex2293 wrote: Mon May 03, 2021 9:32 pm I understand that scaling this displacement hull in every directions will increase its displacement at power of 3. However, is it acceptable to use some lead ballast in the bilge to make it float at or near its line?

I would like to stretch 8% to make it 20ft long with a 8ft 6in beam.

I would use this boat on the St-Lawrence river in Quebec, mostly on Lake Saint-Pierre. Between Montreal and Quebec, the St-Lawrence river widens to the Lake Saint-Pierre. It's almost 20 miles long by 9 miles wide. It's a shallow lake (average depth around 10ft, a maximum depth of 33ft in the seaway) and can get quite choppy when the wind is against the current.

How would this boat do in these conditions? Anyone have a video of this boat?

Thanks
Alex
Alex. I don't have any good video of my HMD out in rough water. But I can say that it will handle more chop and bigger waves that most men can. lol. I have already had mine out in seas that I KNOW I shouldn't have been in and the boat handles it without breaking a sweat. Be aware that it is relatively light, and the cabin acts as a bit of a sail in even the lightest wind.

As far as ballast. I carry ~150lbs in the the very front under the berth and I should probably add another 50lbs or so to be ideal. It sat WAY too high without it. I generally try to store as much as i can in the cabin while on the boat and keep the deck open. I had 4 people out on Saturday for the first time and it worked really well.

I am already contemplating my next boat, and a scaled up HMD20/21 is certainly on the short list, i would shrink the cabin to a bare minimum length, same with the pilothouse roof to try to add a few more feet of cockpit space out back for fishing and hanging out.

If you are on instagram, I do have some videos on my Instagram page "CowBroFab" under the stories highlight titled "Boat".

alex2293
Frequent Poster
Frequent Poster
Posts: 10
Joined: Mon May 03, 2021 12:40 pm
Location: Quebec, Canada

Re: HMD 19 Scaling Plans

Post by alex2293 »

That is a sweet boat. It looks like 7 mph is fast enough to catch some fish.

I'm also thinking about a smaller cabin, probably something like an Orkney Longliner 19 or Fastliner 19, Wilson Flyer 17, Sea Hog 15, etc.

Image

Image

They are are set up in a way that you can sit at the helm and see through the cuddy or stand and see over the roof. At displacement standing up should not be an issue. It also gives great visibility for docking and getting the boat on the trailer.

Unfortunately, none of those boats are available in North America. They look like great fishing boat with a lot of deck, a small cudy for kids to take a nap with good gas mileage (the ones with displacement hull). I guess we like to buy a lot of gas around here.

If more shelter is needed, a small dodger on the cuddy could be made and/or a bimini top.

Image

An advantage of using a small 9.9HP outboard is there is money left to buy nice accessories, canvas, electronics. Around here a new 90HP is around 12K + rigging...

Again, nice boat!

User avatar
Evan_Gatehouse
Very Active Poster
Very Active Poster
Posts: 3210
Joined: Tue Aug 27, 2002 1:00 am
Location: Vancouver, BC, Canada

Re: HMD 19 Scaling Plans

Post by Evan_Gatehouse »

You can certainly add ballast if you scale up the boat.

It doesn't have to be lead. Scrap steel, concrete, etc. are all acceptable. Bottles of wine, in a container in the bilge so they don't roll is also totally fine.

A spare small anchor in case the main anchor is lost is a good idea too.
designer: FB11/GV10,11,13/ HMD18/
SK17,MM21/MT24

Post Reply

Who is online

Users browsing this forum: No registered users and 13 guests